581  
FXUS02 KWBC 210658  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
258 AM EDT SAT MAY 21 2022  
 
VALID 12Z TUE MAY 24 2022 - 12Z SAT MAY 28 2022  
 
...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...  
 
   
..WEATHER PATTERN OVERVIEW
 
 
A RATHER ACTIVE 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 WESTERN HIGH  
PLAINS THAT WILL SLOWLY MOVE EASTWARD THROUGH THE WEEK WITH THE  
FRONT REACHING THE EAST COAST BY FRIDAY. MEANWHILE, A SECOND  
STORM SYSTEM IS PROGGED TO REACH THE PACIFIC NORTHWEST BY LATE  
THURSDAY AND THEN REACH THE ROCKIES AND THE NORTHERN PLAINS BY  
EARLY SATURDAY, ALTHOUGH NOT CURRENTLY EXPECTED TO BE AS IMPACTFUL  
AS THE EARLIER EVENT ACROSS THE PLAINS.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
THE 00Z MODEL GUIDANCE SUITE IS IN DECENT SYNOPTIC SCALE AGREEMENT  
FOR THE BEGINNING TO MIDDLE OF NEXT WEEK, AND THERE HAS BEEN MORE  
CONSOLIDATION AND LESS MODEL SPREAD COMPARED TO THIS TIME  
YESTERDAY. HOWEVER, THERE IS STILL UNCERTAINTY WITH REGARDS TO  
PLACEMENT OF HEAVIEST QPF MAXIMA AS THESE WILL BE THE RESULT OF  
MULTIPLE MCS CLUSTERS. THERE ARE MORE MODEL DIFFERENCES APPARENT  
WITH THE TROUGH ENTERING THE PACIFIC NORTHWEST BY THURSDAY, WITH  
THE 00Z GFS INDICATING A FASTER SOLUTION AND BECOMING MORE  
AMPLIFIED BY FRIDAY AND SATURDAY WITH A CLOSED UPPER LOW  
DEVELOPING. THE WPC FRONTS/PRESSURES FORECAST WAS PRIMARILY  
DERIVED FROM A MULTI-DETERMINISTIC MODEL CONSENSUS THROUGH  
WEDNESDAY, AND THEN INCORPORATED MORE OF THE ENSEMBLE MEANS FOR  
THE THURSDAY-SATURDAY TIME PERIOD WHILE STILL MAINTAINING SOME OF  
THE 18Z GFS AND 12Z ECMWF.  
 
   
..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 CENTRAL/EASTERN 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 BOTH TUESDAY AND  
WEDNESDAY ACROSS THE ARKLATEX REGION AND EXTENDING ACROSS ARKANSAS  
AND INTO WESTERN TENNESSEE, 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.  
 
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 BY  
SATURDAY AS THE NEXT FRONT ENTERS THIS REGION.  
 
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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