Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
405 PM EDT Thu Mar 28 2019

Valid 00Z Fri Mar 29 2019 - 00Z Mon Apr 01 2019


...Central Rockies and High Plains...

Phasing energy ejecting east out ahead of a weakening low anchored
along the Pacific Northwest coast is forecast turn east-southeast
as it moves across the Rockies and begins to interact with an
amplifying trough over central Canada.  Overall, models are in
good agreement showing significant snows developing on the west
side of a weak low level circulation dropping southeast across
Wyoming and along a trailing baroclinic zone extending back across
northern Utah on Friday.  Upslope regions of the southern Wind
River Range and Rattlesnake Hills of central Wyoming, as well as
the Unitas of northern Utah are expected to see some of the higher
totals, with WPC Day 1 probabilities (ending 00Z Saturday)
indicating a Moderate Risk for accumulations of 8-inches or more
for portions of the region.  As the northern stream trough and
colder air pushes south, rain changing to snow is expected for the
High Plains late Friday, with some significant accumulations
extending from eastern Wyoming out along the western
Nebraska-South Dakota border, where a Moderate Risk for
accumulations of 4-inches or more is indicated on Day 1.

...Great Lakes and Northeast...

Models show the previously noted upper trough over Canada
continuing to amplify -- digging into the upper Midwest and
northern Great Lakes Saturday morning.  As it continues to
interact with energy emanating from the West, a surface wave
developing over the mid Mississippi valley is forecast lift
east-northeast toward the Great Lakes.  This will push moisture
well north of a stalled frontal boundary, with rain changing to
snow before precipitation ends on Saturday.  While widespread
heavy amounts are not expected, WPC probabilities do indicate a
Slight Risk for accumulations of 4-inches or more from southern
Wisconsin to Lower Michigan on Day 2 (ending 00Z Sunday).  This
can be attributed to the NAM and some of the SREF members which
are more amplified than the general model consensus, both in the
northern and southern streams.

Favorable upper jet forcing and surface wave development will
continue to support precipitation west of the front, with rain
changing to snow, as it pushes farther south and east into the
Ohio valley and Northeast Saturday night into Sunday.  Again,
widespread heavy amounts are not expected, however WPC
probabilities do indicate a Slight Risk for accumulations of
4-inches or more from portions of northern New England and Upstate
New York southeastward into the Ohio valley.

Pereira