Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
232 PM EDT Mon Jun 23 2025

Valid 12Z Thu Jun 26 2025 - 12Z Mon Jun 30 2025

...Record heat is less likely by later week, but dangerous heat
continues for the Ohio/Tennessee Valleys and
Mid-Atlantic/Southeast...

...Heavy rain and flash flooding possible in the Upper
Midwest/Great Lakes late week...


...Overview...

Into the latter part of the the week, the peak of the significant
and extremely dangerous heat wave will have waned. However,
temperatures will remain quite hot across the Ohio and Tennessee
Valleys into the Mid-Atlantic and Southeast, and the long duration
of the heat wave could cause exacerbated impacts, maintaining Major
to Extreme HeatRisk in some areas into late week. Tropical and
subtropical moisture will advect north across New Mexico and then
east around the southeastern U.S. upper ridge in a "ring of fire"
setup. The moisture should interact with a wavy frontal boundary
and promote potentially heavy rain and flash flooding in the
Midwest and Great Lakes regions late week. Additional rounds of
scattered thunderstorms are possible across much of the central and
eastern U.S. into the weekend.


...Guidance/Predictability Assessment...

Model guidance remains in very good overall agreement with the
depiction of the large scale pattern through the medium range
period. Models continue to advertise the large and expansive ridge,
which is bringing record-setting and dangerous heat to much of the
eastern half of the country this week, breaking down and weakening
heading into the weekend. Combined with weakening troughing across
the Western U.S., the synoptic pattern is progged to become much
more zonal through at least Sunday before showing signs of
amplifying again during the first half of next week. A faster and
more zonal pattern puts much more emphasis on the speed, depth, and
evolution of individual shortwaves, which can be more difficult to
nail down at extended time ranges. For the most part, models
generally agreed with the smaller scale wavelengths and their
surface features, even for the latter half of the forecast period.
However, similar to last night's package, the 00Z and 06Z runs of
the GFS differed enough with their handling of multiple waves
across southern Canada, the north-central U.S. and the Great Lakes
region (compared to the EC, CMC, and UKMET) that their
contributions to the overall composite forecast blend were
significantly reduced by Day 5 and beyond.

The latest WPC forecast was initially based on a composite blend
of the deterministic guidance, favoring the non-NCEP models over
the GFS. Additionally, beyond Day 5, introduced and gradually
increased the proportion of the EC and GEFS ensemble means to half
to lessen the influence of individual model variability while still
maintaining continuity.


...Weather/Hazards Highlights...

On Thursday, some anomalously high tropical and subtropical
moisture should still be filtering into New Mexico. However, with
the upper trough in the Interior West weakening, there will be less
upper level support for widespread convection compared to the
short range period. Regardless, heavy rain could still be a concern
in New Mexico, especially considering the wet antecedent
conditions by then. Will maintain Marginal Risks in the Days 4/5
(Thursday/Friday) EROs with a particular focus on the Sacramento
Mountains, where orographic support could enhance rainfall totals
and where burn scars and steep terrain make the area sensitive to
heavy rain. Some showers and storms are possible there into the
weekend.

The plume of moisture will arc northeastward into the Upper
Midwest/Great Lakes region, where the additional lift around a weak
surface low and frontal boundary in the vicinity and potential
training will favor areas of heavier rainfall and some flash
flooding potential. For the Day 4/Thursday ERO, continue to show a
Slight Risk across the Upper Midwest/much of Wisconsin and the U.P.
of Michigan, given potential for 2 to 4 inches to accumulate
despite continued spread in the exact positioning. Some convection
with locally heavy rain could traverse the northern side of the
ridge farther east into New York State and the northern Mid-
Atlantic, and have captured these areas within the Marginal Risk on
Thursday. By Friday the surface low/frontal system will continue
to track east, bringing some potentially enhanced rain amounts to
the Lower Great Lakes region and Interior Northeast. There still
remains some uncertainty with the positioning of the heaviest QPF,
including some models showing the heaviest rain staying in Canada,
so will maintain a Marginal Risk in the Day 5/Friday ERO rather
than introducing a Slight Risk for this cycle. That being said,
will
continue to monitor trends since some of the higher terrain there
can be sensitive to heavy rainfall. Meanwhile, another shortwave
may move through the north-central U.S. while instability is
likely to be high (MUCAPE of 3000-5000 J/kg already shown by the
global models). Have a Marginal Risk delineated in parts of the
Dakotas to Minnesota since locally heavy rain rates are likely in
this unstable atmosphere.

