221  
FXUS02 KWBC 051600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1100 AM EST MON FEB 05 2018  
 
VALID 12Z THU FEB 08 2018 - 12Z MON FEB 12 2018  
   
..OVERVIEW AND GUIDANCE/UNCERTAINTY ASSESSMENT
 
 
MODELS AND ENSEMBLES CONTINUE TO SHOW INCREASINGLY DRAMATIC SPREAD  
REGARDING SPECIFICS OF WHAT SHOULD BE GENERALLY CYCLONIC FLOW OVER  
MOST OF NORTH AMERICA...WHILE RIDGES ALOFT PERSIST/BUILD OFF THE  
WEST COAST AND NEAR THE BAHAMAS. THIS SPREAD KEEPS CONFIDENCE  
LOWER THAN DESIRED FOR SOME ASPECTS OF THE FORECAST...BUT LATEST  
GUIDANCE TRENDS ARE SUGGESTING MORE HEIGHT FALLS TO DIG INTO THE  
W-CENTRAL US THAN EARLIER RUNS. THE OVERALL MEAN PATTERN STILL  
FAVORS HIGHEST PRECIP TOTALS FROM THE SRN TIER/GULF COAST  
NORTHEASTWARD.  
 
IN THIS FLOW THE LATEST GFS RUNS OFFER MUCH MORE TROUGH DIGGING  
INTO THE WRN US THAN THE MORE PROGRESSIVE ECMWF/UKMET/CANADIAN  
THAT ARE NONETHELESS HAVE OVERALL TRENDED WESTWARD FROM PRIOR  
RUNS. THE ENSEMBLE MEANS ARE IN CLOSER AGREEMENT...BUT REPRESENT  
QUITE SPREAD MEMBERSHIP THAT DISGUISES INDIVIDUAL SHORTWAVES THAT  
HAVE SOME FAVORABLE PREDICTABILITY IN THEIR EXISTENCE IN THE  
DETERMINISTIC MODELS. ACCORDINGLY...HAVE BLENDED THE 00 UTC  
GFS/ECMWF AND GEFS/ECMWF ENSEMBLE MEAN TO INCORPORATE THE WESTWARD  
HEIGHT FALL SHIFT TREND AND ALLOW FOR AT LEAST MODEST SHORTWAVE  
DEPICTIONS.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
THE HIGHEST PRECIP TOTALS THIS PERIOD ARE EXPECTED TO DEVELOP FROM  
THE LOWER MS VALLEY/W-CENTRAL GULF COAST NORTHEASTWARD THROUGH THE  
MID-SOUTH AND ERN STATES FRI INTO NEXT MON. THE COMBINATION OF A  
PERIOD OF AT LEAST MODERATE LOW LEVEL GULF INFLOW AHEAD OF THE  
FRONT PUSHING SOUTHEAST FROM THE PLAINS AND SOUTHWESTERLY FLOW  
ALOFT WITH ONE OR MORE EMBEDDED SRN STREAM SHORTWAVES SHOULD HELP  
TO ENHANCE RAINFALL/CONVECTION.  
 
AMOUNTS WILL BE LIGHTER BUT LOCALLY ENHANCED FOR SOME PERIODS OF  
SNOW FROM THE NRN ROCKIES TO THE N-CENTRAL STATES AND GREAT LAKES.  
THE VARIABILITY AND SPREAD OF GUIDANCE FOR DETAILS OF FLOW ALOFT  
CONTINUE TO TEMPER CONFIDENCE IN PRECISE  
LOCATION/INTENSITY/DURATIONS. THE DEGREE OF INTERACTION BETWEEN  
THE SRN TIER MOISTURE SHIELD AND COLDER AIR TO THE NORTH WILL NEED  
TO BE MONITORED BY SAT-MON. GUIDANCE NOW ALSO INCREASINGLY DIG  
AMPLE SHORTWAVES/HEIGHT FALLS AND MODEST PRECIPITATION POTENTIAL  
FROM THE COOLING NWRN US THEN GREAT BASIN AND CENTRAL ROCKIES  
DURING THIS PERIOD...ALBEIT WITH HIGH VARIANCE.  
 
SCHICHTEL  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page