Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 200825
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
425 AM EDT THU APR 20 2017

VALID 12Z THU APR 20 2017 - 12Z SUN APR 23 2017


...NORTHERN AND CENTRAL ROCKIES...

A WELL-DEFINED SHORTWAVE SLIDING SOUTHEAST INTO THE BASE OF A
NEGATIVELY TILTED TROUGH THAT IS FORECAST TO SHIFT EAST ACROSS THE
ROCKIES IS EXPECTED TO SUPPORT WIDESPREAD MOUNTAINS SNOWS FROM
NORTHERN ID TO NORTHERN UT AND CENTRAL CO THU-FRI.  LOCALLY HEAVY
ACCUMULATIONS ARE POSSIBLE...WITH THE GREATEST THREAT CENTERING
ALONG THE ABSAROKA...WIND RIVER AND BIG HORNS OF WY.  MODELS SHOW
A LOW LEVEL CENTER DEVELOPING AND THEN LINGERING OVER
CENTRAL-EASTERN WY LATE THU INTO FRI...RESULTING IN A PERIOD OF
PRONOUNCED LOW LEVEL INFLOW/UPSLOPE FLOW...SUPPORTING
ACCUMULATIONS OF AT LEAST SEVERAL INCHES ACROSS THE HIGHER PEAKS.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

...UPPER GREAT LAKES AND NORTHERN NEW ENGLAND...

A MID-UPPER LEVEL SHORTWAVE IS EXPECTED TO AMPLIFY AS IT MOVES
FROM THE NORTHERN PLAINS INTO THE UPPER MS VALLEY/GREAT LAKES ON
THU.  A DEEPENING SURFACE LOW IS FORECAST TO TRACK NORTHEAST FROM
THE MID MS VALLEY INTO THE UPPER GREAT LAKES BY THU EVENING.  A
COMBINATION OF DYNAMIC COOLING AND COLD AIR ADVECTION ON THE
NORTHWEST SIDE OF THE LOW IS EXPECTED TO SUPPORT RAIN CHANGING TO
SNOW...WITH A FEW INCHES OF ACCUMULATING SNOW POSSIBLE ACROSS THE
WESTERN U.P. OF MI AND THE ARROWHEAD REGION OF MN ON THU.

THIS SYSTEM IS EXPECTED TO SLIDE EAST...WITH THE PARENT SURFACE
LOW MOVING MOVING INTO NORTHERN NEW ENGLAND AS A SECONDARY LOW
DEVELOPS ALONG THE LONG ISLAND/SOUTHERN NEW ENGLAND COAST FRI
NIGHT-SAT MORNING.  RAIN CHANGING TO SNOW IS EXPECTED ACROSS
NORTHERN MAINE FRI NIGHT...WITH A FEW INCHES OF ACCUMULATING SNOW
POSSIBLE...ESPECIALLY ACROSS THE HIGHER ELEVATIONS BEFORE
PRECIPITATION COMES TO AN END ON SAT.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

PEREIRA

$$




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