228  
FXUS02 KWBC 220700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
159 AM EST SAT JAN 22 2022  
 
VALID 12Z TUE JAN 25 2022 - 12Z SAT JAN 29 2022  
   
..OVERVIEW
 
 
GUIDANCE CONTINUES TO SHOW A STRONG EASTERN PACIFIC RIDGE HELPING  
TO KEEP A BROAD MEAN TROUGH ACROSS A MAJORITY OF THE LOWER 48  
THROUGH WEDNESDAY. THE PACIFIC RIDGE WILL LIKELY DRIFT INTO THE  
WEST BY THURSDAY-FRIDAY, FOLLOWED BY SOME WEAKENING DEPENDING ON  
VERY UNCERTAIN DETAILS OF UPSTREAM SHORTWAVE ENERGY. MEANWHILE  
WITHIN THE LOWER 48 MEAN TROUGH, ONE SHORTWAVE WILL ROTATE THROUGH  
THE EASTERN HALF OF THE COUNTRY DURING THE FIRST HALF OF THE  
PERIOD AND THEN ANOTHER SHORTWAVE DROPPING INTO THE CENTRAL U.S.  
LATE IN THE WEEK MAY REACH NEAR THE EAST COAST BY EARLY SATURDAY.  
THERE IS A DECENT SIGNAL THAT THIS LATTER SHORTWAVE WILL SUPPORT A  
DEVELOPING EAST COAST/WESTERN ATLANTIC STORM BY NEXT WEEKEND BUT  
WITH LOW CONFIDENCE IN DETAILS. THE PATTERN THROUGH THE PERIOD  
WILL GENERALLY FAVOR BELOW TO WELL BELOW NORMAL TEMPERATURES OVER  
THE EASTERN HALF OF THE COUNTRY AND MILD TEMPERATURES FROM THE  
WEST INTO THE NORTHERN/CENTRAL PLAINS. PRECIPITATION COVERAGE AND  
INTENSITY ACROSS THE LOWER 48 WILL TEND TO BE LOW ASIDE FROM AN  
AREA OF MOISTURE CROSSING THE EAST ON TUESDAY AND THEN POSSIBLY  
OVER PARTS OF THE SOUTH AND EAST BY THE END OF THE WEEK/NEXT  
WEEKEND DEPENDING ON DETAILS OF UPPER FLOW AND SURFACE DEVELOPMENT.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
AT THE START OF THE PERIOD, GUIDANCE STILL VARIES SOMEWHAT ON THE  
FINE-SCALE DETAILS OF INITIAL NORTHERN GULF OF MEXICO LOW PRESSURE  
QUICKLY TRACKING INTO THE ATLANTIC AS SUPPORTING DYNAMICS SHEAR  
OUT WITHIN ACCELERATING FLOW ALOFT. A BLEND APPROACH MAINTAINS  
THE PREVAILING THEME OF THE EVOLUTION. THEN CONTINUITY AND  
AGREEMENT ARE DECENT WITH A CANADIAN SYSTEM DROPPING INTO THE  
GREAT LAKES BY LATE IN THE WEEK AND THEN WEAKENING.  
 
THE REST OF THE LATE-PERIOD FORECAST BECOMES MORE UNCERTAIN AS  
MODELS AND ENSEMBLES DIVERGE CONSIDERABLY FOR EASTERN  
PACIFIC/WESTERN U.S. DETAILS. WITH SOME POSSIBLE INFLUENCE FROM  
THESE ISSUES, THE EVOLUTION OVER AND NEAR THE EAST BY LATE  
FRIDAY-SATURDAY ALSO DISPLAYS A FAIR DEGREE OF UNCERTAINTY. IN  
CONTRAST TO PREVIOUS TREND, OVER THE PAST DAY GUIDANCE HAS TRENDED  
STRONGER WITH THE UPPER RIDGE REACHING THE WEST LATE IN THE WEEK  
AND INCREASINGLY VARIED WITH HOW ENERGY WITHIN THE SHORTWAVE  
APPROACHING FROM THE WEST MAY SEPARATE (AS ILLUSTRATED MOST SIMPLY  
BY THE 12Z AND NEW 00Z ECMWF RUNS). BY DAY 7 SATURDAY THE END  
RESULT OVER THE WEST IS A CHAOTIC ENSEMBLE SPAGHETTI PLOT WITH  
ANYTHING BETWEEN A SHORTWAVE OR LINGERING RIDGE A POSSIBILITY.  
THE 12Z ECMWF MEAN'S SHORTWAVE DID NOT HAVE MUCH AGREEMENT AMONG  
OTHER 12Z/18Z MODELS AND MEANS BUT THE NEW 00Z CMC HAS COME IN  
WITH A SIMILAR FEATURE AND THE NEW ECMWF HAS A FAIRLY STRONG  
SHORTWAVE. THERE IS A SOMEWHAT BETTER SUGGESTION THAT ENERGY  
ROUNDING THE RIDGE MAY SUPPORT A WAVE/FRONT DROPPING INTO THE  
NORTHERN TIER ON SATURDAY. THE MOST COMMON THEME FARTHER EAST IS  
FOR LOW PRESSURE TO BE ORGANIZING OVER THE WESTERN ATLANTIC BY  
EARLY SATURDAY. THE 18Z/00Z GFS RUNS ARE CLOSEST TO THE  
RELATIVELY HIGHER DENSITY OF ENSEMBLE SURFACE LOWS AT THAT TIME  
WHILE RECENT CMC RUNS HAVE BEEN SOMEWHAT IN THE NEIGHBORHOOD. THE  
12Z GFS/ECMWF WERE ON THE SOUTHWESTERN EDGE OF THE SPREAD. THE  
NEW 00Z ECMWF IS CLOSER TO THE MAJORITY CLUSTER IN PRINCIPLE.  
 
