817  
FXUS02 KWBC 061853  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
152 PM EST THU JAN 06 2022  
 
VALID 12Z SUN JAN 09 2022 - 12Z THU JAN 13 2022  
   
..GENERAL PATTERN OVERVIEW
 
 
AN AMPLIFIED UPPER FLOW REGIME WILL PREVAIL FROM THE WEEKEND INTO  
EARLY NEXT WEEK WITH A RIDGE OVER PARTS OF THE WESTERN U.S. NORTH  
INTO CANADA AND A DEEP UPPER TROUGH CROSSING THE EASTERN HALF OF  
THE COUNTRY. GUIDANCE HAS BEEN SUGGESTING THAT A DEVELOPING SPLIT  
FLOW PATTERN FROM THE EASTERN PACIFIC INTO THE WEST WILL DECREASE  
PREDICTABILITY OF FORECAST DETAILS--INCLUDING LEADING ENERGY THAT  
MAY REACH OVER OR NEAR THE SOUTHWEST IN THE FORM OF A  
TROUGH/EMBEDDED LOW, UPSTREAM PACIFIC ENERGY, AND NORTHERN STREAM  
IMPULSES CARRIED ALONG INTO CYCLONIC FLOW THAT MAY LINGER OVER THE  
EASTERN U.S.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
FOR THE MOST PART GUIDANCE HAS REMAINED CONSISTENT AND AGREEABLE  
WITH THE DEEP UPPER TROUGH CROSSING THE EAST ALONG WITH THE  
LEADING COLD FRONT EXPECTED TO CLEAR MOST OF THE EAST COAST BY  
EARLY SUNDAY. THE SAME IS TRUE FOR THE UPPER RIDGE BUILDING INTO  
THE WEST SUNDAY-MONDAY. MODELS AND ENSEMBLES CONTINUE TO VARY FOR  
THE SPECIFICS OF SPLITTING PACIFIC ENERGY EARLY NEXT WEEK. LATEST  
TRENDS SEEM TO BE FAVORING A MODERATELY SOUTH AND SLOW UPPER LOW  
SCENARIO, WITH THIS FEATURE STILL NEAR BAJA CALIFORNIA INTO DAY 6  
WEDNESDAY (MAKING WED'S 12Z ECMWF LOOK LIKE AN OPEN/FAST EXTREME).  
THE UPPER LOW/TROUGH MAY FINALLY GET KICKED OUT BY THURSDAY AS  
ADDITIONAL PACIFIC ENERGY APPROACHES. HOWEVER THIS LATTER ENERGY  
HAS CONSIDERABLE UNCERTAINTY WITH A LOT OF MODEL/ENSEMBLE SPREAD  
AND THE OVERALL MEANS SHOWING ANOTHER RIDGE BUILDING OVER THE WEST  
COAST AT THAT TIME. GUIDANCE ALSO DIVERGES FOR SHORTWAVE DETAILS  
WITHIN THE PROGRESSIVE NORTHERN STREAM FLOW FROM THE PACIFIC,  
AROUND/THROUGH THE WESTERN U.S./CANADA RIDGE, AND EAST-SOUTHEAST  
THROUGH CANADA AND THE LOWER 48. CONFIDENCE IN ANY SPECIFIC  
SOLUTION IS MINIMAL.  
 
THE UPDATED FORECAST USED AN OPERATIONAL MODEL BLEND FOR THE FIRST  
HALF OF THE PERIOD AND THEN INCORPORATED SOME 06Z GEFS/00Z ECMWF  
MEAN INPUT. THIS APPROACH REFLECTED CONSENSUS EARLY IN THE PERIOD  
AND THEN THE MOST COMMON IDEAS LATER ON WHILE BECOMING  
CONSERVATIVE WITH SPECIFICS GIVEN THE INCREASING GUIDANCE SPREAD.  
   
