Quantitative Precipitation Forecast
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FOUS11 KWBC 270907
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
505 AM EDT THU APR 27 2017

VALID 12Z THU APR 27 2017 - 12Z SUN APR 30 2017


...UPPER MIDWEST...

MODERATE CHANCES...GENERALLY 30-50%... OF AT LEAST 4 INCHES OF WET
SNOW ARE EXPECTED ACROSS THE FAR EASTERN PORTION OF THE MN
ARROWHEAD...PORTIONS OF WESTERN UPPER MI...AND FAR NORTH-CENTRAL
WISCONSIN. MEANWHILE...30-50% PROBABILITIES OF AT LEAST 0.10" OF
ICE ARE CONFINED IN A COMPARATIVELY SMALLER AREA OVER THE HIGHER
TERRAIN WEST OF MARQUETTE.
THE 00Z NAM AND MAJORITY OF SREF ENSEMBLES WERE A BIT MORE BULLISH
WITH THE SNOW AMOUNTS...COMPARED TO THE GFS AND ECMWF. WPC
UTILIZED A GFS/ECMWF BLEND WITH THE THERMAL FIELDS...AND TAPERED
AMOUNTS A BIT GIVEN THE TIME OF YEAR/COMPACTION EXPECTED DURING
THE DAYTIME.

...EASTERN GREAT BASIN...ROCKIES...FRONT RANGE...CENTRAL HIGH
PLAINS...

A MAJOR LATE SEASON SNOW EVENT IS STILL ON TAP OVER THE NEXT FEW
DAYS ACROSS THE CO/WY ROCKIES AS WELL AS THE NORTHERN WASATCH IN
NORTHEAST UT. IN TERMS OF MODEL PREFERENCES...PER THE PMDHMD A
BLEND OF THE 00Z GFS AND ECMWF WAS PREFERRED THROUGH THE
PERIOD...AS THE CMC WAS ON THE DEEPER SIDE WHILE THE NAM AND UKMET
ON THE FASTER SIDE OF THE GUIDANCE SPREAD. QPF AND THERMAL FIELDS
WERE COMPRISED FROM A BLEND OF THE GFS AND ECMWF...THEREBY SETTING
THE MODE FOR THE SNOWFALL PROBABILITIES WHICH INCORPORATE THE
MULTI-MODEL WPC ENSEMBLE SUITE. PROBABILITIES OF 8+ INCHES DURING
DAY 1 WERE HIGHEST (OVER 70 PERCENT) OVER THE BIG HORN MTNS IN
NORTH-CENTRAL WY...WHILE 40-70% PROBABILITIES WERE NOTED OVER THE
SOUTHERN ABSAROKAS AND EASTERN WIND RIVER MTNS. BY DAYS 2 AND
3...THE MODERATE PROBABILITIES OF 8+ INCHES DROP INTO THE EASTERN
SLOPES OF THE CO AND (BY DAY 3) FAR NORTHERN NM ROCKIES ABOVE 6000
FT. AT THE SAME TIME...50% PROBABILITIES OF AT LEAST 4 INCHES
SPREAD EASTWARD INTO THE FRONT RANGE ON EITHER SIDE OF THE PALMER
DIVIDE...INCLUDING DEN AND PUB...OWING TO THE DEEPENING
LOW...STRENGTHENING E TO EVENTUALLY N LOW-LEVEL FLOW...AND
STEEPENING THETA-E LAPSE RATES ALOFT WITHIN THE CCB/COMMA HEAD
ALONG THE AXIS OF STRONGEST MID LEVEL DEFORMATION/FRONTOGENESIS.
ALL OF THESE FACTORS...ALONG WITH THE POTENTIAL CONVECTIVE
CONTRIBUTION...WOULD FAVOR OPTIMAL DYNAMICAL COOLING AND ENHANCE
THE ACCUMULATING SNOWFALL POTENTIAL FRI NIGHT/SAT MORNING OVER THE
FRONT RANGE AND PERHAPS INTO THE CENTRAL HIGH PLAINS. PLEASE REFER
TO WFO WATCHES/WARNINGS/ADVISORIES FOR MORE INFORMATION ON THIS
POTENTIALLY HIGH-IMPACT WINTER WEATHER EVENT.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

HURLEY

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