Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
152 AM EST Tue Jan 25 2022
Valid 12Z Fri Jan 28 2022 - 12Z Tue Feb 01 2022
...Winter Coastal Storm Threat from the Mid-Atlantic to especially
New England Friday into the Weekend...
From late this week to the start of next week the models and
ensembles continue to show an upper level pattern consisting of a
mean trough over the East, varying degrees of ridging over the
West, and a developing northeastern Pacific trough that should
approach/reach the West Coast. Guidance expects the inland
progression of the Pacific trough by Monday-Tuesday to flip the
pattern somewhat, with decreasing heights over the West and rising
heights over the East. Perhaps due in part from improving
agreement for a lead Pacific shortwave/possible weak embedded low
nearing California by Saturday, there is likewise narrowing spread
of solutions for energy digging into an amplified U.S. trough that
looks increasingly likely to support a significant and rapidly
deepening western Atlantic coastal storm Friday into the weekend
with effects from the Mid-Atlantic to New England in particular.
Some differences persist for details of the upper trough moving
into the West.
...Guidance Evaluation/Predictability Assessment...
Emerging trends from yesterday along both coasts of the lower 48
during the late week/weekend time frame held up fairly well in the
12Z/18Z cycle of guidance. Slower and more separated evolution of
the shortwave approaching California, likely yielding a weak upper
low, allows for a more persistent upper ridge over the West and in
turn somewhat stronger and slightly westward digging of shortwave
energy (which is finally reaching northwestern North America
today) into the East. Yet to be resolved is exactly when and where
eastern energy closes off an upper low, with 12Z/18Z GFS runs
doing so a bit later/northeastward than other models. In the new
00Z cycle the CMC has deviated significantly from other guidance
over the eastern Pacific, leading to question marks in its
forecast farther eastward--specifically a storm track a bit to the
east of consensus versus multiple prior runs that were on the
western side. Some important fine-scale details will still take a
while to be resolved satisfactorily. A multi-model blend with some
manual enhancement to maintain continuity in depth also provided
reasonable consistency for a track just offshore New England.
The relatively small and weak nature of the upper low that may
track into the Southwest this weekend could still lead to
predictability issues for a while. Trends over the past day have
been slower, delaying the development of any potential
precipitation along and north of the Gulf Coast. The new 00Z ECMWF
has trended faster though. There is still a wide array of possible
tracks after emerging from the Southwest early next week, with GFS
runs tending to be the farthest north and thus driest.
The upper trough eventually reaching into the western U.S. will be
from some combination of progressive North Pacific energy and flow
descending from Alaska. Differences by day 7 Tuesday are within
the realm of typical guidance spread/error at that time frame but
depend in part on whether there is a break in Pacific and
Alaska/Siberia upper ridging (GFS/GEFS keep it connected, most
other guidance shows a break), an issue that can ultimately lead
to more significant differences over the lower 48.
The aforementioned model blend used for the western Atlantic storm
worked well elsewhere for the first half of the period as well.
The forecast then transitioned toward half models/half means by
late in the period to resolve some of the timing and detail
differences that arise.
Key Messages for January 28-30 (Friday-Weekend) Winter Storm:
Confidence is increasing that a significant winter storm will
create considerable impacts Friday through the weekend from the
Mid-Atlantic through the Northeast. While uncertainty continues
with the track and intensity of this system, it is becoming more
likely that it will bring significant snow, sleet, and freezing
rain to the region, including the I-95 metropolitan areas.
Hazardous travel conditions are possible due to the combination of
snow, sleet, freezing rain, and wind. Close to the immediate
Atlantic coastline, strong winds combined with high astronomical
tides may lead to coastal flooding. Please continue to monitor for
future updates as this system develops.
Currently it appears that the upper trough/low that may track into
California and the Southwest this weekend could be weak enough not
to produce much if any precipitation over that region. Its
strength and track thereafter will determine how much
precipitation may develop from the Gulf Coast northward by the
first part of next week. Confidence is very low given a wide array
of possibilities between meaningful amounts and dry conditions.
Ahead of the northeastern Pacific upper trough, moisture should
begin to move into the Northwest on Sunday and then continue to
spread across more of the West with time. Highest totals of
rain/mountain snow should be over the Pacific Northwest. A series
of waves/fronts may bring episodes of light and scattered snow
into parts of the Great Lakes.
Much of the eastern half of the country will be quite chilly
through the weekend, with Saturday-Sunday having the broadest
coverage of temperatures 10-20F below normal. Expect a warming
trend to bring readings back close to normal by Monday or Tuesday.
Much of the Plains will see above normal temperatures (up to plus
10-20F anomalies) late this week into Monday, aside from a cool
Friday over far southern areas. Northern locations will see a
colder trend Monday-Tuesday while the relative warmth farther
south spreads a bit farther eastward. The West should see plus
5-10F or so anomalies through the weekend followed by a cooler
trend early next week as upper troughing moves in.
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are at: