Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
251 AM EST Tue Jan 21 2025

Valid 12Z Tue Jan 21 2025 - 12Z Thu Jan 23 2025

...Dangerously cold temperatures and wind chill values to linger for much
of the South and eastern U.S. through mid-week...

...Rare winter storm to bring heavy snow as well as areas of sleet and
freezing rain to the Gulf Coast and Southeast with widespread travel
impacts expected...

...Extremely Critical Risk of fire weather for southern California will
continue into Tuesday...

A bitterly cold airmass will remain in place for much of the South and
eastern U.S. over the next couple of days following an Arctic frontal
passage over the holiday weekend. Forecast temperatures on Tuesday will be
upwards of 20-30 degrees below January averages for most locations with
highs ranging from the single digits and teens in the Midwest, the teens
and 20s in the Northeast, and the 20s and 30s across the central/southern
Plains and Southeast. Many record lows are possible Wednesday morning,
especially along the Gulf Coast and into the Tennessee Valley. Sub-zero
wind chills will continue for the central/southern Plains and Ohio Valley,
and may expand into the Mid-Atlantic and Mid-Mississippi Valley through
Wednesday. After another brutal morning with dangerous wind chills
reaching 30 to 55 degrees below zero, portions of the northern Plains will
see a return to relatively warmer, more typical January temperatures in
the 20s and 30s by Tuesday afternoon as downsloping air from the Rockies
spreads eastward across the region. These temperatures will reach the
Upper Midwest by Wednesday, while temperatures will also moderate into the
40s and 50s for western portions of the central/southern Plains.

The combination of this Arctic air reaching the Gulf Coast and a
developing low pressure system over the Gulf will lead to a rare,
significant winter storm for the Gulf Coast and Southeast the next couple
of days. A historic snowfall is possible along the Gulf Coast, with
snowfall rates of 1"/hour or more possible from eastern Texas through the
western Florida Panhandle. This may produce snowfall totals as much as
3-6" for the I-10 corridor, including the cities of Houston, New Orleans,
Mobile, and Pensacola. A combination of heavy snow, sleet, and freezing
rain is expected further east into Georgia, northern Florida, and the
eastern Carolinas. This storm may lead to major highway and air traffic
disruptions, including possible road closures and flight cancellations,
which may continue for several days even after the snowfall ends. Power
outages are also possible and will exacerbate the threat from the frigid
temperatures.

Unfortunately, dangerous fire weather conditions look to continue through
at least mid-week for southern California with very strong offshore flow
and low humidity in place. The Storm Prediction Center has outlined an
Extremely Critical Risk of fire weather (level 3/3) for the regional
mountains around the LA Basin as wind gusts may reach 70-100 mph. A
Critical Risk (level 2/3) is also in place for the regional valleys and
coastal regions with gusts of 50-80 mph expected. A Critical Risk
continues for the mountains Wednesday. Elsewhere in the West, conditions
will be dry, with generally mild high temperatures. Forecast highs range
from the 40s and 50s for the Pacific Northwest and Great Basin, the 50s
and 60s in California, and the 60s and 70s in the Desert Southwest.
Morning lows will be a bit chilly, however, and may drop close to freezing
for more sensitive areas of the Desert Southwest and the central
California Valleys.

Elsewhere, scattered showers and thunderstorms are expected across
Florida. Bands of heavy lake effect snow will continue the next couple of
days for favorable downwind locations of the Great Lakes with persistent
northwesterly flow in place. A clipper system dropping south from Canada
into the northern Plains and Upper Midwest will bring some snow showers
through mid-week.

Putnam


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 PM EST Tue Jan 21 2025

Valid 12Z Fri Jan 24 2025 - 12Z Tue Jan 28 2025


...Overview...

Mean troughing over the east-Central U.S. on Friday will progress
eastward and cross the East Coast by the weekend. Behind this, weak
ridging and more zonal flow will develop, finally helping to
moderate the bitterly cold temperatures in the South and East. A
shortwave dropping into the northern Rockies late this week will
split, sending northern stream energy across the northern tier of
the nation while trailing energy dives south to form a closed low
over the Southwest that will linger through early next week. The
upper low will likely bring beneficial precipitation to parts of
southern California that have been dealing with devastating
wildfires. Precipitation will also be enhanced across the Lower
Mississippi Valley Sunday and Monday as a slow moving frontal
boundary moves through the region.


