Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 110944
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
443 AM EST WED JAN 11 2017

VALID 12Z WED JAN 11 2017 - 12Z SAT JAN 14 2017


...WESTERN U.S....

ALONG THE SIERRA...HEAVY SNOWS ARE EXPECTED TO CONTINUE INTO THE
EARLY PART OF THE PERIOD AS A WELL-DEFINED SHORTWAVE TROUGH AND
ASSOCIATED COLD FRONT MOVE ACROSS CENTRAL CA WED MORNING.  SNOW
LEVELS WILL BE ON THE DECLINE AS THE COLD FRONT PUSHES FURTHER
SOUTH.  SNOWFALL RATES ARE EXPECTED TO DECREASE AS THE LOW LEVEL
WINDS AND STRONG MOISTURE ADVECTION WEAKEN.  HOWEVER...PERSISTENT
ONSHORE FLOW IS EXPECTED TO SUPPORT ADDITIONAL SNOWS THROUGH THE
EVENING AND OVERNIGHT HOURS.  SNOWS WILL CONTINUE WITH THE ARRIVAL
OF ONE MORE SHORTWAVE TROUGH ON THU BEFORE THIS AMPLIFYING SYSTEM
DIRECTS THE DEEPER FURTHER SOUTH...WITH NORTHERLY FLOW USHERING
DRIER AIR INTO NORTHERN AND CENTRAL CA LATE THU INTO EARLY FRI.
BEFORE THE SNOWS END...ADDITIONAL ACCUMULATIONS WILL LIKELY EXCEED
ANOTHER FOOT OR MORE OVER THE CENTRAL HIGH SIERRA.

ACROSS THE CENTRAL AND SOUTHERN ROCKIES...RESIDUAL MOISTURE AND
ENERGY SPREADING EAST...ALONG WITH LOW TO MID LEVEL
FRONTOGENESIS...ARE EXPECTED TO SUPPORT ADDITIONAL MODERATE TO
HEAVY SNOWS ALONG THE WESTERN WY...NORTHERN UT AND WESTERN CO
RANGES ON WED.  ON THU...AXIS OF HEAVIER PRECIPITATION IS EXPECTED
TO SHIFT INTO THE SOUTHERN GREAT BASIN TO THE CENTRAL ROCKIES AS
THE AMPLIFYING TROUGH TO THE WEST STEERS THE DEEPER MOISTURE
FURTHER TO THE SOUTH.  HOWEVER...AS MOISTURE BECOMES MORE LIMITED
THE THREAT FOR HEAVY SNOWS IS EXPECTED TO BECOME MORE
LIMITED...WITH LITTLE TO NO THREAT FOR WIDESPREAD HEAVY SNOWS
EXPECTED BY LATE FRI INTO EARLY SAT.

...SOUTHERN PLAINS/MID MS AND LOWER OH VALLEYS...

A SHORTWAVE TROUGH EMANATING FROM THE WEST IS FORECAST TO LIFT
FROM THE CENTRAL HIGH PLAINS LATE WED TO THE UPPER MIDWEST ON
THU...DRIVING A WAVY COLD FRONT SOUTH INTO THE OH/MID MS VALLEYS
AND NORTHERN TX.  THIS FRONT IS EXPECTED TO STALL ACROSS THE
REGION AS A STRONG RIDGE BUILDS OVER THE SOUTHEAST.  MEANWHILE
NORTH OF BOUNDARY...CONFLUENT FLOW ALOFT WITH STRONG SURFACE HIGH
PRESSURE IS SHOWN ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST.
AS MID-UPPER LEVEL PACIFIC MOISTURE AND LOW LEVEL GULF MOISTURE
INCREASES AHEAD OF THE AMPLIFYING TROUGH IN THE WEST...THIS WILL
SET THE STAGE FOR THE ONSET FOR WHAT MANY GUIDANCE MEMBERS SHOW TO
BE A MAJOR ICING EVENT ACROSS PORTIONS OF THE SOUTHERN PLAINS/MID
MS AND OH VALLEYS.  SOUTHERLY FLOW DRIVING 850 MB TEMPS UP AROUND
7-10 C...WITH NORTHERLY WINDS MAINTAINING A SHALLOW ARCTIC AIRMASS
AT THE SURFACE WILL SUPPORT THE DEVELOPMENT OF FREEZING RAINS
ACROSS PORTIONS OF THE REGION.  WHILE CONFIDENCE IN THE FORECAST
DETAILS IS LIMITED AT THIS POINT...ON FRI AREAS OF ACCUMULATING
ICE CAN BE EXPECTED FROM THE TX PANHANDLE TO THE LOWER OH VALLEY.
BY EARLY SAT...SEVERAL OF THE OVERNIGHT GUIDANCE MEMBERS WERE
SHOWING LOCALLY HEAVY ACCUMULATIONS OF A QUARTER-INCH OR MORE
CENTERING ACROSS NORTHERN OK...SOUTHEASTERN KS INTO CENTRAL MO.
FOR ADDITIONAL DETAILS CONCERNING THIS EVENT THROUGH THE REMAINDER
OF THE WEEKEND...REFER TO WPC EXTENDED RANGE PRODUCTS.

PEREIRA



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