809  
FOUS11 KWBC 250801  
QPFHSD  
 
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EST SUN FEB 25 2024  
 
VALID 12Z SUN FEB 25 2024 - 12Z WED FEB 28 2024  
 
 
...PACIFIC NORTHWEST AND CALIFORNIA TO THE NORTHERN AND CENTRAL  
ROCKIES...  
DAYS 1-3...  
 
A STRONG WINTER STORM AND COLD FRONT WILL BEGIN TO IMPACT THE  
NORTHWESTERN U.S. LATER TODAY, BEFORE PROGRESSING FURTHER  
SOUTHEAST MONDAY AND TUESDAY -- PRODUCING WIDESPREAD HEAVY  
MOUNTAIN SNOW AND DANGEROUS TRAVEL CONDITIONS ACROSS THE REGION.  
 
A DYNAMIC SHORTWAVE TROUGH, CURRENTLY POSITIONED OVER THE GULF OF  
ALASKA, IS FORECAST TO DIVE SOUTHEAST -- CARVING OUT AN AMPLIFIED  
TROUGH ACROSS BRITISH COLUMBIA INTO THE PACIFIC NORTHWEST LATER  
TODAY AND THROUGH THE OVERNIGHT. INCREASING ONSHORE FLOW AHEAD OF  
THE WAVE WILL SUPPORT HEAVY SNOW DEVELOPING INITIALLY OVER THE  
OLYMPICS, NORTHERN CASCADES, AND THE NORTHERN ROCKIES, BEFORE  
SPREADING SOUTH ALONG WITH A SHARP COLD FRONT THAT WILL BEGIN TO  
PLUNGE SOUTHEAST ACROSS THE NORTHWEST BY THIS EVENING. SNOW IS  
EXPECTED TO QUICKLY ACCUMULATE, WITH GUIDANCE CONTINUING TO SHOW  
SNOWFALL RATES OF 1-2 IN/HR DEVELOPING OVER THE NORTHERN CASCADES,  
AND PORTIONS OF THE NORTHERN IDAHO AND THE NORTHWESTERN MONTANA  
ROCKIES BY THE AFTERNOON, WITH THESE RATES CONTINUING AS THE SNOW  
EDGES SOUTH DURING THE EVENING AND OVERNIGHT HOURS. BY EARLY  
MONDAY, WPC PWPF CONTINUES TO INDICATE THAT ACCUMULATIONS OF A  
FOOT OR MORE WILL BE COMMON ACROSS THE NORTHERN CASCADES AND THE  
NORTHERN IDAHO AND NORTHWESTERN MONTANA RANGES -- LIKELY IMPACTING  
TRAVEL AS SNOW LEVELS DROP BELOW PASS LEVEL.  
 
THE UPPER TROUGH WILL CONTINUE TO AMPLIFY AND DIG SOUTHEAST --  
PUSHING ITS ASSOCIATED COLD FRONT INTO NORTHERN CALIFORNIA, THE  
GREAT BASIN, AND THE CENTRAL ROCKIES BY LATE MONDAY. THIS WILL  
BRING AREAS OF SNOW THROUGH THE OREGON CASCADES AND INTO THE  
SIERRA NEVADA, AS WELL AS ACROSS THE REMAINDER OF THE NORTHERN AND  
INTO CENTRAL ROCKIES. WPC PWPF SHOWS THAT WIDESPREAD SNOW  
ACCUMULATIONS OF 6 INCHES OR MORE ARE LIKELY ACROSS THESE AREAS ON  
MONDAY INTO EARLY TUESDAY. SUPPORTED BY STRONG ONSHORE FLOW AND  
FAVORABLE UPPER FORCING, PORTIONS OF THE OREGON CASCADES ARE  
LIKELY TO SEE OVER A FOOT OF SNOW DURING THIS PERIOD. THE WPC  
PWPF ALSO INDICATES THAT AMOUNTS OF A FOOT MORE ARE ALSO LIKELY  
ALONG THE TETONS, AS RIGHT-ENTRANCE UPPER JET FORCING HELPS TO  
INCREASE ASCENT ACROSS WESTERN WYOMING LATE MONDAY.  
 
AS IT PLUNGES SOUTHEAST ACROSS THE REGION, SNOW SQUALLS ARE LIKELY  
ALONG THE PATH OF THE COLD FRONT, ESPECIALLY OVER THE NORTHERN  
GREAT BASIN AND ROCKIES ON MONDAY. BRIEF, BUT INTENSE SNOWFALL,  
ALONG WITH STRONG GUSTY WINDS MAY RAPIDLY REDUCE VISIBILITY AND  
CONTRIBUTE TO DANGEROUS TRAVEL CONDITIONS.  
 
WHILE AMOUNTS WILL BE LESS THAN THE PREVIOUS DAY, PERSISTENT  
ONSHORE FLOW, ALONG WITH TRAILING ENERGY DROPPING INTO THE BASE OF  
THE BROADER SCALE TROUGH, WILL SUPPORT ADDITIONAL SNOWFALL FROM  
WESTERN WASHINGTON STATE TO THE NORTHERN ROCKIES. SNOW LEVELS,  
WHICH ARE ALREADY EXPECTED TO BE BELOW 500 FT ACROSS MUCH OF THE  
REGION EARLY MONDAY, WILL DIP EVEN FURTHER, BRINGING THE POTENTIAL  
FOR ACCUMULATING SNOW TO THE COAST AND ONTO THE VALLEY FLOORS FROM  
WASHINGTON STATE THROUGH THE INTERMOUNTAIN WEST MONDAY INTO  
TUESDAY.  
 