Scattered showers and thunderstorms will become more widespread
across much of the eastern third of the country through the period.
A weak upper low may track across Florida and vicinity on
Thursday-Friday and provide additional support for convection.
Will continue to hold off on introducing any ERO risk areas for
the time being given lower end QPF with relatively high flash
flood guidance. Scattered convection is also likely across the
Appalachians and into the Eastern Seaboard each day as the heat
creates an unstable airmass.

The strong upper high/ridge stretching across the south-central to
eastern U.S. will weaken somewhat into late week, but remain
generally in place, maintaining hot temperatures albeit slightly
moderated from the short range period and less likely to break
records. Nevertheless, temperatures will be well into the 90s in
many central and eastern areas, while dewpoints in the 70s will
raise heat indices into the 100s. Overnight lows will only drop
into the low/mid 70s for many areas, bringing little relief from
the heat and exacerbating potential impacts. Especially after the
extreme heat in the short range, through late week HeatRisk values
will be Major to Extreme for portions of the Midwest and Ohio
Valley to Eastern states -- levels 3 and 4 on a scale from 1 to 4
(4 being Extreme). This indicates an intensity and duration of heat
that is extremely dangerous to anyone without adequate cooling or
hydration. Extreme heat is the number 1 weather-related killer --
please take precautions if you are outside during the hottest part
of the day and seek cooling if you are without adequate means.
Temperatures may continue to slowly moderate into the weekend for
closer to normal summer heat. Elsewhere, the Northeast should see
relief from the heat by the medium range period behind a backdoor
front. The north-central U.S. can expect warmer than average
temperatures by 5 to 10 degrees around Friday-Saturday and then
cool behind a cold front. Temperatures in the Northwest will warm
by early next week under an upper ridge. The Desert Southwest can
expect typical summer heat with temperatures in the 100s and 110s.


Miller/Tate


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
327 PM EDT Tue Jun 24 2025

Valid 12Z Fri Jun 27 2025 - 12Z Tue Jul 01 2025

...Tail end of heat wave lingers over the eastern Ohio Valley
Friday...

...Overview...

Heat relief arrives Friday for much of the Mid-Atlantic, but
the heat wave lingers over portions of the eastern Ohio Valley.
Moisture continues to advect north and then east around the broad
southeastern U.S. ridge in a "ring of fire" setup into Saturday. A
wavy frontal boundary interacting with the above average moisture
should allow for localized heavy rain and flash flooding in the
Sacramento Mountains of New Mexico, Northern Plains and Northeast
Friday- Saturday. Additional scattered thunderstorms across much
of the central and eastern U.S. this the weekend and early next
week could have flooding potential.


...Guidance/Predictability Assessment...

Model guidance continues to be agreeable in showing
weakening/widening ridging across the southeastern U.S. through
this weekend with a trough developing along the West Coast for
early next week. This creates a more zonal pattern east of the
Great Basin with the jet stream over the northern tier with
embedded shortwaves. The Friday shortwave and weak surface low
atop the Great Lakes continues to have convective QPF differences
over the Northeast into Friday night with the main concern of
whether the QPF max will be in Canada or northern New England. The
next trough comes across the Northwest Friday and reaches the
north- central U.S. by Sunday. A stripe of heavy rain should
develop over the northern Plains/Upper Midwest with 12Z guidance in
better agreement than prior runs. Meanwhile ridging is forecast to
build with its axis along the Rockies.