..HAZARDS/SENSIBLE WEATHER HIGHLIGHTS
 
 
RAIN AND THUNDERSTORMS LIKELY TO BE IN PROGRESS AHEAD OF A GREAT  
LAKES TO SOUTHERN PLAINS COLD FRONT AS OF EARLY SUNDAY SHOULD  
CONTINUE TO SPREAD EASTWARD DURING THE DAY AND INTO SUNDAY NIGHT.  
EXPECT THE HIGHEST RAINFALL TOTALS TO BE OVER PORTIONS OF THE  
SOUTH/TENNESSEE VALLEY/SOUTHERN MID-ATLANTIC, WHERE SOME HEAVIER  
ACTIVITY MAY BE POSSIBLE. LOCALIZED FLOODING COULD BE WITHIN THE  
REALM OF POSSIBILITY WHERE THE MOST INTENSE RAINFALL COINCIDES  
WITH AREAS THAT HAVE SEEN WELL ABOVE AVERAGE PRECIPITATION  
RECENTLY. AMOUNTS WILL BE LIGHTER OVER THE NORTHERN HALF OF THE  
EAST. AREAS FROM THE UPPER GREAT LAKES TO THE NORTHEAST COULD SEE  
WINTRY WEATHER, WITH THE BEST SNOWFALL PROSPECTS OVER MICHIGAN AND  
NORTHERN NEW YORK AS A RESULT OF LAKE EFFECT SNOW. FREEZING RAIN  
AND/OR SLEET MAY BE AMONG THE HAZARDS OVER AND NEAR PARTS OF THE  
NORTHERN HALF OF THE APPALACHIANS FOR A TIME AS MOISTURE OVERRUNS  
COLD AIR AT THE SURFACE. ELSEWHERE THE MAIN AREAS OF  
PRECIPITATION SHOULD BE OVER THE PACIFIC NORTHWEST AS ONE OR MORE  
SYSTEMS BRUSH THE REGION AS THEY WEAKEN, AND OVER THE SOUTHWEST  
INTO SOUTHERN PLAINS IN ASSOCIATION WITH THE UPPER LOW/TROUGH  
CURRENTLY FORECAST TO BE AROUND THE SOUTHWEST/BAJA CALIFORNIA INTO  
MIDWEEK. COVERAGE AND AMOUNTS FOR THIS LATTER AREA WILL DEPEND ON  
UNCERTAIN DETAILS FOR THE UPPER SYSTEM.  
 
THE NEXT BLAST OF ARCTIC AIR WILL MAKE ITS PRESENCE KNOWN ACROSS  
THE NORTHERN PLAINS AND UPPER MIDWEST BY SUNDAY IN THE WAKE OF THE  
STRONG COLD FRONT WITH TEMPERATURES 10-25F BELOW NORMAL. THE COLD  
WEATHER WILL EVENTUALLY REACH THE EAST COAST IN MODIFIED FORM BY  
TUESDAY, BRINGING HIGHS DOWN TO 10-25F OR SO BELOW NORMAL FROM THE  
MID-ATLANTIC THROUGH NEW ENGLAND FOR ONE OF THE COLDEST DAYS OF  
THE SEASON THUS FAR. IT SHOULD STILL BE RATHER MILD ACROSS THE  
SOUTH AHEAD OF THE FRONT ON SUNDAY FOLLOWED BY A COLDER TREND.  
THE CENTRAL U.S. WILL SEE A PRONOUNCED WARMING TREND NEXT WEEK  
WITH EXPANDING COVERAGE OF MAX/MIN TEMPERATURES 10-20F ABOVE  
NORMAL TUESDAY ONWARD WITH SOME LOCALLY WARMER READINGS POSSIBLE  
ON SOME DAYS. EXPECT MOST OF THE WEST TO SEE TEMPERATURES WITHIN  
10F ON EITHER SIDE OF NORMAL THROUGH THE PERIOD.  
 
RAUSCH/HAMRICK  
 
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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