186  
FXUS02 KWBC 220700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
200 AM EST FRI DEC 22 2017  
 
VALID 12Z MON DEC 25 2017 - 12Z FRI DEC 29 2017  
 
...ARCTIC AIR TO GRIP MOST OF THE LOWER 48 NEXT WEEK ALONG WITH  
SOME SNOW THREAT...  
 
   
..GUIDANCE AND PREDICTABILITY ASSESSMENT
 
 
WHILE A SIGNIFICANT SPREAD OF ARCTIC AIR ACROSS MUCH OF THE LOWER  
48 NEXT WEEK SEEMS WELL ADVERTISED BY GUIDANCE...THE SPECIFICS AND  
LONGER TERM RAMIFICATIONS/TRANSITIONS WITHIN THIS WINTERY PATTERN  
INCLUDING ICE/SNOW THREATS REMAIN MUCH LESS CLEAR. MODEL MASS  
FIELDS AND IN PARTICULAR THE GFS/ECMWF AND THEIR ENSEMBLES SEEM IN  
REASONABLE AGREEMENT FOR DAY 3/CHRISTMAS...BUT RECENT  
DETERMINISTIC MODEL RUNS CONTINUE TO OFFER POOR RUN TO RUN  
CONTINUITY WITH THE OVERALL FLOW IN THE 4-7 DAY TIME  
FRAME...ESPECIALLY WITH THE TIMING AND LOCAL WEATHER FOCUS OF  
NUMEROUS EMBEDDED SMALLER SCALE SYSTEMS. WPC WINTER WEATHER  
OUTLOOK FOCUS HEAVIER SNOW PROBABILITIES OVER THE  
NORTHEAST...GREAT LAKES...AND NW US TERRAIN FOR CHRISTMAS.  
PERIODIC LATER WEEK POTENTIAL HOLDS OVER THE NWRN/WEST US AND THE  
GREAT LAKES AS AN EMERGING THREAT AREA DEVELOPS NEXT WEEKEND INTO  
NEW YEARS ACROSS THE MID-LATITUDES OF THE CENTRAL AND ERN US WITH  
POTENTIAL FOR HIGH PRESSURE OVER-RUNNING ICE/SNOW.  
 
OPTED TO USE A BLEND OF MORE COMPATABLE GEFS/NAEFS/ECMWF ENSEMBLE  
MEANS FOR CONSTRUCTION OF THE WPC MEDIUM RANGE PRODUCT SUITE  
CONSIDERING THIS UNCERTAINTY...ALBEIT WITH AN EYE FOR WPC  
CONTINUITY AND WITH ONLY MINIMAL INCLUSION OF DETERMINITSIC MODEL  
INPUT. LEANED THE AFOEMENTIONED BLEND TOWARD THE ECMWF ENSEMBLE  
MEAN THAT WITH TIME OFFERS A SOMEWHAT COOLER AND PRECIPITATION  
SUPPRESSED PATTERN THAT SEEMS MORE CONSISTENT WITH THE ADVENT OF  
SO MUCH COLD HIGH PRESSURE ACROSS THE CENTRAL AND ERN US. WRN US  
PRECIPITATION FROM THESE MEANS ARE IN BETTER AGREEMENT...BUT  
RECENT DETERMISTIC MODELS TRENDS OFFER UNCERTAINTY WITH THEIR  
DEPICTION OF MORE MID-UPPER LEVEL TROUGH DEVELOPENT OVER THE WEST  
TO RING IN THE NEW YEAR.  
 
SCHICHTEL  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page