852  
FXUS02 KWBC 100709  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
209 AM EST MON JAN 10 2022  
 
VALID 12Z THU JAN 13 2022 - 12Z MON JAN 17 2022  
   
..OVERVIEW
 
 
A COMPLEX SPLIT FLOW PATTERN WILL OCCUR DURING THE MEDIUM RANGE  
PERIOD, WITH PROGRESSIVE SHORTWAVES DIVING THROUGH THE  
NORTH-CENTRAL AND EASTERN U.S. WHILE SOUTHERN STREAM ENERGY  
INITIALLY LINGERS WELL OFFSHORE BAJA CALIFORNIA BEFORE ADDITIONAL  
PACIFIC ENERGY DROPS INTO THE WEST AND DISRUPTS MEAN RIDGING  
THERE. AT THE SURFACE, A MILLER-A TYPE CYCLONE COULD DEVELOP THIS  
WEEKEND AND MOVE FROM THE SOUTHEAST INTO THE WESTERN ATLANTIC, BUT  
WITH QUITE A BIT OF UNCERTAINTY WITH ITS TRACK AND THUS THE  
IMPACTS ALONG THE EASTERN SEABOARD.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
GIVEN THE COMPLEXITY OF THE PATTERN, CONFIDENCE IS SOMEWHAT LOW  
FOR THE DETAILS OF THE MEDIUM RANGE FORECAST. HOWEVER, THERE ARE  
SOME GENERAL COMMONALITIES AMONG RECENT MODELS. THE INITIAL  
SOUTHERN STREAM ENERGY/TROUGHING WELL WEST OF BAJA CALIFORNIA ON  
THURSDAY CONTINUES TO TREND TOWARD MAINLY WEAKENING OFF THE COAST  
BEFORE TRACKING OVER THE SOUTHWEST MORE SLOWLY AS IT JOINS UP WITH  
ADDITIONAL ENERGY DROPPING SOUTH THROUGH THE WEST, AS OPPOSED TO A  
FASTER CLOSED LOW MOVING EASTWARD THAT MOST GUIDANCE SHOWED ABOUT  
A DAY AGO. THE UKMET WAS FIRST TO SHOW THIS TYPE OF SOLUTION THAT  
GUIDANCE HAS NOW TRENDED TOWARD. THERE ARE STILL SOME  
UNCERTAINTIES WITH THE MAGNITUDE OF THE UPSTREAM ENERGY DROPPING  
SOUTHWARD FROM THE PACIFIC AND THE INTERACTION WITH THE INITIAL  
SOUTHERN STREAM ENERGY AND THE EXISTING MEAN RIDGE ACROSS THE WEST  
ON FRIDAY, BUT THE LARGE VARIATIONS IN ENSEMBLE MEMBER 500MB  
HEIGHTS FOR EXAMPLE MAKE IT DIFFICULT TO DETERMINE OUTLIERS AT  
THIS TIME.  
 
MEANWHILE IN THE EAST, A TROUGH AXIS HAS GOOD AGREEMENT EARLY IN  
THE PERIOD THURSDAY BUT DIFFERENCES IN SHORTWAVE ENERGY TRACKING  
THROUGH THE MEAN TROUGH LEAD THE 00Z GFS TO CLOSE OFF A MID-UPPER  
LOW BY FRIDAY IN THE WESTERN ATLANTIC, WHICH IS NOT FAVORED BY  
OTHER GUIDANCE. REGARDLESS, THE TROUGH COULD DIG SOMEWHAT, AND  
GUIDANCE SHOWS AN ASSOCIATED SURFACE LOW DEEPENING CONSIDERABLY IN  
THE WESTERN ATLANTIC ON FRIDAY INTO SATURDAY, BUT MAINLY FAR  
ENOUGH OFFSHORE OF THE U.S. NOT TO CAUSE MUCH PRECIPITATION OVER  
THE EASTERN SEABOARD--THOUGH, WINDS COULD BE A CONCERN WITH A  
TIGHTENING PRESSURE GRADIENT NEAR THE NEW ENGLAND COAST.  
 
