291
FOUS11 KWBC 211935
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
335 PM EDT TUE APR 21 2026
VALID 00Z WED APR 22 2026 - 00Z SAT APR 25 2026
..CALIFORNIA
DAY 1...
THE MID-LEVEL CLOSED LOW CURRENTLY OFF OF THE CALIFORNIA/OREGON
COAST WILL MOVE INLAND TONIGHT THROUGH EARLY TOMORROW MORNING.
LARGE-SCALE ASCENT, SUPPORTED IN PART BY LEFT-EXIT REGION JET
DYNAMICS, IN COMBINATION WITH MOIST ONSHORE FLOW, WILL CONTRIBUTE
TO THE CONTINUATION OF HEAVY PRECIPITATION INTO THE EVENING, WITH
SNOW RATES OF 1-2"/HR ACROSS PARTS OF THE SIERRA NEVADA. SNOW
LEVELS WILL DROP THROUGH THE EVENING AND OVERNIGHT TO BELOW 5,000
FT. HOWEVER, PRECIPITATION RATES ARE EXPECTED TO DIMINISH AS THE
LOW MOVES ONSHORE, MOISTURE ADVECTION DECREASES, AND THE BETTER
FORCING TRANSLATES DOWNSTREAM. ACROSS CALIFORNIA, THE BULK OF THE
ADDITIONAL PRECIPITATION IS EXPECTED TO OCCUR BEFORE DAYBREAK,
BEFORE ENTIRELY DIMINISHING LATER IN THE DAY. AN ADDITIONAL 6-12
INCHES OF SNOW IS LIKELY FOR PARTS OF THE CENTRAL SIERRA NEVADA,
ESPECIALLY FOR AREAS ABOVE 6,000 FT, THIS INCLUDES BOTH THE I-80
AND U.S. 50 PASSES.
..INTERMOUNTAIN WEST TO THE NORTHERN HIGH PLAINS
DAYS 1-3...
AS THE PREVIOUSLY DESCRIBED SYSTEM MOVES INLAND, SNOW WILL DEVELOP
INITIALLY OVER THE HIGHER ELEVATIONS OF NEVADA AND THE EASTERN
OREGON MOUNTAINS TONIGHT, BEFORE REACHING INTO THE NORTHERN ROCKIES
BY EARLY TOMORROW. LEFT-EXIT REGION UPPER JET FORCING INTERACTING
WITH RESIDUAL MOISTURE WILL HELP TO FOCUS SOME OF THE HEAVIER
ACCUMULATIONS OVER THE OREGON BLUE MOUNTAINS TONIGHT AND THEN THE
CENTRAL TO NORTHERN IDAHO, WESTERN MONTANA, AND WESTERN WYOMING
RANGES BEGINNING LATE TOMORROW AND CONTINUING THROUGH THURSDAY.
SNOW LEVELS WHICH ARE EXPECTED TO START AS HIGH AS 9,000+ FT AROUND
THE ONSET OF PRECIPITATION ARE EXPECTED TO FALL STEADILY TO
4,000-5,000 FT ACROSS MOST LOCATION BY THURSDAY MORNING.
AS PERIODS OF LIGHT TO MODERATE SNOW CONTINUE FARTHER WEST, STRONG
UPWARD ASCENT AFFORDED BY A STRONG SHORTWAVE DIVING SOUTHEAST OUT
OF WESTERN CANADA AND UPSLOPE FLOW ON THE BACKSIDE OF ITS
ASSOCIATED LOW LEVEL CYCLONE WILL SUPPORT THE DEVELOPMENT OF HEAVY
SNOW OVER THE BIG HORNS. AS THE PRIMARY SURFACE LOW DEEPENS OVER
EASTERN MONTANA AND MOVES INTO CANADA, WRAP AROUND MOISTURE WILL
SPREAD ACROSS PORTIONS OF EASTERN MONTANA AND NORTH DAKOTA ON
THURSDAY. HOWEVER, GUIDANCE SUGGESTS THAT WARM BOUNDARY LAYER
CONDITIONS WILL LIMIT SNOW ACCUMULATIONS. IN CONTRAST TO PREVIOUS
RUNS, THE MODELS HAVE MOVED INTO BETTER ALIGNMENT WITH THE
EVOLUTION OF THIS SYSTEM, WITH THE GFS SHOWING ONE OF THE BIGGER
ADJUSTMENTS FROM ITS PREVIOUS RUN.
FOR MANY OF THE HIGHLIGHTED AREAS, PROBABILISTIC GUIDANCE INDICATES
THAT TOTAL ACCUMULATIONS OF 8-12 INCHES WILL BE COMMON, ESPECIALLY
FOR AREAS ABOVE 6,000 FT.
THE PROBABILITY FOR SIGNIFICANT FREEZING RAIN EXCEEDING 0.1 INCHES
ACROSS THE CONUS IS LESS THAN 10 PERCENT.
PEREIRA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page