Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
248 PM EDT Sun Mar 23 2025

Valid 12Z Wed Mar 26 2025 - 12Z Sun Mar 30 2025


...Overview...

Expect the amplified western ridge/eastern trough upper pattern
lingering into Wednesday to move steadily eastward while trending a
little flatter, as dynamics from a strong East Pacific upper
trough Wednesday-Thursday (supporting a storm system off the
Pacific Northwest coast) push into the western and central U.S.
With a slightly slower trend noted in the guidance, the mean ridge
should reach the East by next weekend. Expect very warm
temperatures under the western upper ridge through midweek or so
with some daily records possible. Anomalous warmth will then move
into the Plains, followed by moderation farther east. Upper
dynamics and the leading front arriving from the Pacific will bring
rain and high elevation snow to the Northwest mid-late week, with
another system possibly approaching by next Sunday. A southern tier
shortwave will support the threat of locally heavy rainfall over
parts of Texas late in the week. This moisture and additional Gulf
inflow may combine to spread a broader area of precipitation over
parts of the Plains and east-central U.S. late week into the
weekend, in association with Plains through Upper Midwest low
pressure.

...Guidance/Predictability Assessment...

Guidance continues to show good agreement on the large scale upper
pattern and progression, but a lot of uncertainty in the details.
A leading shortwave into the West from a deepened low off the
Pacific Northwest coast shows good agreement, but there is
continued question on timing and amplitude of a deeper trough into
the West later in the week. The GFS has trended slightly deeper in
recent days, but the last several runs of the CMC continues to be
the outlier as it eventually spins up a closed low over the Central
Plains next weekend. Better cluster of guidance suggests this
should be more of an open wave. Ahead of this though, there remains
uncertainty in the details of a southern stream shortwave into the
Southern Plains and Midwest later this week, which has impacts on
heavy rainfall potential across Texas. Then by next weekend
guidance shows spread with a front that reaches into the Mid-
Atlantic, likely with a pronounced temperature gradient.

The WPC forecast today was able to use a blend of the latest
deterministic guidance for Wednesday and Thursday, amidst good
model agreement. Began incorporating the ECENS/GEFS by Friday/Day
5, eventually reaching a 50/50 split of deterministic/ensemble
means by Day 7. Did not include the CMC in the late period blend
due to the outlier solution described above. Overall, this approach
maintained good continuity with the previous WPC forecast.

...Weather/Hazards Highlights...

From Wednesday into Thursday night the most prominent heavy
rainfall focus should be over portions of Texas by Thursday as
moist southeasterly low level flow from the Gulf interacts with an
upper shortwave crossing northern Mexico. Some activity may
initiate in the Day 4 period near the Rio Grande Valley but the
signal is diffuse enough not to merit any risk area in the
Excessive Rainfall Outlook. By Day 5 there is a much stronger
signal, though with typical spread for where the heaviest rainfall
axis will be. Overall the best overlap of guidance exists over
southern Texas. The Day 5 ERO maintains a broader Marginal Risk
area, with no embedded Slight Risk depicted yet due to initially
dry ground conditions and guidance spread. Improved clustering for
location and amounts in the heavier part of the envelope could
eventually merit an upgrade. Elsewhere, consensus amounts along the
Pacific Northwest coast in association with the Wednesday-
Thursday system have generally decreased somewhat from 24 hours
ago, while the signal for a potential band of enhanced rainfall
over the Mid Mississippi Valley ahead of a warm front is too
diffuse to warrant a risk area yet on Day 5.

Precipitation will spread across northern and central parts of the
West late this week, with Plains low pressure and its trailing
front eventually pushing the Texas rainfall eastward while
spreading a broader shield of moisture across the central and east-
central U.S. Some wintry weather will be possible over far
northern latitudes but otherwise most precipitation should be in
the form of rain. How much snow falls over the northern Plains next
weekend will depend on how strongly the Plains/Upper Midwest
system develops, with low confidence in specifics at this time. The
next Pacific system may increase precipitation along the West
Coast by next Sunday.

The weak wave forecast to track off the Mid-Atlantic/New England
coast on Wednesday may produce some light precipitation early but
most likely just near the coast.

