202  
FXUS02 KWBC 081601  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1100 AM EST WED NOV 08 2017  
 
VALID 12Z SAT NOV 11 2017 - 12Z WED NOV 15 2017  
   
..PATTERN OVERVIEW/MODEL EVALUATION/UNCERTAINTIES/PREFERENCES
 
 
MODELS THIS MORNING CONTINUE TO AGREE WITH AN OVERALL ACTIVE AND  
PROGRESSIVE SYNOPTIC PATTERN ACROSS THE CONUS THROUGH NEXT  
WEDNESDAY. THE MEDIUM-RANGE PERIOD BEGINS WITH A COLD AIR  
MASS...COLDEST OF THE SEASON SO FAR...DOMINATING MUCH OF THE  
EASTERN U.S. IN THE MEAN TIME...THE NEXT SIGNIFICANT UPPER TROUGH  
WILL BE MOVING OFF THE ROCKIES INTO THE PLAINS. THERE ARE STILL  
NOTABLY DIFFERENCES AMONG MODELS REGARDING THE DEGREE OF PHASING  
BETWEEN THE NORTHERN STREAM ENERGY AND THE SOUTHERN STREAM. THE  
TREND THIS MORNING APPEARS TO EMPHASIZE THE SOUTHERN STREAM  
DEVELOPMENT AND DOWNPLAY THE NORTHERN STREAM. THIS HAS LED TO A  
WEAKER SURFACE LOW GRADUALLY DISSIPATING AS IT MOVES TOWARD THE  
GREAT LAKES ON MONDAY...WHICH IS MORE IN LINE WITH WHAT THE ECMWF  
HAS BEEN INDICATING. BY TUESDAY...THE SYSTEM SHOULD CONTINUE TO  
PUSH TOWARD THE EAST COAST WHILE THE FORMATION OF A COASTAL FRONT  
IS INDICATED BY ALL MODELS. THE MERGER OF THESE TWO FEATURES  
CONTINUE TO PRODUCE HIGH UNCERTAINTY REGARDING THE POSSIBILITY OF  
CYCLOGENESIS JUST OFF THE EAST COAST NEXT TUESDAY AND WEDNESDAY.  
THE MOST RECENT ECMWF IS INDICATING CYCLOGENSIS OFF NEW ENGLAND  
COAST BY THEN...WITH THE ENSEMBLES SHOWING A LARGE SPREAD OF THE  
LOW CENTER POSITION. THE GFS HAS SUDDENLY CHANGED ITS TUNE FOR  
THE PAST COUPLE OF RUNS AND CALLS FOR CYCOGENESIS OFF NEW ENGLAND  
COAST MORE IN LINE WITH THE ECMWF. THE WPC MORNING GRID FIELDS  
WERE DERVIED BASED ON A BLEND OF 65% OF THE 00Z ECMWF/EC MEAN WITH  
THE REMAINING PORTION GIVEN TO THE 06Z GFS/GEFS TO HANDLE THIS AND  
OTHER SYSTEMS IN THE U.S. OUT WEST...MODELS AGREE FAIRLY WELL  
WITH THE NEXT PACIFIC SYSTEM MOVING ONSHORE ACROSS THE PACIFIC  
NORTHWEST ON MONDAY AS MORE UPSTREAM ENERGY PUSHING ONSHORE  
THROUGH WEDNESDAY OF NEXT WEEK.  
   
..SENSIBLE WEATHER HIGHLIGHTS/THREATS
 
 
EXCEPT FOR SATURDAY WHICH WILL BE DOMINATED BY BELOW AVERAGE  
TEMPERATURES...THE HEAVY INFLUENCE OF PACIFIC AIR MASSES SHOULD  
CONTRIBUTE TO READINGS CLOSER TO CLIMATOLOGY OR ABOVE IN SOME  
CASES. BEGINNING IN THE EASTERN THIRD OF THE COUNTRY...STRONG  
SURFACE RIDGING WILL ALLOW FOR ADEQUATE RADIATIONAL COOLING ON  
SATURDAY MORNING. THIS WILL BRING THE FIRST FREEZE TO MANY  
LOCATIONS AS SUCH TEMPERATURES PUSH AS FAR SOUTH AS NASHVILLE TN  
INTO THE INTERIOR CAROLINAS. WHILE NO DAILY TEMPERATURE RECORDS  
ARE EXPECTED TO BE BROKEN...SOME RECORD LOWS ARE POSSIBLE OVER THE  
UPPER GREAT LAKES INTO THE UPPER MID-ATLANTIC/LOWER NEW ENGLAND.  
LOOKING TO AN AREA WHERE ABOVE NORMAL TEMPERATURES WILL BE THE  
NORM...GENERAL WESTERLY FLOW SHOULD KEEP CONDITIONS MILD FROM THE  
ROCKIES EASTWARD TO THE GREAT PLAINS. AT TIMES READINGS 5 TO 10  
DEGREES ABOVE CLIMATOLOGY WILL BE WIDESPREAD BY EARLY NEXT WEEK.  
ACROSS THE PACIFIC NORTHWEST AND INTO NORTHERN CA...AN ACTIVE  
STORM TRACK SHOULD KEEP CONDITIONS COOL GIVEN THE EXPECTATIONS OF  
ABUNDANT CLOUDS AND BANDS OF PRECIPITATION.  
 
WARM ADVECTION PRECIPITATION ALONG THE ADVANCING FRONT IS IN THE  
FORECAST FROM THE ARKLATEX UP TO THE GREAT LAKES. GIVEN STRONGER  
FORCING TO THE NORTH...LOCALLY HEAVIER PRECIPITATION IS POSSIBLE  
OVER THE GREAT LAKES THIS WEEKEND WITH A THREAT FOR SNOW GIVEN  
SOME REMNANT ARCTIC AIR REMAINING IN PLACE. THE CHANCES FOR SNOW  
WILL MOVE TOWARD INTERIOR NEW ENGLAND BY LATE IN THE WEEKEND INTO  
EARLY NEXT WEEK. AS THE COASTAL LOW DEVELOPS...ANY CLOSER TO  
TRAJECTORY TO THE COAST WOULD BRING HIGHER AMOUNTS NEAR FAR  
EASTERN SECTIONS OF THE MID-ATLANTIC/NEW ENGLAND. THE MOST  
CONSISTENT AREA OF UNSETTLED WEATHER WILL BE ACROSS NORTHERN  
CA/PACIFIC NORTHWEST INTO THE UPPER INTERMOUNTAIN WEST WITH  
COASTAL RAIN AND HIGHER ELEVATION SNOWS. THIS MULTI-DAY EVENT  
SHOULD PERSIST INTO THE MIDDLE OF NEXT WEEK WHICH MAINTAINS THE  
FAIRLY WET PATTERN. EVENTUALLY A RETURN OF ADDITIONAL SHOWERS ARE  
POSSIBLE OVER THE MIDDLE MS VALLEY/UPPER MIDWEST/GREAT LAKES BY  
MID-WEEK AS THE LEAD PACIFIC TROUGH TRACKS EASTWARD.  
 
KONG/RUBIN-OSTER  
 

 
 
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