Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
435 AM EDT Sun Mar 10 2019

Valid 12Z Sun Mar 10 2019 - 12Z Wed Mar 13 2019


...Northern Great Lakes...

Day 1...
The southern stream system that shifted northeast over the
north-central US over the past day will phase with a northern
stream trough that has been over the Canadian Prairies today as
the surface low lifts north from MI. Mainly light snow will
persist over the northern Great Lakes region today under the upper
trough of the phasing low. Enhancement from Superior is not
expected as the lake is essentially frozen over. Still, with snow
most of the day, moderate probabilities for four inches are over
the Keweenaw Peninsula.


...Northeast...

Days 1-2...
A warm front lifting out ahead of the low crossing MI will
continue supporting wintry precipitation as it lifts north across
New England today. A 1036mb surface high departing Maine today is
cold enough to support snow on the front end with a mix of sleet
and freezing rain following with plain rain this afternoon over
southern New England. Mainly light snow and ice accumulations are
expected, with one swath of heavier snow northeast from the White
Mountains into interior Maine where there are moderate Day 1
probabilities for six inches. Moderate Day 1 probabilities for a
tenth inch of ice are generally limited to higher elevations such
as the Catskills, Berkshires and along that same swath as the snow
northeast from the White Mountains.


...Southwest to the Central and Southern Rockies...

Day 1...
A positively-tilted upper trough extending off the northern CA
coast this morning develops into closed low off the southern CA
coast tonight. Shortwave energy rounding the trough today pushes
Pacific moisture from the Sierra Nevada and across the Great
Basin. Moderate Day 1 probabilities for eight inches extend east
from the central Sierra Nevada and across the many ranges of
central NV.

Days 2-3...
The closed low off the southern CA coast tonight drifts into the
northern Baja Monday night drawing tropical Pacific moisture
across northwestern Mexico and into the Four Corners in a 110+kt
southwesterly jet. Snow elevations on the left side of this jet
will generally be 6000 to 7000ft over AZ and across southwest CO.
This allows high elevation heavy snows along the Mogollon Rim
where Day 2 probabilities are moderate for 8 inches and especially
the San Juans of CO where there are moderate to high probabilities
for 12 inches.

This low and trough drift east through Day 3 and allow snow
elevations over the Four Corners region to drop to around 5000ft
though the moisture focus is farther east. Day 3 probabilities are
moderate again for 8 inches over the high parts of the Mogollon
Rim, San Juans, and also the Sangre de Christo with low
probabilities for 8 inches over other higher terrain of the Four
Corners states.


...Pacific Northwest...

Days 2-3...
An amplifying upper level trough and associated cold front shifts
from the Gulf of Alaska Monday and crosses the WA/OR coast Tuesday
morning and the northern Intermountain West Tuesday night. At
atmospheric river is directed inland ahead of the trough with
locally heavy precip starting on the WA coast Monday night. Snow
elevations generally remain 2000ft west of the Cascades and 1000ft
inland. The Olympics and WA/OR Cascades and northern Rockies have
moderate to high probabilities for 8 inches on Day 2.5.

Jackson