476  
FXUS02 KWBC 201850  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
150 PM EST SUN FEB 20 2022  
 
VALID 12Z WED FEB 23 2022 - 12Z SUN FEB 27 2022  
 
...HEAVY TO EXCESSIVE RAINFALL THREAT FROM THE LOWER  
MISSISSIPPI/TENNESSEE VALLEYS TO THE MID-ATLANTIC ALONG WITH A  
HEAVY SNOW/ICE THREAT FROM THE SOUTHERN PLAINS TO THE NORTHEAST  
WEDNESDAY-FRIDAY...  
 
   
..PATTERN OVERVIEW
 
 
EXPECT AN ACTIVE MID-WINTER PATTERN THIS WEEK AS COLD CANADIAN  
HIGH PRESSURE DIGS ACROSS MUCH OF THE LOWER 48 STATES. UPPER LEVEL  
TROUGHS WILL DIG THROUGH THE WEST, WITH EJECTING ENERGIES AND  
INDUCED FRONTAL WAVES PROGRESSING DOWNSTREAM THEN OVERTOP A  
WARMING SOUTHEAST/EAST UPPER RIDGE. THE MAIN UPPER TROUGH SHOULD  
SHIFT EASTWARD INTO THE CENTRAL PLAINS AND MIDWEST BY LATER WEEK  
AS AMPLIFIED RIDGING BUILDS FROM THE EAST PACIFIC INTO THE WEST  
COAST. THIS AMPLIFIED PATTERN FAVORS A HEAVY TO EXCESSIVE RAINFALL  
THREAT FROM THE LOWER MISSISSIPPI/TENNESSEE VALLEYS TO THE  
MID-ATLANTIC ALONG WITH A HEAVY SNOW AND ICE THREAT FROM THE  
SOUTHERN PLAINS TO THE NORTHEAST WEDNESDAY INTO FRIDAY.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE LATEST SUITE OF MODELS AND ENSEMBLES CONTINUE TO OFFER A  
SIMILAR LARGE SCALE FLOW EVOLUTION THROUGH AT LEAST DAY 5. AS  
SUCH, A COMPOSITE BLEND OF THE 06Z GFS AND 00Z ECMWF/UKMET/CMC  
WERE USED. AFTER DAY 5/NEXT WEEKEND, THERE REMAINS QUESTIONS ON  
HOW QUICKLY THE PATTERN WILL DEAMPLIFY AND THE UPPER TROUGH ENERGY  
WEAKENS AND SHIFTS EAST. THE 00Z ECMWF IS NOTABLY STRONGER WITH  
THIS ENERGY AND SLOWER, WITH THE 06Z/12Z GFS TRENDING MUCH FASTER.  
THE 00Z/12Z CMC ACTUALLY PROVIDES A DECENT MIDDLE GROUND SOLUTION,  
ALONG WITH THE ENSEMBLE MEANS. THESE DIFFERENCES CONTRIBUTE TO  
FRONTAL PLACEMENT UNCERTAINTIES ACROSS THE SOUTH ON DAY 7 AND SOME  
RATHER SIGNIFICANT QPF DIFFERENCES TOO. FOR DAYS 6-7, PREFER A  
SOLUTION MORE AMPLIFIED THAN THE GFS, BUT MAYBE NOT QUITE AS  
ROBUST AS THE ECMWF. THE WPC BLEND USED SMALLER PORTIONS OF THE  
CMC/ECMWF BLENDED WITH THE ENESMBLE MEANS, WHICH ALSO KEPT GOOD  
CONTINUITY WITH THE PREVIOUS WPC FORECAST.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
MODERATE TO HEAVY MOUNTAIN SNOWS ARE LIKELY MIDWEEK FOR THE  
SOUTH-CENTRAL GREAT BASIN/ROCKIES WITH THE APPROACH/PASSAGE OF  
POTENT UPPER TROUGH ENERGY AND AS ENHANCED BY UPSLOPE FETCH. AMPLE  
UPPER ENERGIES WORKING DOWNSTREAM FROM THE WEST WILL ALSO ACT TO  
INDUCE WAVES ALONG A LEAD FRONT AND TAP DEEPENING MOISTURE FROM  
THE GULF OF MEXICO. THIS IS EXPECTED TO FUEL A HEAVY TO EXCESSIVE  
RAINFALL AND CONVECTION THREAT FROM THE LOWER  
MISSISSIPPI/TENNESSEE VALLEYS TO THE MID-ATLANTIC, MAINLY  
WEDNESDAY/THURSDAY. SOME PARTS OF ESPECIALLY THE TENNESSEE VALLEY  
MAY RECEIVE ADDITIONAL HEAVY RAINFALL DURING THIS TIME, AFTER AN  
INITIAL ROUND IN THE SHORT RANGE PERIOD, WHICH COULD LEAD TO AN  
INCREASED THREAT FOR FLOODING AND/OR FLASH FLOODING. WAVE  
ORGANIZATION AND REDEVELOPMENT SHOULD ALSO SUPPORT THE SPREAD OF A  
POTENTIALLY SIGNIFICANT HEAVY SNOW/ICE THREAT FROM PARTS OF THE  
SOUTHERN PLAINS AND MID-MISSISSIPPI/OHIO VALLEYS TO A COLD AIR  
DAMMED NORTHERN MID-ATLANTIC AND NORTHEAST WEDNESDAY-FRIDAY.  
 