...Guidance/Predictability Assessment...

Model guidance is in good agreement on the overall weather pattern
through the medium range period. Uncertainty surrounding a
potential upper low closing off over the Southwest this weekend
into early next week is gradually decreasing. The ECMWF has shown
the highest run-to-run consistency with this feature, depicting the
low closing off over the Southwest on Sunday and slowly drifting
east-southeast through early next week, and this is consistent with
the ensemble means from the GEFS/ECENS/CMCE. The 00Z GFS and CMC
kept the upper low further west, but the 06Z and 12Z runs have
shifted eastwards, closer to the ECMWF solution. The CMC still
remains the outlier with the low placement farther west than the
general consensus. There is a bit more uncertainty late in the
period as a potential shortwave drops into the northern Plains or
Upper Midwest on Monday and progresses east across the Great Lakes
or Northeast on Tuesday. There is a significant amount of model
spread in placement and strength of this feature, which could
impact the sensible weather across the northern tier Monday and
Tuesday.

Given good model agreement, a near even blend of the 06Z GFS and
00Z ECMWF/CMC/UKMET was used for days 3-5 (Friday through Sunday).
For days 6 and 7, the weight placed on the CMC and UKMET were
decreased and ensemble means from the GEFS and ECENS were added,
resulting in a good middle of the road forecast that falls close to
the means and general consensus. This blend kept good continuity
with WPC's previous forecast as well.


...Weather/Hazards Highlights...

Colder than normal temperatures will linger through Friday in the
East and through Saturday in the South and Southeast. The coldest
anomalies will be focused along the Gulf Coast where cold could be
hazardous at night when lows dip below freezing. Temperatures will
gradually moderate, returning to near normal Sunday through early
next week. Anomalously cold temperatures will also develop in the
High Plains, Rockies, and much of the West this weekend under the
influence of upper troughing. The coldest anomalies will be in the
High Plains and Rockies where high temperatures could be 10-20
degrees below normal.

Precipitation wise, a couple clipper systems may produce some light
scattered precipitation from the Northern Plains to the Midwest,
Great Lakes, Ohio Valley, and Northeast. More widespread rain and
mountain snows will move into the West by the end of the week as a
frontal system drops south across the region, which will likely
provide beneficial rain to Southern California over the weekend. A
tight gradient behind the cold front dropping south may produce an
episode of strong winds along parts of the Rockies late this week
and over California and Nevada on Saturday. Farther east, some Gulf
moisture will likely interact with a front approaching the Lower
Mississippi Valley to Tennessee and Ohio Valleys by this coming
weekend/early next week. Latest guidance continues to trend heavier
with enhanced rainfall over parts of the southern U.S., with the
potential for heavy rain and thunderstorms on Sunday across the
Lower Mississippi Valley. Snow will be possible farther north
across the Great Lakes, with a wintry mix possible across the Ohio
Valley, central Appalachians, and potentially the Tennessee Valley
as well. Precipitation may spread towards the East Coast early next
week as the frontal system progresses.


Dolan/Santorelli


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
258 AM EST Tue Jan 21 2025

Valid 00Z Wed Jan 22 2025 - 00Z Wed Jan 29 2025

Generally dry and stable conditions will continue through about
Tuesday, with light trade winds. By Wednesday-Thursday though, the
guidance continues to indicate a cut-off upper low forming north
of Hawaii and guidance has finally come into better agreement with
this feature to suggest the low remaning well north. An associated
cold front should still bring an uptick in precipitation (moderate
to locally heavy at times) and possibly gusty winds. Still plenty
of uncertainty in the details though. The low should lift out of
the region by Friday into Saturday. Another trough looks to
amplify north of the region Sunday into Monday of next week with a
cold front swinging through the state and another chance for
increased precipitation.

Santorelli

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
140 PM EST Tue Jan 21 2025
Day 1
Valid 16Z Tue Jan 21 2025 - 12Z Wed Jan 22 2025


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

Otto


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
140 PM EST Tue Jan 21 2025
Day 2
Valid 12Z Wed Jan 22 2025 - 12Z Thu Jan 23 2025

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

Pereira


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
140 PM EST Tue Jan 21 2025
Day 3
Valid 12Z Thu Jan 23 2025 - 12Z Fri Jan 24 2025

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

Pereira


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 PM EST Tue Jan 21 2025


Colder than normal temperatures will linger through Friday in the
East and through Saturday in the South and Southeast. The coldest
anomalies will be focused along the Gulf Coast where cold could be
hazardous at night when lows dip below freezing. Temperatures will
gradually moderate, returning to near normal Sunday through early
next week. Anomalously cold temperatures will also develop in the
High Plains, Rockies, and much of the West this weekend under the
influence of upper troughing. The coldest anomalies will be in the
High Plains and Rockies where high temperatures could be 10-20
degrees below normal.

