500  
FXUS02 KWBC 091946  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
245 PM EST SUN JAN 09 2022  
 
VALID 12Z WED JAN 12 2022 - 12Z SUN JAN 16 2022  
   
..OVERVIEW
 
 
GENERAL RIDGING OVER THE WESTERN U.S. IS EXPECTED TO CONTINUE INTO  
THE MEDIUM-RANGE PERIOD AS SHORTWAVES DIVE ACROSS CENTRAL CANADA  
INTO THE NORTHERN TIER WHILE A LINGERING LOW/TROUGH OFF BAJA  
CALIFORNIA IS FORECAST TO EVENTUALLY TRACK INTO THE SOUTHERN  
PLAINS. THIS SPLIT FLOW PATTERN COULD POTENTIALLY PHASE NEAR THE  
EAST COAST WHERE CYCLOGENESIS WOULD BE POSSIBLE BY NEXT WEEKEND.  
MODEL ENSEMBLE MEANS FAVOR THIS PHASING SCENARIO IN CONTRAST WITH  
THE DETERMINISTIC SOLUTIONS WHICH CONTINUE TO INDICATE A SPLIT  
DECISION IN THIS REGARD.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
OVERALL, THE ENSEMBLE MEANS HAVE MAINTAINED RELATIVELY GOOD  
RUN-TO-RUN CONSISTENCY IN PREDICTING THE PATTERN EVOLUTION ACROSS  
THE U.S. THROUGH THE MEDIUM-RANGE PERIOD. THE LARGEST DISCREPANCY  
WAS NOTED WITH REGARD TO HOW THE UPPER LOW/TROUGH OFF BAJA  
CALIFORNIA IS HANDLED. THE 00Z ECMWF SWITCHED TO A MUCH SLOWER  
SOLUTION BEGINNING IN THE SHORT-RANGE, THUS KEEPING THIS FEATURE  
WELL OFF THE COAST INTO THE MEDIUM-RANGE. THE GFS TRENDED TOWARD  
THIS SLOW SOLUTION AS WELL STARTING WITH THE 06Z RUN. THIS SUDDEN  
SLOW DOWN OF THE UPPER LOW HAS RESULTED IN A MARKED LOWERING OF  
RAIN CHANCES OVER THE SOUTHERN PLAINS MIDWEEK. THE ENSEMBLE MEANS  
INDICATE THAT THIS UPPER LOW/TROUGH WILL EVENTUALLY LIFT TOWARD  
THE SOUTHWEST LATE THIS WEEK AS THE NEXT SHORTWAVE DIVES ACROSS  
THE CANADIAN PRAIRIES TOWARD THE NORTHERN PLAINS. MODELS THEN  
BEGIN TO DIVERGE AS TO WHETHER THESE TWO FEATURES WILL EVENTUALLY  
PHASE OR REMAIN SPLIT AS THEY REACH THE VICINITY OF THE EAST COAST  
BY NEXT WEEKEND. IT APPEARS THAT THE ENSEMBLE MEANS SUPPORT THE  
PHASING SCENARIO IN CONTRAST WITH THE DETERMINISTIC SOLUTIONS  
WHICH CONTINUE TO INDICATE A SPLIT DECISION IN THIS REGARD. THE  
ECMWF AND CMC HAVE BEEN IN FAVOR OF PHASING AND CYCLOGENESIS NEAR  
THE EAST COAST WHEREAS THE GFS SUPPORTS A MORE SEPARATION BETWEEN  
THE TWO STREAMS WITH ITS TYPICALLY FASTER SOLUTION.  
 
PRIOR TO THE WEEKEND, MODELS AND ENSEMBLES ARE IN GOOD AGREEMENT  
FOR A DEEP TROUGH TO EXIT THE EAST COAST THU-FRI WITH A STRONG  
SIGNAL FOR CYCLOGENESIS OFF THE EAST COAST. IT APPEARS THAT THE  
HEAVY RAIN AND WOULD STAY OFF SHORE WITH WHAT APPEARS TO BE A DEEP  
CYCLONE IN THE MAKING. THE GFS HAS BECOME MUCH MORE AGGRESSIVE  
WITH CYCLOGENESIS OFF THE EAST COAST TOGETHER WITH A TENDENCY TO  
TRACK IT CLOSER TO LAND IN RECENT RUNS.  
 
