109  
FXUS02 KWBC 280708  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
307 AM EDT THU APR 28 2022  
 
VALID 12Z SUN MAY 01 2022 - 12Z THU MAY 05 2022  
   
..OVERVIEW
 
 
AN ACTIVE PATTERN IS LIKELY DURING THE MEDIUM RANGE PERIOD WITH A  
SERIES OF PACIFIC SYSTEMS ENTERING AND PROGRESSING ACROSS THE  
LOWER 48. THE FIRST SYSTEM WILL BE A CLOSED UPPER LOW AND  
ASSOCIATED SURFACE LOW PRESSURE THAT SHOULD LIFT SLOWLY  
NORTHEASTWARD FROM THE MIDWEST TO THE GREAT LAKES AND THE  
NORTHEASTERN U.S./SOUTHEASTERN CANADA AS IT WEAKENS  
MONDAY-TUESDAY. THIS WILL SPREAD RAIN ACROSS MUCH OF THE CENTRAL  
U.S. WITH SOME ENHANCED RAIN TOTALS AND POTENTIAL FOR SEVERE  
WEATHER IN THE SOUTHERN PLAINS TO PORTIONS OF THE MISSISSIPPI  
VALLEY, WITH LIGHTER RAINFALL EXTENDING FARTHER EAST. THE NEXT  
SYSTEM SHOULD BE SOMEWHAT WEAKER, PROGRESSING FROM THE WEST COAST  
TO NEAR THE EAST COAST DURING THE PERIOD. THEN A STRONGER SYSTEM  
IS LIKELY TO TRACK FROM THE WEST COAST MONDAY ACROSS THE ROCKIES,  
PLAINS, AND POTENTIALLY INTO THE MIDWEST BY THURSDAY. THESE LATTER  
TWO SYSTEMS WILL BRING RAIN AND HIGH ELEVATION SNOW TO THE  
NORTHWEST AND THEN AREAS OF SHOWERS AND THUNDERSTORMS TO PARTS OF  
THE CENTRAL AND EASTERN U.S., WITH SPECIFIC AREAS OF ENHANCED  
PRECIPITATION DEPENDING ON SYSTEM/FRONTAL DETAILS.  
 
   
..MODEL GUIDANCE EVALUATION
 
 
RECENT MODEL GUIDANCE HAS CONTINUED TO SHOW FAIR AGREEMENT WITH  
THE OVERALL PATTERN WITH TYPICAL DIFFERENCES IN THE  
DETAILS/SPECIFICS OF INDIVIDUAL SYSTEMS. MODEL SOLUTIONS HAVE  
CONVERGED FAIRLY WELL FOR THE LEADING SYSTEM TRACKING ACROSS THE  
MIDWEST EARLY NEXT WEEK, THOUGH WITH SOME DIVERGENCE BY  
MONDAY-TUESDAY WITH THE SURFACE LOW TRACK AND SPEED AS IT HEADS  
INTO CANADA WHILE WEAKENING. MEANWHILE THERE ARE STILL MEANINGFUL  
DETAIL AND TRACK ISSUES WITH THE TROUGH OVER THE NORTHWEST  
SUNDAY--ECMWF RUNS HAVE BEEN PERSISTENT WITH AN INITIAL UPPER LOW,  
WHICH THE 00Z CMC HAS NOW JOINED, BUT GUIDANCE HAS A TREND TOWARD  
SOME WEAKENING OF THE ENERGY AS IT TRACKS EAST ACROSS THE COUNTRY  
DURING THE FIRST HALF OF THE WEEK. HOWEVER, THE SHORTWAVE SHOULD  
STILL BE STRONG ENOUGH TO PRODUCE A SURFACE WAVE OVER ~ILLINOIS AS  
SHOWN BY MODEL GUIDANCE FROM THE LAST DAY OR SO, WITH SOME VARIETY  
IN POSITION FROM CYCLE TO CYCLE. NEWER 00Z GUIDANCE HAS SHOWN A  
BIT OF A WESTWARD POSITION WITH THE LOW OVER THE MID-MISSISSIPPI  
VALLEY TUESDAY MORNING COMPARED TO THE 12/18Z CYCLE. THE TIMING OF  
THE SURFACE LOW TUESDAY-WEDNESDAY IS AFFECTED BY THE POTENTIAL FOR  
STREAM INTERACTION OVER EASTERN NORTH AMERICA AND THE TIMING OF  
THE ABSORPTION OF THE SHORTWAVE.  
 
