Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
307 PM EDT Sun Oct 12 2025

Valid 12Z Wed Oct 15 2025 - 12Z Sun Oct 19 2025


...Guidance/Predictability Assessment...

The models into the medium range period continue to show good
agreement on an amplified pattern consisting initially of a Western
U.S. deep trough and building ridge downstream from the central to
eastern states. The evolution of this, as the Western trough/low
opens up and progresses eastward, is generally in good agreement
but with some variability in the details and timing of the trough
next weekend. Around Friday, the GFS is a bit faster with a
northern stream shortwave into southern Canada and also faster and
more aggressive with a following shortwave, resulting in a deep
closed low over the Great Lakes next Sunday. The better consensus
would be for something a bit slower and more open and the WPC
forecast today weighted a bit more towards the ECMWF/CMC early
period and the ensemble means later in the period. The guidance
agrees on another amplified shortwave moving into the Pacific
Northwest late period, but again with some question on the timing.
For the sensible weather grids, the 13z NBM served as a good
starting point and basis, but with some modifications based on the
ECMWF which was the preferred model. Overall, maintained good
continuity with the previous WPC forecast.


...Weather/Hazards Highlights...

A lead short range coastal storm will be working well out to sea
across the western Atlantic by midweek but still support continued
unsettled/windy conditions over New England through late week with
impulses digging behind the system bring some lingering showers.

An incoming upper low/amplified trough slated to bring rain/snow
to California early week will lift increasingly inland across the
West/Rockies mid-late week. A Day 4/Wednesday WPC Excessive
Rainfall Outlook Marginal Risk area remains over New Mexico and
southern Colorado where leading moisture levels may fuel some
lingering local downpours with runoff issues. Upper system and wavy
frontal progression will also drive organized rain/snow over the
north-central Intermountain West/Rockies Wednesday/Wednesday night.
Much of the West will see at least some rain or snow, with snow
levels lowering as colder air moves in. Temperatures will be well
below normal into Wednesday (by 10-20 deg) with some slight
moderation for the rest of the week, but still cooler than normal.
Later period, there is also some upstream guidance signal
supporting approach of another amplified Northeast Pacific storm
system toward the Pacific Northwest/Northwest next weekend that may
offer quite unsettled flow and enhanced rainfall to monitor.

Downstream for the central states, southwesterly upper flow will
increase the chances of rain for mid-late week over the Northern
Plains into the Upper Midwest closer to the jet stream with wavy
surface system translation/genesis. Mild and more moisture-laden
air to the south over the central Plains and Mid-Mississippi Valley
will support a growing pattern with showers and thunderstorms
ahead of the western/Rockies system into Thursday/Friday. Activity
may flourish as focus shifts slowly with more uncertainty into the
east-central states into next weekend in an emerging return flow
pattern to monitor for enhanced rainfall/runoff issue potential.


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
304 PM EDT Mon Oct 13 2025

Valid 12Z Thu Oct 16 2025 - 12Z Mon Oct 20 2025


...Guidance/Predictability Assessment...

The models and ensembles generally agree on the large-scale
pattern over the next week, favoring strong troughing in the West
that will slowly lift into the Plains and then push into the
Northeast by early next week. Another trough is expected to move
into the Pacific northwest late next weekend. By the Sat-Mon
period, the GFS/GEFS were generally quicker than the ECMWF/ECMWF
EPS and ECMWF- AIFS/ECMWF-EPS-AIFS by about 12 hours which is well
within tolerance for that time range. For the fronts/pressures,
utilized a multi- model/ensemble blend for the first few days of
the forecast before trending to the 00Z ECMWF ensemble mean in
order to maintain better depiction of the features vs a blend of
the ensembles. For the sensible weather grids, the NBM was
reasonable through the period.


...Weather/Hazards Highlights...

No areas were noted in the Day 4-5 Excessive Rainfall Outlooks as
the QPF across the CONUS was on the lighter side.

Lingering upper troughing in Atlantic Canada (tied to the current
coastal storm) still supports continued unsettled/windy conditions
over New England through late week with cooler than normal
temperatures to start that will slowly moderate.

The troughing and associated surface frontal boundary in the West
will promote cool and showery (with some snow at higher elevations)
conditions over the Northern/Central Rockies to start, with
broader light rain in advance of the surface low that is poised to
track from the Northern Plains into southern Canada. As the
attendant cold front passes through the Plains, moisture will
increase in advance of it through the Mid-MS Valley where rainfall
could increase by Saturday. This rainfall will continue eastward
next Sunday and Monday into the Northeast near the track of the low
pressure (and into the Southeast ahead of the cold front).
Temperatures will be mild ahead of the cold front -- well into the
70s/80s Friday from the Corn Belt to the Ozarks with 90s across
South Texas.