Precipitation wise, a couple clipper systems may produce some light
scattered precipitation from the Northern Plains to the Midwest,
Great Lakes, Ohio Valley, and Northeast. More widespread rain and
mountain snows will move into the West by the end of the week as a
frontal system drops south across the region, which will likely
provide beneficial rain to Southern California over the weekend. A
tight gradient behind the cold front dropping south may produce an
episode of strong winds along parts of the Rockies late this week
and over California and Nevada on Saturday. Farther east, some Gulf
moisture will likely interact with a front approaching the Lower
Mississippi Valley to Tennessee and Ohio Valleys by this coming
weekend/early next week. Latest guidance continues to trend heavier
with enhanced rainfall over parts of the southern U.S., with the
potential for heavy rain and thunderstorms on Sunday across the
Lower Mississippi Valley. Snow will be possible farther north
across the Great Lakes, with a wintry mix possible across the Ohio
Valley, central Appalachians, and potentially the Tennessee Valley
as well. Precipitation may spread towards the East Coast early next
week as the frontal system progresses.


Dolan/Santorelli

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 PM EST Tue Jan 21 2025


Colder than normal temperatures will linger through Friday in the
East and through Saturday in the South and Southeast. The coldest
anomalies will be focused along the Gulf Coast where cold could be
hazardous at night when lows dip below freezing. Temperatures will
gradually moderate, returning to near normal Sunday through early
next week. Anomalously cold temperatures will also develop in the
High Plains, Rockies, and much of the West this weekend under the
influence of upper troughing. The coldest anomalies will be in the
High Plains and Rockies where high temperatures could be 10-20
degrees below normal.

Precipitation wise, a couple clipper systems may produce some light
scattered precipitation from the Northern Plains to the Midwest,
Great Lakes, Ohio Valley, and Northeast. More widespread rain and
mountain snows will move into the West by the end of the week as a
frontal system drops south across the region, which will likely
provide beneficial rain to Southern California over the weekend. A
tight gradient behind the cold front dropping south may produce an
episode of strong winds along parts of the Rockies late this week
and over California and Nevada on Saturday. Farther east, some Gulf
moisture will likely interact with a front approaching the Lower
Mississippi Valley to Tennessee and Ohio Valleys by this coming
weekend/early next week. Latest guidance continues to trend heavier
with enhanced rainfall over parts of the southern U.S., with the
potential for heavy rain and thunderstorms on Sunday across the
Lower Mississippi Valley. Snow will be possible farther north
across the Great Lakes, with a wintry mix possible across the Ohio
Valley, central Appalachians, and potentially the Tennessee Valley
as well. Precipitation may spread towards the East Coast early next
week as the frontal system progresses.


Dolan/Santorelli

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
259 AM EST Tue Jan 21 2025

Valid 12Z Tue Jan 21 2025 - 12Z Fri Jan 24 2025

...Great Lakes...
Days 1-2...

A potent shortwave trough rotating beneath the base of an expansive
longwave trough that stretches from the Great Lakes to the Davis
Strait will enhance an already favorable LES setup thanks to the
added upper level ascent out ahead of the approaching shortwave
trough. Not only will this trough aid in upper-level ascent, but
strong CAA via 850mb temps plummeting from an already very cold -20C
to an even colder -30C over the Lakes. The coldest of the 850mb
temps will reside over the Michigan U.P., but the more favored wind
convergence will be located over Lakes Erie and Ontario. This will
allow for robust LES single-banded streamers to form and produce
prolific snowfall rates today and into Tuesday night. This is due
to lake-induced instability that tops 500 J/kg at the peak of
these LES bands intensity, resulting in snowfall rates between
2-3"/hr. LES bands will taper off down wind of Lakes Erie and
Ontario by Wednesday morning as a clipper system tracks through the
Upper Midwest, bringing a broader WAA snow setup to the Great
Lakes. LES streamers off Lake Michigan will produce locally heavy
snowfall totals in the western lower MI peninsula. By Thursday,
some LES streamers may return over the eastern Great Lakes as weak
CAA returns, but are likely to be less intense compared to
Tuesday's LES bands.