The WPC forecast is nearly all based on a composite blend of the
00Z/06Z deterministic guidance with only some ensemble means for
Days 6/7 as necessity beyond the range of the UKMET.


...Weather/Hazards Highlights...

Moisture advection around the southeastern U.S. upper ridge
combined with shortwaves aloft and a wavy frontal boundary will
provide a favorable environment for convection for portions of the
northern tier Friday/Saturday. An initial wave moving across the
Lower Great Lakes and Northeast Friday-Saturday will allow for some
possibly heavy rain in the Interior Northeast on the cusp of the
instability gradient and where a weak surface low tracks along the
front. A Marginal Risk remains in effect for Days 4 and 5 over
portions of the Northeast (and the central Appalachians for Day 4).
High QPF maxes on Friday may allow an upgrade at some point.
delineated in the Day 4/Friday and Day 5/Saturday EROs for
localized flash flooding with this activity.

Another shallow upper trough and frontal system will push through
the north-central U.S. Friday night into Sunday, providing forcing
for thunderstorms. Instability is likely to be high (MUCAPE of
3000-5000 J/kg already shown by the global models. The Day 4
Marginal Risk is maintained for ND/MN with more east-west expansion
to the Day 4 Marginal Risk from SD into the U.P. of Michigan based
on convergence along a frontal zone. Convection is forecast to
shift southeast across the Midwest and central Plains/Middle
Mississippi Valley early next week ahead of the trough and front.

Ring of fire moisture advection over the southern Rockies/adjacent
high plains continues with elevated moisture through Saturday. Day
4 and 5 Marginal Risks are now in effect for the Sacramento
Mountains for diurnally driven isolated flash flooding. Monsoonal
moisture looks to increase early next week, bringing rain and
thunderstorm chances to the southern and central Rockies and High
Plains.

The central Gulf Coast may see a few days of more focused
convection, with heavier amounts possible early next week (after
the ERO period, and would have to battle against high flash flood
guidance to see flooding concerns there).

Weakening/suppression of the east-central ridge Friday into
Saturday will allow moderation of temperatures with a backdoor cold
front over much of the Mid-Atlantic Friday, though warming is
expected early next week. The north-central U.S. can expect
temperatures to be 5-10 degrees above average Friday- Saturday and
then cool behind a cold front. Temperatures in the interior
Northwest
will warm by early next week under an upper ridge and north of the
trough along the Coast. The Desert Southwest can expect a return to
above normal temperatures starting Sunday from advection east of
the West Coast trough.


Jackson


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
254 PM EDT Wed Jun 25 2025

Valid 12Z Sat Jun 28 2025 - 12Z Wed Jul 02 2025

...Overview...

A broad dome of high pressure with above average 500mb heights over
the South/Southeast will shunt troughs and associated fronts
across the northern tier states. These northern shortwaves will
support fronts and rounds of possibly heavy rain across the
Northeast Saturday and in the north- central U.S. Saturday-Sunday.
Above average temperatures may linger in the Midwest to Carolinas
and possibly compound heat stress for areas that have been seeing
extreme heat. Upper troughing may deepen some as it digs into the
Great Lakes/Ohio Valley/Northeast, pushing a cold front gradually
southeast. Hot temperatures and scattered to widespread showers and
thunderstorms are likely ahead of the front across the central
U.S. to Eastern Seaboard.

Further west, monsoonal moisture is expected to increase for the
Southern/Central Rockies and adjacent High Plains, while the West
should see increasing heat underneath an upper ridge.


...Guidance/Predictability Assessment...

The latest suite of guidance continues to have a decent handle on
the synoptic pattern with the southern tier ridging and an active
northern stream. All indicate the trough tracking from the Northern
High Plains Sunday through to the Great Lakes/Northwest Tuesday
and Wednesday will deepen somewhat and usher in rounds of heavy
rainfall with the potential for local flash flooding concerns,
particularly for the north-central states. Subtleties in the
details persist which will affect the exact location and timing of
frontal features, sensible weather and precipitation amounts. Once
the trough reaches the East and ridging expands into the Four
Corners region. A southern stream trough gradually approaches
California while a northeastern Pacific upper low may send
(uncertain) shortwaves toward the Northwest next week.