By late next weekend into next Monday, another system will enter
the Pacific Northwest with another round of valley rain and higher
mountain snow that will spread into the Northern Rockies.
Temperatures will again cool over Idaho southwestward to Nevada and
NorCal.


Fracasso


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
245 PM EDT Tue Oct 14 2025

Valid 12Z Fri Oct 17 2025 - 12Z Tue Oct 21 2025


...Guidance/Predictability Assessment...

Model guidance remains in relatively good agreement during the
medium range period, handling the evolution of several large scale
trough/ridge features across the CONUS reasonably well despite a
highly amplified 500mb flow pattern. Only minor differences were
noted for Days 3 and 4, so a composite blend of the 00Z EC, 00Z
UKMET, 00Z CMC and 06Z GFS deterministic runs sufficed to begin the
period. However, larger discrepancies started cropping up by Day
5, most notably with the evolution of a potent Pacific trough that
is progged to push inland over British Columbia and the Pacific
Northwest late in the weekend into early next week. While the
EC/GFS/UKMET all had similar solutions depicting the trough digging
deeper along the West Coast, the CMC shows the trough becoming
completely sheared apart as it moves across the Pacific Northwest.
As a result of being much faster and flatter than consensus, the
00Z CMC was removed from the blend starting on Day 5 and was not
considered for the remainder of the forecast. To compensate, more
weighting was placed on the EPS and GEFS ensemble means, which
ultimately made up slightly more than 50% of the blend for Day 6
and 7. The greater weighting of the ensemble means resulted in a
more stable forecast that preserved continuity while reducing some
of the timing and positional differences that are typical for the
latter half of the medium range forecast period.

...Weather/Hazards Highlights...

Lingering upper troughing in Atlantic Canada (tied to the current
coastal storm) still supports continued unsettled and borderline
windy conditions over New England through late week with cooler
than normal temperatures that will slowly moderate with time.

The troughing and associated surface frontal boundary in the West
will promote cool and showery weather (with some snow at higher
elevations) over the northern/central Rockies to start, with
broader light rain in advance of the surface low that is poised to
track from the northern Plains into southern Canada. As the
attendant cold front passes through the Plains, moisture will
increase in advance of it through the Mid-MS Valley where rainfall
could increase by Saturday. The WPC Day 5/Saturday Excessive
Rainfall Outlook (ERO) maintains a Marginal Risk area centered over
the Mid-South given favorable upper support, moisture and
instability. Given the somewhat progressive nature of the upper-
level and surface features, this rainfall will continue to spread
eastward into the Northeast later Sunday into early next week,
particularly near and along the track of a deepening/consolidating
low pressure system (and into the Southeast ahead of the cold
front). Temperatures will be mild ahead of the cold front with
highs well into the 70s/80s Friday from the Corn Belt to the Ozarks
with 90s across South Texas.

By late next weekend into early next week, another deepened system
will enter the Pacific Northwest/West Coast with another round of
valley rain and higher mountain snow that will then dig and spread
across the West and downstream to the Rockies. The Day 5/Saturday
ERO maintains a coastal Washington Marginal Risk area given a
favorable guidance signal.

Miller/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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
358 PM EDT Wed Oct 15 2025

Valid 12Z Sat Oct 18 2025 - 12Z Wed Oct 22 2025


...Guidance/Predictability Assessment...

The depiction of the large scale pattern by the latest model
guidance remains reasonably good to start off the medium range
period, but uncertainty increases quite a bit for Day 5 and beyond.
Given only minor differences of the strength and timing of an
eastern U.S. ridge, central U.S. trough and western U.S. ridge, a
composite blend of the 00Z EC, 00Z UKMET, 00Z CMC and 06Z GFS were
utilized for the Day 3 and Day 4 forecast. By Day 5, the trough
progged to push from the Pacific across the Pacific Northwest is
trending to be much more progressive compared to yesterday's
package. In fact, most of yesterday's guidance aside from the CMC
was on board with a much slower and more amplified solution, with a
deepening trough digging southward along the West Coast. Instead,
the more progressive solution is now looking more likely, with all
guidance including the latest machine learning guidance all
depicting this evolution fairly similarly. The latest 00Z and 06Z
runs of the GFS were slow to catch on (and thus were not used in
the composite blend for Days 5-7) but the most recent 12Z run has
joined consensus as well. Given the strength and amplitude of the
eastern U.S. ridge at the beginning of the period, the faster and
more progressive flow upstream is leading to a sharper and more
negatively tilted trough pushing from the central U.S. into the
eastern U.S. this weekend into early next week. As a result, a
stronger and more consolidated surface low is looking more likely
to track across the Great Lakes, with implications to QPF and
hazards. More on that below. Given the above, the Days 5-7 forecast
consisted of a blend that increasingly relied on the ensemble means
of the EPS, CMCE, and GEFS, which provided more stability and less
noise from individual deterministic guidance sources.