The strong upper ridge over the West into Wednesday will bring
well above normal temperatures to the region, with a broad area of
highs 10-20F above normal with locally higher anomalies. There will
also be potential for numerous daily records for highs/warm lows,
especially during Wednesday. As the upper ridge shifts eastward
with time, the West will cool down while already above normal
anomalies over the central U.S. will increase. Locations from the
northern-central Plains into Midwest should see one or two days of
highs reaching 20-25F or so above normal by Thursday-Friday, with
best potential for some daily records over the central High Plains
on Thursday. The East will see near to slightly below normal
temperatures Wednesday-Thursday and then increasing coverage of
highs 10-20F above normal Friday into the weekend. However a front
reaching the Northeast/Mid-Atlantic may define a sharp gradient
between this warmth and cooler readings just to the north.

Santorelli/Rausch


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
305 PM EDT Mon Mar 24 2025

Valid 12Z Thu Mar 27 2025 - 12Z Mon Mar 31 2025

19Z Update: The 12Z model guidance suite maintains good synoptic
scale agreement across the Continental U.S. for the end of the work
week. For the storm system developing across the Plains and Upper
Midwest this weekend, the UKMET is a bit more to the northwest of
the model consensus with the front placement, but not a major
outlier. More substantial diffences become apparent with the next
Pacific storm system, with the GFS taking the main low center well
to the north of the CMC and GFS, and lingering model spread in the
wake of that system. For the East Coast, the GFS is faster with the
front exiting the coast Monday night.

Taking these factors into account, Thursday and Friday incorporated
a general deterministic model blend, and then the ensemble means
were gradually increased to about 40% by early next week. The
previous forecast discussion is appended below for reference.
/Hamrick
-------------------

...Overview...

Most guidance shows a reloading mean trough over the eastern
Pacific with a strong system affecting the Pacific Northwest
Thursday into Friday with potential for another meaningful system
to affect the West Coast by Sunday-Monday. The downstream pattern
looks moderately progressive, with a very warm Rockies/Plains ridge
eventually moving off the East Coast while trailing shortwave
energy supports low pressure that should track northeastward from
the Plains during the weekend into early next week. The eastern
Pacific systems will bring areas of enhanced precipitation to the
West Coast while the system affecting the central/eastern U.S. by
Saturday-Monday should spread a broad area of moisture east of the
Rockies with some wintry weather possible over far northern
latitudes. A southern stream shortwave crossing northern Mexico and
Texas late this week may also produce some heavy rainfall along
and inland from the western half of the Gulf Coast.

...Guidance/Predictability Assessment...

Latest guidance agrees decently with the larger scale aspects over
the overall pattern but there is still plenty of uncertainty for
details of shortwave energy moving into the West late this week and
continuing inland thereafter, affecting the forecast for low
pressure that should ultimately track northeastward from the
Plains. Trends over the past couple days have been leading toward
an intermediate solution for the leading energy reaching the West
while significant differences develop for the relative emphasis of
leading energy versus trailing energy arriving from the Pacific. At
least there is a somewhat coherent clustering of GFS/ECMWF runs
and most ensemble means as the overall shortwave trough reaches the
eastern half of the country, with surface low pressure near the
eastern Great Lakes as of early next Monday. CMC runs had been too
eager to close off an upper low but the new 00Z run seems to be
tempering that tendency. Machine learning (ML) model spread is
disconcerting though, with a couple suggesting potential for a
faster leading wave and another one hanging back to the southwest,
while another subset is closer to the model/ensemble majority. Off
the West Coast, there is decent clustering for the strong system
near the Pacific Northwest late this week though the new 00Z UKMET
looks somewhat disjointed. There is still a lot of spread for
specifics of the Sunday-Monday system but with the average of
guidance trending somewhat stronger. ML models are still not
developing this system too strongly though.

Latest guidance comparisons based on 18Z/12Z guidance led to
starting Day 3 Thursday with an operational model composite. The
CMC was removed thereafter in favor of the CMCens mean, while the
blend introduced some 18Z GEFS/12Z ECens after early Saturday. Day
7 Monday featured an even weight of models (18Z GFS/12Z ECMWF) and
the means.

...Weather/Hazards Highlights...

