Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
152 PM EST Sun Jan 02 2022
Valid 12Z Wed Jan 05 2022 - 12Z Sun Jan 09 2022
...Arctic air sets stage for multiple heavy snow threats from the
Great Lakes and OH/TN Valleys/Appalachians to the
Mid-Atlantic/Northeast...
...Additional rounds of heavy coastal rain and mountain focusing
snow from the Northwest/Northern California through the
north-central Great Basin/Rockies/High Plains...
...Guidance assessment and uncertainty...
Model and ensemble forecast spread and uncertainty remains lower
than normal for the most part through medium range time scales. A
composite of reasonably well clustered mass field guidance from
the 06 UTC GFS/GEFS mean, the 00 UTC ECMWF/ECMWF ensemble
mean/UKMET/Canadian along with the 13 UTC National Blend of Models
seems to offer a good basis for the WPC product suite for days 3/4
(Wed/Thu). Opted to increase WPC blend weight emphasis on the
ensemble means into days 5-7 (Fri/next weekend) to maintain max
WPC continuity. The composite tends to mitigate lingering embedded
system timing/strength differences and run to run variable lower
atmospheric temperature profiles. It should be noted that by
Thu/Fri with the Southern to Eastern U.S./coastal system, the
plausible but less likely 00/06/12 UTC GFS and a minority amount
of GEFS/ECMWF ensemble members are more suppressed by the cold
airmass in the wake of a midweek deep Great Lakes low than the
00/12 UTC ECMWF/UKMET/Canadian runs, with a farther offshore track
of the southern based coastal low/storm.
...Pattern Overview and Weather/Hazard Highlights...
The upper level flow pattern over the nation will be rather
amplified through the end of the week with a large scale trough
over the east-central U.S. and a broad ridge over the West Coast,
before transitioning to a more quasi-zonal flow by next weekend.
A deepening storm will track into the Great Lakes and eastern
Canada Wed/Thu. Arctic air will dig across the central then
eastern U.S. behind the windy and precipitation focusing low to
include a threat of plowable snow from the Great Lakes/Ohio Valley
to the Northeast. Another quickly developing heavy snow/ice threat
with some aforementioned uncertainty is on tap underneath Thu into
Fri from the TN/OH Valleys through the Appalachians/Mid-Atlantic
to the Northeast by frontal low/coastal storm genesis.
Meanwhile, multiple Pacific systems with moderate atmospheric
river blueprints will meanwhile take aim at the Pacific
Northwest/northern CA this week, that will fuel multi-day coastal
rainfall and terrain/mountain enhancing snows. Energies will work
inland across a snowy north-central Great Basin/Rockies/High
Plains where lift will be further enhanced by post-frontal
upslope. Downstream by next weekend, return flow from the Gulf of
Mexico is also expected to fuel an emerging enhanced rainfall area
inland over the Gulf Coast states/TN Valley in advance of yet
another Arctic frontal surge down through the central to
east-central U.S..
Temperatures are expected to be frigid across the central/northern
Plains to the Upper Midwest through the end of the week with a
large surface high of arctic origin governing the weather pattern
for this region. Highs in the double digits below zero are once
again likely for portions of eastern Montana and into North
Dakota, and highs in the teens settling as far south as southern
Kansas on Thursday. Some abatement in the severe cold may come to
pass across this region ahead of the next arctic surge next
weekend. Elsewhere, seasonably cold conditions are expected west
of the Continental Divide with readings generally within 10
degrees of climatological averages, and cold next weekend over the
East with highs 10+ degrees below normal.
Hamrick/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