Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 210855
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
454 AM EDT TUE MAR 21 2017

VALID 12Z TUE MAR 21 2017 - 12Z FRI MAR 24 2017

...WESTERN U.S....

GUIDANCE SHOWS A SPLIT FLOW PATTERN EVOLVING ACROSS THE WESTERN
U.S. THIS PERIOD...WITH AN AMPLIFYING SOUTHERN STREAM TROUGH
MOVING ACROSS CA LATE WED INTO EARLY THU.  AS THE TROUGH CONTINUES
FURTHER EAST...GUIDANCE SHOWS A MID-UPPER LEVEL CENTER CLOSING OFF
OVER THE GREAT BASIN THU MORNING SPINNING INTO THE CENTRAL
ROCKIES/HIGH PLAINS LATE THU-EARLY FRI.

THE GREATEST THREAT FOR HEAVY SNOW ON DAY 1 (ENDING 12 UTC WED) IS
EXPECTED TO CENTER ALONG THE SIERRA WHERE DEEP SOUTHWESTERLY
INFLOW ORTHOGONAL TO THE TERRAIN ALONG WITH FAVORABLE UPPER
FORCING IS EXPECTED TO SUPPORT MODERATE TO HEAVY PRECIPITATION.
SNOW LEVELS AT THE ONSET WILL BE HIGH BUT ARE EXPECTED TO FALL AS
THE ASSOCIATED COLD FRONT PUSHES THROUGH THE REGION ON TUE.
ACCUMULATIONS OF A FOOT OR MORE ARE POSSIBLE...ESPECIALLY IN AREAS
ABOVE 7000 FT.

FOR DAY 2 (ENDING 12 UTC THU)...POST-FRONTAL ONSHORE FLOW WILL
CONTINUE TO SUPPORT SNOW SHOWERS ALONG THE SIERRA...HOWEVER THE
THREAT FOR WIDESPREAD HEAVY AMOUNTS IS EXPECTED TO DIMINISH.
SNOWS WILL TRANSITION FURTHER EAST INTO THE GREAT BASIN AND
CENTRAL ROCKIES.  WPC PROBABILISTIC GUIDANCE SHOWS LOW
PROBABILITIES FOR HEAVIER ACCUMULATIONS ACROSS THE CENTRAL NV
MOUNTAINS TO THE WASATCH AND UINTAS OF UT...WHERE LOW TO MID LEVEL
FRONTOGENESIS ALONG WITH FAVORABLE UPPER FORCING MAY SUPPORT
ORGANIZED SNOWS.  HOWEVER...LIMITED MOISTURE IS EXPECTED TO HAMPER
THE THREAT FOR MORE WIDESPREAD HEAVIER AMOUNTS.

SNOWS WILL SHIFT FURTHER EAST INTO THE CO ROCKIES...WITH HEAVY
SNOWS BECOMING LIKELY ALONG THE FRONT RANGE THU NIGHT-FRI MORNING
AS A LOW SPINS UP RAPIDLY IN THE LEE OF THE ROCKIES.  STRONG
NORTHEASTERLY-EASTERLY LOW LEVEL FLOW NORTH OF THE CENTER ALONG
WITH STRONG MID-UPPER LEVEL FORCING WILL SUPPORT THE GROWING
THREAT FOR HEAVY ACCUMULATIONS OF A FOOT OR MORE ALONG THE CO
FRONT RANGE ON DAY 3 (ENDING 12 UTC FRI).

THE PROBABILITY OF ICE ACCUMULATIONS OF 0.25 INCH OR MORE IS LESS
THAN 10 PERCENT.

...NORTHERN NEW ENGLAND...

A BROAD UPPER TROUGH IS EXPECTED TO MOVE EAST FROM CENTRAL CANADA
AND THE UPPER MIDWEST THIS PERIOD.  A SHORTWAVE MOVING THROUGH THE
BASE OF THE BROADER SCALE TROUGH IS EXPECTED TO AMPLIFY AS IT
MOVES ACROSS THE NORTHEAST WED MORNING.  SURFACE LOW PRESSURE
MOVING OUT OF SOUTHERN QUEBEC IS EXPECTED TO STRENGTHEN AS IT
TRACKS ACROSS THE NORTHERN GULF OF MAINE/BAY OF FUNDY INTO THE
CANADIAN MARITIMES.  THIS IS EXPECTED TO SPREAD SOME LIGHT TO
MODERATE SNOWS ACROSS EASTERN MAINE...PRODUCING A SLIGHT CHANCE
FOR ACCUMULATIONS OF 4-INCHES OR MORE DURING THE DAY 2 PERIOD
(ENDING 12 UTC THU).

THE PROBABILITY OF ICE ACCUMULATIONS OF 0.25 INCH OR MORE IS LESS
THAN 10 PERCENT.

PEREIRA

$$





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