BASED ON LATEST GUIDANCE COMPARISONS, THE UPDATED FORECAST  
REFLECTED A BLEND OF 12Z/18Z OPERATIONAL MODELS EARLY IN THE  
PERIOD AND THEN TRANSITIONED TOWARD GREATER WEIGHT OF THE  
GEFS/ECENS/CMCENS DUE TO THE UNCERTAINTY OF UPPER DETAILS OVER THE  
WEST TOWARD THE END OF THE PERIOD AND TO YIELD THE HIGHEST  
PROBABILITY TRACK FOR WESTERN ATLANTIC LOW PRESSURE BY SATURDAY.  
MANUAL DEPICTION OF THIS LOW WILL LIKELY TREND DEEPER AS  
CONFIDENCE IN STRENGTH AND TRACK IMPROVES.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
THE COMBINATION OF A NORTHERN GULF OF MEXICO WAVE QUICKLY MOVING  
INTO THE ATLANTIC AND A COLD FRONT CROSSING THE EAST WILL SPREAD  
AN AREA OF PRECIPITATION ACROSS THE EAST ON TUESDAY. MOST AMOUNTS  
WILL BE IN THE LIGHT TO MODERATE RANGE, WITH SOME PROPORTION OF  
THE PRECIPITATION POSSIBLY BEING IN THE FORM OF SNOW FROM THE OHIO  
VALLEY/CENTRAL APPALACHIANS INTO THE NORTHEAST. A PERIOD OF LAKE  
EFFECT SNOW WILL BE POSSIBLE BEHIND THE FRONT. A TRAILING  
WAVE/FRONT MAY SPREAD AREAS OF LIGHT SNOW FROM THE NORTHERN PLAINS  
INTO THE GREAT LAKES AND NORTHEAST FROM ABOUT MIDWEEK INTO THE  
WEEKEND. SUPPORTING DYNAMICS COULD BE AMPLIFIED ENOUGH TO SUPPORT  
SOME PRECIPITATION FARTHER SOUTH AS WELL BUT WITH LOW CONFIDENCE  
OVER COVERAGE AND AMOUNTS. BY NEXT SATURDAY THE  
COVERAGE/INTENSITY/TYPE OF PRECIPITATION ALONG THE EAST COAST ARE  
LIKEWISE UNCERTAIN AT THIS TIME AND WILL REQUIRE CLOSE MONITORING.  
PARTS OF THE HIGH PLAINS MAY SEE LIGHT SNOW ON TUESDAY. MUCH OF  
THE WEST SHOULD BE DRY DURING THE PERIOD. SOME MOISTURE COULD  
EVENTUALLY REACH THE PACIFIC NORTHWEST BY NEXT SATURDAY.  
 
A SURGE OF COLD AIR WILL INITIALLY BE OVER THE UPPER MISSISSIPPI  
VALLEY AND MIDWEST ON TUESDAY, WITH SOME AREAS SEEING TEMPERATURES  
20-25F BELOW NORMAL FROM TUESDAY INTO EARLY WEDNESDAY. THIS COLD  
WILL THEN SPREAD TOWARD/INTO THE SOUTH AND EAST WITH TIME,  
BRINGING A DAY OR SO OF READINGS THAT ARE 10-20F ABOVE NORMAL. BY  
FRIDAY-SATURDAY THE MID-ATLANTIC AND NORTHEAST MAY MODERATE SOME  
WHILE PARTS OF THE SOUTHEAST MAY SEE HIGHS AT LEAST 10F BELOW  
NORMAL. AFTER LESS EXTREME COLD PASSES THROUGH THE  
CENTRAL/SOUTHERN PLAINS EARLY IN THE PERIOD, MOST OF THE PLAINS  
WILL SEE A WARMING TREND WITH SOME AREAS SEEING TEMPERATURES AT  
LEAST 10F ABOVE NORMAL. THE WEST WILL SEE MODERATELY ABOVE NORMAL  
TEMPERATURES NEXT WEEK WITH SOME LOCALIZED PLUS 10-15F ANOMALIES  
FOR HIGHS.  
 
RAUSCH  
 
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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