Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
200 PM EST Sat Jan 01 2022
Valid 12Z Tue Jan 04 2022 - 12Z Sat Jan 08 2022
...Multi-system coastal heavy rain and mountain focusing heavy
snow threat from the Pacific Northwest/northern California to the
north-central Great Basin/Rockies next week...
...Arctic blasts spread out from the north-central U.S. to fuel a
mid-later next week heavy snow threat from the Great Lakes/Ohio
Valley/Appalachians to the Northeast with coastal storm genesis...
...Pattern Overview and Weather/Hazard Highlights...
A deepening storm will track from the northern Plains Tue to 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/Appalachians to the Northeast, with trailing
frontal rains down to the Southeast. The snow threat is expected
to be exacerbated by lake effect, terrain lift and over the
Northeast by coastal storm genesis into Fri.
Meanwhile, multiple Pacific systems with moderate atmospheric
river blueprints will meanwhile take aim at the Pacific
Northwest/northern CA next 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 where lift
will be further enhanced by post-frontal upslope.
...Guidance/Predictability Assessment...
Model and ensemble forecast spread and uncertainty now seems lower
than normal through medium range time scales. A composite of well
clustered mass field guidance from the 06 UTC GFS/GEFS mean, 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 3-7 (Tue-next Sat) in a pattern with good
continuity. The composite tends to mitigate lingering embedded
system timing/strength differences and run to run variable lower
atmospheric temperature profiles consistent with predictability.
For example the blend addresses a 06 GFS that seems too warm in
the Arctic air over the northern Plains Day 4/Wed, the 00 UTC
Canadian seems too aggressive with northern High Plains Arctic air
Day 6/7, and recent ECMWF run to run temperature continuity has
overall been less than stellar.
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