Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
342 PM EST Mon Jan 31 2022

Valid 00Z Tue Feb 01 2022 - 00Z Fri Feb 04 2022

...Pacific Northwest to the Northern Rockies...
Days 1-3...
Broad cyclonic flow across Canada will send a sheared shortwave
through the area late Day 1 into Day 2 as ridging over the
northeast Pacific slowly builds to the northeast into Washington.
Another weak shortwave will round the top of the ridge across the
Gulf of Alaska late Tue/early Wed and dive southeastward into the
Pac NW on Thu. Each will bring a small surge in limited moisture
driven by a jet streak aloft and upslope into the Cascades. WPC
probabilities indicate that additional accumulations of 8-12
inches, with locally heavier amounts, can be expected over the
next three days across portions of the northern and central
Cascades, as well as the Blue Mountains, and parts of the northern
Rockies. Areas that may receive higher totals include portions of
the Bitterroots in northern Idaho and the Glacier region in
northwestern Montana. With snow levels remaining low, additional
significant accumulations are expected within the northern Cascade
passes.

...Central and Southern Rockies...
Days 2-3...
Shortwave moving through northern Plains overnight will lift to
the northeast into Ontario as a trailing cold front plunges
southward through the northern Plains and Rockies. Post-frontal
easterly flow, along with increasing synoptic scale ascent ahead
of an amplifying trough digging through Utah and Arizona, is
expected to support widespread mountain snows across the Colorado
and northern New Mexico ranges by late Tuesday, with locally heavy
accumulations possible by early Wednesday and modest accumulations
across the Front Range. WPC probabilities for at least four inches
of snow are moderate to high along and east of the Rockies.

The potential for heavy snow is expected to increase across
southern Colorado and northern New Mexico and spread south on
Wednesday. Upper trough will move east out of Arizona into/through
New Mexico, enhancing northeasterly flow and the development of
heavy snows spreading south through the central/southern New
Mexico ranges (as well as over parts of eastern Arizona) Wednesday
night into Thursday morning before tapering off later Thursday.
The San Juan and Sangre de Cristo mountains are expected to see
some of the highest two day totals, with WPC probabilities
indicating amounts of a foot or more are likely with highest
totals approaching two feet.


...South-Central Great Plains through the lower Great Lakes...
...Prolonged wintry mix event anticipated to begin over the
south-central Plains and Midwest Tuesday night and shift south
through Thursday...
Days 2-3...
Wednesday morning is expected to mark the onset of what will
likely become a prolonged, multi-round and multi-precipitation
type winter weather event impacting a large portion of the central
to northeastern U.S. into Friday (beyond this forecast period).
Deepening moisture (precipitable water anomalies of +1 to +3 sigma
near and south of the front) supplied by low-to-mid level
southerly flow from the Gulf of Mexico into the central U.S. is
expected to support precipitation developing north of a strong
cold front as it drops southeastward through the central Plains,
mid-Mississippi Valley, and south of the western Great Lakes
Wednesday morning. A bit slower exit of the southwestern shortwave
and quicker progression of the shortwave across Canada may allow
for a bit colder solution overall especially along/east of the
Mississippi Valley. Favorable upper jet forcing overlapping
mid-level frontogenesis is expected to support an expanding area
of wintry precipitation from Kansas and Oklahoma to Lower Michigan
Day 2. Precipitation will continue to develop and propagate
northeastward in tandem with an increasing jet (~150kts) into the
Corn Belt as another area of organized precipitation develops back
to the southwest.

As the upper trough in the Southwest moves into the southern
Plains Day 3, right-entrance region upper jet forcing along with
the strong low-to-mid level frontogenesis will support an area of
moderate to heavy snow developing over eastern Oklahoma and Kansas
Wednesday evening before shifting northeast through the
mid-Mississippi Valley and into the southern Great Lakes region
overnight. 

By early Thursday, these two events are expected to combine to
produce a long swath of snow accumulations of 4 inches or more --
extending from the Texas Panhandle and Oklahoma through the
Midwest/Lower Michigan and into western/northern New York. Within
this area, accumulations of a foot or more are possible through
the two-day period. Latest WPC probabilities indicate that
accumulations of a foot or more are most likely from east-central
Kansas to northern Indiana and southern Lower
Michigan/northwestern Ohio.

South of the heavier snow, a wintry mix, including freezing rain,
will likely impact areas from North Texas to central Ohio.
Significant ice accumulations are likely, with amounts of a 0.25
inch or more possible, especially across portions of eastern
Oklahoma, northern Arkansas, southern Missouri/Illinois eastward
into central Ohio. There, WPC probabilities of at least 0.25 inch
ice are moderate (40-70%) and probabilities of at least 0.50 inch
are more than 10%.

Fracasso/Pereira


~~~ Key Messages for Feb 1-3 Winter Storm ~~

-- A large and significant winter storm is expected to impact much
of the central U.S. beginning Tuesday night, bringing a variety of
winter weather hazards including heavy snow, sleet, and freezing
rain.

-- The storm will be prolonged with several rounds of winter
weather lasting through Thursday for portions of the central U.S.
before shifting to the interior Northeast.

-- Heavy snow is expected over the southern Rockies and from the
south-central Great Plains through the eastern Great Lakes and
interior Northeast. A corridor of heavy ice accumulation is likely
from Texas through the Ohio River Valley.

-- Locations impacted by snow and/or ice are expected to have
temperatures remain below freezing, and well below average, for at
least a couple days after the wintry precip ends.

-- Plan now for prolonged hazardous winter weather conditions and
disrupted travel.