706  
FXUS02 KWBC 030553  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
152 AM EDT FRI NOV 03 2017  
 
VALID 12Z MON NOV 06 2017 - 12Z FRI NOV 10 2017  
   
..PATTERN OVERVIEW/GUIDANCE/UNCERTAINTY ASSESSMENT/PREFERENCES
 
 
THE LONGWAVE PATTERN AFFECTING THE UNITED STATES NEXT WEEK WILL  
FEATURE A BROAD LONGWAVE TROUGH EXTENDING OVER MUCH OF THE REGION.  
MEANWHILE...AN EXPANSIVE RIDGE SHOULD HOLD STRONG ACROSS MEXICO  
AND INTO THE GULF OF MEXICO. THIS IS EXPECTED TO REMAIN THE THEME  
THROUGHOUT THE WEEK WITH A SERIES OF PERTURBATIONS IN THE FLOW  
BEING FOCI FOR SEMI-ORGANIZED BANDS OF PRECIPITATION. ONE FEATURE  
OF INTEREST WILL BE A SHORTWAVE PUSHING THROUGH THE CENTRAL GREAT  
BASIN ON MONDAY WHILE TRACKING EASTWARD IN TIME. THERE ARE SOME  
INDICATIONS A MORE PRONOUNCED AREA OF LOW PRESSURE WILL DEVELOP IF  
THE SHORTWAVE CAN OBTAIN SUBSTANTIAL DEPTH. FARTHER UPSTREAM...A  
POWERFUL NORTHEASTERN PACIFIC SYSTEM IS FORECAST TO SINK SOUTHWARD  
WITH THE EVENTUAL FATE OF THIS SYSTEM UNCERTAIN. SOLUTIONS ARE  
VARIABLE WHICH LEADS TO A GREAT DEAL OF UNCERTAINTY DURING THE DAY  
5-7...NOVEMBER 8-10 TIMEFRAME.  
 
WITHIN THE ACTIVE LONGWAVE PATTERN...THERE WILL BE A NUMBER OF  
FEATURES TO NOTE. A DEPARTING CYCLONE LIFTING TOWARD HUDSON BAY IS  
NOTED ON MONDAY MORNING WITH THE TRAILING COLD FRONT EXITING THE  
I-95 CORRIDOR BY MIDDAY MONDAY. WHILE THIS IS WELL AGREED  
UPON...THE UPSTREAM PATTERN CONSISTS OF A MORE NEBULOUS FORECAST  
AT BEST. A SHORTWAVE EXITING THE PACIFIC NORTHWEST WILL CONTINUE  
ITS MARCH EASTWARD WITH RECENT MODEL TRENDS SHOWING A MORE  
STRETCHED OUT BAND OF VORTICITY WITH MANY OF THE GFS RUNS AHEAD OF  
THE ECMWF. HOWEVER...THE 00Z GFS DID SLOW RATHER SIGNIFICANTLY  
BRINGING IT BACK CLOSER TO THE 12Z ECMWF. WHILE THE IMPULSE SHOULD  
BE MORE SUBTLE IN NATURE...THERE HAVE BEEN A HANDFUL OF SOLUTIONS  
WHICH SHOW A BIT MORE AMPLITUDE...NAMELY THE PREVIOUS 00Z  
ECMWF/GFS FROM YESTERDAY. HOWEVER...THIS APPEARS TO BE IN THE  
MINORITY AT THIS TIME. FARTHER UPSTREAM...AN EVEN MORE UNCERTAIN  
SYSTEM ENTERS THE NORTHWESTERN U.S. AS AN UPPER LOW DROPS DOWN  
FROM THE GULF OF ALASKA. ENSEMBLE SPAGHETTI PLOTS AND MANY OF THE  
OPERATIONAL MODELS VARY CONSIDERABLY FROM ONE ANOTHER. THE PAST  
COUPLE OF ECMWF/UKMET RUNS FAVOR A SLOWER SOLUTION WITH A  
POTENTIAL FOR EVEN SOME RETROGRESSION. ON THE CONTRARY...THE PAST  
FOUR RUNS OF THE GFS FAVOR A MORE PROGRESSIVE FORECAST. THE 12Z  
CMC WAS EVEN QUICKER WITH THIS KIND OF SCENARIO.  
OVERALL...ENSEMBLE SPAGHETTI PLOTS ARE RATHER NOISY SUGGESTING A  
BELOW AVERAGE CONFIDENCE FORECAST. BY THE END OF THE PERIOD...THE  
GFS/ECMWF DISAGREE ON WHETHER A TROUGH OR A RIDGE WILL BE IN PLACE  
ACROSS THE WEST COAST.  
 