As previously noted, the CMC pushed the northeastern Pacific low
progressively into Canada while the rest of the solutions held
back. Towards middle/latter periods the CMC was out of phase with
the broader model consensus. The WPC preferred blend started with a
multi-model compromise that trended toward an EC/GFS and ensemble
means solution.


...Weather/Hazards Highlights...

An initial shortwave and weak low pressure system along a frontal
boundary could bring locally heavy rain in the Northeast lingering
into Saturday. Ample moisture (PWs likely over the 90th percentile)
and some instability could allow for heavy rain rates and possible
flash flood concerns. WPC held onto the Marginal Risk in the Day
4/Saturday ERO for this activity with minor expansions made for
this issuance. Farther west, thunderstorms are likely to form
ahead of the broader upper trough and the surface frontal boundary
in the northern Plains to Upper Midwest Saturday. Global models
have already been showing high instability with MUCAPE 4000-6000
J/kg for this region, so severe storms are likely, and this will
also support heavy rain rates that could cause flash flooding. A
similar setup is likely on Sunday, just with the cold front a bit
more progressive southeastward. This allows for a broad Marginal
Risk in the Upper/Middle Mississippi Valley back into the central
Plains for the Day 5/Sunday ERO. The latest guidance and WPC QPF
supported the expansion of the Marginal Risk across Wisconsin and
Michigan. Further refinements may be needed in future cycles since
there is uncertainty in the placement of heaviest rain.

Over the weekend into early next week, scattered thunderstorms are
likely farther south in the broad warm sector as well. There will
be less forcing for organization and sustaining of storms across
the central and southern tier away from the upper jet, but
instability could allow for heavy rain rates that may cause nonzero
chances of localized flash flooding, but that are likely dependent
on smaller scale boundaries and are less predictable at this
point. One area of focus that the models show for some heavier rain
is across the central to eastern Gulf Coast region. Will monitor
if there will be flash flooding concerns there but it would have to
battle with very high flash flood guidance. Into the workweek as
the main cold front continues to press south and east, heavier rain
and thunderstorms could stretch across the south-central Plains
into the Ohio/Tennessee Valleys and into the East.

Monsoonal type moisture is likely to increase over the
Southern/Central Rockies and Plains where there could be a
weakness in the upper ridge. On Saturday main flash flooding
concerns will be across the Sacramento Mountains, where the steep
terrain and burn scars cause the area to be particularly sensitive
to rain, so WPC is covering this with a small Marginal Risk in the
Day 4 ERO. But moisture levels and thus coverage and rain amounts
of storms should increase into early next week. A Marginal Risk is
in place across eastern New Mexico and far West Texas in the Day
5/Sunday ERO with this activity. These areas are seeing heavy rain
in the near term, and the wetter antecedent conditions enhance
flash flooding concerns.

By the weekend, heat will be much less extreme than currently, but
above average temperatures by 5-12 degrees are likely across the
north-central U.S., Mississippi Valley, and into southern parts of
the Mid-Atlantic. HeatRisk shows some Major (level 3 of 4) areas in
these regions, indicating heat levels that affect anyone without
effective cooling and/or adequate hydration. Meanwhile the
Northeast will be much cooler behind a backdoor cold front. Into
next week, slightly above average temperatures will shift east
ahead of a cold front and moderate. Farther west, building heat is
expected next week as an upper ridge takes hold. Temperatures in
the Northwest are likely to be 10-15 (locally 20) degrees above
normal, for highs nearing 100F. In the Desert Southwest,
temperatures a few degrees above already high averages will equate
to 100s and 110s. Moderate to Major HeatRisk is shown for much of
the Interior West.


Campbell/Tate


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
227 PM EDT Thu Jun 26 2025

Valid 12Z Sun Jun 29 2025 - 12Z Thu Jul 03 2025

...Overview...