A MULTI-MODEL/ENSEMBLE BLEND WAS USED TO COMPOSE THIS MORNING'S  
WPC MEDIUM-RANGE FORECASTS. THE 06Z GFS WAS TAKEN OUT OF THE  
BLEND BEYOND DAY 5 AS IT APPEARS TO BUILD TOO MUCH HIGH PRESSURE  
ACROSS THE GREAT LAKES, THEREBY MAKING THE NORTHERN STREAM LOW TOO  
WEAK. THE 00Z GFS WAS NOT USED AS A SUBSTITUTE EITHER BECAUSE IT  
TRACKS THE LOW TOO FAST TO THE EAST. THE REST OF THE BLEND  
CONSISTS OF THE 00Z ECMWF/EC MEAN, THE 06Z GEFS, AND THE 00Z  
CMC/CMC MEAN THROUGH DAY 7.  
   
..WEATHER HIGHLIGHTS
 
 
MODERATE TO HEAVY PRECIPITATION CONTINUING INTO WEDNESDAY ACROSS  
THE OLYMPIC PENINSULA AND NORTHERN CASCADES SHOULD BEGIN TO WIND  
DOWN AS THE ASSOCIATED LOW PRESSURE SYSTEM IS FORECAST TO WEAKEN.  
MEANWHILE, THE SOUTHERN STREAM PACIFIC UPPER LOW IS FORECAST TO  
SPREAD PRECIPITATION INTO THE FOUR CORNERS STATES INTO LATE THIS  
WEEK BUT THE CHANCE OF RAIN ACROSS THE SOUTHERN PLAINS AND LOWER  
MISSISSIPPI VALLEY HAS DECREASED CONSIDERABLY ON WED-THU. GULF  
MOISTURE IS EXPECTED TO RETURN ALONG THE WESTERN GULF COAST REGION  
BY FRIDAY AND INTO THE WEEKEND. MEANWHILE, AS THE NORTHERN STREAM  
SHORTWAVE AND SURFACE LOW TRACK ACROSS THE NORTHERN TIER LATE  
WEEK, A SWATH OF WINTRY PRECIPITATION CAN BE EXPECTED TO SPREAD  
FROM WEST TO EAST FROM THE UPPER MIDWEST THROUGH THE GREAT LAKES  
AND EVENTUALLY INTO NEW ENGLAND. THEREAFTER, WE WILL NEED TO  
MONITOR HOW MUCH THE SPLIT FLOW PATTERN WILL PHASE NEAR THE EAST  
COAST THIS WEEKEND TO DETERMINE THE EXTENT AND TYPES OF WEATHER  
IMPACTS THE SYSTEM MAY BRING TO THE EASTERN SEABOARD.  
 
TEMPERATURE-WISE, AFTER A COLD START TO THE DAY ALONG THE EAST  
COAST ON WEDNESDAY, TEMPERATURES WILL REBOUND CLOSER TO NEAR OR  
ABOVE NORMAL BY THURSDAY. THE CENTRAL U.S. WILL SEE VERY MILD AND  
DRY CONDITIONS THROUGH MIDWEEK, WITH A WIDESPREAD HIGH  
TEMPERATURES REACHING 10-20F ABOVE AVERAGE. MEANWHILE, LOWS WILL  
BE 15-25F ABOVE NORMAL IN THE NORTHERN PLAINS. COOLER AIR WILL  
THEN OVERSPREAD THE PLAINS AS THE SPLIT FLOW PATTERN MIGRATES  
TOWARD THE EAST COAST WHERE THE POTENTIAL FOR CYCLOGENESIS EXISTS  
BY NEXT WEEKEND.  
 
KONG  
 
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDICES ARE 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  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 

 
 
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