Quantitative Precipitation Forecast
Issued by NWS

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276
FOUS11 KWBC 280733
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
333 AM EDT TUE MAR 28 2017

VALID 12Z TUE MAR 28 2017 - 12Z FRI MAR 31 2017


...WESTERN U.S....

NM/CO/WY ROCKIES...THE MODELS SHOW A MID-UPPER LEVEL CIRCULATION
DEVELOPING AND CROSSING SLOWLY FROM WEST TO EAST ACROSS WY/CO/NM.
WELL DEFINED UPPER DIVERGENCE/LOWER CONVERGENCE COUPLETS IN THE
VICINITY OF THE LOW LEVEL FRONT COMBINE WITH UPSLOPE FLOW TO
SUPPORT HEAVY MOUNTAIN SNOWS IN THE FRONT RANGE OF CO/ADJACENT
SOUTHEAST WY/SANGRE DE CRISTO MNTNS IN SOUTHEAST CO AND NORTHERN
NM. GUIDANCE INDICATES POTENTIAL FOR SNOW ACCUMULATIONS OF 8-12
INCHES WITH LOCALLY HIGHER TOTALS.

FOR THE DAY 2 PERIOD (WED AND WED NIGHT)...AS THE AFOREMENTIONED
LOW CONTINUES  FURTHER TO THE EAST INTO THE CENTRAL PLAINS...THE
HEAVY SNOW THREAT IS EXPECTED TO WANE THEREAFTER...WITH A BRIEF
PERIOD OF SNOW POSSIBLE ON THE HIGH PLAINS BEFORE THE SYSTEM MOVES
AWAY AND PRECIP ENDS.

...WA/OR CASCADES TO THE RANGES OF ID AND UT...
CONFLUENT FLOW SUPPORTS A ZONAL UPPER LEVEL JET FORECAST BY THE
ECMWF TO BE 110-130 KT CROSSING NORTHERN WA STATE ON TUE AND THEN
STREAMING INLAND ACROSS THE ID PANHANDLE AND NORTHWEST MT.
SOUNDINGS SHOW A WARM ADVECTION PROFILE WITH DEEP MOISTURE
STREAMING ONSHORE AND INLAND...WITH DEEP LAYERED ASCENT FROM THE
SFC-500 MB SUPPORTING AN EXTENDED PERIOD OF SNOW IN THE WA
CASCADES. THE HEAVIEST SNOWS ARE FORECAST ON TUE AND TUE NIGHT
ACROSS THE WA CASCADES...WITH LESSER SECONDARY MAXIMA IN THE
OLYMPICS TO THE ID PANHANDLE AND NORTHWEST MT.

ON WED ADDITIONAL SNOW ARE EXPECTED IN THE WA/OR CASCADES AS THE
NEXT UPPER TROUGH AMPLIFIES AND DRIFTS EAST TOWARDS THE COAST.
UPPER JET MAXIMA EXTEND ONSHORE AND INLAND ACROSS WA/OR INTO
ID...WITH UPPER DIVERGENCE MAXIMA SUPPORTING ASCENT AND RESULTANT
SNOW IN THE RANGES OF SOUTHERN TO CENTRAL ID.

BY EARLY THU...EXPECT THE MID-UPPER LEVEL PATTERN TO BECOME MORE
AMPLIFIED AS A DIGGING SHORTWAVE MOVES ONSHORE.  WELL DEFINED 700
MB CONVERGENCE MAXIMA ARE FCST BY THE GFS TO CROSS THE RANGES OF
SOUTHERN AND CENTRAL ID INTO SOUTHWEST MT IN CONJUNCTION WITH THE
TROUGH AND LOW LEVEL FRONT PROGRESSING ACROSS THE REGION.
LIKEWISE...THE FORMING 700 MB CIRCULATION FOCUSES
CONVERGENCE/ASCENT ALONG ITS PATH ACROSS NV INTO UT...WHERE THE
FRONTAL CIRCULATION IS EXPECTED TO SPREAD THE POTENTIAL FOR
ACCUMULATIONS.

...UPSTATE NEW YORK THU/THU NIGHT...
THE MODELS INDICATE HIGH PRESSURE DRIFTING EAST ACROSS QUEBEC
TOWARDS NEW ENGLAND THU-THU NIGHT.  AN INVERTED TROUGH DEVELOPS
NEAR THE LAKES AS LOW PRESSURE DRIFTS INTO THE OH VALLEY.  LOW-MID
LEVEL WARM ADVECTION DEVELOPS WITH LIGHT SNOW DEVELOP IN PARTS OF
UPSTATE NY...CONTINUING BEYOND THIS PERIOD WITH POTENTIAL FOR A
MORE SUBSTANTIAL EVENT IN HIGHER ELEVATIONS OF EASTERN NY AND NEW
ENGLAND JUST BEYOND THIS PERIOD.

THE PROBABILITY OF RECEIVING A QUARTER INCH OF FREEZING RAIN IS
LESS THAN 10 PERCENT DAYS 1-3.

PETERSEN

$$





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