WPC probabilities show, through 00Z Thursday, high chances (>70%)
for additional snowfall totals >18" just east of Lake Ontario and
over the Tug Hill with similar probabilities for >12" in the South
Towns of Buffalo. Along the western coasts of Michigan's Mitten,
there are moderate chances (40-70%) for snowfall totals >8" through
Wednesday night. The WSSI shows Major to even locally Extreme
Impacts in the Tug Hill and South Towns of NY, while the western-
most portions of Michigan's Mitten witness Minor Impacts (locally
Moderate in areas with heavier snowfall totals).

...Northern Rockies/High Plains...
Days 1-3...

These regions remain sufficiently cold enough to support snow ahead
of series of upper level troughs that have modest 700-300mb
moisture to work with and divergence aloft to support periods of
snow through Thursday. The mountainous terrain of Montana and
Wyoming, as well as the Black Hills, are favored for locally heavy
snowfall. WPC probabilities shows moderate-to-high chances (50-70%)
for snowfall >8" over the next few days in these ranges with the
Little Belt and Big Snowy of Montana sporting moderate chances
(40-60%) for snowfall amounts >12". Minor accumulations (1-4") are
possible in the High Plains of central Montana and northeast
Wyoming with WPC probabilities showing low-to-moderate chances
(20-40%) for snowfall totals >2".

...Texas, Gulf Coast, and Southeast...
Days 1-3...

...Significant, potentially historic, winter storm to spread across
the Gulf Coast and portions of the Southeast through Wednesday...

A rare, potentially historic, Gulf-Coast and Southeast Atlantic
Coast winter storm has begun thanks to a positively-tilted upper
level trough tracking through the Southern Plains this morning.
Ahead of the upper-trough, a healthy and anomalous SWrly IVT
(>500 kg/m/s, >90th climatological percentile per NAEFS) will be
directed in the direction of an Arctic-airmass that, per NAEFS,
are below the 1st climatological percentile and well below
freezing. This overrunning setup will produce a robust 850-700mb
FGEN signal that results in snow bands that would support 1-2"/hr
snowfall rates per WPC's Snowband Probability Tracker. Lastly, a
250mb SW to NE oriented jet streak will top 150 kts while placing
its diffluent right-entrance region over the Gulf Coast and
Southeast, thus fostering deep layer ascent. All of these
ingredients; lift, moisture, frigid air-mass, and mesoscale
influence, will result in a swath of impactful winter weather from
the Upper Texas Coast to the Carolina coast today and through
Wednesday morning. In fact, there are low chances (10-30%) for
localized snowfall amounts in southwest LA that could surpass 8"
Tuesday.

In South Texas, an ongoing wintry mix will make for treacherous
travel conditions tonight and into Tuesday morning. Focusing on
amounts and impacts along the Gulf Coast next, snow will be
heaviest this morning from the Upper Texas Coast on east along the
I-10 corridor. This band will move east along I-10 through the New
Orleans on east towards Mobile Bay through Tuesday afternoon with
>1"/hr snowfall rates possible. WPC probabilities show moderate-to-
high chances (50-70%) for >4" of snowfall from the lower TX/LA
state border on east towards Lake Pontchartrain. Farther east,
east of NOLA, WPC probabilities show those same moderate-to- high
chances (50-70%) for >2" of snowfall in southern MS/AL, the western
FL Panhandle, and southwest GA.

Farther east into Georgia, the northern Florida Peninsula, and the
Carolinas, guidance shows a similar significant snow/ice event in
these regions Tuesday afternoon and into Tuesday night. Similar to
the central Gulf Coast, snowfall rates along the Southeast coast
could approach 1"/hr in northern FL, southern GA, and along the
Carolina coast. Meanwhile, in the northern FL Peninsula freezing
rain and sleet will make for exceptionally dangerous travel
conditions for areas very unfamiliar with >0.1" of ice. Snow and
ice should be finished not long after sunrise Wednesday morning.
WPC probabilities for >2" are 40-60% from Cape Fear to the Outer
Banks of NC. For freezing rain, WPC probabilities show moderate-to-
high chances for >0.1" of ice accumulation in the northern FL
Peninsula and far southern GA with even some moderate chances
(40-50%) for >0.25" of ice in northern FL. Such amounts would make
for incredibly dangerous travel conditions that residents are not
used to seeing, and could also result in some tree damage and power
outages.

