Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 260924
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
524 AM EDT WED APR 26 2017

VALID 12Z WED APR 26 2017 - 12Z SAT APR 29 2017


UPPER MIDWEST...

MODERATE PROBABILITIES (40-60 PERCENT) OF 4 INCHES OF SNOW ARE
STILL FORECAST ACRPSS FAR NORTH-CENTRAL MINNESOTA
WEDNESDAY...WHILE THE HIGHEST PROBS FOR RECEIVING 0.1 INCH OF ICE
WERE CONFINED ACROSS THE HIGHER TERRAIN IN WESTERN UPPER MI.
DEEPENING LOW PRESSURE TRACKING NE-N WILL BECOME INCREASINGLY
EFFECTIVE IN DYNAMICALLY COOLING THE LOWER TROPOSPHERE...AS THE
NEGATIVELY-TILTED TROUGH COUPLED WITH THE 110-120 KT 20 MB JET
STREAK TO THE NORTH PROVIDE STRENGTHENING UPPER DIVERGENCE AND
THUS ROBUST DEEP LAYER ASCENT. THE MODELS ARE A BIT BETTER
CLUSTERED WITH THE TRACK AND STRENGTH OF THE 850-700 MB
LOWS...WHICH DESPITE THE TIME OF YEAR LEADS TO SOMEWHAT HIGHER
FORECAST CONFIDENCE WITH THE SNOW PROBABILITIES WITHIN THE COMMA
HEAD/EVOLVING TROWAL. WITHIN THIS AREA...STRONG MID LEVEL
DEFORMATION/FRONTOGENESIS AND ATTENDANT 700-500 MB NEUTRAL TO
NEGATIVE THETA-E LAPSE RATES WILL LIKELY RESULT IN THE DEVELOPMENT
OF MESOSCALE BANDS...WHICH IN TURN WOULD POTENTIALLY LEAD TO A
SIGNIFICANT SPREAD WITH THE SNOW TOTALS.


GREAT BASIN AND ROCKIES...

ANOTHER POWERFUL UPPER LEVEL JET STREAK WILL DIVE SOUTHEASTWARD
ACROSS THE PAC NW AND SIGNIFICANTLY DEEPEN THE LARGE SCALE TROUGH
OVER THE 4 CORNERS AND THE ROCKIES BY THE END OF THE PERIOD.
STRENGTHENING UPPER LEVEL DIFFLUENCE AND DIVERGENCE...LOWERING
SNOW LEVELS...AND STRENGTHENING LOW LEVEL EASTERLY (UPSLOPE) FLOW
ALONG WITH THE POSSIBLE DEVELOPMENT OF A BARRIER JET WILL LEAD TO
INCREASED SNOW PROBABILITIES INTO THE FRONT RANGE BY FRI. UNTIL
THEN...MODERATE TO HIGH PROBABILITIES (40 TO ABOVE 70 PERCENT) OF
4 TO 8 INCHES OF SNOW EXIST FOR PORTIONS OF THE
BITTERROOTS/TETONS/WASATCH/BIG HORNS/LARAMIES/COLORADO ROCKIES
THROUGH THE NEXT 3 DAYS...WITH THE SNOW CHANCES GENERALLY
PROGRESSING SOUTHEASTWARD AND INCREASING AS SNOW LEVELS LOWER. THE
WWD DETERMINISTIC TOTALS REFLECT A MULTI-MODEL CONSENSUS EMBEDDED
WITHIN A MODEST TO AT TIMES LARGE SOLUTION ENVELOPE, WITH THE
CHARACTER OF SNOW A MIXTURE OF STRATIFORM FOR THE FAVORED UPSLOPE
AREAS AND SCATTERED PRECIPITATION ELSEWHERE. THE MOST CHALLENGING
ASPECT OF THE FORECAST OCCURS ON DAY 3 (FRI-FRI NIGHT)...AS
PROBABILITIES FOR 4+ INCHES INCREASE TO 40% DOWN INTO THE FRONT
RANGE JUST WEST OF DENVER-BOULDER-FORT COLLINS AND SOUTH ACROSS
THE PALMER DIVIDE.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

HURLEY

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