Fairly typical summertime pattern will be in place over the Lower
48 next week, with warmer than normal temperatures for the
Northwest and cooler than normal temperatures for the southern
Rockies. Scattered showers and thunderstorms will focus along and
east of the Rockies near the mostly progressive frontal
boundaries, across the Southeast, and perhaps over the northeast
Gulf.


...Guidance/Predictability Assessment...

The latest 00/06Z guidance offered reasonable clustering through
the period, though the 06Z GFS was notably quicker to lower heights
into the Northwest than the other models/ensemble means by next
Wed/Thu. The ECMWF AIFS and AIFS ensemble were closer to the larger
ECMWF-led cluster, which formed the basis for the starting point
of the surface fronts/pressures.


...Weather/Hazards Highlights...

Thunderstorms are likely to form ahead of the broad but shallow
upper trough and a surface frontal boundary in the Upper Midwest to
central Plains Sunday. Global models have already been showing
high instability with MUCAPE 4000-6000 J/kg for this region, so
strong storms are possible, and this will also support heavy rain
rates that could cause flash flooding. A Marginal Risk is in place
in the Upper/Middle Mississippi Valley back into the south-central
Plains for the Day 4/Sunday ERO. By Monday the setup will be
similar, but with the trough and cold front pressing southeast. A
large Marginal Risk is located along and ahead of the front from
the Ohio/Tennessee Valleys, Mid/Lower Mississippi Valley, and the
south-central Plains where storms are likely in the moist and
unstable airmass on Day 5/Wednesday. For both days, further
refinements may be needed in future cycles, including possible
embedded Slight Risks, but model agreement in the specifics remains
low for now. The front will continue to push eastward Tuesday,
leading to a wet day in the Northeast/Mid-Atlantic before drying
out midweek, and southward for thunderstorm chances across the
Southeast Tuesday-Wednesday. Even before the front approaches,
scattered thunderstorms are likely farther south in the broad warm
sector as well. There will be less forcing for organization and
sustaining of storms across the southern tier away from the upper
jet, but instability could allow for heavy rain rates that may
cause non-zero chances of localized flash flooding, but that are
likely dependent on smaller scale boundaries and are less
predictable at this point. One area of focus that the models show
for some heavier rain is across the central to eastern Gulf Coast
region. Will monitor if there will be flash flooding concerns there
but it would have to battle with very high flash flood guidance.

Monsoonal moisture is likely to increase next week in the
Southern/Central Rockies and Plains with southerly flow under the
upper ridge, thus increasing coverage of and rain amounts in
storms. Marginal Risks are in place for the southern High Plains
Day 4/Sunday and stretching north into eastern Colorado Day
5/Monday as the back end of the front nears. Areas like the
Sacramento Mountains, where the steep terrain and burn scars cause
the area to be particularly sensitive to rain, are likely most
vulnerable to rain causing potential flash flooding, especially
with wet antecedent conditions there.

Elsewhere, showers and storms may develop across parts of the
Great Basin Monday and toward the Northern Rockies by Tuesday. Then
depending on a shortwave, rain chances are forecast to increase in
the north-central U.S. by midweek.

Temperatures are forecast to be around 5-10 degrees above average
across the Midwest/Great Lakes early next week, while the southern
half of the Plains to Southeast can expect typical summer heat.
HeatRisk shows some Major (level 3 of 4) areas in these regions,
indicating heat levels that affect anyone without effective cooling
and/or adequate hydration. Temperatures and dewpoints will
decrease behind the cold front as it progresses southeast. Farther
west, building heat is expected next week as an upper ridge takes
hold. Temperatures in the Northwest are likely to be 10-15 (locally
20) degrees above normal, for highs nearing 100F. In the Desert
Southwest, temperatures a few degrees above already high averages
will equate to 100s and 110s. Moderate to Major HeatRisk is shown
for much of the Interior West peaking Monday-Tuesday.