ON TUESDAY, DRIER CONDITIONS WILL SPREAD FROM WEST TO EAST ACROSS  
CALIFORNIA AND THE GREAT BASIN AS THE UPPER TROUGH BEGINS TO PIVOT  
EAST AND IS FOLLOWED BY A SHORTWAVE RIDGE THAT WILL MOVE ACROSS  
THE WEST BEGINNING LATE IN THE DAY. HOWEVER, HEAVY SNOW WILL  
CONTINUE INTO LATE TUESDAY FOR PORTIONS THE CENTRAL ROCKIES.  
ADDITIONAL ACCUMULATIONS OF 8 INCHES OR MORE ARE LIKELY FOR MANY  
OF THE WESTERN COLORADO RANGES AND INTO FAR NORTH-CENTRAL NEW  
MEXICO ALONG THE SAN JUANS BEFORE ENDING WEDNESDAY MORNING.  
 
BY EARLY WEDNESDAY, THE RIDGE IN THE NORTHWEST WILL BEGIN TO GIVE  
WAY TO THE NEXT APPROACHING UPPER TROUGH, WITH WARM ADVECTION  
PRECIPITATION AND THE THREAT FOR HEAVY SNOW RETURNING TO THE  
OLYMPICS AND THE NORTHERN CASCADES. ALTHOUGH SNOW LEVELS WILL BE  
RISING ACROSS WESTERN WASHINGTON, THE CASCADE PASSES ARE LIKELY TO  
BE IMPACTED BY SEVERAL MORE INCHES OF SNOW LATE TUESDAY INTO  
WEDNESDAY.  
   
..NORTHERN PLAINS TO THE NORTHERN GREAT LAKES
 
 
DAYS 2-3...  
ON MONDAY, LIGHT SNOW WILL SPREAD EAST OF THE ROCKIES, WITH A BAND  
OF POTENTIALLY HEAVIER SNOW SETTING UP ACROSS EASTERN NORTH DAKOTA  
INTO NORTHERN MINNESOTA MONDAY NIGHT INTO TUESDAY. WHILE THE  
GENERAL MODEL CONSENSUS DOES NOT INDICATE WIDESPREAD HEAVY AMOUNTS  
AT THIS POINT, THERE IS GOOD SIGNAL FOR A POTENTIAL NARROW BAND OF  
HEAVY SNOW, SUPPORTED BY AN UPPER JET COUPLET AND LOW LEVEL  
FRONTOGENESIS, SETTING UP ACROSS THE REGION.  
 
THIS INITIAL BAND IS EXPECTED TO BE FOLLOWED BY A SECOND BAND,  
SETTING UP A LITTLE FURTHER TO THE EAST ACROSS NORTHERN WISCONSIN  
AND THE U.P. OF MICHIGAN AS A SECONDARY WAVE DEVELOPING ALONG THE  
TRAILING COLD FRONT, BECOMES THE PRIMARY LOW AND LIFTS ACROSS THE  
REGION TUESDAY NIGHT. WPC PWPF SHOWS HIGH PROBABILITIES FOR  
ACCUMULATIONS OF 4 INCHES OR MORE EXTENDING FROM NORTHWESTERN  
WISCONSIN INTO THE WESTERN U.P.  
 
PEREIRA  
 
*** KEY MESSAGES FOR SIGNIFICANT WESTERN U.S. STORM ***  
 
--A STRONG WINTER STORM AND COLD FRONT WILL MOVE INTO THE  
NORTHWEST LATER TODAY AND PROGRESS SOUTHEASTWARD ON MONDAY INTO  
THE NORTHERN ROCKIES.  
 
--HEAVY MOUNTAIN SNOW OVER THE CASCADES WILL IMPACT THE PASSES BY  
LATE TONIGHT, WHERE THERE IS >80% CHANCE OF AT LEAST A FOOT OF  
SNOW ABOVE 1500 FT THROUGH EARLY TUESDAY.  
 
--SNOWFALL WILL BECOME HEAVY AT TIMES WITH RATES OF 1-2"/HR ALONG  
WITH STRONG WINDS, CREATING AREAS OF BLOWING AND DRIFTING SNOW AS  
WELL AS SIGNIFICANTLY REDUCED VISIBILITY.  
 
--SNOW SQUALLS ARE LIKELY ALONG THE PATH OF THE COLD FRONT ON  
MONDAY OVER THE NORTHERN GREAT BASIN/ROCKIES, WHICH COULD CREATE A  
RAPID DROP IN VISIBILITY AND A FLASH FREEZE ON ROADS LEADING TO  
DANGEROUS TRAVEL.  
 
--MUCH COLDER AIR BEHIND THE STRONG COLD FRONT WILL DROP  
TEMPERATURES INTO THE TEENS AND COLDER BY TUESDAY MORNING.  
 

 
 
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