020  
FXUS02 KWBC 010700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
159 AM EST THU FEB 01 2018  
 
VALID 12Z SUN FEB 04 2018 - 12Z THU FEB 08 2018  
   
..PATTERN OVERVIEW AND GUIDANCE/UNCERTAINTY ASSESSMENT
 
 
MEDIUM RANGE FLOW ALOFT SHOULD CONTINUE TO FEATURE RIDGING OFF THE  
WEST COAST AND BROAD CYCLONIC FLOW/TROUGHING DOWNSTREAM OVER MUCH  
OF THE REST OF THE LOWER 48. MODELS AND ENSEMBLES OFFER SIMILAR  
LARGER SCALE FLOW PATTERNS AND HAVE BECOME A BIT BETTER CLUSTERED  
WITH LESS PREDICTABLE SMALLER SCALE EMBEDDED FEATURES. THERE  
REMAINS VARIANCE WITH BOTH THE SPECIFICS OF COLD HIGH DIGGING TO  
THE LOWER 48 AND THE DEVELOPMENT OF PRECIPITATION AND WINTER  
WEATHER ASSOCIATED WITH FRONTAL WAVES ON THE LEADING EDGE OF THE  
COLD DOME.  
 
THE WPC MEDIUM RANGE PRODUCT SUITE WAS MAINLY DERIVED FROM THE 18  
UTC GEFS AND 12 UTC NAEFS/ECMWF ENSEMBLE MEANS AND WPC CONTINUITY.  
THE MEANS BLENDED WELL WITH DETERMINISTIC MODEL GUIDANCE  
SUN/MON...BUT OFFERED A MUCH MORE RUN TO RUN CONSISTENT MESSAGE BY  
NEXT TUE-THU.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
A LONG SERIES OF PROGRESSIVE IMPULSES DIGGING SEWD TO THE LEE OF  
AN ERN PACIFIC MID-UPPER LEVEL MEAN RIDGE POSITION WILL SUPPORT  
PERIODS OF MODEST PAC NW PRECIPITATION OVER THE NEXT WEEK. FURTHER  
EXPECT TERRAIN ENHANCED SNOWS ACROSS THE NWRN US AND ESPECIALLY  
THE NRN ROCKIES WITH ADDITIONAL NRN STREAM IMPULSE  
PASSAGES...ALONG WITH POST-FRONTAL UPSLOPE SNOWS.  
 
DOWNSTREAM...A SUPERBOWL SUNDAY CLIPPER SYSTEM SUPPORTED BY NRN  
STREAM SHORTWAVE ENERGIES WILL SPREAD SNOWS FROM THE MIDWEST/GREAT  
LAKES TO THE NORTHEAST. UNDERNEATH...RAINS WILL MEANWHILE INCREASE  
OVER THE GULF COAST/TN VALLEY/SERN US INTO SUNDAY WITH RETURN FLOW  
AS PER SRN STREAM IMPULSE AND INDUCED SURFACE WAVE PASSAGE.  
WIDESPREAD MODERATE TO HEAVIER PCPN WILL EXPAND RAPIDLY NEWD  
ACROSS THE ERN US INTO MONDAY WITH LOW DEVELOPMENT. LATEST  
GUIDANCE OFFERS AN INTERIOR ERN US TO NERN STATES WINTER WEATHER  
THREAT AS MOISTURE WRAPS OVER THE WAVY FRONT ON THE ERN PERIPHERY  
OF AN EXPANDING CENTRAL TO ERN US ARCTIC AIRMASS.  
 
FORECAST SPREAD INCREASES IN THIS FLOW REGIME FROM THE S-CENTRAL  
TO ERN US MID-LATER NEXT WEEK WITH GUIDANCE OFFERING A WIDE  
VARIETY OF FRONTAL LOW DEVELOPMENTS OF LESS THAN AVERAGE  
PREDICTABILITY. HOWEVER...THE 00 UTC ECMWF HAS JOINED RECENT  
TRENDS FROM THE GFS TO DEVELOP A MUCH DEEPER EAST-CENTRAL TO ERN  
US LOW WED/THU COMPARED TO MOST EARLIER GUIDANCE. THIS WOULD  
CLEARLY ENHANCE SYSTEM POTENTIAL/THREAT AS DEEPER MOISTURE  
REBOUNDS IN THE WAKE OF THE LEAD SYSTEM ON THE LEADING FRONTAL  
EDGE OF THE NEXT COLD HIGH SURGE.  
 
SCHICHTEL  
 

 
 
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