Fracasso/Tate


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
206 PM EDT Fri Jun 27 2025

Valid 12Z Mon Jun 30 2025 - 12Z Fri Jul 04 2025



...Guidance/Predictability Assessment...

The latest model and ensemble guidance for today continues to show
relatively good agreement through much of the period on what looks
like a generally progressive summertime pattern. There remain some
differences in the details of smaller scale systems though. The CMC
and UKMET are a bit sharper/farther south with a weak shortwave
through the Great Lakes next Wednesday-Thursday, and the models are
unsure on the details and evolution of wave energy into the
Northwest. The GFS is a little stronger with leading energy into
the central U.S. late week, which erodes the central/southern U.S.
ridge moreso than the other guidance. The WPC forecast for today
was based on a blend of the deterministic guidance the first half
or so of the period, with a 50/50 blend of the ensemble means and
the deterministic ECMWF and CMC for the second half. This
maintained good continuity with the previous WPC forecast as well.


...Weather/Hazards Highlights...

Widespread thunderstorms with favorable moisture/instability and
right entrance region upper jet lift will fuel locally strong/heavy
convective downpours likely to form ahead of the broad but shallow
upper trough and a surface frontal boundary working southeastward
over the Midwest on Monday. An elongated WPC Marginal Risk
Excessive Rainfall Outlook (ERO) area is located along and ahead
of the front from the Ohio/Tennessee Valleys, Mid/Lower Mississippi
Valley, and the south-central Plains Day 4/Monday. The front will
continue to push onward Tuesday, leading to a wet day from the
Northeast/Mid- Atlantic back through the Appalachians and into the
South Tuesday where a Day 5 Marginal Risk ERO is drawn. These
areas will dry out and and moderate post-frontal, but activity will
linger as the front slows across the South/Southeast into mid-late
next week. Even before the front approaches, scattered
thunderstorms are likely farther south in the broad warm sector as
well. There will be less forcing for organization and sustaining of
storms across the southern tier away from the upper jet, but
instability could allow for heavy rain rates that may cause non-
zero chances of localized flash flooding, but that are likely
dependent on smaller scale boundaries and are less predictable at
this point. One area of focus with a growing model signal for some
heavier rain is across the central to eastern Gulf Coast region.
Will monitor if there will be flash flooding concerns there, but it
would have to battle with very high flash flood guidance.

Monsoonal moisture with some connection to possible Pacific
tropical development is likely to increase next week in the
Southern/Central Rockies and High Plains with southerly flow under
the upper ridge, thus increasing coverage of rain amounts in
storms. Marginal Risks are planned for the southern Rockies/High
Plains Day 4/Monday and Day 5/Tuesday. Areas like the Sacramento
Mountains, where the steep terrain and burn scars cause the area to
be particularly sensitive to rain, seem likely most vulnerable to
rain causing potential flash flooding, especially with wet
antecedent conditions there.

Elsewhere, showers and storms may develop over parts of the Great
Basin Monday and toward the Northern Rockies by Tuesday. Downstream
shortwave energy translations support increasing rain/convection
chances over the north-central U.S. Wednesday into Thursday as
moisture/instability pool along/overtop a retreating front.

Temperatures are forecast to be around 5-10 degrees above average
across the Midwest/Great Lakes early next week, while the southern
half of the Plains to Southeast can expect typical summer heat.
HeatRisk shows some Major (level 3 of 4) areas in these regions,
indicating heat levels that affect anyone without effective cooling
and/or adequate hydration. Temperatures and dewpoints will
decrease behind the cold front as it progresses southeast. Farther
west, building heat is expected next week as an upper ridge takes
hold. Temperatures in the Northwest are likely to be 10-15 (locally
20) degrees above normal, for highs nearing 100F. In the Desert
Southwest, temperatures a few degrees above already high averages
will equate to 100s and 110s. Moderate to Major HeatRisk is shown
for much of the Interior West peaking Monday-Tuesday.

Santorelli/Schichtel


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