MODEL GUIDANCE REMAINS LEAST AGREEABLE WITH THE LAST SYSTEM OF  
NOTE DURING THE PERIOD--SIGNIFICANT ENERGY SPILLING INTO THE WEST  
MONDAY THAT LIKELY FORMS A CLOSED LOW AS IT TRACKS EASTWARD  
EVENTUALLY INTO THE CENTRAL U.S. BY WEDNESDAY-THURSDAY,  
ACCOMPANIED BY A SURFACE LOW PRESSURE/FRONTAL SYSTEM. THE TREND  
FOR EASTERN/FASTER GFS RUNS AND WESTERN/SLOWER ECMWF RUNS HAS  
STAYED CONSISTENT THROUGH THE 12/18Z AND 00Z CYCLES, AND THE  
ENSEMBLE MEANS FOR BOTH HAVE GENERALLY FOLLOWED THEIR OPERATIONAL  
MODEL TRENDS. THE 12Z AND NOW 00Z CMC AS WELL AS THE 12Z CMC  
ENSEMBLE MEAN HAVE PROVIDED A MIDDLE GROUND IN BETWEEN THESE SLOW  
AND FAST SOLUTIONS WITH THIS FEATURE. HOWEVER, THE CMC RUNS DO  
SHOW AN UPPER LOW FARTHER NORTH IN SOUTH-CENTRAL CANADA AROUND  
TUESDAY MOVING EAST THROUGH THURSDAY WHERE OTHER GUIDANCE HANDLED  
THESE NORTHERN STREAM FEATURES DIFFERENTLY--THOUGH THE 00Z ECMWF  
IS NOW A LITTLE CLOSER TO THIS--AND HAS THE NORTHERN FEATURE  
PHASING WITH THE U.S. UPPER LOW UNLIKE OTHER GUIDANCE. THUS WHILE  
THE CMC RUNS SEEM TO BE A GOOD MIDDLE GROUND OVER THE U.S. ITS  
PATTERN FARTHER NORTH AND THE EVOLUTION OF THOSE FEATURES IS  
SOMEWHAT QUESTIONABLE.  
 
THE WPC FORECAST EARLY IN THE PERIOD USED A BLEND OF THE  
DETERMINISTIC GUIDANCE LED BY THE 12Z ECMWF AND 18Z GFS. AS THE  
PERIOD PROGRESSED, LESSENED THE INFLUENCE OF THE FAST GFS AND SLOW  
ECMWF IN FAVOR OF THE ECMWF AND THE CMC ENSEMBLE MEANS, WHILE  
KEEPING THE 12Z CMC IN THE MIX. THIS ATTEMPT AT AN INTERMEDIATE  
SOLUTION LED TO REASONABLY GOOD CONSISTENCY WITH THE PREVIOUS  
FORECAST AT LEAST AT THE 500MB LEVEL, THOUGH THE CONTINUED  
UNCERTAINTY WITH THE TRACK OF SURFACE FEATURES COULD CONTINUE  
LEADING TO SOME CHANGES IN THE FRONTAL, TEMPERATURE, AND  
PRECIPITATION FORECASTS GOING FORWARD.  
 
