441  
FXUS02 KWBC 041613  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1213 PM EDT SAT NOV 04 2017  
 
VALID 12Z TUE NOV 07 2017 - 12Z SAT NOV 11 2017  
 
...GUIDANCE/UNCERTAINTY ASSESSMENT AND WEATHER  
HIGHLIGHTS/THREATS...  
 
A WAVY FRONT SLATED TO SINK/TRAIL DOWN FROM THE WRN ATLC TO THE  
MID-LOWER LATITUDES OF THE ERN AND CENTRAL US WILL BE THE FOCUS OF  
SOME MODERATE TO HEAVIER RAINS. POST-FRONTAL HIGH PRESSURE WILL  
COOL TEMPS IN ITS WAKE OVER MUCH OF THE CENTRAL AND ERN US. THESE  
LOWS HAVE SOME POTENTIAL TO FURTHER DEVELOP OFF THE EAST COAST  
WITH ACTIVITY WORKING MORE INTO THE NERN US/CANADIAN  
MARITIMES...BUT REQUIRED SHORTWAVE SUPPORT FOR THIS HAS BEEN  
HIGHLY INCONSISTENT WITH RECENT GUIDANCE TO LOWER FORECAST  
CONFIDENCE IN PARTICULAR DEVELOPMENTS. CONFIDENCE IS HIGHER THAT A  
MAIN PCPN THREAT WILL REMAIN OVER THE SRN/SERN US AS THE FRONT  
FILTERS THROUGH TO THE GULF OF MEXICO AND BAHAMAS LATER WEEK INTO  
NEXT WEEKEND.  
 
UPSTREAM...GUIDANCE HAS BEEN STRONGLY TRENDING TO DEVELOPMENT OF  
AN AMPLIFIED CLOSED LOW/TROUGH DIGGING FROM THE GULF OF AK TO THE  
NWRN US INTO MIDWEEK WHOSE ENERGIES ARE SLATED TO EJECT INLAND  
OVER THE WRN US/ROCKIES DAYS 6/7 ALONG WITH ASSOCIATED UNSETTLED  
WEATHER A PCPN ENHANCEMENT. THIS WOULD INCLUDE A ROUND OF PAC  
NW/NRN CA MODERATE TO HEAVY RAINS AND ANOTHER MOUNTAIN/INTERIOR  
WEST TERRAIN ENHANCED THREAT OF HEAVY SNOWS IN A PATTERN WITH  
COOLING POST-FRONTAL TEMPS. SUBSEQUENT HEIGHT FALLS WORKING  
DOWNSTREAM INTO THE PLAINS MAY THEN SPAWN  
FRONTOGENESIS/CYCLOGENESIS AND EVENTUAL FAVORABLE RETURN MOISTURE  
PATTERN FROM THE GULF OF MEXICO/INCREASINGLY WET FLOW BACK INTO  
THE CENTRAL US.  
 
OVERTOP...A SERIES OF DYNAMIC SHIRTWAVES WILL MEANWHILE DIG  
UNDERNEATH A MEAN CLOSED HUDSON BAY LOW AND FORCE SEVERAL SURGES  
OF COLD CANADIAN AIR INTO THE N-CENTRAL AND NERN US TO FURTHER  
REINFORCE A COOLED MID-LATER NEXT WEEK AUTUMN PATTERN. THESE  
SURGES HAVE MODEST PCPN POTENTIAL/MOISTURE...BUT DO OFFER GREAT  
LAKE SNOW POTENTIAL AND COULD ACT TO INTERACT DOWNSTREAM WITH  
POTENTIAL LEAD WRN ATLANTIC LOWS.  
 
OVERALL...THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED  
FROM A BLEND OF ECMWF/ECMWF ENSEMBLES THAT SHOW A SLIGHTLY MORE  
AMPLIFIED PATTERN AND ASSOCIATED DEEPER AND LESS PROGRESSIVE  
SURFACE SYSTEMS AND PCPN FOCUS THAN RECENT GFS AND GEFS RUNS. THE  
CANADIAN OFFERS AN EVEN LESS PROGRESSIVE AND STREAM SEPARTE  
SOLUTION AND EVEN DEVELOPS A POTENT EAST COAST LOW THREAT AS EARLY  
AS FRIDAY. WHILE AN OUTLIER SOLUTION...THIS SCENARIO IS NOT  
IMPOSSIBLE CONSIDERING GUIDANCE TRENDS TO AN OVER MORE AMPLIFIED  
OVERALL FLOW REGIME.  
 
SCHICHTEL  
 

 
 
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