054  
FXUS02 KWBC 271536  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1036 AM EST SAT JAN 27 2018  
 
VALID 12Z TUE JAN 30 2018 - 12Z SAT FEB 03 2018  
   
..POTENTIAL WINTRY WEATHER IN THE EAST LATER NEXT WEEK
 
 
   
..OVERVIEW AND GUIDANCE PREFERENCES
 
 
PROGRESSIVE QUASI-ZONAL FLOW WILL TREND TOWARD BUILDING HEIGHTS  
WEST OF THE WEST COAST AND BROAD TROUGHING OVER MUCH OF THE LOWER  
48 FROM THURSDAY INTO NEXT WEEKEND. THIS WILL BRING IN COLDER AIR  
FOR MOST OF THE CONUS EAST OF THE ROCKIES STARTING ON THURSDAY. IN  
ADDITION, A FRONTAL SYSTEM WILL SPREAD SOME RAIN OVER THE EAST  
WITH SNOW ON ITS NORTHERN SIDE. THE LATEST GFS/ECMWF/CANADIAN RUNS  
OFFERED GOOD CLUSTERING THROUGH THE FORECAST (AND UKMET FOR  
TUE/WED) TO USE AS A BLENDED STARTING POINT, WITH INCREASED  
ENSEMBLE MEAN WEIGHTING BY NEXT FRI/SAT TO ACCOUNT FOR FRONTAL  
TIMING/STRENGTH DIFFERENCES IN THE EAST.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
PESKY SYSTEM JUST OFF THE NORTHEAST COAST WILL EXIT INTO THE  
CANADIAN MARITIMES ON TUESDAY WITH A LINGERING SNOW THREAT FOR  
EASTERN NEW ENGLAND. MOST OF THE AFFECTS OF THIS STORM LIE IN THE  
SHORT RANGE - PLEASE CONSULT OTHER WPC PRODUCTS (E.G.  
PROBABILISTIC SNOWFALL GRAPHICS AND DISCUSSION) ON THIS SYSTEM AS  
IT SLIDES INTO THE SHORT TERM.  
 
MAIN FRONT OF INTEREST WILL PUSH OUT OF THE INTERIOR WEST/NORTHERN  
ROCKIES TUESDAY AND INTO THE GREAT LAKES WED/THU, DRAGGING ITS  
ATTENDANT COLD FRONT THROUGH THE PLAINS AND INTO THE LOWER MS/OH  
VALLEY. SFC LOW CENTER WILL TRACK THROUGH SOUTHERN CANADA WITH  
MOST OF THE PRECIPITATION TO START, BUT INCREASED GULF MOISTURE  
WILL SUPPORT AN EXPANDED PRECIPITATION AREA ALONG/AHEAD OF THE  
COLD FRONT WED/THU INTO THE SOUTHEAST. MODELS HAVE THEN BEEN  
SHOWING VARYING DEGREES OF SFC WAVE DEVELOPMENT OUT OF THE LOWER  
MS VALLEY NORTHEASTWARD THROUGH THE MID-ATLANTIC ON FRIDAY THEN  
INTO THE ATLANTIC ON SATURDAY JUST OFF THE NEW ENGLAND COAST. ALL  
OPTIONS REMAIN ON THE TABLE, THOUGH THE DETERMINISTIC RUNS MOSTLY  
SHOW A MORE SUPPRESSED WAVE WITH MINIMAL DEVELOPMENT OVER LAND.  
SINCE SUCH DEVELOPMENT IS SENSITIVE TO SMALLER SCALE FEATURES WITH  
LONG LEAD TIMES, ENSEMBLE TRENDS WILL BE MUCH MORE USEFUL FOR THE  
NEXT FEW DAYS THAN ANY GIVEN DETERMINISTIC RUN. ENOUGH COLD AIR  
SHOULD BE IN PLACE TO THE NORTH OF THE FRONT TO SUPPORT A SWATH OF  
SNOW PARALLEL TO THE SFC LOW TRACK (IF ONE DOES DEVELOP) OR AT  
LEAST PARALLEL TO THE UPPER TROUGH AXIS PROPAGATION.  
 
BY THE END OF THE PERIOD, ANOTHER PACIFIC SYSTEM MAY PUSH INTO  
WA/OR/ID WITH ANOTHER ROUND OF RAIN/SNOW. TEMPERATURES WILL REMAIN  
NEAR AVERAGE IN THE PAC NW BUT GENERALLY ABOVE AVERAGE OVER  
CA/NV/AZ/UT AS WELL AS AHEAD OF THE MAIN FRONT EARLY IN THE PERIOD  
OVER THE PLAINS THEN INTO THE NORTHEAST TUE-THU.  
 
FRACASSO  
 

 
 
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