Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EST Sat Feb 15 2025
Valid 12Z Sat Feb 15 2025 - 12Z Mon Feb 17 2025
...A life-threatening flash flooding event emerging over the lower to
mid-Mississippi, Tennessee and Ohio Valleys into parts of the Appalachians
with severe thunderstorms across the Deep South...
...Widespread moderate to locally heavy snowfall along with increasing
winds from the upper Midwest through the Great Lakes and New England this
weekend with a swath of sleet/ice just to the south...
...Another surge of arctic air will spread southward across the northern
U.S. this weekend into early next week with snow developing from the
northern Rockies into the north-central Plains...
...Pacific system will bring renewed round of lower elevation
coastal/valley rain and higher elevation snow to the Pacific Northwest by
Sunday...
As a low pressure system exits the western U.S. and moves into the central
Plains early this morning, a high pressure system associated with a large
pool of arctic air in Canada is poised to surge southward into the Plains.
The interaction between the two systems will result in a rather large
cyclone to develop and intensify as it tracks from southwest to northeast
across the eastern half of the country through the next couple of days,
where widespread impactful to locally life-threatening weather is expected
in the path of this cyclone. Of immediate concern is a life-threatening
flash flooding event currently developing from the lower to
mid-Mississippi into the Tennessee Valleys, and gradually spreading into
the Ohio Valley. The combination of favorably strong dynamics interacting
with plentiful moisture along a warm front will contribute to widespread
intense thunderstorms increasing in coverage across these areas through
the day. Repeated rounds of intense storms will lead to rainfall rates of
1-2" per hour and totals of 3-6", with isolated amounts up to 8" as the
storms move parallel to and back build along the front. The greatest risk
for this intense rainfall prompting life-threatening flash flooding will
be across portions of northwestern Tennessee and western Kentucky, where a
High Risk of Excessive Rainfall (level 4/4) is in effect. A broader
Moderate Risk (level 3/4) covers portions of the Mid-South to Ohio Valley,
with a Slight Risk (level 2/4) encompassing the general region east to the
Appalachians. Still potentially significant, but more scattered instances
of flash flooding will be possible in these areas. In addition to the
flood risk, severe weather is also expected, with an Enhanced Risk (level
3/5) issued by the Storm Prediction Center for portions of the lower
Mississippi Valley. Supercell thunderstorms ahead of the front will be
capable of all severe hazards today, including the risk for strong
tornadoes. The progress of a potent cold front will speed up across the
South into this evening, transitioning the threat to damaging winds and
QLCS tornadoes, which may continue further east into the Southeast
overnight Saturday. The system will continue eastward on Sunday, with a
broad area of showers and thunderstorms spreading across the Mid-Atlantic
and Southeast producing moderate to locally heavy rainfall, with some
isolated flash flooding possible in the southern Mid-Atlantic.
To the north, a band of moderate to locally heavy snow is quickly
expanding from the upper Midwest into the Great Lakes today. Winter
Weather Advisories are in place for totals generally in the 3-6" range. A
wintry mix will be possible in the transition zone along the storm track
through portions of the Midwest. As the storm intensifies, a more
significant winter storm is becoming likely for upstate New York and
northern New England late tonight into Sunday. Increasingly strong and
gusty winds may also lead to periods of blowing snow and very difficult
travel conditions as the intensifying cyclone passes through. Some
moderate snow totals will also be possible further south across higher
elevations of the Appalachians. By Monday morning, the deep storm will
begin to move east of New England with much of the rain moved off the East
Coast and the snow tapering off in New England. However, blusterly
northwesterly winds will usher much colder air into the eastern U.S. with
re-newed rounds of lake-effect snows downwind from the Great Lakes.
Daytime high temperatures will be above average and rather mild for
regions ahead of the storm system from the central to eastern U.S. this
weekend. Forecast highs in the 50s to 70s are expected from the Ohio
Valley southward to the lower Mississippi Valley/Texas/Gulf Coast for
today. By Sunday, much warmer temperatures are forecast across the
Mid-Atlantic and Carolinas as temperatures reach into the 50s and 60s here
as well, with 60s and 70s in the Southeast ahead of the front. Arctic air
from Canada will then spread southward behind the front, bringing well
below average, bitterly cold temperatures to areas of the northern and
central Plains beginning today, with highs in the single digits and teens
for many locations. Some highs may not even reach above zero by Sunday.
By Monday morning, -30 degrees or colder temperatures are possible near
the Canadian border of the High Plains. Blustery winds will lead to wind
chills well below zero, particularly across the northern Plains. These
colder temperatures will expand into the Mississippi Valley and southern
Plains by Sunday with highs dropping into the 30s and 40s for most
locations.
Back to the West, an upper-level trough/Pacific storm system will bring a
renewed round of precipitation to the Pacific Northwest beginning late
Saturday which will spread inland across the northern Great Basin/Rockies
into Sunday. This will include periods of moderate rainfall for coastal
locations, a mix of rain and snow for interior valleys, and moderate to
locally heavy snow accumulations for higher mountain elevations,
particularly across the Cascades and northern Rockies. By Sunday night
into Monday morning, moisture from the Pacific system will begin to
interact with a stationary arctic front to expand a swath of accumulating
snowfall from the northern Rockies toward and into the northern Plains.
Kong/Putnam
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php