STRONG RIDGING BUILDING OVER THE WESTERN U.S. MID TO LATE PERIOD  
SHOULD RESULT IN A VERY DRY PERIOD ACROSS MUCH OF THE WEST, THOUGH  
SOME RAIN/MOUNTAIN SNOW MAY TRY TO MOVE BACK INTO THE PACIFIC  
NORTHWEST NEXT WEEKEND ASSOCIATED WITH NORTHEAST PACIFIC SHORTWAVE  
ENERGY. ACROSS THE SOUTH, SIGNIFICANT UNCERTAINTY CONCERNING  
AMPLITUDE/SPEED OF THE WESTERN TROUGH RESULTS IN LARGE DIFFERENCES  
IN POTENTIAL QPF ACROSS THE MID-SOUTH, ESPECIALLY THE LOWER  
MISSISSIPPI VALLEY TO TENNESSEE VALLEY. GENERALLY LIGHT TO  
MODERATE RETURN FLOW MOISTURE INTO THE REGION IS EXPECTED,  
ALTHOUGH THERE ARE SOME MODEL SOLUTIONS SUGGESTING A HEAVIER EVENT  
COULD MATERIALIZE RESULTING IN ANOTHER ROUND OF HEAVY RAINFALL FOR  
AN ALREADY WATER LOGGED REGION.  
 
THE COLD HIGH PRESSURE SURGE WILL SPREAD MUCH BELOW TEMPERATURES  
ACROSS MUCH OF THE WESTERN AND CENTRAL U.S. BY MID-LATE WEEK TO  
INCLUDE WIDESPREAD RECORD COLD VALUES, ESPECIALLY FRIGID FROM THE  
NORTHERN HIGH PLAINS TO THE NORTHERN/CENTRAL PLAINS WHERE DAYTIME  
HIGHS AND OVERNIGHT LOWS COULD BE 30-40+ DEGREES BELOW NORMAL.  
THIS VERY COLD AIR WILL SPREAD, BUT GRADUALLY MODIFY LATER WEEK  
ACROSS THE MIDWEST/EAST. MEANWHILE, MUCH ABOVE NORMAL PRE-FRONTAL  
TEMPERATURES ARE EXPECTED ACROSS THE SOUTHEAST/EAST WITH SOME  
RECORD WARMTH LIKELY, ESPECIALLY OVERNIGHT MINS WITH UPPER LEVEL  
RIDGING AND ENHANCED PRE-FRONTAL MOISTURE INTO THE REGION.  
 
SANTORELLI/SCHICHTEL  
 
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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