Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
313 AM EDT Fri Oct 17 2025

Valid 12Z Fri Oct 17 2025 - 12Z Sun Oct 19 2025

...Showers and storms increasing in coverage from the Great Lakes to the
Mid-South...

...Rain returns to Washington state by late Saturday...

A developing low pressure system currently over the Dakotas will continue
lifting northeast across western Ontario through Friday evening, with a
lingering frontal boundary situated across the Upper Midwest and western
Great Lakes region. A new wave of low pressure develops along this front
over Wisconsin and into Michigan on Saturday into early Sunday, which
becomes the next main weather maker from the Mid-South to the Great Lakes
over the weekend. Showers and thunderstorms increase in coverage from
Arkansas to eastern Michigan along and ahead of a strong cold front, with
the heaviest rainfall expected from central Illinois to northern Indiana
where 1-3 inches could fall, which may lead to some instances of flooding
where convection is most persistent.

Farther south from the ArkLaTex to western Kentucky, the Storm Prediction
Center has a Slight Risk of severe thunderstorms in their outlook for
Saturday, with a more favorable dynamical environment in tandem with
higher instability. This could lead to some instances of damaging winds,
large hail, and a few tornadoes with the strongest storms that develop. A
Marginal Risk for severe weather extends farther north across the Ohio
Valley.

Elsewhere across the nation, it will be a crisp and cool end to the work
week for much of the Eastern U.S. with a pristine airmass in place. Frost
and freeze advisories/warnings are in effect for interior portions of the
Mid-Atlantic and Northeast states. Across Montana, high winds will be
possible starting Saturday night across northern portions of the state as
a strong Pacific storm system approaches from the west, and rain and
mountain snow reaches Washington state by Saturday afternoon and beyond.
Dry conditions will continue for all of the southwestern U.S. and the East
Coast states as high pressure continues to govern the overall weather
pattern through Saturday.

Hamrick



Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
410 AM EDT Fri Oct 17 2025

Valid 12Z Mon Oct 20 2025 - 12Z Fri Oct 24 2025


...Overview...

A couple of progressive upper troughs are forecast to move through
the eastern two-thirds of the country through the medium range
period, with a tendency for them to close off into upper lows as
they near the New England coast. Meanwhile, an upper low is
forecast to push onshore into the Southwest amid general ridging
across the Northwest before ridging takes over late next week while
progressing east into the northern High Plains.


...Guidance/Predictability Assessment...

The latest model guidance shows reasonably good agreement on the
aforementioned synoptic scale pattern through the medium range
period. There has been a continued tendency for the models to
hasten the eastward progression of both troughs, and for them to
close off as they near the New England coast. Meanwhile, the EC
mean has been most consistent in depicting an upper ridge
amplifying toward the end of next week across the northern Rockies
to northern High Plains. For the upper low that is forecast to move
into the Southwest midweek next week, the EC mean is showing a
faster trend for the low to move inland and to open up the low
earlier. In contrast, the GEFS and CMC mean are trending slower
with the forward motion of the low while delaying the onset of
opening up the low into a trough.

The WPC medium range forecast package was based on a composite
blend of the 18Z GFS/GEFS, with the 12Z EC/EC mean together with
the 12Z CMC/CMCE, with increasing weighting toward the
EPS/GEFS/CMCE consensus on Day 7. This blend showed good continuity
with the previous WPC forecasts with the faster eastward motion of
the troughs as noted above.


...Weather/Hazards Highlights...

The medium range period should begin with moderate to locally heavy
rain possibly with embedded thunderstorms across northern New
England ahead of the first trough that could develop into a closed
low. A marginal risk of flash flooding has been maintained for this
area. Meanwhile, another upper trough may develop into a closed
low over the Great Lakes on Tuesday but with modest amounts of
rainfall.

Out West, increasing chance of moderate to heavy precipitation is
seen near the Pacific Northwest coast toward the end of next week
ahead of an approaching upper trough. Meanwhile, there are
increasing model signals for an expanding area of rain across the
Mid-South later next week but with a fair amount of uncertainty in
the amounts and placement at this point in time.