REGARDING PREFERENCES...DID NOT FEEL COMFORTABLE KEEPING ANY  
OPERATIONAL SOLUTIONS IN THE MIX BEYOND DAY 5/WEDNESDAY. INITIALLY  
TOOK AN EVEN SPLIT OF THE 18Z GFS/GEFS MEAN AND 12Z ECMWF/ECMWF  
ENSEMBLE MEAN BEFORE INTRODUCING INCREASING AMOUNTS OF THE 12Z  
NAEFS MEAN. WAS NOT TOO KEEN ON UTILIZING THE EVOLUTION SUGGESTED  
BY THE ECMWF SUITE. THUS...LEANED SLIGHTLY MORE UPON A COMBINATION  
OF THE 18Z GEFS/12Z NAEFS ENSEMBLE MEAN RELATIVE TO THE 12Z ECMWF  
ENSEMBLE MEAN DURING THE DAY 6/7...NOVEMBER 9/10 PERIOD.  
 
   
..SENSIBLE WEATHER/THREAT HIGHLIGHTS
 
 
THE FRONTAL BOUNDARY STRETCHING FROM THE LOWER GREAT LAKES BACK  
TOWARD THE SOUTHERN/CENTRAL PLAINS WILL BE THE FOCUS FOR A VERY  
SHARP TEMPERATURE GRADIENT. OVERNIGHT LOWS WITHIN THE WARM SECTOR  
FROM THE SOUTHERN PLAINS INTO THE TN/OH VALLEYS WILL FEATURE  
TEMPERATURE ANOMALIES IN THE 20 TO 25 DEGREES ABOVE AVERAGE RANGE.  
THUS...A FEW DAILY RECORDS MAY BE BROKEN GIVEN SUCH WARM NIGHTTIME  
TEMPERATURES. EVENTUALLY...MUCH OF THE COUNTRY CAN EXPECTED COLDER  
WEATHER GIVEN THE PERSISTENT LONGWAVE TROUGHING. THE HEART OF THE  
COLD CONDITIONS CAN BE EXPECTED FROM THE UPPER INTERMOUNTAIN WEST  
INTO THE NORTHERN PLAINS/UPPER MIDWEST. FORECAST ANOMALIES SHOULD  
BE IN THE 15 TO 25 DEGREE BELOW CLIMATOLOGY RANGE WITH THE NUMBERS  
GRADUALLY DIMINISHING AS THE AIR MASS MODERATES IN TIME.  
 
REGARDING PRECIPITATION...A STEADY BAND OF RAINFALL IS LIKELY  
ALONG THE ATTENDANT FRONT STRETCHING FROM THE TN/OH VALLEYS UP  
INTO THE MID-ATLANTIC/NEW ENGLAND ON MONDAY/TUESDAY. IT COULD  
LINGER INTO WEDNESDAY AS THE BOUNDARY HANGS UP ACROSS THE  
MID-SOUTH TOWARD THE CAROLINAS. SOME WINTRY PRECIPITATION WILL BE  
POSSIBLE OVER THE INTERIOR NORTHEAST AS COLDER AIR SPILLS IN FROM  
CANADA. OUT WEST...WET WEATHER WILL SPREAD IN ADVANCE OF THE  
EVOLVING UPPER LOW OFF THE COAST. IT IS DIFFICULT TO SAY HOW FAR  
SOUTH THE PRECIPITATION WILL SPREAD GIVEN MODEL DIFFERENCES.  
SNOWFALL IS EXPECTED OVER THE HIGHER ELEVATIONS ACROSS MUCH OF THE  
WESTERN U.S.  
 
RUBIN-OSTER  
 

 
 
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