Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 252012
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
411 PM EDT TUE APR 25 2017

VALID 00Z WED APR 26 2017 - 00Z SAT APR 29 2017


UPPER MIDWEST...

MODERATE PROBABILITIES (40-70 PERCENT) OF 4 INCHES OF SNOW AND
0.25 INCHES OF ICE ARE PROJECTED ACROSS PARTS OF NORTHERN
MINNESOTA AND THE ARROWHEAD RESPECTIVELY THROUGH WEDNESDAY. THE
SOLUTION ENVELOPE IS MODERATELY LARGE FOR A DAY 1 FORECAST, OWING
TO SUBTLE DIFFERENCES IN RESPONSES TO THE SHORTWAVE TROUGH
ORIGINATING FROM WYOMING AS WELL AS BOUNDARY LAYER TEMPERATURES
RESULTING FROM THE VARIOUS RADIATION AND LAND-SURFACE MODEL
SCHEMES. THE MAJORITY OF SREF ARW CORE AND ECMWF ENSEMBLE MEMBERS
ARE NEAR THE CONSENSUS AND THE WWD FORECAST, WHILE THE GEFS
MEMBERS ARE NORTH AND SREF NMMB CORE MEMBER SOUTH. WITHIN THE
DETERMINISTIC GUIDANCE, MOST SOLUTIONS HAVE TRENDED WESTWARD AND
INTO BETTER AGREEMENT WITH THE NAM IN ALLOWING A MESOSCALE BAND OF
MODERATE TO PERHAPS HEAVY SNOW TO DEVELOP OVER FARGO AND ABERDEEN
LATE TONIGHT THROUGH MIDDAY WEDNESDAY, WITH THE NAM SUGGESTING AS
MUCH AS 8 INCHES COULD FALL. HOWEVER, THERE ARE ALSO SOLUTIONS
THAT SUGGEST MUCH LESS, WHICH IS SUPPORTED BY THE WIDE RANGE
WITHIN THE ENSEMBLES AND SMALL-SCALE NATURE OF THE EVENT. GIVEN
THE POTENTIAL FOR THE MESOSCALE TO PLAY AN IMPORTANT ROLE IN THIS
AREA, CONFIDENCE IS QUITE LOW, WITH THE DETERMINISTIC WWD SNOW
AMOUNTS SHOWING AN INTERMEDIATE AMOUNT OF 2 TO 4 INCHES.

GREAT BASIN AND ROCKIES...

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, ALONG WITH SNOW LEVELS
LOWERING. 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.
WITHIN THE ENSEMBLES, THE SREF MEMBERS ARE LIGHTER ACROSS THE
BITTERROOTS AND TETONS THROUGH WEDNESDAY COMPARED TO THE GEFS AND
ECMWF ENSEMBLE MEMBERS. FOR WEDNESDAY NIGHT AND THURSDAY, THE
SPREAD IS A BIT LARGER, WITH THE GEFS MEMBERS HEAVIER ACROSS THE
BITTERROOTS AND LIGHTER ACROSS THE WASATCH COMPARED TO THE
SREF/ECMWF ENSEMBLE MEMBERS, WHILE FOR DAY 3 (THU NIGHT THROUGH
FRI), THE ENSEMBLE MEMBERS MOST AGREE WITH SNOW FALLING ACROSS
WYOMING, YET DIFFER ELSEWHERE, WITH THE GEFS MEMBERS EXTENDING
INTO THE HIGH PLAINS OF SOUTH DAKOTA/NEBRASKA, AND INTO PARTS OF
ARIZONA/NEW MEXICO, WHILE SREF ARW CORE MEMBERS ARE HEAVIEST
ACROSS THE COLORADO ROCKIES.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

JAMES

$$





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