Guidance continues to show a late-week threat of locally heavy
rainfall over parts of Texas and then extending eastward, as low
level Gulf moisture and a warm front interact with an upper trough
progressing across northern Mexico and Texas. The Day 4/Thursday
Excessive Rainfall Outlook will now depict a small Slight Risk area
across portions of south-central Texas given an enhanced model
signal for QPF with some convective training possible, even though
there are still some placement differences in the main QPF axis. As
this activity likely drifts eastward, the Day 5/Friday ERO shows a
Marginal Risk area along and somewhat inland from a majority of
the Texas and Louisiana coast. This reflects the best overlap of
guidance and is where heavier rainfall should be more likely based
on instability. The Day 4 period also introduces a Marginal Risk
area for the Pacific Northwest coastal areas with increased model
signal for 1-2 inch totals during this time period.


In addition to supporting Pacific Northwest precipitation, the
strong storm offshore on Thursday may produce some strong winds
near coastal areas. As the system's front and shortwave dynamics
continue eastward, moderate amounts of rain and high elevation snow
will progress across the northern half or so of the West late this
week. Expect Low pressure developing over the Plains and tracking
northeastward to spread an increasingly broad shield of
precipitation across the central and eastern U.S. from the end of
this week into next Monday. Some wintry weather will be possible
over far northern latitudes but otherwise most precipitation should
be in the form of rain, with some potentially on the heavy side.
How much snow falls over the northern Plains during the weekend
will depend on how strongly the system develops, with confidence in
specifics remaining in the lower half of the spectrum. Another
potentially vigorous eastern Pacific system may bring areas of
enhanced precipitation to the West by Sunday-Monday.

The strong upper ridge reaching the Rockies/Plains by Thursday
will bring very warm temperatures to the region, with some areas
over the Plains and eastern Rockies/Midwest seeing up to plus
20-30F anomalies for highs and/or morning lows during Thursday
and/or Friday. Some daily records are possible over the High
Plains. System progression will push a moderated form of this
warmth farther eastward by the weekend, with plus 10-20F anomalies
for highs. However a front settling into the Northeast/Mid-Atlantic
may define a sharp gradient between the warm air and cooler
readings just to the north. Behind the front anchored by the
developing Plains low, near to slightly below normal highs will
progress from the West through the central U.S., followed by a
rebound over and near the Rockies by next Monday.

Rausch


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 PM EDT Tue Mar 25 2025

Valid 12Z Fri Mar 28 2025 - 12Z Tue Apr 01 2025

...Overview...

Latest guidance shows a moderately progressive pattern that will
bring active weather to portions of the Lower 48. A southern stream
shortwave will promote a threat of heavy rain along the western-
central Gulf Coast late this week. Behind this feature, eastern
Pacific into western U.S. dynamics will spread precipitation across
northern parts of the West and then develop one or more
waves/fronts from the Plains eastward with associated areas of
enhanced rainfall as well as winter weather potential over far
northern latitudes. Another Pacific system should spread
precipitation into the West from late weekend into early next week.
Very warm temperatures will prevail ahead of the overall area of
Plains low pressure, while trailing cooler air will bring readings
back down to near or slightly below normal.

...Guidance/Predictability Assessment...

The main area of uncertainty in the models exists around the west
to central Gulf Coast system later this week. Non-GFS models tended
to cluster better together than pre-12z GFS/GEFS guidance on the
timing of the shortwave propagating across the western Gulf Coast
on Friday into Saturday. Elsewhere, the NBM probabilities of > 0.25
in. of snow or freezing rain were notably lower than the ensemble
means.

A general model blend weighted towards the Euro/Euro ensemble mean
were utilized through day 5. Ensemble means dominated the blend
beyond that.

...Weather/Hazards Highlights...

Latest guidance is consistent with the general theme of heavy rain
potential along and near the west-central into central Gulf Coast,
as an upper trough interacts with low level Gulf moisture and a
warm front. The Day 4/Friday Excessive Rainfall Outlook has
introduced a Slight Risk area covering parts of southeastern Texas
and southwestern Louisiana, with models/ensembles now clustering
better for this region seeing the best focus. By Day 5/Saturday,
guidance becomes much more diffuse with the rainfall signal. Recent
ECMWF/ECMWF AIFS/UKMET runs show the most agreeable theme of some
activity from Friday-Friday night continuing into Saturday, with
some instability, before trending lighter. Thus the Day 5 ERO
depicts a Marginal Risk area along and north of the central Gulf
Coast region.