Kong


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

Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
500 AM EDT Fri Oct 17 2025

Valid 00Z Sat 18 Oct 2025 - 00Z Sat 25 Oct 2025


A trade wind pattern is expected to prevail through next week
with the subtropical surface high slowly edges closer to Hawaii
from the northwest. Meanwhile, a positively-tilted mid- to upper-
level trough/low that has been lingering near or just northwest of
the main islands is forecast to slowly push southward as a
subtropical high builds in from the northwest. The associated
instability and moisture pumping from the ITCZ farther south will
provide opportunities for additional local downpours and
thunderstorms from time to time. As an upper low center shifts
slowly westward and the subtropical high builds in from the
northwest, rain chances should gradually decrease later next week.
Meanwhile, trade winds will continue to favor windward terrain
rain activities.

Kong

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1100 AM EDT Fri Oct 17 2025
Day 1
Valid 16Z Fri Oct 17 2025 - 12Z Sat Oct 18 2025

...16Z Update...

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Wegman

Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1100 AM EDT Fri Oct 17 2025
Day 2
Valid 12Z Sat Oct 18 2025 - 12Z Sun Oct 19 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM NORTHWEST
ARKANSAS, ACROSS SOUTHERN MISSOURI INTO SOUTHERN ILLINOIS...

The latest models remain in good agreement on the overall
sharpening of the mid to upper level trof across the mid section of
the nation Saturday into early Sunday. Well defined upper difluence
likely between the northern stream vort moving east southeast
across the Central Plains and the southern stream vort moving east
northeast across the Southern Plains. PW values will increase to 1
to 2+ standard deviations above the mean in this broad upper
diffluent axis from eastern portions of the Southern Plains,
northeastward into the Mid MS Valley and Great Lakes, along and
ahead of the associated eastward moving frontal boundary. Model
consensus is for a broad area of moderate to heavy rainfall amounts
in this axis. All of this region has been very dry with relative
soil moisture low, low stream flows and subsequently FFG values
very high, which will be a detriment to widespread runoff issues.
The previous slight risk area was shrunk considerably, focusing it
where the HREF and RRFS means show higher probabilities for 1 and
2"+ amounts in the 12 hour period from 12Z Sat Oct 18 to 00Z Sun
Oct 19 from northwest AR, across southern MO into southern IL. This
region also corresponds to where the relative soil moisture is not
as low as points farther to the northeast and southwest, although
overall, still low. There may be a period of training of cells in
the slight risk area during the first half of the day 2 period,
before the convection begins to accelerate to the east and
southeast during the second half of day 2. The previous marginal
risk area was also decreased significantly, narrowing the eastern
extent through the OH and TN Valleys.

Oravec


Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1100 AM EDT Fri Oct 17 2025
Day 3
Valid 12Z Sun Oct 19 2025 - 12Z Mon Oct 20 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE EASTERN
GREAT LAKES INTO THE CENTRAL APPALACHIANS...

The amplifying mid to upper level trof across the mid section of
the nation day 2, will continue to accelerate eastward day 3,
becoming increasingly negatively tilted as it moves through the OH
Valley, Central Appalachians, Mid- Atlantic and eastern Lakes. The
fast eastward movement will continue to be a limiting factor for
very heavy rainfall amounts and any widespread runoff issues. While
FFG values are much lower across the eastern Lakes into the Upper
OH Valley and Central Appalachians than areas farther south and
west during the day 2 period, the aforementioned progressive
nature of the day 3 system should preclude most areas exceeding
FFG values. No changes made to the previous marginal risk area from
the eastern Lakes, south into the Upper OH Valley and Central
Appalachians.

Oravec
Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
410 AM EDT Fri Oct 17 2025


The medium range period should begin with moderate to locally heavy
rain possibly with embedded thunderstorms across northern New
England ahead of the first trough that could develop into a closed
low. A marginal risk of flash flooding has been maintained for this
area. Meanwhile, another upper trough may develop into a closed
low over the Great Lakes on Tuesday but with modest amounts of
rainfall.

Out West, increasing chance of moderate to heavy precipitation is
seen near the Pacific Northwest coast toward the end of next week
ahead of an approaching upper trough. Meanwhile, there are
increasing model signals for an expanding area of rain across the
Mid-South later next week but with a fair amount of uncertainty in
the amounts and placement at this point in time.

