Quantitative Precipitation Forecast
Issued by NWS

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135
FOUS11 KWBC 232051
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
451 PM EDT THU MAR 23 2017

VALID 00Z FRI MAR 24 2017 - 00Z MON MAR 27 2017


DAYS 1 THROUGH 3...

...WESTERN U.S....

HIGHER ELEVATIONS FROM THE WEST COAST TO THE ROCKIES WILL CONTINUE
TO SEE A CHANCE FOR SNOW LATE THIS WEEK AND THROUGH THE WEEKEND AS
MULTIPLE SYSTEMS PROGRESS INLAND OVER THE WESTERN U.S..

THE INITIAL THREAT FOR HEAVY SNOW WILL BE WITH AN UPPER TROUGH
EXPECTED TO EDGE EASTWARD THROUGH THE FOUR CORNERS REGION BEFORE
CLOSING OFF NEAR SOUTHEAST COLORADO THURSDAY NIGHT. AN AXIS OF
MID-LEVEL FRONTOGENETIC FORCING AND POSITIVE PRECIPITABLE WATER
ANOMALIES EXTENDING FROM UTAH INTO CENTRAL WYOMING THURSDAY
EVENING SHOULD TRANSITION EASTWARD THURSDAY NIGHT...SHIFTING THE
FOCUS FOR HEAVY SNOW TO THE FRONT RANGE OF THE COLORADO ROCKIES BY
EARLY FRIDAY...ESPECIALLY AS WINDS STRENGTHEN AROUND A SURFACE LOW
DEEPENING IN THE LEE OF THE COLORADO ROCKIES AND UPSLOPE FLOW
INCREASES ACROSS THE REGION.  THE CLOSED MID-LEVEL ENERGY AND
ASSOCIATED SURFACE LOW SHOULD EJECT OUT INTO THE CENTRAL PLAINS ON
FRIDAY...AND...EXCLUDING THE NAM...THE MAJORITY OF MODEL THERMAL
PROFILES SUGGESTS CONDITIONS WILL NOT BE ABLE TO COOL OFF ENOUGH
TO SUPPORT MUCH ACCUMULATING SNOW WITHIN THE DEVELOPING
DEFORMATION BAND.

UPSTREAM...SNOW WILL BE POSSIBLE WITH A LONGWAVE TROUGH AND
ASSOCIATED COLD FRONT EXPECTED TO MOVE INLAND OVER THE PACIFIC
NORTHWEST AND NORTHERN CALIFORNIA THURSDAY NIGHT INTO FRIDAY AND
THEN DROP SOUTHEASTWARD TO THE NORTHERN ROCKIES...CENTRAL GREAT
BASIN...AND CENTRAL CALIFORNIA FRIDAY NIGHT.  IN
GENERAL...PRECIPITATION SHOULD BE RELATIVELY LIGHT TO MODERATE
COMPARED TO THE INITIAL SYSTEM CLOSING OFF OVER THE CENTRAL
ROCKIES.  HOWEVER...MOIST ONSHORE FLOW AHEAD OF THE UPPER TROUGH
COULD STILL SUPPORT PERIODS OF HEAVY SNOW OVER THE WINDWARD
TERRAIN OF THE OLYMPICS...CASCADES...SISKIYOUS OF NORTHERN
CALIFORNIA...AND ESPECIALLY SIERRA NEVADA RANGE.

FINALLY...JUST AS THE AFOREMENTIONED COLD FRONT PRESSES EASTWARD
THROUGH THE CENTRAL ROCKIES SATURDAY NIGHT INTO SUNDAY...THE NEXT
UPPER TROUGH APPROACHING THE WESTERN U.S. COULD BRING ADDITIONAL
SNOW TO THE CASCADES AND HIGHER ELEVATIONS OF NORTHERN CALIFORNIA
BY THE END OF THE FORECAST PERIOD (00Z MONDAY).


...UPPER GREAT LAKES TO THE NORTHEAST...

AREAS OF SNOW...SLEET...AND FREEZING RAIN WILL BE POSSIBLE WITHIN
THE NORTHERN EDGE OF PRECIPITATION DEVELOPING TO THE NORTH OF A
FRONTAL BOUNDARY EXPECTED TO STRETCH FROM THE UPPER GREAT LAKES TO
THE NORTHEAST FRIDAY THROUGH SUNDAY...WITH RETREATING HIGH
PRESSURE OVER THE EASTERN U.S. AND AN ARCTIC AIRMASS SLIDING
SOUTHEASTWARD OUT OF CANADA INTO THE GREAT LAKES AND NORTHEAST
THIS WEEKEND SUPPLYING THE LOW-LEVEL COLD AIR.  FOR NOW...WPC
WINTER WEATHER PROBABILITIES KEEP ANY SLIGHT RISK (AT LEAST 10%
PROBABILITY) OF SNOWFALL EXCEEDING 4" OR ICE ACCUMULATIONS
EXCEEDING 0.25" CONFINED TO THE ADIRONDACKS IN NEW YORK.


GERHARDT

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