THEN BY THE WEEKEND, ENERGY DIVING SOUTHEASTWARD INTO THE  
NORTH-CENTRAL U.S. WILL DEEPEN A POSSIBLY POSITIVELY-TILTED (AT  
LEAST ON SATURDAY) TROUGH THAT TRACKS INTO THE EASTERN U.S. ON  
SUNDAY. THIS TROUGH ALSO MAY BE SUPPORTED BY THE WESTERN ENERGY,  
BUT THERE REMAINS SOME DISAGREEMENT WITH THEIR INTERACTION, AND  
MOST GUIDANCE SEEMS TO LEAVE ENERGY BEHIND IN THE SOUTHWEST AND  
FORM AND MAINTAIN A CLOSED LOW THERE OVER THE WEEKEND, WITH THE  
12Z ECMWF THE MAIN EXCEPTION AS A SECOND NORTHERN STREAM SHORTWAVE  
CROSSING INTO THE NORTH-CENTRAL U.S. COULD DOMINATE AND PHASE WITH  
THE SOUTHERN STREAM ENERGY. WITH PHASING AND SHORTWAVE INTENSITY  
DIFFERENCES, PREDICTABILITY REMAINS LOW AND THIS AFFECTS THE  
SURFACE PATTERN AS WELL. DETERMINISTIC GUIDANCE FOR THE  
12/18Z/INCOMING 00Z CYCLE VARIED QUITE A BIT WITH THEIR LOW TRACKS  
OVER THE CENTRAL/EASTERN U.S. AND WESTERN ATLANTIC.  
 
FOR THE WPC MEDIUM RANGE FRONTS/PRESSURES FORECAST, A BLEND OF THE  
18Z GFS AND 00Z ECMWF, CMC, AND UKMET WORKED FOR THE BEGINNING OF  
THE PERIOD, WITH FAIRLY EVEN WEIGHTING GIVEN THE UNCERTAINTY IN  
ANY PARTICULAR OUTLIERS, AND TRANSITIONED TOWARD UTILIZING MORE OF  
THE ENSEMBLE MEANS AS THE PERIOD PROGRESSED.  
   
..WEATHER HIGHLIGHTS
 
 
SOME LIGHT PRECIPITATION IS LIKELY FOR PARTS OF THE SOUTHWEST AND  
INTO THE FOUR CORNERS STATES FOR THE LATTER PART OF THE WEEK GIVEN  
THE UPPER LOW'S INFLUENCE, WHILE PRECIPITATION CHANCES CONTINUE TO  
DECREASE ACROSS THE SOUTH-CENTRAL U.S. GIVEN MODEL TRENDS. THEN AS  
THE NORTHERN STREAM SHORTWAVE AND SURFACE LOW TRACK ACROSS THE  
NORTHERN TIER LATE WEEK, A SWATH OF WINTRY PRECIPITATION IS  
CURRENTLY EXPECTED TO SPREAD FROM WEST TO EAST FROM THE UPPER  
MIDWEST THROUGH THE GREAT LAKES AND EVENTUALLY INTO NEW ENGLAND.  
AREAS FARTHER SOUTH SUCH AS THE OHIO VALLEY, MUCH OF THE  
APPALACHIANS, AND THE MID-ATLANTIC COULD ALSO SEE WINTER WEATHER,  
BUT DEPENDENT ON THE LOW TRACK AND THE POTENTIAL FOR THE SPLIT  
FLOW PATTERN TO PHASE IN THE UPPER LEVELS, WHICH ARE QUITE  
UNCERTAIN AT THIS POINT. MEANWHILE, THE SOUTH-CENTRAL AND  
SOUTHEASTERN U.S. SHOULD SEE LIGHT TO MODERATE RAIN ALONG THE  
SOUTHERN EXTENT OF THE COLD FRONT ON SATURDAY.  
 
TEMPERATURE-WISE, THE CENTRAL U.S. WILL SEE VERY MILD AND DRY  
CONDITIONS ON THURSDAY AND INTO FRIDAY, WITH WIDESPREAD HIGH  
TEMPERATURES REACHING 10-25F ABOVE AVERAGE. MEANWHILE, LOWS WILL  
BE 15-25F ABOVE NORMAL IN THE NORTHERN PLAINS. TEMPERATURES SHOULD  
MODERATE SOMEWHAT BY THE WEEKEND THERE, WHILE COLDER THAN AVERAGE  
TEMPERATURES ARE FORECAST FOR THE NORTHEAST ON FRIDAY INTO THE  
WEEKEND.  
 
TATE  
 
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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