Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
159 AM EST Sat Jan 29 2022
Valid 12Z Tue Feb 01 2022 - 12Z Sat Feb 05 2022
...Next week to bring heavy precipitation to the central and
eastern U.S., including winter weather from the Central Plains to
Great Lakes and interior Northeast around midweek...
...Overview...
Upper level ridging over both the western Atlantic and East
Pacific will allow for a shortwave to dig into the western U.S.
Tuesday-Wednesday, shifting east into the Plains on Thursday.
Another shortwave should drop into the base of the trough on
Thursday across the Southwest which will help to reinforce/amplify
the trough as it tracks into the Midwest/East Friday and Saturday.
This evolution is expected to bring widespread precipitation along
and ahead of a leading frontal boundary into much of the eastern
half of the country mid-late next week, with increasing potential
for wintry weather on the backside of the system.
...Guidance Evaluation/Predictability Assessment...
Recent model guidance remains in generally good agreement for the
overall large scale pattern, but with continuing uncertainty in
the smaller scale details. Models remain pretty consistent with
the track of the initial compact southern stream upper low over
the Gulf on Tuesday before shearing out with somewhat variable
timing as upper ridging builds off the East Coast. Meanwhile, in
the northern stream, a shortwave moving across the Great Lakes and
Northeast early in the workweek also shows good agreement in the
deterministic models.
There continues to be increasing consensus with energy diving
south through the Intermountain West Tuesday-Wednesday, serving to
deepen the trough into the Central U.S.. A trend towards less
separation of streams with the trough has remained, but models are
showing timing differences into the southern Plains/Midwest which
affects frontal and surface low position by Friday. The ECMWF and
CMC are faster than the GFS and UKMET (through day 5 at least),
but the ensemble means tend to fall somewhere in between. There
also seems to be a trend towards a stronger shortwave diving into
the Southwest around Friday but with a lot of uncertainty by
Saturday/day 7 regarding strength and timing, as exhibited by the
latest ensemble spaghetti plots.
The WPC forecast for tonight used a purely multi-model
deterministic blend for days 3-5. After that, increased weighting
of the GEFS/ECENS ensemble means to help mitigate some of the late
period differences. Given better than average agreement on the
large scale though, was still able to maintain 50 percent of the
deterministic GFS/ECMWF (and smaller parts CMC) through day
7/Saturday. Overall, this maintained good continuity with the
previous WPC forecast for days 3-6.
...Weather Highlights/Threats...
Some moderate rain may be possible along the central Gulf Coast on
Tuesday associated with weakening southern stream energy out over
the Gulf and increasing moisture ahead of the next system into the
West. The bigger threat during the medium range period though is a
developing trough over the West and into the Central U.S. by
Wednesday. Initially on Tuesday, this feature should spread mainly
light to moderate lower elevation rain and mountain snow across
the Rockies. The forecast however remains on track for a
significant increase of coverage and intensity of precipitation
over the east-central U.S. by Wednesday and beyond as the upper
trough emerges from the Rockies and the leading cold front
interacts with a strong low level feed of Gulf moisture. The best
chance for heaviest rainfall extends across the lower half of the
Mississippi Valley into parts of the Ohio/Tennessee Valleys to the
Appalachians and the East. The pattern certainly favors a heavy to
excessive rainfall threat, but the exact location of where this
sets up any flooding/flash flooding impacts remains quite
uncertain still. Wintry weather will be possible on the northwest
side of the moisture shield, with increasing potential for
meaningful snow from central parts of the Plains and Mississippi
Valley northeastward through the Great Lakes and into the interior
Northeast. While heavy rainfall to the south seems fairly certain,
the details with the wintry precipitation in the colder air may be
more dependent on lower-confidence details of ejecting shortwave
energy and frontal waves.
Above average temperatures will spread eastward Tuesday-Thursday
across the Eastern third of the country with daytime highs as much
as 15-20 degrees above normal along the East Coast on Friday. At
the same time, arctic high pressure dives into the Central U.S.
behind the cold front midweek, bringing chilly and much below
normal temperatures all the way from the northern Rockies/High
Plains southward into Texas. Widespread daytime highs (and
slightly less extreme overnight lows) as much as 10-25 degrees
below average are possible. The below normal temps may moderate
slightly as they shift east into the Ohio Valley/Gulf Coast states
next Friday and the East on Saturday. The West Coast states should
be near normal through much of next week owing to amplified
ridging across the East Pacific.
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, winter weather outlook probabilities
and heat indices are at:
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/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml