Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 180753
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
352 AM EDT TUE APR 18 2017

VALID 12Z TUE APR 18 2017 - 12Z FRI APR 21 2017


...WESTERN U.S....

A MID-UPPER LEVEL SHORTWAVE IS EXPECTED TO LIFT NORTHEAST ALONG
THE LEADING EDGE OF A BROAD UPPER TROUGH THAT EXTENDS FROM THE
EASTERN PACIFIC INTO THE GREAT BASIN.  THIS ENERGY ALONG WITH
FAVORABLE UPPER JET DYNAMICS AND LOW-MID LEVEL FRONTOGENESIS IS
EXPECTED TO SUPPORT MODERATE TO LOCALLY HEAVY SNOWS ALONG THE
CENTRAL SIERRA...AS WELL AS PORTIONS OF THE ROCKIES FROM WESTERN
WY TO NORTHERN UT ON TUE.  SNOW SHOWERS ARE EXPECTED TO DIMINISH
FROM WEST TO EAST ACROSS THE REGION BEGINNING LATE TUE AS A
SHORTWAVE RIDGE BUILDS AND SHIFTS EAST OVER THE WESTERN U.S.
GUIDANCE SHOWS THE PACIFIC TROUGH BEGINNING TO SHARPEN AND MOVE
INLAND WED NIGHT AS THE PARENT UPPER LOW STARTS TO WEAKEN AND ITS
ASSOCIATED ENERGY DIGS SOUTHEAST. ON THU MODELS SHOW A NEGATIVELY
TILTED UPPER TROUGH MOVING ACROSS THE INTERMOUNTAIN WEST INTO THE
ROCKIES.  AMPLIFYING LOW LEVEL SOUTHEASTERLY-EASTERLY INFLOW NEAR
THE TRACK A MID LEVEL CENTER...ALONG WITH THE STRONG UPPER FORCING
IS EXPECTED TO SUPPORT SIGNIFICANT PRECIPITATION WITH LOCALLY
HEAVY SNOW ACCUMULATIONS IN THE SOUTHWESTERN MT/NORTHWESTERN WY
RANGES TO THE BIGHORNS THU NIGHT INTO FRI.

THE PROBABILITY OF SIGNIFICANT IS LESS THAN 10 PERCENT.

...UPPER GREAT LAKES...

THE AFOREMENTIONED SHORTWAVE MOVING ACROSS THE WESTERN U.S. ON TUE
IS FORECAST TO AMPLIFY AS IT LIFTS ACROSS THE CENTRAL AND NORTHERN
PLAINS ON WED BEFORE REACHING THE UPPER MS VALLEY EARLY
THU....WITH A CLOSED LOW DEVELOPING OVER THE UPPER GREAT LAKES
LATE THU-EARLY FRI.  WITH AMPLE MOISTURE...LOW TO MID LEVEL
FRONTOGENESIS IS EXPECTED TO SUPPORT SIGNIFICANT PRECIPITATION
ACROSS THE UPPER GREAT LAKES REGION.  DYNAMIC COOLING ALONG WITH A
STRONG SURFACE LOW TO THE SOUTH DRAWING COLDER AIR DOWN OUT OF THE
CANADA WILL SUPPORT RAIN CHANGING TO SNOW BY LATE ACROSS THE U.P.
OF MI...WITH LOCALLY HEAVY ACCUMULATIONS POSSIBLE...PARTICULARLY
IN THE UPSLOPE REGIONS OF THE PENINSULA.

THE PROBABILITY OF SIGNIFICANT IS LESS THAN 10 PERCENT.

PEREIRA

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