   
..SENSIBLE WEATHER/THREATS
 
 
THE FIRST SURFACE LOW PRESSURE SYSTEM AFFECTING THE LOWER 48 EARLY  
NEXT WEEK WILL SPREAD PRECIPITATION ACROSS MUCH OF THE EASTERN  
U.S. WITH GENERALLY LIGHT TO MODERATE RAIN, BUT WITH POTENTIAL FOR  
LOCALLY HEAVY TO EXCESSIVE AMOUNTS BACK ACROSS THE CENTRAL U.S.  
WHERE FRONTS ARE EXPECTED TO STALL. CURRENT FORECASTS SHOW THE  
HEAVIEST RAINFALL AMOUNTS IN THE SOUTHERN PLAINS SUNDAY-SUNDAY  
NIGHT AND SPREADING INTO THE LOWER/MIDDLE MISSISSIPPI VALLEY ON  
MONDAY, BUT EXACT POSITIONING OF THE HEAVIEST RAIN COULD SHIFT  
WITH FUTURE FORECASTS GIVEN LINGERING UNCERTAINTY. THE SAME IS  
TRUE FOR SEVERE WEATHER, BUT THE STORM PREDICTION CENTER CURRENTLY  
INDICATES THE BEST POTENTIAL FOR SEVERE THUNDERSTORMS ACROSS THE  
SOUTHERN PLAINS SUNDAY AND MONDAY. WITH ANOTHER POTENTIAL  
EARLY-MID WEEK WAVE PLUS A TRAILING ONE REACHING THE PLAINS BY  
AROUND WEDNESDAY, RAIN SHOWERS AND THUNDERSTORMS WILL LIKELY  
PERSIST FROM THE PLAINS EASTWARD THROUGH MUCH OF NEXT WEEK. SOME  
AREAS OVER THE CENTRAL U.S. NEED TO MONITOR FORECASTS OF THE  
MIDWEEK SYSTEM GIVEN ITS POTENTIAL TO PRODUCE SIGNIFICANT WEATHER  
AND SENSITIVITY TO ADDITIONAL RAINFALL. THE LATTER TWO UPPER  
SHORTWAVES/SURFACE SYSTEMS WILL BRING ROUNDS OF MOSTLY LIGHT TO  
MODERATE PRECIPITATION (SNOW IN THE HIGHER ELEVATIONS AND RAIN IN  
THE LOWER ELEVATIONS) ACROSS THE NORTHWEST, MAINLY IN THE  
SATURDAY-MONDAY PERIOD AND PERHAPS LINGERING OVER PARTS OF THE  
ROCKIES AFTER THEN.  
 
TEMPERATURE-WISE, THE GENERAL TREND OVER THE LOWER 48 WILL BE FOR  
COOLER THAN AVERAGE WEATHER IN THE NORTHERN TIER AND WARMER THAN  
AVERAGE IN THE SOUTHERN TIER. THE CORE OF THE COLDEST AIR SHOULD  
BE ACROSS THE NORTHERN HIGH PLAINS TO MIDWEST, WHERE HIGHS WILL BE  
AROUND 10-20F BELOW AVERAGE DUE TO BEING IN THE COLD SECTOR OF  
INITIAL LOW PRESSURE AFFECTING THE REGION FOLLOWED BY INFLUENCE  
FROM THE SOUTHERN PERIPHERY OF CANADIAN HIGH PRESSURE AND MOISTURE  
ARRIVING WITH ANOTHER SYSTEM TOWARD MIDWEEK. LOWS SHOULD STAY  
CLOSER TO NORMAL THOUGH. MEANWHILE, SLIGHTLY ABOVE NORMAL  
TEMPERATURES SHOULD STRETCH ACROSS MUCH OF THE SOUTHERN TIER, WITH  
MAINLY WARMER THAN AVERAGE LOWS ALSO SPREADING INTO THE  
OHIO/TENNESSEE VALLEYS DURING THE WEEKEND AND MORE OF THE EAST  
NEXT WEEK. BEST POTENTIAL FOR SOME PLUS 10-15F ANOMALIES FOR HIGHS  
WILL BE OVER THE SOUTHERN HIGH PLAINS EARLY NEXT WEEK WHILE  
SIMILAR ANOMALIES FOR MORNING LOWS MAY BE A LITTLE MORE COMMON ON  
SOME DAYS.  
 
TATE/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, EXPERIMENTAL EXCESSIVE RAINFALL  
OUTLOOK, 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/#PAGE=ERO  
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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