Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 120811
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
411 AM EDT SUN APR 12 2015

VALID 12Z SUN APR 12 2015 - 12Z WED APR 15 2015


DAYS 2 THROUGH 3...


...PACIFIC NORTHWEST/NORTHERN ROCKIES...

A DEEPENING UPPER TROUGH WILL AGAIN APPROACH THE PACIFIC NORTHWEST
COAST LATE MONDAY AND MONDAY NIGHT WITH A RAPID INFLUX OF PACIFIC
MOISTURE AND SHARPLY DROPPING SNOW LEVELS ACROSS WASHINGTON/OREGON
AND NORTHERN CALIFORNIA ON MONDAY NIGHT INTO TUESDAY MORNING. A
BURST OF PRECIPITATION IS EXPECTED WITHIN THE FIRST SEVERAL HOURS
OF FRONTAL PASSAGE WITH MORE SHOWERY PRECIPITATION FOLLOWING.  BY
TUESDAY MORNING/DAY 2...SNOWFALL LEVELS COULD FALL AS LOW AS 2500
FEET WITH THE MOST SIGNIFICANT SNOWFALL ACCUMULATIONS ACROSS THE
OLYMPICS/THE WASHINGTON AND OREGON CASCADES AND EVEN ACROSS THE
BLUE MOUNTAINS IN NORTHEAST OREGON...WHERE MOST OF THE SIGNIFICANT
SNOWFALL WILL BE IN THE 4 TO 8 INCH RANGE...WITH THE HIGHEST
AMOUNTS LIKELY ACROSS THE OLYMPICS AND NORTHERN WASHINGTON
CASCADES...WHERE 8 OR MORE INCHES ARE POSSIBLE.

AS THE RATHER DEEP UPPER TROUGH MOVES EASTWARD FROM THE COAST TO
THE NORTHERN ROCKIES/GREAT BASIN ON TUESDAY INTO EARLY
WEDNESDAY/DAY 3...SNOW WILL DIMINISH ACROSS THE HIGH ELEVATIONS OF
WASHINGTON AND OREGON BUT WILL BECOME MORE WIDESPREAD OVER THE
NORTHERN ROCKIES AND GREAT BASIN...ESPECIALLY ACROSS THE MOUNTAINS
OF CENTRAL AND EASTERN IDAHO/WESTERN MONTANA AND NORTHERN AND
NORTHWEST WYOMING.  AGAIN...THERE IS AT LEAST A LOW TO MODERATE
PROBABILITY OF AT LEAST 4 INCHES OF NOW IN SOME OF THESE AREAS. A
MULTI MODEL BLEND WAS USED FOR THE QPF AMOUNTS AND TEMPERATURE
PROFILES WITH CONSIDERABLE FINE TUNING FOR PROVIDING DETAILS IN
THE MOUNTAINOUS WEST.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

KOCIN

$$




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