289  
FXUS02 KWBC 050723  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
221 AM EST MON MAR 5 2018  
 
VALID 12Z THU MAR 8 2018 - 12Z MON MAR 12 2018  
   
..OVERVIEW
 
 
ANOTHER NOR'EASTER WILL PARALLEL THE NEW ENGLAND COAST WED/THU AND  
DELIVER A SWATH OF SIGNIFICANT SNOW ACROSS AT LEAST THE INTERIOR  
OF THE NORTHEAST AND NORTHERN MID-ATLANTIC. IN THE WEST, AN UPPER  
LOW AND ASSOCIATED SURFACE FRONT WILL PUSH ACROSS THE PACIFIC  
NORTHWEST THURSDAY AND THROUGH THE INTERIOR WEST AND ROCKIES ON  
FRIDAY. THIS WILL REDEVELOP IN THE SOUTHERN PLAINS ON SATURDAY AND  
MOVE THROUGH THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST NEXT  
SUNDAY.  
 
   
..GUIDANCE AND PREDICTABILITY ASSESSMENT
 
 
THE LATEST DETERMINISTIC GUIDANCE OFFERS GOOD CLUSTERING WITH THE  
NOR'EASTER OFF THE NEW ENGLAND COAST WEDNESDAY NIGHT AND INTO  
THURSDAY MORNING WITH A POSITION JUST EAST OF CAPE COD BY 12Z  
THURSDAY. THE MODELS ARE BEGINNING TO COME INTO BETTER FOCUS WITH  
THE UPPER LEVEL PATTERN OVER SOUTHEAST CANADA, SUGGESTING TWO  
SEPARATE UPPER LOWS EMBEDDED WITH A BROADER GYRE. THE UPPER LOW  
OVER THE GREAT LAKES ON THURSDAY IS EXPECTED TO RESULT IN A NEW  
SURFACE LOW DEVELOPING WELL OFFSHORE BY FRIDAY MORNING. ALTHOUGH  
THE 12Z CMC WAS DISPLACED TOO FAR EAST WITH THE NOR'EASTER, THE  
NEW 00Z CMC IS NOW MUCH BETTER ALIGNED WITH THE MODEL CONSENSUS,  
AND A BLEND OF THE DETERMINISTIC GUIDANCE WAS USED FOR THE  
PREFERRED TRACK OF THE STORM. FOR THE WESTERN U.S., THE 00Z  
MODELS BRING A SHORTWAVE INLAND OVER THE PACIFIC NORTHWEST  
FOLLOWED BY LOW AMPLITUDE RIDGING. BY THE WEEKEND, ENSEMBLES SHOW  
THAT TROUGH DIVING SOUTHEAST ACROSS THE PLAINS AND THEN THE LOWER  
MS VALLEY WITH DIFFERENCES ON TIMING, WITH THE ENSEMBLE MEANS  
BEING USED FOR PLACEMENT.  
 
   
..WEATHER HIGHLIGHTS
 
 
THE NORTHEAST QUADRANT OF THE NATION IS EXPECTED TO HAVE THE  
GREATEST WEATHER IMPACTS FOR THE END OF THIS WEEK AS THE  
DEVELOPING NOR'EASTER BRINGS A MULTITUDE OF HAZARDS TO THE REGION.  
MODEL GUIDANCE IS INDICATING 985-990MB PRESSURES WITH THE LOW  
CENTER WITH A TRACK CLOSE ENOUGH TO MERIT CONCERN. STRONG ONSHORE  
FLOW NORTH OF THE LOW WILL INCREASE THE THREAT OF COASTAL FLOODING  
FOR THE NORTHEAST COAST, AND MODERATE TO LOCALLY HEAVY SNOW IS  
LIKELY FOR INTERIOR PORTIONS OF NEW YORK AND NEW ENGLAND,  
ESPECIALLY FOR THE HIGHER ELEVATIONS. MIXED PRECIPITATION IS  
LIKELY CLOSER TO THE INTERSTATE 95 CORRIDOR.  
 
PRECIPITATION MAKES A RETURN TO THE WEST COAST BY THE END OF THE  
WEEK. DESPITE LINGERING MODEL DIFFERENCES FOR THE WEST COAST  
REGION IN TERMS OF MASS FIELDS, SHOWERS AND MOUNTAIN SNOW ARE  
EXPECTED FROM CENTRAL CALIFORNIA TO WASHINGTON STATE, AND LIGHTER  
QPF EXPECTED TO REACH THE NORTHERN ROCKIES. THE HEAVIEST SNOW IS  
LIKELY FOR THE NORTHERN SIERRA AND THE CASCADES. BY THE END OF  
THE FORECAST PERIOD NEXT WEEKEND, A DEVELOPING LOW PRESSURE SYSTEM  
OVER THE CENTRAL PLAINS IS EXPECTED TO INCREASE MOISTURE RETURN  
FROM THE GULF OF MEXICO AND ENHANCE RAINFALL CHANCES FROM THE  
CENTRAL GULF COAST TO THE MIDWEST. THERE MAY BE SOME AREAS OF  
ENHANCED RAINFALL AND ORGANIZED THUNDERSTORM ACTIVITY ACROSS  
PORTIONS OF THE SOUTHEAST U.S. OVER THE WEEKEND.  
 
TEMPERATURES ARE EXPECTED TO BE BELOW NORMAL BY EARLY MARCH  
STANDARDS ACROSS MUCH OF THE CENTRAL AND EASTERN U.S. FOR THE END  
OF THE WEEK, WITH THE GREATEST TEMPERATURE ANOMALIES FOR THE  
NORTHERN PLAINS ON THURSDAY WITH THE CANADIAN SURFACE HIGH IN  
PLACE. ABOVE NORMAL READINGS ARE LIKELY OVER THE SOUTH-CENTRAL  
U.S. GOING INTO THE WEEKEND WITH WIDESPREAD HIGHS IN THE 70S TO  
MIDDLE 80S FOR THE DESERT SOUTHWEST AND MUCH OF TEXAS.  
 
D. HAMRICK  
 

 
 
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