...Weather/Hazards Highlights...

A sharpening upper trough/shortwave and strengthening surface low
pressure pushing across the Great Lakes region this weekend will
draw anomalous moisture and instability northward in advance of a
cold front. PW anomalies of >200% of normal combined with
instability of 500-1500 j/kg will support an axis of heavier
rainfall across parts of the Upper Midwest, Ohio Valley and Mid-
South on Saturday. As a result, the Day 4/Saturday Excessive
Rainfall Outlook (ERO) expanded the Marginal Risk northward to
include southeast Wisconsin and southwest Michigan. The recently
introduced Slight Risk area centered over the Mid-South was
maintained given the overlap with the greatest instability and
relatively lower FFG. SPC also shows a threat for severe weather in
this pattern. The slowly progressive nature of the upper-level and
surface features will then spread organized rainfall eastward into
the East/Northeast Sunday into early next week. This will
especially be the case near and along the track of a
deepening/consolidating coastal low pressure system (and more
modestly into the Southeast ahead of the cold front). A Day
5/Sunday ERO Marginal Risk area was maintained and broadened to
capture local runoff potential into the Appalachians and parts of
the Ohio Valley.

Out West, the now more progressive trough and surface low will
quickly approach and push across the Pacific Northwest and northern
Rockies over the weekend to produce a period of moderately heavy
coastal and valley rains along with higher mountain snow. The Day
4/Saturday ERO maintains a coastal Washington Marginal Risk area
given a favorable QPF signal while our Day 4-7 Winter Weather
Outlook shows mountain snow potential inland from the Northwest to
the Northern Rockies Sunday into Monday.

Miller/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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
335 PM EDT Thu Oct 16 2025

Valid 12Z Sun Oct 19 2025 - 12Z Thu Oct 23 2025


...Guidance/Predictability Assessment...

The latest model runs continue to show reasonably good agreement
with their depiction of the large scale pattern through the medium
range period, particularly through Day 5. Uncertainty increases
heading into Days 6 and 7, but overall the pattern shows better
agreement than in previous forecasts. The period starts off with a
potent negatively tilted trough ejecting to the northeast from the
Ohio Valley to the Great Lakes into southeast Canada. Guidance is
fairly well clustered with this feature, with only minor
differences in phasing and timing. This trough forces the
development of strong cyclogenesis across the Great Lakes on Sunday
with possible secondary development near New England later Monday
into Tuesday. Models differ on exactly when and where secondary
development occurs, but the signal is strong enough that a
compromise between the EC/GFS/CMC looked reasonable. Expect more
adjustments to the surface reflection in coming forecasts. The
other feature we are tracking is a fast moving trough that quickly
scoots across the Pacific Northwest and northern Rockies Sunday
into Monday before tracking through the Upper Midwest, Great Lakes
and Northeast to round out the period. Guidance is well clustered
with this system through Day 5/6, with uncertainty regarding
possible phasing with a northern stream disturbance followed by
closing off into a large upper low.

The WPC forecast consisted of a composite blend of the 00Z/06Z
EC/GFS/CMC/UK through Day 4/5 before increasing weighting of the
EPS/GEFS/CMCE ensemble means in place of the CMC/UK for Days 5, 6,
and 7. This blend showed good continuity while offering stability
through the period.

...Weather/Hazards Highlights...

A lead main upper trough and deepening surface low pushing across
the Great Lakes region this weekend will draw anomalous moisture
and instability northward in advance of a cold front. The slowly
progressive nature of the upper-level and surface features will
then spread organized rainfall eastward into the East/Northeast
Sunday into early next week. Activity will also focus with
development of a deepening/consolidating coastal low pressure
system near New England. A WPC Day 4/Sunday Excessive Rainfall
Outlook Marginal Risk area was maintained from the central
Appalachians to the eastern Great Lakes/Ohio Valley. For Day 5, a
Marginal Risk was introduced for coastal regions of New England
given a decent QPF/instability signal and remarkable consistency
from machine learning models such as the EC-AIFS and Graphcast GFS.

Out West, a main/complex upper trough and surface low/frontal
system will approach and push across the Pacific Northwest and
northern Rockies over the weekend to produce a period of moderately
heavy coastal and valley rains along with higher mountain snow.
The WPC Day Winter Weather Outlook shows mountain snow potential
inland to the Northern Rockies into Monday. Downstream system
translation and some lead return flow looks to support moderate
rainfall emergence in an expanding pattern over the north-central
to east central U.S. into next Wednesday/Thursday to monitor.

Miller/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