Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 240750
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
250 AM EST WED DEC 24 2014

VALID 12Z WED DEC 24 2014 - 12Z SAT DEC 27 2014

WEST COAST/INTERMOUNTAIN WEST/ROCKIES...

MODEL AGREEMENT CONCERNING THE SPEED AND INTENSITY OF THE
SHORTWAVE TROUGH REACHING THE PACIFIC NORTHWEST LATER TODAY IS
QUITE GOOD AS IT MOVES INTO THE INTERMOUNTAIN WEST BY THURSDAY.
BEYOND THURSDAY THOUGH...THE FORECAST OF LIQUID EQUIVALENT AMOUNTS
AND THERMAL PROFILES BEGINS TO SHIFT TOWARD A BLEND OF THE 12Z
ECMWF/12Z ECMWF ENSEMBLE MEAN...WHICH ACCOUNTS FOR THE SLOWING
TREND AS THE TROUGH REACHES THE SOUTHERN ROCKIES AND BEGINS TO
INFLUENCE THE HIGH PLAINS.  THE PROBABILITIES FOR HEAVY SNOW TODAY
AND TONIGHT ARE ACROSS THE OREGON CASCADES/SIERRAS/NORTHERN
ROCKIES/TETONS...WHILE BY THURSDAY...THE PROBABILITIES TRANSITION
COMPLETELY INTO THE INTERMOUNTAIN WEST...INCLUDING THE WASATCH AND
HIGHER ELEVATIONS OF COLORADO AND WYOMING.  BY FRIDAY AND FRIDAY
NIGHT...THE SLIGHTLY SLOWER ECMWF SOLUTION FAVORS LOW
PROBABILITIES OF 4 INCHES ACROSS CENTRAL AND NORTHERN NEW
MEXICO...AS WELL AS THE SAN JUANS IN COLORADO.  A NARROW RIBBON OF
ICE MAY ALSO DEVELOP OVER THE HIGH PLAINS OF TEXAS AND OKLAHOMA
BEHIND A COLD FRONT...ALTHOUGH PROBABILITIES OF 0.25 INCHES ARE
PRESENTLY LESS THAN 10 PERCENT.

WESTERN OH VALLEY INTO MICHIGAN...

THE MAJORITY OF MODELS HAVE TRENDED TOWARD A WARMER BOUNDARY LAYER
AS WELL AS WEAKER AND FARTHER EAST WITH THE SURFACE LOW LIFTING
NORTHWARD THROUGH THE OH VALLEY...WITH GOOD CONSENSUS AMONG THE
00Z GUIDANCE PRESENTLY SHOWN.  THE RESULT IS AN EASTWARD SHIFT AND
SLIGHT REDUCTION IN SNOW AMOUNTS ACROSS THE OH VALLEY...WITH A
SLIGHT RISK OF 4 INCHES SHIFTED EAST ACCORDINGLY BUT OTHERWISE
MAINTAINED FOR CONTINUITY...ALTHOUGH OBJECTIVELY SPEAKING...IT NOW
APPEARS THAT THE PROBABILITIES ARE SLIGHTLY LESS THAN 10 PERCENT
OVER MOST OF ILLINOIS...PERHAPS SLIGHTLY HIGHER OVER PARTS OF
INDIANA.  GIVEN THE POSSIBILITY FOR THE MESOSCALE
BANDING...LOCALIZED TOTALS CERTAINLY SEEM POSSIBLE.
OTHERWISE...FARTHER NORTH GOOD CONTINUITY FOR MODERATE PROBABILITY
OF 8 INCHES OF SNOW CONTINUE ACROSS NORTHWEST MICHIGAN...WITH A
TIGHT RAIN/SNOW LINE POSSIBLY FORMING TO ITS EAST.

THE PROBABILITY OF 0.25 INCHES OF ICE IS LESS THAN 10 PERCENT.

JAMES

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