Quantitative Precipitation Forecast
Issued by NWS

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
000
FOUS11 KWBC 062128
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
427 PM EST TUE DEC 06 2016

VALID 00Z WED DEC 07 2016 - 00Z SAT DEC 10 2016


DAYS 1-3...


...PACIFIC NORTHWEST AND NORTHERN CALIFORNIA TO THE NORTHERN
ROCKIES...

A WIDESPREAD WINTER WEATHER EVENT IS EXPECTED FROM THE PACIFIC
NORTHWEST AND NORTHERN CALIFORNIA TO THE NORTHERN ROCKIES FOR THE
LATER HALF OF THE WEEK.  LOW LEVEL COLD AIR ENTRENCHED ACROSS THE
REGION SHOULD SET THE STAGE FOR THE EVENT AS THE NEXT PACIFIC
SYSTEM APPROACHES THE COAST WEDNESDAY NIGHT.  WARM MOIST AIR
MOVING IN AHEAD OF THE SYSTEM AND ACROSS THE TOP OF THE COLD AIR
IS EXPECTED TO PRODUCE A VARIETY OF PRECIPITATION TYPES OVER THE
PACIFIC NORTHWEST INTO THE INTERMOUNTAIN WEST...INCLUDING FREEZING
RAIN WITH ACCUMULATING ICE IN THE BASINS AND VALLEYS WHERE THE
COLD AIR REMAINS ENTRENCHED.  EASTERLY FLOW IN THE BOUNDARY LAYER
IS EXPECTED TO HELP MAINTAIN THE COLD AIR EAST OF THE CASCADES
BEFORE SOUTHWESTERLY WINDS PREVAIL.  WHILE WIDESPREAD HEAVY ICE
ACCUMULATIONS ARE NOT EXPECTED...SEVERAL AREAS FROM THE PACIFIC
NORTHWEST INTO THE INTERMOUNTAIN WEST MAY SEE AT LEAST SOME MINOR
ICE ACCUMULATIONS LATE WED INTO THU.  MEANWHILE...THE THREAT FOR
HEAVY SNOWS IS EXPECTED TO INCREASE ACROSS THE HIGHER TERRAIN OF
THE NORTHERN CASCADES INTO THE NORTHERN ROCKIES AS THE SYSTEM
MOVES INLAND THURSDAY INTO FRIDAY.  PLEASE REFER TO WPC`S MODEL
DIAGNOSTIC DISCUSSION (PMDHMD) FOR DETAILS ON THE LARGE AMOUNT OF
MODEL SPREAD AND UNCERTAINTY WITH THIS FEATURE.


...CENTRAL ROCKIES/PLAINS...

SNOW IS EXPECTED WITH A BROAD SHORTWAVE PROGRESSING EASTWARD OUT
OF THE CENTRAL GREAT BASIN TUESDAY NIGHT.  LIMITED MOISTURE AND
THE RELATIVELY QUICK NATURE OF THIS SYSTEM SHOULD KEEP
ACCUMULATIONS GENERALLY LIGHT...WITH THE EXCEPTION OF OROGRAPHIC
EFFECTS ENHANCING SNOWFALL OVER THE CENTRAL ROCKIES.  ALSO...AS
THE LEADING EDGE OF THE SHORTWAVE REACHES THE PLAINS AND A SURFACE
LOW SINKS SOUTHEASTWARD OUT OF THE LEE OF THE COLORADO
ROCKIES...SNOW COULD DEVELOP WITHIN AN STRENGTHENING FRONTOGENESIS
AXIS SETTING UP OVER THE CENTRAL CENTRAL PLAINS...BUT AGAIN THE
LIMITED MOISTURE AND QUICK PROGRESSION SHOULD KEEP SNOWFALL TOTALS
LIGHT.  THE WPC ENSEMBLE BLEND KEEPS THE GREATEST CHANCE FOR
ACCUMULATING SNOW IN THE HIGHER ELEVATIONS OF THE CENTRAL
ROCKIES...BUT ALSO SHOWS A SLIGHT RISK (GREATER THAN 10%
PROBABILITY) OF GREATER THAN FOUR INCH SNOWFALL ACCUMULATIONS
EXTENDING EASTWARD OVER SOUTHWESTERN NEBRASKA AND NORTHWESTERN
KANSAS.


...UPPER MIDWEST/GREAT LAKES...

THE UPPER LOW AND DEEP SURFACE CYCLONE THAT BROUGHT BLIZZARD
CONDITIONS TO PORTIONS OF THE NORTHERN PLAINS ON TUESDAY WILL
STEADILY LIFT INTO CANADA TUESDAY NIGHT...BUT SNOW AND HIGH WINDS
WILL BE SLOW TO DIMINISH ACROSS THE REGION.  ALSO...AS THE UPPER
LOW PROGRESSES NORTHEASTWARD AND EVENTUALLY TRANSITIONS TO A BROAD
TROUGH OVER THE GREAT LAKES/NORTHEAST...STRONG COLD AIR ADVECTION
AND DEEP CYCLONIC NORTHWEST TO WEST FLOW WILL SET THE STAGE FOR A
PROLONGED LAKE EFFECT SNOWFALL EVENT...ESPECIALLY DOWNWIND OF
LAKES ERIE AND ONTARIO.


...CENTRAL APPALACHIANS TO THE NORTHEAST...

SNOW...AND AREAS OF SLEET AND FREEZING RAIN...WILL BE POSSIBLE
WITHIN THE NORTHERN EDGE OF PRECIPITATION SPREADING INTO THE
NORTHEASTERN U.S. TUESDAY NIGHT AS WEAKENING SHORTWAVE ENERGY
LIFTS THROUGH THE MID-ATLANTIC STATES AND A SURFACE LOW DEEPENS
OFF THE CAROLINA COAST.  THE COMBINATION OF MARGINAL BOUNDARY
LAYER TEMPERATURES AND THE QUICK PROGRESSION OF THE
SHORTWAVE...WHICH IS EXPECTED TO STREAK AWAY FROM THE COAST EARLY
WEDNESDAY...SHOULD KEEP ANY SNOW ACCUMULATIONS LIGHT TO MODERATE
AND MOSTLY CONFINED TO THE HIGHER ELEVATIONS. AN ENSEMBLE BLEND OF
MODEL GUIDANCE SUGGESTS THE GREATEST CHANCE FOR ACCUMULATING SNOW
WILL EXTEND FROM NORTHWESTERN PENNSYLVANIA INTO CENTRAL NEW YORK.



GERHARDT

$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.