Kong

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
410 AM EDT Fri Oct 17 2025


The medium range period should begin with moderate to locally heavy
rain possibly with embedded thunderstorms across northern New
England ahead of the first trough that could develop into a closed
low. A marginal risk of flash flooding has been maintained for this
area. Meanwhile, another upper trough may develop into a closed
low over the Great Lakes on Tuesday but with modest amounts of
rainfall.

Out West, increasing chance of moderate to heavy precipitation is
seen near the Pacific Northwest coast toward the end of next week
ahead of an approaching upper trough. Meanwhile, there are
increasing model signals for an expanding area of rain across the
Mid-South later next week but with a fair amount of uncertainty in
the amounts and placement at this point in time.

Kong

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
259 AM EDT Fri Oct 17 2025

Valid 12Z Fri Oct 17 2025 - 12Z Mon Oct 20 2025

...Northern Rockies...
Day 1...

A 125kt jet along 50N into southwestern BC will dip down across
the US/Canadian border as mid-level height falls push into western
MT late this afternoon and overnight. A surface cold front will
move quickly through the region with NW flow in its wake,
supporting a broader area of light snow and some enhanced upslope-
driven snow for the MT Absarokas and into the Bighorns. WPC
probabilities of at least 4 inches of snow are about 20-60% above
8000-9000ft.

...Pacific Northwest and Northern Rockies...
Days 2-3...

A buckled upper jet will move into the Pacific Northwest early
Sunday, with a cold front and attendant atmospheric river of
moisture aimed into the region from the southwest. High snow levels
above 7000ft early Sunday (coincident with the heavier
precipitation) will lower to just under 5000ft Sunday
afternoon/evening as heights reach their lowest point in the fast
flow. Snow will quickly spread from the WA Cascades eastward to the
northern Rockies (western MT/Idaho into northwestern WY) as the
cold front races eastward. WPC probabilities for at least 8 inches
of snow days 2-3 are >50% above about 5000ft over the WA Cascades
and around 6500ft in northwestern MT.

The probability of significant freezing rain across CONUS is less
than 10 percent.


Fracasso

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
410 AM EDT Fri Oct 17 2025

Valid 12Z Mon Oct 20 2025 - 12Z Fri Oct 24 2025


...Overview...

A couple of progressive upper troughs are forecast to move through
the eastern two-thirds of the country through the medium range
period, with a tendency for them to close off into upper lows as
they near the New England coast. Meanwhile, an upper low is
forecast to push onshore into the Southwest amid general ridging
across the Northwest before ridging takes over late next week while
progressing east into the northern High Plains.


...Guidance/Predictability Assessment...

The latest model guidance shows reasonably good agreement on the
aforementioned synoptic scale pattern through the medium range
period. There has been a continued tendency for the models to
hasten the eastward progression of both troughs, and for them to
close off as they near the New England coast. Meanwhile, the EC
mean has been most consistent in depicting an upper ridge
amplifying toward the end of next week across the northern Rockies
to northern High Plains. For the upper low that is forecast to move
into the Southwest midweek next week, the EC mean is showing a
faster trend for the low to move inland and to open up the low
earlier. In contrast, the GEFS and CMC mean are trending slower
with the forward motion of the low while delaying the onset of
opening up the low into a trough.

The WPC medium range forecast package was based on a composite
blend of the 18Z GFS/GEFS, with the 12Z EC/EC mean together with
the 12Z CMC/CMCE, with increasing weighting toward the
EPS/GEFS/CMCE consensus on Day 7. This blend showed good continuity
with the previous WPC forecasts with the faster eastward motion of
the troughs as noted above.


...Weather/Hazards Highlights...

The medium range period should begin with moderate to locally heavy
rain possibly with embedded thunderstorms across northern New
England ahead of the first trough that could develop into a closed
low. A marginal risk of flash flooding has been maintained for this
area. Meanwhile, another upper trough may develop into a closed
low over the Great Lakes on Tuesday but with modest amounts of
rainfall.

Out West, increasing chance of moderate to heavy precipitation is
seen near the Pacific Northwest coast toward the end of next week
ahead of an approaching upper trough. Meanwhile, there are
increasing model signals for an expanding area of rain across the
Mid-South later next week but with a fair amount of uncertainty in
the amounts and placement at this point in time.

Kong


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