397  
FXUS02 KWBC 190648  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
248 AM EDT THU MAY 19 2022  
 
VALID 12Z SUN MAY 22 2022 - 12Z THU MAY 26 2022  
 
...EXCESSIVE HEAT CONTINUES INTO SUNDAY FOR PARTS OF THE  
MID-ATLANTIC/NORTHEAST...  
 
...HEAVY RAIN THREAT SHIFTS FROM THE CENTRAL GULF COAST ON SUNDAY  
INTO THE SOUTHERN PLAINS EARLY NEXT WEEK...  
 
   
..OVERVIEW
 
 
THE UPPER FLOW PATTERN DURING THE MEDIUM RANGE PERIOD SHOULD STAY  
AMPLIFIED AND ACTIVE INTO MID NEXT WEEK. THE PERIOD BEGINS SUNDAY  
WITH A SHORTWAVE PUSHING A STRONG COLD FRONT THROUGH THE EASTERN  
U.S. WHICH SHOULD FINALLY BRING AN END TO RECORD OR NEAR RECORD  
HEAT THIS UPCOMING WEEKEND. A DIGGING TROUGH ACROSS THE WESTERN  
U.S. WILL SHIFT EAST WITH TIME, WITH AN INCREASING SIGNAL FOR A  
POTENTIAL MULTI-DAY HEAVY RAINFALL EVENT FOR THE SOUTH-CENTRAL  
U.S. EARLY NEXT WEEK. MEANWHILE, LEADING SOUTHERN STREAM ENERGY  
WILL INTERACT WITH INCREASING TROPICAL MOISTURE TO FUEL HEAVY RAIN  
AND STORMS ACROSS THE CENTRAL GULF COAST AND PARTS OF THE  
SOUTHEAST ON SUNDAY.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
THE GUIDANCE CONTINUES TO SHOW GOOD ENOUGH AGREEMENT THE FIRST  
HALF OF THE PERIOD FOR A PURELY DETERMINISTIC MODEL BLEND BETWEEN  
THE LATEST AVAILABLE RUNS OF THE GFS, ECMWF, AND CMC. THE PAST FEW  
DAYS OF RUNS HAVE SHOWN SIGNIFICANT UNCERTAINTY PAST THE WEEKEND  
REGARDING EVOLUTION OF TROUGHING ACROSS THE WEST/CENTRAL U.S., BUT  
TODAY, MODELS ARE FINALLY SHOWING MUCH BETTER AGREEMENT ON A MORE  
AMPLIFIED PATTERN THAN PREVIOUS SUGGESTED BY SOME OF THE GUIDANCE.  
THE NOTABLE DIFFERENCE WAS THE 12Z/YESTERDAY UKMET WHICH CONTINUED  
TO SHOW A MUCH WEAKER/FASTER SHORTWAVE PROGRESSION THROUGH  
TUESDAY, AND THUS WAS NOT INCLUDED IN TONIGHTS BLEND. TONIGHTS 00Z  
RUN OF THE UKMET DID TREND SLIGHTLY STRONGER AND MORE TOWARDS THE  
CONSENSUS. BY NEXT TUESDAY-THURSDAY, THERE ARE SOME TIMING  
DIFFERENCES WHICH BEGIN TO ARISE WITH THE ECMWF/CMC SLIGHTLY  
FASTER/LESS AMPLIFIED THAN THE GFS WHICH HOLDS BACK THE TROUGHING  
OVER THE SOUTHERN PLAINS MUCH LONGER. THE WPC FORECAST TRENDED  
TOWARDS THE ENSEMBLE MEANS NEXT WEDNESDAY-THURSDAY WHICH ACTUALLY  
SHOWS A MORE MODERATE AND MIDDLE GROUND SOLUTION. EITHER WAY, THE  
TREND OVER THE PAST DAY HAS BEEN TOWARDS A HEAVIER QPF THREAT  
FOCUSED OVER THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY  
EARLY NEXT WEEK.  
 
   
..WEATHER/THREAT HIGHLIGHTS
 
 
THE RELENTLESS HEAT THAT HAS PLAGUED THE SOUTHERN U.S. FOR THE  
PAST WEEK SHOULD FINALLY BREAK THIS WEEKEND AS THE UPPER RIDGE  
PUSHES INTO THE EAST. AHEAD OF THE COLD FRONT ON SUNDAY THOUGH,  
EXCESSIVE HEAT WITH SOME LINGERING RECORD TEMPS (ESPECIALLY FOR  
WARM LOWS) WILL STILL BE POSSIBLE. MEANWHILE, EXPECT LOCALLY HEAVY  
RAIN AND POSSIBLY STRONG STORMS TO ACCOMPANY THE COLD FRONT AS IT  
PUSHES THROUGH THE OHIO VALLEY/EAST ON SUNDAY. TEMPERATURES BEHIND  
THE FRONT NEXT WEEK SHOULD HOVER NEAR SEASONABLE NORMAL VALUES.  
LOW PRESSURE FORMING ALONG THE TRAILING FRONT AS IT BEGINS TO LIFT  
BACK NORTH AS A WARM FRONT MAY CONTINUE A RAINFALL THREAT INTO  
MONDAY AS WELL FOR PARTS OF THE SOUTHERN MID-ATLANTIC.  
 
LEADING SOUTHERN STREAM IMPULSE ENERGY MAY ALSO FOCUS HEAVY  
RAINFALL ACROSS PARTS OF THE SOUTH, ESPECIALLY THE GULF COAST,  
WITH TROPICAL MOISTURE SURGING NORTHWARD FROM THE GULF OF MEXICO  
ON SUNDAY. AT LEAST A LOCALIZED FLOOD AND FLASH FLOOD THREAT  
SHOULD EXIST AS THE ENVIRONMENT COULD BE FAVORABLE FOR HIGH  
RAINFALL RATES. THE NEXT SYSTEM DIGGING INTO THE SOUTH-CENTRAL  
U.S. NEXT WEEK HAS BECOME INCREASINGLY LIKELY TO RE-KINDLE  
WIDESPREAD CONVECTION/RAINFALL ACROSS THE SOUTH-CENTRAL U.S. AS  
THE GUIDANCE SIGNAL HAS IMPROVED AT THESE LONGER TIME FRAMES,  
ALBEIT STILL HIGHLY DEPENDENT ON FLOW DETAILS AND CONVECTIVE  
INTERACTIONS. AGAIN, FLASH FLOODING IS EXPECTED TO BE A CONCERN  
WITHIN A VERY MOIST AND UNSTABLE ATMOSPHERE. DEPENDING ON FLOW  
PROGRESSION, SOME GUIDANCE SUGGESTS THE THREAT COULD LINGER FOR A  
COUPLE OF DAYS.  
 
THE WESTERN-CENTRAL U.S. TROUGH SHOULD KEEP TEMPERATURES BELOW  
NORMAL ACROSS ROCKIES AND PLAINS THROUGH AT LEAST TUESDAY. WITH  
THE EXCEPTION OF LIGHT PRECIP ACROSS THE ROCKIES ON SUNDAY, THE  
WESTERN U.S. SHOULD REMAIN DRY THROUGH THE MIDDLE OF NEXT WEEK AS  
UPPER RIDGING BUILDS OVER THE REGION AND WARMERS THAN AVERAGE  
TEMPERATURES EXPAND ACROSS THE REGION.  
 
SANTORELLI  
 
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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