793  
FXUS02 KWBC 291600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1100 AM EST TUE JAN 29 2019  
 
VALID 12Z FRI FEB 01 2019 - 12Z TUE FEB 05 2019  
   
..OVERVIEW
 
 
THE DEPARTURE OF A DEEP UPPER LEVEL VORTEX OVER QUEBEC AT THE  
BEGINNING OF THE FORECAST PERIOD THURSDAY AND GRADUAL WEAKENING OF  
MEAN TROUGHING ALOFT OVER THE EASTERN U.S. LATE THIS WEEK AND THE  
WEEKEND WILL PROMOTE A SIGNIFICANT WARMING TREND OVER THE EASTERN  
U.S. AT THE SAME TIME THE SHORT-RANGE WEST COAST MEAN RIDGE ALOFT  
WILL GIVE WAY TO A SERIES OF PACIFIC SYSTEMS THAT WILL BRING A  
RETURN OF SIGNIFICANT PRECIPITATION TO PARTS OF THE WEST WITH  
MOISTURE THAT WILL THEN SPREAD FARTHER EASTWARD. BY THE LATTER  
HALF OF THE PERIOD, THE SYNOPTIC SCALE PATTERN SHOULD EVOLVE  
TOWARD A POSITIVELY TILTED MEAN TROUGH OVER THE WEST AND POSITIVE  
HEIGHT ANOMALIES WITH SOME DEGREE OF RIDGING OVER THE EAST.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
MODELS AND ENSEMBLES ARE IN RELATIVELY GOOD AGREEMENT FRIDAY SO  
PREFER A COMPOSITE SOLUTION. THE ECMWF AND ECMWF ENSEMBLE MEAN  
BECOME FASTER THAN MOST OTHER GUIDANCE TO DIG ANOTHER ARCTIC SHOT  
SOUTHWARD THROUGH THE N-CENTRAL U.S. THIS WEEKEND INTO EARLY NEXT  
WEEK. WHILE NOT QUITE AS COLD AS THE SHORT RANGE EVENT, SUSPECT A  
SOLUTION CLOSER TO THE ECMWF/ECMWF ENSEMBLE MEAN WOULD BE MORE  
LIKELY GIVEN PATTERN HISTORY AND SUPPORTING SURFACE HIGH STRENGTH.  
MEANWHILE, RUN TO RUN MODEL VARIANCE ALSO CONTINUES TO INCREASE  
WITH SYSTEMS WORKING UNDERNEATH ACROSS THE U.S. SOUTHERN TIER AND  
WITH PACIFIC SYSTEMS MOVING INTO/ACROSS THE WEST THEN DOWNSTREAM.  
THIS SUGGESTS TRANSITION TO AN ENSEMBLE MEAN BASED FORECAST  
PROCESS AND ECMWF ENSEMBLES SEEM TO HAVE THE BEST HANDLE ON THE  
MEDIUM RANGE STRENGTH OF THESE SYSTEMS CONSIDERING THEY SEEM  
PRETTY ENERGETIC AT SHORTER RANGES. WPC ACCORDINGLY LEANED  
FORECAST WEIGHTING STRONGLY IN FAVOR OF THE 00 UTC ECMWF ENSEMBLE  
MEAN AND APPLIED LESS WEIGHT TO THE 06 UTC GEFS MEAN FOR THIS  
PERIOD.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
PACIFIC SYSTEM PASSAGE WILL PRODUCE A SWATH OF RAIN AND MOUNTAIN  
SNOWS ACROSS CA FRIDAY THAT FURTHER MODERATES ACROSS THE SOUTHWEST  
AND SOUTHERN GREAT BASIN/ROCKIES. STRONGER SYSTEM APPROACH AND  
PASSAGE OVER THE WEEKEND WILL SPREAD MORE ROBUST  
WINDS/PRECIPITATION ACROSS CA WITH ADDITIONAL EFFECT OVER THE  
NORTHWEST AND INLAND. DURING THE LATTER HALF OF THE PERIOD,  
EJECTING MID-UPPER LEVEL TROUGH ENERGY SHOULD SPAWN SURFACE  
CYCLOGENESIS OVER THE CENTRAL U.S. WHOSE INCREASED MOISTURE FOCUS  
INTO AN ARCTIC FRONT OFFERS A SIGNIFICANT THREAT OF OVERRUNNING  
ICE/SNOW TO THE NORTH, WITH WARM SECTOR RAINS/CONVECTION TO THE  
SOUTH. THE FOCUS FOR HEAVIEST COVERAGE WILL SPREAD EASTWARD  
THROUGH EARLY NEXT WEEK WITH SYSTEM PROGRESSION.  
 
HAMRICK/SCHICHTEL  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION AND WINTER WEATHER OUTLOOK  
PROBABILITIES ARE FOUND AT:  
 
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page