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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 2004Z Mar 23, 2024)
 
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Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
403 PM EDT Sat Mar 23 2024

Valid 00Z Sun Mar 24 2024 - 00Z Wed Mar 27 2024

...Northeast...
Day 1...

Right-entrance region forcing associated with a strengthening
upper
jet centered over southeastern Canada will support a deepening
surface low that will move north from the northern Mid Atlantic to
the New England coast this evening.  In addition to the strong
upper
forcing, increasing low level frontogenesis west of the low track
will support moderate to heavy precipitation continuing across
portions of New England into the evening.  With the cold air
locked
in, snow will continue across interior New England, with rates
increasing up to 2 in/hr across northern Maine.  An icy transition
zone is expected further south from western Massachusetts to
coastal
Maine into the evening, before ending as snow as the cold air
deepens behind the departing low. Precipitation will taper off
from
west to east overnight, exiting the region by daybreak as the low
tracks quickly into Atlantic Canada.

WPC PWPF shows high probabilities (greater than 70 percent) for
additional snow accumulations of 6 inches or more covering much of
northern Maine this evening.  Further south, moderate (greater
than
40 percent) to high probabilities for accumulating ice extend from
western Massachusetts through portions of southern New Hampshire
and
coastal Maine.


...The West/Four Corners...
Days 1-3...

Multi-stream troughing moving into the West will feature an upper
low moving into Oregon this evening along with a southern shortwave
tied to a 180kt jet moving through SoCal and into the Desert
Southwest. Leading surface cold front has already pushed inland,
coincident with the height falls, spreading generally light snow
over much of the Great Basin toward the central Rockies. The
southern shortwave will track across AZ/NM, favoring D1 snowfall
over the Mogollon Rim and Utah ranges into especially the San
Juans, enhanced by favorable orographic upslope. There, WPC
probabilities of at least 6 inches are high (>70%), generally above
7000-8000ft. By D2, surface low pressure will form/organize and
deepen over southeastern CO as colder air rushes southward on
increasingly northerly flow east of the Rockies. This will turn
rain to snow from south to north with snow expanding down the I-25
corridor. Snowfall accumulations will generally be a few inches,
with the highest probabilities for at least 4 inches (>50%) above
6000ft, including the Sangre de Cristos to the Raton Mesa. Snowfall
will linger into D3, primarily over northeastern NM where a few
inches are likely.

The northern stream upper low this evening will weaken into an open
wave and dive SSE through NorCal, helping to maintain snowfall into
the Sierra D1 (along with the northern extent of the southern
stream shortwave). WPC probabilities for at least 6 inches of snow
are >50% above about 5000ft. Farther north, another system into the
Pac NW will bring in several inches of snow to the Cascades, esp
D2-3 and above 5000-5500ft.


...Northern Rockies & High Plains, Central Rockies, Upper
Midwest...
Days 1-3...

**Major Winter Storm to Impact Northern High Plains to the Upper
 Midwest into Early Next Week**


Height falls out of the Rockies will help spur cyclogenesis in
southeastern CO by Sunday morning as the upper jet starts to
amplify along 105W. Easterly upslope will persist over much of MT
and back toward northeasterly to northerly flow, promoting modest
to occasionally heavier snow over eastern areas as minor shortwaves
punch through and weaken the upper ridge axis. By Sunday afternoon,
low pressure will start to trek out of SE CO into SW KS with
southerly flow increasing over the Plains on 850mb winds of 50kts.
WAA-driven snow (and/or a mixture of sleet/freezing rain) north of
a forming surface boundary will expand across the central Plains to
the Upper Midwest, with heavier snow into MN. Icing potential will
be highest over SD/NE D1 where a few hundredths to a tenth of an
inch of ice is possible.

On D2, low pressure will lift into Iowa as the upper pattern
amplifies, surging warmer and more moisture- laden air northward,
changing snow to rain from south to north over Iowa into southern
MN. Highest snowfall totals will be transient, and generally north
of the warm front near the best dynamics and mid- level FGEN.
However, northeast of the low pressure, the rain/snow line will
lift northward toward/into Lake Superior while areas on the
northwest side of the low will lie near the pivot point in the
flow, resulting in a maximum in snowfall -- likely over
northeastern SD (Coteau des Prairies) and across central MN.
Snowfall rates will likely exceed 1"/hr with increasingly wind
conditions, resulting in areas of blowing and drifting snow. Into
the MN Arrowhead, warm surge may slow its northward progression,
allowing colder northeasterly flow to persist over land with
easterly flow across the lake, enhancing snow totals near and
northeast of Duluth (assuming the column can stay below freezing).

By D3, the surface low will continue northeastward toward the
Bayfield Peninsula/far western U.P. of Michigan, with additional
snow northwest of the low across north central MN. Snow will
eventually wind down by the end of the period (Tues evening) as the
low pulls into Ontario.

For more details on impacts, please review our latest Key Messages
below.

Fracasso/Pereira


***Key Messages for Northern Plains Winter Storm***

--A high-impact winter storm developing

An extensive system will continue to develop today, producing
widespread heavy snow and gusty winds that will persist over parts
of the Northern Plains and Upper Midwest through early next week.

--Widespread heavy snow expected

Heavy snow will spread across much of central and eastern Montana
by tonight, expand into the Northern Plains and Upper Midwest on
Sunday, and continue into Tuesday. There is a high chance (>70%)
of at least eight inches of snow extending from central South
Dakota northeastward to northeastern Minnesota and northwestern
Wisconsin.

--Hazardous impacts due to snow, snow load, and wind

Heavy snow and gusty winds will produce areas of blowing and
drifting snow and possible blizzard conditions Sunday into Monday.
Hazardous travel and road closures are expected late today into
early next week. Strong winds and heavy, wet snow on trees and
power lines may damage trees and cause power outages.

--Strong wind gusts in the Central and Southern Plains

Wind gusts over 50 mph on Sunday may result in power outages,
blowing dust with reduced visibility, difficult travel, and
property damage.