Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
413 AM EDT Tue May 09 2023

Valid 12Z Tue May 09 2023 - 12Z Fri May 12 2023

...North Central & Colorado Rockies...
Days 2-3...

By Wednesday morning, a potent 500mb low tracking through the
Lower Colorado River Basin will move east and into the Four
Corners region, taking on a negative tilt as it does. Strong upper
level divergence out in front of the upper low and beneath the
left exit region of a 100 knot 250mb jet streak will coincide with
increasing 700mb moisture flux from the Colorado Rockies on north
to the north-central Rockies. The 500mb low will generally be
below the 10th climatological percentile, and its track places the
Colorado Rockies on the northern flank of the 500mb low track
Wednesday night into Thursday morning, which is ideal for heavy
snowfall. That being said, if the calendar read "April 10" rather
than "May 10" as it will Wednesday morning, this could be a far
more impactful winter storm. While the upper low and strong
synoptic scale forcing aloft is present, there is a noticeable
lack of sufficiently cold air for a more widespread snow event for
early-mid May. Most snow levels, from the Colorado Rockies on
north to the Wind River, Absaroka, and Bighorn Ranges of Wyoming
will be around 8,000ft, with areas at or above 10,000ft having the
best odds of picking up snowfall totals >6". Latest WPC
probabilities through Thursday evening show 40-60% probabilities
for >6" of snow for elevations >10,000ft. Impacts at and above
10,000 feet, according to the WSSI, are forecast to reach Minor
criteria late Wednesday night into Thursday in the mountain ranges
mentioned above with a combination of Snow Amount and Snow Load
being the main drivers. Periods of snow may linger through
Thursday night and into Friday morning as the upper low slowly
moves north and east through the central Plains, but not quite as
heavy as Thursday morning. Snow should taper off by Friday evening
as the upper low heads for the Upper Midwest by the start of the
weekend.

The probability of ice accumulations greater than 0.25 inch is
less than 10 percent.

Mullinax