Quantitative Precipitation Forecast
Issued by NWS

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438
FOUS11 KWBC 222014
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
413 PM EDT SAT APR 22 2017

VALID 00Z SUN APR 23 2017 - 00Z WED APR 26 2017

...NORTHERN NORTH DAKOTA/MINNESOTA...

A RELATIVELY NARROW BAND OF SNOW IS EXPECTED TONIGHT INTO SUN FROM
PORTIONS OF NORTHERN ND TO MN, IN AN AREA OF RELATIVELY STRONG
FRONTOGENETIC FORCING NORTH OF A COLD FRONT WHICH IS SWEEPING
SOUTH ACROSS THE REGION TODAY. THE FRONTAL BOUNDARY IS FORECAST TO
BECOME STATIONARY FROM SD INTO SOUTHERN MN ON SUN, POTENTIALLY
KEEPING PRECIP IN PLACE FARTHER NORTH THROUGH THE DAY. THERMAL
PROFILES IN THIS BAND OF HEAVIER PRECIP WILL BE MARGINAL FOR SNOW
ACCUMULATION INITIALLY, BUT AS FORCING INCREASES ALONG WITH
SNOWFALL RATES OVERNIGHT, EXPECT BOUNDARY LAYER TEMPS TO DROP TO
NEAR FREEZING. BEST PERIOD FOR ACCUMULATING SNOWS APPEARS TO BE
BETWEEN 06-12Z SUN MORNING, WHEN THE BEST VERTICAL VELOCITIES ARE
CENTERED IN THE DENDRITIC GROWN ZONE. THE BEST POTENTIAL FOR 4+
INCH SNOWFALL TOTALS APPEARS TO BE ACROSS PORTIONS OF EASTERN ND,
WHERE THE BEST COMBINATION OF SNOWFALL RATES AND COOLING BL TEMPS
APPEARS LIKELY. WPC PROBABILITIES FOR DAY 1 (00Z SUN-00Z MON) SHOW
A SLIGHT RISK OF EXCEEDING 4 INCHES OF SNOW ACROSS THIS AREA.

SUN NIGHT INTO MON MORNING, A WAVE OF LOW PRESSURE IS FORECAST TO
DEVELOP ALONG THE FRONT ACROSS THE NORTHERN PLAINS AS A
MID/UPPER-LEVEL SHORTWAVE MOVES FROM THE NORTHERN ROCKIES INTO THE
NORTHERN PLAINS. THE SURFACE LOW IS THEN FORECAST TO MOVE EAST
INTO THE UPPER MIDWEST MON AFTERNOON/EVENING. NORTH OF THIS
SURFACE LOW, AN ADDITIONAL AREA OF FRONTOGENETICALLY FORCED
PRECIPITATION IS EXPECTED TO DEVELOP ACROSS THE UPPER MIDWEST ON
MON. SUBSTANTIAL LOW-LEVEL WARM ADVECTION IS EXPECTED TO MODERATE
TEMPERATURES ACROSS THE UPPER MIDWEST BY THIS TIME, AND THERMAL
PROFILES LOOK VERY MARGINAL FOR SNOW FOR ALL AREAS EXCEPT RIGHT
ALONG THE CANADIAN BORDER IN ND/MN. A STRONG SURFACE HIGH CENTERED
TO THE NORTH OVER CANADA WILL KEEP LOW-LEVEL COLD AIR IN PLACE FOR
THESE AREAS, AND SOME RELATIVELY LIGHT SNOW ACCUMULATIONS ARE
EXPECTED. WPC PROBABILITIES ON DAY 2 (00Z MON-00Z TUE) SHOW A
SLIGHT TO MODERATE RISK OF EXCEEDING 4 INCHES OF SNOW ACROSS
PORTIONS OF EXTREME NORTHEASTERN ND AND EXTREME NORTHERN MN. THE
HEAVIEST SNOWS ON DAY 2 ARE EXPECTED TO REMAIN FARTHER NORTH,
ACROSS SOUTHWESTERN ONTARIO.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

...PACIFIC NORTHWEST/NORTHERN AND CENTRAL ROCKIES...

A SERIES OF MID/UPPER-LEVEL SHORTWAVES WILL AFFECT THE NORTHWEST
AND NORTHERN ROCKIES OVER THE NEXT FEW DAYS, WITH HEIGHTS ACROSS
THE REGION LOWERING A BIT WITH EACH ONE AS A BROADER UPPER-LEVEL
TROUGH GRADUALLY DIGS ACROSS THE WEST. A SHORTWAVE ARRIVING ON MON
WILL FINALLY LOWER HEIGHTS AND SNOW-LEVELS ENOUGH THAT LIGHT TO
MODERATE SNOW ACCUMULATIONS WILL BE POSSIBLE ON DAY 2 ACROSS THE
CASCADES AND THE NORTHERN INTERMOUNTAIN WEST/NORTHERN ROCKIES,
WHERE WPC PROBABILITIES SHOW A SLIGHT TO MODERATE RISK OF
EXCEEDING 4 INCHES OF SNOW. BY DAY 3 (00Z TUE-00Z WED) AS
ADDITIONAL SHORTWAVE ENERGY CONTINUES TO AMPLIFY THE TROUGH OVER
THE WEST, MODERATE TO HEAVY SNOWS ARE EXPECTED FOR PORTIONS OF THE
NORTHERN ROCKIES. WPC PROBABILITIES FOR DAY 3 SHOW A MODERATE TO
HIGH RISK OF EXCEEDING 4 INCHES OF SNOW FOR PORTIONS OF THE
NORTHERN ROCKIES, WITH A SLIGHT TO MODERATE RISK OF EXCEEDING 8
INCHES.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

RYAN

$$





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