Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
446 AM EDT Mon Mar 21 2022

Valid 12Z Mon Mar 21 2022 - 12Z Thu Mar 24 2022

...Southern Rockies onto the Great Plains...
Day 1...

A closed upper low over New Mexico this morning will shift to the
Texas Panhandle today before turning northeast tonight the Desert
Southwest late tonight. The surface low will track ahead of the
upper low and help to strengthen the baroclinic zone from a cold
front moving down the High Plains. Ahead of the low, the low level
will be very strong with 850mb winds exceeding 50 kts out of the
Gulf of Mexico drawing subtropical moisture into the central
Plains. This moisture wraps around the low into a TROWAL, which
will combine with upslope flow over the southern High Plains to
set up snow banding with a sharp gradient between heavy rain to
the east and heavy snow to the west. That this will occur
tonight/nocturnal, accumulations will be maximized where rates are
best.

First, upslope flow onto the Palmer Divide, and particularly the
Raton Mesa will allow heavy snow with over 8" likely near Raton
Pass at the CO/NM border. Day 1 snow probabilities for over 4' are
low, but are notably higher than before from the northern TX
Panhandle across western KS. Snow is likely to fall into Neb with
a stripe of low Day 1.5 probabilities for over 2" over
east-central Neb.


...Northern Plains through the Great Lakes into the Northeast...
Days 1-3...

A northern stream shortwave trough crossing ND today will followed
by reinforcing shortwave energy dropping out of Manitoba Tuesday
and into the sprawling occluded low over the central Plains and
Midwest Tuesday into Thursday. The surface low drifts from the
KS/MO border tonight to MI Wednesday night. During this period, a
zonally oriented jet streak downstream of the primary trough axis
will shift east, placing increasingly favorable right entrance jet
diffluence for ascent across the Midwest/Great Lakes. A warm front
ahead of the slow surface low and associated pronounced moisture
advection will surge northward into the Great Lakes tonight
through Wednesday. This WAA will likely expand the precipitation
shield, and while low-level thermals will be marginal, there is
likely to be an area of moderate to heavy snow along the
international border, with a secondary area of mixed
precipitation/freezing rain in the Upper Great Lakes.

For the snow areas, Day 1.5 WPC snow probabilities remain high for
over 4" over northern MN/The Arrowhead which will have enhancement
from Lake Superior...local maxima over 8" are possible in the
Arrowhead. This snow threat area shifts east to the central U.P.
of MI for Days 2/2.5 with moderately high probabilities for over
4".

Areas of freezing rain are likely as the WAA overruns the cold
surface air into the northern Great Lakes. Moderate 24hr WPC ice
probabilities for over 0.1" of accretion shift east from the area
around Duluth to the northern L.P. of MI Days 1-3. The warm front
shifts into the Northeast Wednesday with moderate Day 3 ice
probabilities over over 0.1" accretion for the Catskills,
Adirondacks, and Green Mtns/Berkshires.


Jackson