Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
157 AM EST Thu Jan 20 2022
Valid 12Z Sun Jan 23 2022 - 12Z Thu Jan 27 2022
...Pattern Overview and Guidance/Predictability Assessment...
Models and ensembles are in good agreement with the amplified mean
flow over the lower 48 highlighted by an upper ridge off/along the
West Coast and an upper trough over the central to eastern U.S..
Guidance now offers more characteristic run to run continuity
issues with embedded systems within the larger scale flow over
time in a pattern with seemingly near normal forecast
predictability.
Accordingly, the earlier issued WPC medium range product suite was
mainly derived from a composite of the the reasonably well
clustered solutions of the 18 UTC GFS and 12 UTC
ECMWF/UKMET/Canadian along with the 01 UTC National Blend of
Models for days 3/4 (Sunday/Monday). Transitioned to a composite
of the compatible 18 UTC GEFS and 12 UTC ECMWF ensemble means
along with the NBM for days 5-7 (Tuesday-next Thursday). This
along with some applied manual adjustments consistent with
uncertainty maintains decent WPC product continuity that also
remains generally in line with a similar composite plan from newer
00 UTC guidance.
...Weather Highlights/Threats...
A weekend southern stream Southwest U.S/northern Mexico closed low
offers some snow potential for the Southern Rockies/High Plains.
The system will eject eastward across the U.S. southern tier early
next week and wave genesis on a lingering trailing front over the
Gulf of Mexico will induce lead moisture return from the Gulf of
Mexico to fuel a moderate swath of precipitation within a cooled
airmass from Texas eastward across the Gulf Coast/Southeast. This
may include some snow/ice on the northern periphery of
precipitation.
The next in a series of Arctic Blasts will again spread far south
over the central and eastern U.S. Monday-next Thursday as another
mean flow reinforcing upper trough digs southeastward from Canada.
Transitory frontal enhanced upslope snows will dig through the
cooling Rockies and adjacent High Plains. Northern stream upper
system passage and frontal low genesis on the leading edge of
Arctic air starting Monday should support a windy snow swath from
the Dakotas through the Upper Midwest/Great Lakes. Low development
through the Great Lakes/Northeast Tuesday into Wednesday and
trailing cold frontal passage across the East favors lingering
lake effect along with some threat of plowable snows from the
Appalachians through the Northeast. System evolution becomes
complex offshore and into the Canadian Maritime by midweek as the
aforementioned southern stream system phases/lifts on the lead
periphery of the amplified northern stream upper trough.
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