351  
FXUS02 KWBC 211901  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
301 PM EDT SAT MAY 21 2022  
 
VALID 12Z TUE MAY 24 2022 - 12Z SAT MAY 28 2022  
 
...MULTI-DAY HEAVY RAINFALL AND STRONG THUNDERSTORM THREAT FROM  
THE SOUTHERN PLAINS AND LOWER MISSISSIPPI/TENNESSEE VALLEYS TO THE  
OHIO VALLEY AND GREAT LAKES EARLY-MID NEXT WEEK TO WORK ACROSS THE  
EAST LATER WEEK...  
 
   
..WEATHER PATTERN OVERVIEW
 
 
A STORMY WEATHER PATTERN IS EXPECTED TO DEVELOP ACROSS THE  
CONTINENTAL U.S. GOING INTO THE MIDDLE OF NEXT WEEK, AS MULTIPLE  
WAVES OF LOW PRESSURE DEVELOP ALONG A FRONTAL BOUNDARY SITUATED  
OVER THE PLAINS AND EXTENDING TO THE GREAT LAKES. THIS WILL BE IN  
RESPONSE TO A BUILDING UPPER LEVEL TROUGH OVER THE HIGH PLAINS  
THAT WILL SLOWLY MOVE EASTWARD THROUGH THE WEEK WITH THE FRONT  
REACHING THE EAST COAST BY FRIDAY. A SECOND SYSTEM IS SLATED TO  
DIG THROUGH THE NORTHWEST TO THE NORTH-CENTRAL INTERMOUNTAIN  
WEST/ROCKIES AND NORTHERN PLAINS THURSDAY-SATURDAY.  
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
MODELS AND ENSEMBLES CONTINUE TO OFFER BELOW NORMAL FORECAST  
SPREAD/UNCERTAINTY DAYS 3-7, BOLSTERING FORECAST CONFIDENCE TO  
ABOVE NORMAL VALUES. WHILE LOCAL CONVECTIVE RAINFALL FOCUS REMAINS  
LESS SETTLED, GUIDANCE OFFERS CONSISTENT REGIONAL AREAS OF THREAT.  
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A  
COMPOSITE BLEND OF THE 06 UTC GFS AND 00 UTC ECMWF/UKMET/CANADIAN,  
WPC CONTINUITY AND THE 13 UTC NATIONAL BLEND OF MODELS (NBM) DAYS  
3-5 (TUESDAY-THURSDAY) BEFORE ENOUGH UNCERTAINTY WITH FLOW  
PROGRESSION AND CONVECTIVE INTERACTIONS COMPOUNDS TO FAVOR BLEND  
INTRODUCTION OF THE 06 UTC GEFS MEAN AND 00 UTC ECMWF ENSEMBLE  
MEAN TO SMOOTH THE ROUGH EDGES CONSISTENT WITH PREDICTABILITY.  
THIS COMPOSITE SOLUTION NOW ALSO SEEMS OVERALL IN LINE WITH LATEST  
12 UTC MODELS AND ENSEMBLES.  
   
..SENSIBLE WEATHER/THREAT HIGHLIGHTS
 
 
THE NEXT SYSTEM DEVELOPING OVER THE SOUTH-CENTRAL U.S. INTO  
EARLY-MID NEXT WEEK IS EXPECTED TO BECOME THE MAIN WEATHER  
HEADLINE OF THIS FORECAST PERIOD. THERE WILL LIKELY BE WIDESPREAD  
CONVECTION AND HEAVY RAINFALL FROM TEXAS TO THE GREAT LAKES WITH  
MOIST RETURN FLOW INTO ANOTHER SLOW MOVING AND WAVY FRONTAL  
SYSTEM. THERE IS AN INCREASING POTENTIAL FOR SOME FLASH FLOODING  
WITH THE SLOWER MOVING STORMS WITHIN A VERY MOIST AND UNSTABLE  
ATMOSPHERE. THE LATEST WPC EXPERIMENTAL EXCESSIVE RAINFALL OUTLOOK  
INDICATES A SLIGHT RISK AREA FOR TUESDAY INTO THURSDAY FROM THE  
ARKLATEX REGION INTO THE LOWER MISSISSIPPI/OHIO VALLEYS. AND THE  
POTENTIAL EXISTS FOR 3 TO 6+ INCH RAINFALL TOTALS OVER THAT 48  
HOUR TIME PERIOD. SOME SEVERE STORMS ARE CERTAINLY WITHIN THE  
REALM OF POSSIBILITY FOR THESE SAME GENERAL AREAS WHERE PARAMETERS  
OF SHEAR AND INSTABILITY ARE GREATEST, ALTHOUGH MODEL DIFFERENCES  
REMAIN ON THE PLACEMENT OF MCS ACTIVITY. WIDESPREAD CONVECTION  
WILL ALSO SPREAD ACROSS THE EASTERN STATES LATER WEEK WITH LESS  
CERTAINTY/DETAILS BUT LOCAL THREAT POTENTIAL.  
 
THE WEST-CENTRAL U.S. TROUGH SHOULD INITIALLY KEEP TEMPERATURES  
BELOW NORMAL ACROSS ROCKIES AND EXTENDING ACROSS THE CENTRAL  
PLAINS THROUGH ABOUT WEDNESDAY BEFORE MUCH WARMER WEATHER RETURNS  
BY THE END OF THE WEEK. SOME LATE SEASON SNOW SHOWERS WILL ALSO BE  
POSSIBLE ACROSS THE HIGHER TERRAIN OF CENTRAL COLORADO ON TUESDAY.  
MUCH OF THE SOUTHWESTERN U.S. SHOULD REMAIN DRY THROUGH THE END OF  
NEXT WEEK AS UPPER RIDGING BUILDS OVER THE REGION AND WARMER  
TEMPERATURES EXPAND ACROSS THE REGION. BUILDING HEAT ACROSS  
INTERIOR PORTIONS OF CALIFORNIA AND THE DESERT SOUTHWEST COULD  
RESULT IN HIGHS RUNNING 10-20 DEGREES ABOVE NORMAL FOR SOME AREAS,  
WITH WIDESPREAD 100+ DEGREE HIGH TEMPERATURES FOR THE LOWER  
ELEVATIONS. THERE WILL LIKELY BE SOME SHOWERS ACROSS THE PACIFIC  
NORTHWEST BY FRIDAY AND THEN REACHING THE NORTHERN ROCKIES/PLAINS  
WITH SOME THUNDERSTORMS BY SATURDAY AS THE NEXT FRONT ENTERS THIS  
REGION.  
 
SCHICHTEL/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, 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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