085  
FOUS11 KWBC 010703  
QPFHSD  
 
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
303 AM EDT THU MAY 1 2025  
 
VALID 12Z THU MAY 01 2025 - 12Z SUN MAY 04 2025  
 
   
..SIERRA NEVADA
 
 
DAY 3...  
 
A POTENT CLOSED LOW WILL DIG ALONG THE CA COAST SATURDAY INTO  
SUNDAY, WITH RAPID AMPLIFICATION OF THIS FEATURE EXPECTED BY SUNDAY  
MORNING. THIS IS REFLECTED BY NAEFS HEIGHT ANOMALIES FALLING TO  
BELOW THE 1ST PERCENTILE WITH RESPECT TO 700-500MB HEIGHTS OVER  
SOUTHERN CA BY 12Z SUNDAY. ALTHOUGH THE ACCOMPANYING JET STREAK  
WILL INTENSIFY AS WELL AS IT PIVOTS AROUND THE UPSTREAM SIDE OF  
THIS TROUGH AND THROUGH THE BASE, THE OVERALL EVOLUTION WILL KEEP  
THE MOST INTENSE ASCENT DISPLACED SOUTH/EAST OF THE SIERRA, BUT  
SUFFICIENT LIFT AND INCREASING MOISTURE WILL STILL RESULT IN  
PERIODS OF SNOWFALL D3. SNOW LEVELS DURING THIS TIME WILL BEGIN  
AROUND 8000-9000 FT, SO ONLY THE HIGHER SIERRA PASSES WILL BEGIN AS  
SNOW, BUT AS THE UPPER LOW DIGS ACROSS CA, SNOW LEVELS ARE PROGGED  
TO FALL TO AS LOW AS 7000 FT, BRINGING AT LEAST SOME ACCUMULATIONS  
TO DONNER PASS AS WELL. OVERALL, SIGNIFICANT SNOWFALL ACCUMULATION  
WILL BE CONFINED TO ABOVE PASS LEVEL, WHERE WPC PROBABILITIES FOR  
MORE THAN 6 INCHES OF SNOW ARE AS HIGH AS 50%, BUT LIGHT SNOW DOWN  
TO MOST SIERRA PASS LEVELS IS ALSO LIKELY BEFORE PRECIP WINDS DOWN  
BY SUNDAY MORNING.  
 
THE PROBABILITY OF SIGNIFICANT FREEZING RAIN ACROSS THE CONUS IS  
LESS THAN 10%.  
 
WEISS  
 

 
 
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