135  
FOUS11 KWBC 232051  
QPFHSD  
 
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
451 PM EDT THU MAR 23 2017  
 
VALID 00Z FRI MAR 24 2017 - 00Z MON MAR 27 2017  
 
 
DAYS 1 THROUGH 3...  
   
..WESTERN U.S.
 
 
HIGHER ELEVATIONS FROM THE WEST COAST TO THE ROCKIES WILL CONTINUE  
TO SEE A CHANCE FOR SNOW LATE THIS WEEK AND THROUGH THE WEEKEND AS  
MULTIPLE SYSTEMS PROGRESS INLAND OVER THE WESTERN U.S..  
 
THE INITIAL THREAT FOR HEAVY SNOW WILL BE WITH AN UPPER TROUGH  
EXPECTED TO EDGE EASTWARD THROUGH THE FOUR CORNERS REGION BEFORE  
CLOSING OFF NEAR SOUTHEAST COLORADO THURSDAY NIGHT. AN AXIS OF  
MID-LEVEL FRONTOGENETIC FORCING AND POSITIVE PRECIPITABLE WATER  
ANOMALIES EXTENDING FROM UTAH INTO CENTRAL WYOMING THURSDAY  
EVENING SHOULD TRANSITION EASTWARD THURSDAY NIGHT...SHIFTING THE  
FOCUS FOR HEAVY SNOW TO THE FRONT RANGE OF THE COLORADO ROCKIES BY  
EARLY FRIDAY...ESPECIALLY AS WINDS STRENGTHEN AROUND A SURFACE LOW  
DEEPENING IN THE LEE OF THE COLORADO ROCKIES AND UPSLOPE FLOW  
INCREASES ACROSS THE REGION. THE CLOSED MID-LEVEL ENERGY AND  
ASSOCIATED SURFACE LOW SHOULD EJECT OUT INTO THE CENTRAL PLAINS ON  
FRIDAY...AND...EXCLUDING THE NAM...THE MAJORITY OF MODEL THERMAL  
PROFILES SUGGESTS CONDITIONS WILL NOT BE ABLE TO COOL OFF ENOUGH  
TO SUPPORT MUCH ACCUMULATING SNOW WITHIN THE DEVELOPING  
DEFORMATION BAND.  
 
UPSTREAM...SNOW WILL BE POSSIBLE WITH A LONGWAVE TROUGH AND  
ASSOCIATED COLD FRONT EXPECTED TO MOVE INLAND OVER THE PACIFIC  
NORTHWEST AND NORTHERN CALIFORNIA THURSDAY NIGHT INTO FRIDAY AND  
THEN DROP SOUTHEASTWARD TO THE NORTHERN ROCKIES...CENTRAL GREAT  
BASIN...AND CENTRAL CALIFORNIA FRIDAY NIGHT. IN  
GENERAL...PRECIPITATION SHOULD BE RELATIVELY LIGHT TO MODERATE  
COMPARED TO THE INITIAL SYSTEM CLOSING OFF OVER THE CENTRAL  
ROCKIES. HOWEVER...MOIST ONSHORE FLOW AHEAD OF THE UPPER TROUGH  
COULD STILL SUPPORT PERIODS OF HEAVY SNOW OVER THE WINDWARD  
TERRAIN OF THE OLYMPICS...CASCADES...SISKIYOUS OF NORTHERN  
CALIFORNIA...AND ESPECIALLY SIERRA NEVADA RANGE.  
 
FINALLY...JUST AS THE AFOREMENTIONED COLD FRONT PRESSES EASTWARD  
THROUGH THE CENTRAL ROCKIES SATURDAY NIGHT INTO SUNDAY...THE NEXT  
UPPER TROUGH APPROACHING THE WESTERN U.S. COULD BRING ADDITIONAL  
SNOW TO THE CASCADES AND HIGHER ELEVATIONS OF NORTHERN CALIFORNIA  
BY THE END OF THE FORECAST PERIOD (00Z MONDAY).  
 
   
..UPPER GREAT LAKES TO THE NORTHEAST
 
 
AREAS OF SNOW...SLEET...AND FREEZING RAIN WILL BE POSSIBLE WITHIN  
THE NORTHERN EDGE OF PRECIPITATION DEVELOPING TO THE NORTH OF A  
FRONTAL BOUNDARY EXPECTED TO STRETCH FROM THE UPPER GREAT LAKES TO  
THE NORTHEAST FRIDAY THROUGH SUNDAY...WITH RETREATING HIGH  
PRESSURE OVER THE EASTERN U.S. AND AN ARCTIC AIRMASS SLIDING  
SOUTHEASTWARD OUT OF CANADA INTO THE GREAT LAKES AND NORTHEAST  
THIS WEEKEND SUPPLYING THE LOW-LEVEL COLD AIR. FOR NOW...WPC  
WINTER WEATHER PROBABILITIES KEEP ANY SLIGHT RISK (AT LEAST 10%  
PROBABILITY) OF SNOWFALL EXCEEDING 4" OR ICE ACCUMULATIONS  
EXCEEDING 0.25" CONFINED TO THE ADIRONDACKS IN NEW YORK.  
 
GERHARDT  
 

 
 
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