Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 AM EST Sun Feb 20 2022
Valid 12Z Wed Feb 23 2022 - 12Z Sun Feb 27 2022
...Heavy to excessive rainfall threat from the Lower
Mississippi/Tennessee Valleys to the Mid-Atlantic along with a
heavy snow/ice threat from the southern Plains to the Northeast
Wednesday-Friday...
...Pattern Overview...
Expect an active mid-winter pattern this week as cold Canadian
high pressure digs across much of the lower 48 states. Upper level
troughs will dig through the West, with ejecting energies and
induced frontal waves progressing downstream then overtop a
warming Southeast/East upper ridge. The main upper trough should
shift eastward into the Central Plains and Midwest by later week
as amplified ridging builds from the East Pacific into the West
Coast. This amplified pattern favors a heavy to excessive rainfall
threat from the Lower Mississippi/Tennessee Valleys to the
Mid-Atlantic along with a heavy snow and ice threat from the
southern Plains to the Northeast Wednesday into Friday on the
cooled northern periphery of the expanding precipitation shield
with the tapping of deeper moisture from the Gulf of Mexico and
eventually to a lesser extent from the western Atlantic.
...Guidance Evaluation/Predictability Assessment...
Models and ensembles offer similar mid-larger scale flow
evolutions in a pattern with above normal overall predictability.
A composite of the 18 UTC GFS and 12 UTC ECMWF/UKMET/Canadian
along with the 01 UTC National Blend of Models (NBM) seems to
provide a good forecast basis for days 3-5 (Wednesday-Friday).
Composite blending of these decently clustered models tends to
mitigate smaller scale system variances consistent with
predictability. This solution is supported by a composite of 00
UTC guidance, GEFS/NAEFS/ECMWF ensembles and maintains good WPC
product continuity. The WPC product suite into days 6/7 (next
weekend) was mainly derived from the 12 UTC ECMWF ensemble mean
that more consistently maintains the likely slow to de-amplfy
upper flow pattern.
...Weather Highlights/Threats...
Moderate to heavy mountain snows are likely midweek for the
south-central Great Basin/Rockies with approach/passage of potent
upper trough energy and as enhanced by upslope fetch. Ample upper
energies working downstream from the West will also act to induce
waves along a lead front and tap deepening moisture from the Gulf
of Mexico. This is expected to fuel a heavy to excessive rainfall
and convection threat from the Lower Mississippi/Tennessee Valleys
to the Mid-Atlantic, mainly Wednesday/Thursday. Wave organization
and redevelopment should also support the spread of a potentially
significant heavy snow/ice threat from parts of the southern
plains and Mid-Mississippi/Ohio Valleys to a cold air dammed
northern Mid-Atlantic and Northeast Wednesday-Friday.
The cold high pressure surge will spread much below temperatures
across much of the western and central U.S. by mid-late week to
include widespread record cold values, especially frigid from the
northern High Plains to the Northern/Central Plains where daytime
highs and overnight lows could be 30-40+ degrees below normal.
This very cold air will spread, but gradually modify later week
across the Midwest/East. Meanwhile, much above normal pre-frontal
temperatures are expected across the Southeast/East with some
record warmth likely, especially overnight mins with upper level
ridging and enhanced pre-frontal moisture into the region.
Schichtel
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