Elsewhere, rain and high elevation snow will cross the northern
half of the West late this week, followed by an increasing area of
precipitation from the north-central Plains through Northeast and
extending southward through the Mississippi Valley and points east
during the weekend into early next week as one or more frontal
waves evolve and the overall frontal system eventually pushes
eastward. It may be cold enough to support wintry precipitation
types for a time from the northern Plains through the Upper Great
Lakes into northern New England. To the south, some rain could be
locally heavy over the north central Plains as well as from the
Mississippi Valley eastward. In addition, the Storm Prediction
Center is monitoring the potential for severe weather from parts of
the eastern Plains into a large part of the east- central U.S.
during the weekend. Check latest SPC outlooks for the latest info
on severe threats.

After a brief break, another area of precipitation should spread
across the West from Sunday into early next week. There is still a
decent amount of uncertainty for the specifics of supporting
eastern Pacific low pressure, but currently expect highest totals
to be over the central West Coast/northern California.

Very warm temperatures will prevail in the warm sector ahead of
the wavy frontal system evolving over the Plains and then pushing
eastward. Some areas from the central High Plains into the Midwest
may see highs 20-30F above normal on Friday. The warmth will shift
south and east over the weekend with plus 20F or greater anomalies
for morning lows reaching from the Midwest into the Ohio Valley
while plus 10-20F anomalies for highs extend from the southern half
of the Plains into the Mid-Atlantic and Southeast. Continued
frontal progression will confine above normal readings to the East
Coast by Monday. However the Northeast will be on the cool side, to
the north of a front settling over or near the northern Mid-
Atlantic. Behind the main frontal system, modestly below normal
highs will progress from the West late this week into the Great
Lakes/Ohio Valley by next Tuesday.

Rausch


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
235 PM EDT Wed Mar 26 2025

Valid 12Z Sat Mar 29 2025 - 12Z Wed Apr 02 2025

...Overview...

Continue to expect a moderately progressive pattern with active
weather across portions of the Lower 48. A southern stream
shortwave should bring a threat of locally heavy rain into the
east-central Gulf Coast early this weekend, but with less extreme
totals than expected farther west in the short range time frame.
Meanwhile emerging western dynamics will help to develop a wavy
frontal system pushing eastward from the Plains through the East
this weekend into next Monday. This system should produce some
wintry weather over northern latitudes with areas of enhanced
rainfall farther south. A system most likely to track northward
offshore the West coast should spread precipitation into the West
from late weekend into early next week. Additional precipitation
may reach the West into midweek, while leading moisture reaches the
east-central states, but guidance shows a lot of spread for flow
details by then so forecast confidence trends well below average.
Very warm temperatures will prevail ahead of the Plains/eastern
U.S. system while trailing cooler air will bring readings back down
to near or below normal.

...Guidance/Predictability Assessment...

There's agreement on the overall synoptic pattern across the lower
48 this weekend into next week. Models mostly agree on the
presence of mean troughing in the northeast Pacific and shortwaves
ejecting out from it into the CONUS. The 06z GFS/GEFS suite
diverges from the rest of the overnight/morning guidance with
respect to the amplitude of an early-to-mid-week shortwave
propagating through the Northern Rockies/Plains next Tuesday-
Wednesday. The GFS/GEFS are much more suppressed than the other
models.

A general model blend was sufficient for day 3 given little spread
in the guidance. The Euro and GEFS ensemble means are incorporated
into the blend on day 4 to mitigate some notable divergence in the
UKMET solution over the Rockies. The 00z UKMET is removed from the
blend completely on day 5 in favor of a less amplified and more
agreeable EC/CMC/GFS/GEFS/ECE blend. What is a well clustered
pattern over the Pac NW on day 5 becomes less so by next Tuesday
when the GFS/GEFS stalls out over the region while the EC/CMC
suites send energy into the interior. The Day 6 blend reflects this
uncertainty with equal parts 06z GFS/GEFS and 00z ECE/EC in the
blend. A Canadian/Euro favored blend is utilized on day 7 due to
the suppression of shortwave energy over the Rockies by the
GFS/GEFS.

...Weather/Hazards Highlights...

The Day 4/Saturday Excessive Rainfall Outlook maintains a Marginal
Risk area along and somewhat north of the central/east-central
Gulf Coast region, with only minor adjustments from continuity.
Guidance is consistent with the setup for locally heavy rainfall
(but trending somewhat lighter than across areas farther to the
west), as the supporting southern tier upper shortwave pushes
eastward. The distribution of solutions has remained similar as
well, with the ECMWF/UKMET and machine learning models clustered in
showing meaningful rainfall potential given sufficient moisture
and instability versus a more diffuse signal in other guidance. By
Day 5/Sunday expect a broad area of convection to develop over the
east-central U.S. ahead of the wavy front pushing eastward from the
Plains. Current guidance recommends a broad Marginal Risk area
from the Ohio Valley southwest into parts of the lower Mississippi
Valley. Improved guidance clustering especially from the Ohio
Valley southward where soils are on the damp side could eventually
lead to an embedded upgrade in risk level.

More broadly, the wavy frontal system affecting the central and
eastern U.S. will produce meaningful precipitation from the
northern Rockies/High Plains into the Northeast as well farther
south over the East, though the latter should be with lighter
totals than forecast over the area covered by the aforementioned
Day 5 Marginal Risk. In addition, the Storm Prediction Center is
monitoring the potential for severe weather from the east-central
U.S. to the Mid-Atlantic/Southeast during Sunday-Monday. Check
latest SPC outlooks for the latest info on severe threats. Some
snow will be possible across northern latitudes, with Rockies and
Plains totals dependent on elevation and/or time of day. There may
be a band of wintry mix separating the snow from rain from the
Upper Midwest into New England.

After a brief break, an area of rain and high elevation snow
should reach into the West by Sunday-Monday, most likely from
northern California into the Pacific Northwest and perhaps
extending into the northern Rockies by early next week. There is
still spread in the guidance for supporting low pressure but new
solutions are starting to cluster somewhat better for low pressure
wrapping up offshore the Pacific Northwest. Increasingly dramatic
guidance differences for the eastern Pacific/western U.S. pattern
early-mid week lead to low confidence for how much additional
precipitation may reach the West Coast. Initially preferred
ensemble-based guidance suggests a wetter trend focused along the
central West Coast into midweek, but there is a minority of
solutions with a drier forecast.

Very warm temperatures will prevail in the warm sector ahead of
the wavy frontal system evolving over the Plains and then pushing
eastward. During the weekend expect the warmest anomalies to extend
from the southern half of the Plains through the Midwest, Ohio
Valley, and Mid-Atlantic with readings 10-25F above normal (with
morning lows tending to be somewhat more anomalous than daytime
highs). Frontal progression will confine the warmth more toward the
East Coast by next Monday. Northern New England should remain a
lot colder though, as a sharp front stays just to the south. Near
to below normal readings will progress eastward behind the
Plains/eastern U.S. front, with precipitation keeping some
northern-central High Plains locations 10-15F below normal for
highs during the weekend. Periods of unsettled weather will keep
the diurnal spread over the West Coast states more narrow than
usual.

Kebede/Rausch


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
303 PM EDT Thu Mar 27 2025

Valid 12Z Sun Mar 30 2025 - 12Z Thu Apr 03 2025

...Overview...

A progression of systems should bring active weather northern-
central parts of the West with rain and higher elevation snow, as
well as the eastern half of the country where some wintry weather
is possible over far northern latitudes with rain to the south. Low
pressure tracking northeast from the Plains Sunday-Monday will
bring one round of eastern U.S. precipitation. A couple systems
affecting the West early in the period should ultimately lead to
another surface low emerging into the Plains by midweek with a
northeastward track thereafter. Guidance continues to have
difficulty for flow specifics within the blocky pattern over the
Pacific, leading to significant eastern Pacific into Lower 48
guidance spread for upper pattern and Pacific systems by Tuesday-
Thursday. Very warm temperatures will prevail ahead of the first
Plains/eastern U.S. system while trailing cooler air will briefly
bring readings back down to near or below normal before a likely
rebound.