This event has prompted the issuance of collaborated Key Messages
(KeyMessage_1) linked below.

Mullinax

...Winter Storm Key Messages are in effect. Please see current
Key Messages below...

https://www.wpc.ncep.noaa.gov/key_messages/LatestKeyMessage_1.png

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 PM EST Tue Jan 21 2025

Valid 12Z Fri Jan 24 2025 - 12Z Tue Jan 28 2025


...Overview...

Mean troughing over the east-Central U.S. on Friday will progress
eastward and cross the East Coast by the weekend. Behind this, weak
ridging and more zonal flow will develop, finally helping to
moderate the bitterly cold temperatures in the South and East. A
shortwave dropping into the northern Rockies late this week will
split, sending northern stream energy across the northern tier of
the nation while trailing energy dives south to form a closed low
over the Southwest that will linger through early next week. The
upper low will likely bring beneficial precipitation to parts of
southern California that have been dealing with devastating
wildfires. Precipitation will also be enhanced across the Lower
Mississippi Valley Sunday and Monday as a slow moving frontal
boundary moves through the region.


...Guidance/Predictability Assessment...

Model guidance is in good agreement on the overall weather pattern
through the medium range period. Uncertainty surrounding a
potential upper low closing off over the Southwest this weekend
into early next week is gradually decreasing. The ECMWF has shown
the highest run-to-run consistency with this feature, depicting the
low closing off over the Southwest on Sunday and slowly drifting
east-southeast through early next week, and this is consistent with
the ensemble means from the GEFS/ECENS/CMCE. The 00Z GFS and CMC
kept the upper low further west, but the 06Z and 12Z runs have
shifted eastwards, closer to the ECMWF solution. The CMC still
remains the outlier with the low placement farther west than the
general consensus. There is a bit more uncertainty late in the
period as a potential shortwave drops into the northern Plains or
Upper Midwest on Monday and progresses east across the Great Lakes
or Northeast on Tuesday. There is a significant amount of model
spread in placement and strength of this feature, which could
impact the sensible weather across the northern tier Monday and
Tuesday.

Given good model agreement, a near even blend of the 06Z GFS and
00Z ECMWF/CMC/UKMET was used for days 3-5 (Friday through Sunday).
For days 6 and 7, the weight placed on the CMC and UKMET were
decreased and ensemble means from the GEFS and ECENS were added,
resulting in a good middle of the road forecast that falls close to
the means and general consensus. This blend kept good continuity
with WPC's previous forecast as well.


...Weather/Hazards Highlights...

Colder than normal temperatures will linger through Friday in the
East and through Saturday in the South and Southeast. The coldest
anomalies will be focused along the Gulf Coast where cold could be
hazardous at night when lows dip below freezing. Temperatures will
gradually moderate, returning to near normal Sunday through early
next week. Anomalously cold temperatures will also develop in the
High Plains, Rockies, and much of the West this weekend under the
influence of upper troughing. The coldest anomalies will be in the
High Plains and Rockies where high temperatures could be 10-20
degrees below normal.

Precipitation wise, a couple clipper systems may produce some light
scattered precipitation from the Northern Plains to the Midwest,
Great Lakes, Ohio Valley, and Northeast. More widespread rain and
mountain snows will move into the West by the end of the week as a
frontal system drops south across the region, which will likely
provide beneficial rain to Southern California over the weekend. A
tight gradient behind the cold front dropping south may produce an
episode of strong winds along parts of the Rockies late this week
and over California and Nevada on Saturday. Farther east, some Gulf
moisture will likely interact with a front approaching the Lower
Mississippi Valley to Tennessee and Ohio Valleys by this coming
weekend/early next week. Latest guidance continues to trend heavier
with enhanced rainfall over parts of the southern U.S., with the
potential for heavy rain and thunderstorms on Sunday across the
Lower Mississippi Valley. Snow will be possible farther north
across the Great Lakes, with a wintry mix possible across the Ohio
Valley, central Appalachians, and potentially the Tennessee Valley
as well. Precipitation may spread towards the East Coast early next
week as the frontal system progresses.


Dolan/Santorelli


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