Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
447 PM EST Tue Feb 07 2023

Valid 00Z Wed Feb 08 2023 - 00Z Sat Feb 11 2023

...Powerful cold front crosses the Northern and Central Rockies
tonight through Wednesday evening...

...Pacific Northwest to the Northern Rockies...
Day 1...
Ample moisture and strong forcing from a trough crossing BC and WA
this evening will support snowfall rates exceeding 2 in/hr along
the favored terrain of the WA Cascades and the higher ranges of
northern Idaho and northwestern Montana. Snow levels will drop
from around 4000 ft to 2000 ft tonight. Precipitation will
diminish from west to east as the trough moves east of the
Rockies, and a ridge starts to amplify along the West Coast on
Wednesday.
Day 1 snow probabilities for over a foot are moderately high for
the WA Cascades and portions of the Bitterroots along the ID/MT
border.


...Northern to Central Rockies...
Days 1/2...

A strong Arctic cold front pushing south down the Northern Rockies
tonight and the central Rockies through Wednesday evening.
Sufficient low level moisture, instability, and wind looks to
warrant raising a threat for snow squalls right along the cold
front. See the key messages wording below for this case.


...South-Central Plains to the Upper Midwest and Northeast...
Days 2-3...
Low pressure over southern NM this afternoon will swing east over
the southern Plains on Wednesday before quickly lifting northeast
to the Upper Midwest ahead of the shortwave trough digging
southeast down the Rockies. As the leading wave pivots northeast
it takes on a negative tilt, quickly developing a surface low over
Arkansas and over the Midwest into Thursday. For the
Mid-Mississippi Valley, warm air ahead of the system will support
mostly rain.  However, increasing ascent wrapping around the
developing low under coupled upper jet forcing along with
low-to-mid level frontogenesis, will cool enough to support a
changeover to heavy bands of snow, starting over eastern Kansas,
but really getting going over Iowa and continuing through central
Wisconsin.

This is a classic case where the heavy snow areas trend
earlier/farther southwest. Some CAMs such as the 12Z 3km NAMNest
depict snow bands Wednesday afternoon/evening over south-central
KS and north-central OK, spreading east to the Ozarks. So that
threat will need to be monitored. Farther north amounts in
northern Michigan look to be bolstered by lake enhancement as the
system lifts northeast to the region Thursday night.  WPC Day 2
snow probabilities for accumulations of 6 inches or more, are 30
to 50 percent over northeast IA through central WI with day 2.5
probabilities of 40 to 50 percent over northeast WI (around Green
Bay) and the central U.P.

Farther downstream in the warm advection pattern, cold air in
place will support a wintry mix at the onset across portions of
the Northeast, with a few inches of snow likely for northern Maine
and accumulating ice glaze for northern Michigan and from northern
Pennsylvania through Upstate New York and central/northern New
England. Day 2/2.5 WPC guidance for at least a slight risk for ice
accumulations of 0.10 inch are low for parts of the interior
northern L.P. of Michigan, Catskills, Adirondacks, and Green/White
Mountains.


Jackson


...Key Messages for Northern and Central Rockies Snow Squall
threat tonight into Wednesday evening...

--Snow Squalls in Northern and Central Rockies
A cold front pushing through the northern Rockies tonight and
early Wednesday, and the central Rockies on Wednesday, will bring
snow squalls and scattered snow showers.

--Gusty Winds Also Expected in the Region
Widespread wind gusts in excess of 50 MPH, with gusts as high as
65 MPH, will lead to difficult travel conditions, especially to
high profile vehicles in strong crosswinds.

--Bursts of Heavy Snow and Low Visibility
Snow squalls and snow showers will produce brief bursts of heavy
snow. This will lead to sudden reductions in visibility,
especially in areas of strong wind gusts.

--Expect Rapidly Changing Conditions
Anyone traveling on roads through the northern and central Rockies
should be prepared for rapidly changing conditions, potentially
going from sunny skies to near whiteouts in a matter of minutes.
Use caution if traveling.



Jackson