...Guidance/Predictability Assessment...

Guidance is well clustered early in the period followed by notable
uncertainty in the 06z GFS suite. Consensus is for mean troughing
in the West to emit shortwave energy over the northern tier of the
country throughout the period. The GFS suite diverges from the
rest of the guidance beginning on day 5 when it over-amplifies a
trough over the east Pacific. The operational GFS sends many more
shortwaves into the northern tier compared to consensus. For that
reason, the GFS suite was left out of the blend on days 6 and 7.

A general model blend consisting of the 06z GFS and 00z
ECMWF/CMC/UKMET are used on days 3 and 4. The ensemble means (06z
GEFS and 00z ECE/CMCE) are introduced to the blend on day 5 and the
06z GFS is removed due to an over amplified and more progressive
solution compared to the Euro and Canadian guidance. The Euro and
Canadian suites are favored on days 6 and 7 since they cluster
better with one another and the 06z GEFS appears to have more
notable ensemble spread. The GFS and Euro also appear to have
notable run to run consistency on their evolution across the CONUS
during the period which adds to uncertainty and lack of confidence
in the GFS, in particular.


...Weather/Hazards Highlights...

Guidance continues to show convection developing over the east-
central U.S. on Day 4/Sunday ahead of the wavy front pushing
eastward from the Plains. Latest solutions have not added much
definition in terms of more pronounced focus over specific regions
within the broad Day 4 ERO Marginal Risk area in place from the
Ohio Valley southwest into parts of the lower Mississippi Valley,
so the only adjustment for this cycle was a modest westward
expansion based on latest guidance. Will continue to monitor for
improved guidance clustering especially from the Ohio Valley
southward where soils are on the damp side, which could eventually
lead to an embedded upgrade in risk level. What potential exists
for excessive rainfall by Day 5/Monday should be confined more to
parts of the Southeast as the front continues onward, again with a
Marginal Risk area indicated. Meanwhile, the Storm Prediction
Center continues to monitor the potential for severe weather from
the east-central U.S. to the Mid-Atlantic/Southeast during Sunday-
Monday. Check latest SPC outlooks for more details on the severe
threats.

Farther north, there will be potential for some snow from the
Upper Midwest/Upper Great Lakes into northern New England (the
latter having up to 50-70 percent probabilities for 0.25 inch
liquid in the form of snow Sunday-Sunday night). A transition zone
of wintry mix may separate the snow area from the rain to the
south.

Expect multiple systems to bring rain and higher elevation snow to
the West during the period, with rapidly increasing uncertainty in
the details after early next week. During Days 4-5/Sunday-Monday
period of the EROs, the best precipitation focus should be over
southwestern Oregon and northern California. Day 5 looks to have
somewhat higher maximum rainfall totals near the coast, along with
some instability, so that day's ERO introduces a Marginal Risk area
in this region. Some guidance signals potential for another
significant system after Monday but with a lot of spread for
details, while a weaker wave is another possibility. The overall
guidance signals suggest a somewhat heavier trend for precipitation
over the central West Coast/California toward midweek. Leading
dynamics reaching the West should support a central-eastern U.S.
system by Wednesday-Thursday, generating another episode of
meaningful precipitation over the eastern half of the country. Some
snow will be possible from the northern Plains into New England.

The warm sector ahead of the front crossing the eastern half of
the country Sunday-Monday will feature well above normal
temperatures. Expect plus 10-20F anomalies for highs and up to plus
20-25F anomalies for morning lows, the latter extending from the
Midwest to Mid-Atlantic. Northern New England should remain a lot
colder though, as a sharp front stays just to the south. Near to
below normal readings will progress eastward behind the eastern
U.S. front, with precipitation keeping some northern Plains
locations 10-15F or so below normal for highs into Sunday. Expect
more modest cool anomalies to the east. Temperatures may rebound
back above normal over the southern half of the Plains on Tuesday
with the warming trend spreading eastward thereafter. Periods of
unsettled weather will keep the diurnal spread over the West Coast
states more narrow than usual, with cool highs and near or slightly
above normal lows.

Kebede/Rausch


Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw