Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 292007
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
406 PM EDT SAT APR 29 2017

VALID 00Z SUN APR 30 2017 - 00Z WED MAY 03 2017

...CENTRAL PLAINS TO THE UPPER MISSISSIPPI VALLEY...

THE LATE SEASON SNOW EVENT THAT BROUGHT OVER A FOOT OF SNOW TO THE
ROCKIES WILL IMPACT LOCATIONS FROM THE CENTRAL PLAINS TO UPPER
MISSISSIPPI VALLEY OVER THE NEXT FEW DAYS.

MODERATE TO HEAVY PRECIPITATION IS EXPECTED TO DEVELOP WITHIN A
STRENGTHENING  DEFORMATION ZONE AS AN ANOMALOUS UPPER LOW
CONTINUES TO EDGE EASTWARD OUT OF THE FOUR CORNERS REGION AND A
SURFACE LOW DEEPENS OVER THE SOUTHERN PLAINS SATURDAY EVENING.
ENOUGH COLD AIR ON THE BACK SIDE OF THE SYSTEM SHOULD SUPPORT LATE
SEASON SNOW WITHIN THE WESTERN/NORTHWESTERN EDGE OF THE EXPANDING
PRECIPITATION SHIELD...AND THE CHANCE FOR SNOW SHOULD CONTINUE
WHILE THE VERTICALLY STACKED SYSTEM LIFTS FROM THE CENTRAL PLAINS
TO THE UPPER MISSISSIPPI VALLEY SUNDAY INTO MONDAY.  THE GREATEST
THREAT FOR ANY ACCUMULATIONS SHOULD BE DURING THE OVERNIGHT
HOURS...MAINLY IMPACTING WESTERN KANSAS AND CENTRAL NEBRASKA
SATURDAY NIGHT AND THEN EASTERN SOUTH DAKOTA AND MINNESOTA ON
SUNDAY NIGHT.  HOWEVER...THERE IS SOME MODEL GUIDANCE THAT
SUGGESTS SNOWFALL RATES COULD BE HIGH ENOUGH OVERCOME DAYTIME
HEATING AND CAUSE PERIODS OF ACCUMULATING SNOW DURING THE DAYLIGHT
HOURS.  THE CHANCE FOR ACCUMULATING SNOW SHOULD BEGIN TO DIMINISH
ON TUESDAY WHILE THE CYCLONE EXITS INTO THE UPPER GREAT LAKES AND
CANADA.

EXCLUDING A SLOWER 12Z NAM...MODELS ARE SHOWING FAIRLY GOOD
CLUSTERING WITH THE EVOLUTION OF THE UPPER LOW AND ARE SHOWING
GOOD AGREEMENT WITH THE AXIS OF HEAVIEST SNOW...BUT THERE IS STILL
ENOUGH SPREAD WITH THERMAL PROFILES AT THE LOWER-LEVELS TO CREATE
A LARGE AMOUNT OF UNCERTAINTY WITH THE EXACT ACCUMULATIONS.  THE
LATEST WPC PROBABILISTIC GUIDANCE KEEPS THE HIGHEST PROBABILITIES
FOR ACCUMULATING SNOW IN AN AXIS EXTENDING FROM EASTERN COLORADO
AND WESTERN KANSAS INTO NEBRASKA...EASTERN SOUTH DAKOTA...AND
MINNESOTA...WITH A DAY 1 MODERATE RISK OF SNOWFALL EXCEEDING 8
INCHES OVER WESTERN KANSAS AND CENTRAL NEBRASKA AND A DAY 2
MODERATE RISK OF SNOWFALL EXCEEDING 4 INCHES OVER EASTERN SOUTH
DAKOTA AND MINNESOTA.


...NORTHERN ROCKIES...

SNOW IS EXPECTED WITH SHORTWAVE ENERGY DIGGING INTO THE NORTHERN
ROCKIES MONDAY NIGHT INTO TUESDAY.  HOWEVER...LIMITED MOISTURE
WITH THIS SYSTEM SHOULD KEEP ACCUMULATIONS LIGHT AND CONFINED TO
THE HIGHER ELEVATIONS...MAINLY OVER THE TETONS AND BIG HORN
MOUNTAINS OF WYOMING.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.


GERHARDT

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