Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
352 PM EDT Mon Mar 25 2024
Valid 00Z Tue Mar 26 2024 - 00Z Fri Mar 29 2024
...Southern Rockies...
Day 1...
Southwest side of the broad troughing over the western/central US
will carry some embedded vorticity through the Southwest/Southern
Rockies this evening and into Tuesday. A few inches of additional
snowfall are likely over much of the mountainous areas, especially
the White and Mogollon Mountains in AZ and NM, respectively where
over ten inches are possible.
...Northern Plains & Upper Midwest...
Day 1...
Major winter storm will progress through the Corn Belt into the
Upper Midwest tonight/early Tuesday, with the trailing mid-level
vort center becomming the dominant entity that will help carry it
into western Ontario late Tue into early Wed (though again trailed
by another vort center). Deformation snow on the NW side of the low
will continue to translate northeastward this evening over MN with
mid-level-forced snow over NE/KS moving eastward in tandem with CAA
behind the front. Winds will remain quite gusty this evening with
blizzard conditions due to blowing snow possible. Additional snow
will be light- modest, with the highest totals after 00Z over
northern/northeastern MN where WPC probabilities for at least 4
more inches are high (>70%). Southeast of this axis, warm air aloft
atop sub-freezing surface temperatures will promote a SW to NE
axis of freezing rain/sleet from southern MN northeastward across
the Arrowhead. Additional icing will be around several hundredths
to just over a tenth of an inch or so. The entire system will
slowly ramp down with plenty of wrap-around light snow over
northern MN into Tuesday, but with only an inch or two likely
except for perhaps right along the Canadian border.
...PacNW/Northern Great Basin...
Days 1-3...
Northwest flow downstream of an upper ridge axis south of the Gulf
of Alaska will continue to funnel mid-level impulses into the
Pacific Northwest and northern Great Basin through Tuesday, with
snow confined to the Cascades and northern/central Rockies as the
upper jet slowly weakens and moves eastward. By Wednesday, a much
more coherent upper low will form/deepen just south of 50N near
140W with a plume of moisture tied back to the subtropics
approaching the WA/OR coast. This will move ashore starting early
Wednesday with snow levels rising to around 5000ft ahead of the
cold front in the Cascades mid-day Wednesday then fall back to
around 4000ft post-FROPA as precipitation starts to wane and
eventually as low as about 3000ft by Thursday morning. In the
Cascades, WPC probabilities for at least eight inches over the next
few days are >50% above about 4000ft. Precipitation will continue
into the northern Rockies/Great Basin beneath the LFQ of the
advancing upper jet, favored over the Blue Mountains into the
central ID ranges and western WY where WPC probabilities for at
least six inches are high (>70%).
Farther south into California, moisture plume will be a bit more
potent, with IVT values > 400 kg/m/s (~98th percentile) into the
NorCal ranges (Shasta/Siskiyous/Trinity) by late Wednesday (with
the cold front) through Thursday (associated with the trailing
upper jet streak). Snow levels >6000ft ahead of the front will fall
to <5000ft behind it, then even to 4500ft or so by Thursday with
continued onshore flow. Snowfall days 2-3 will be modest over the
northern to central Sierra, with WPC probabilities for at least 12
inches >50% above about 6000ft or so.
Fracasso
***Key Messages for Plains-Upper Midwest Winter Storm***
--Major winter storm continues into Tuesday
Snow and strong winds will continue from the Central Plains to
northern Minnesota through tonight, along with sleet and freezing
rain in parts of the Upper Mississippi Valley.
--Hazardous impacts due to snow and wind
Plan on slippery road conditions. Blowing and falling snow will
significantly reduce visibility, and blizzard conditions will
persist into Tuesday across portions of the Plains and northern
Minnesota. Travel may be very difficult or impossible at times.
Power outages and tree damage are possible in some areas due to
heavy snow, icing, and strong winds.
--Gradual Improvements Snow and winds will gradually diminish from
southwest to northeast across the region on Tuesday. However,
areas of blowing snow may persist.