844  
FXUS02 KWBC 181901  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT WED MAY 18 2022  
 
VALID 12Z SAT MAY 21 2022 - 12Z WED MAY 25 2022  
 
...RECORD HEAT TO ABATE OVER THE SOUTH-CENTRAL U.S., SHIFTING TO  
THE APPALACHIANS/MID-ATLANTIC/NORTHEAST THIS WEEKEND...  
 
...HEAVY RAINFALL AND SEVERE WEATHER THREAT FOR THE EAST-CENTRAL  
U.S. THIS WEEKEND TO REDIRECT OVER THE SOUTH-CENTRAL U.S. EARLY  
NEXT WEEK...  
 
   
..OVERVIEW
 
 
AN AMPLIFIED WEEKEND UPPER FLOW PATTERN WILL BE HIGHLIGHTED BY A  
TROUGH OVER THE WEST/NORTH-CENTRAL U.S. AND STRONG RIDGING IN THE  
EAST. THIS YIELDS COOLER TEMPERATURES ACROSS THE ROCKIES AND  
CENTRAL U.S. AND RECORD HEAT SHIFTING FROM THE SOUTH-CENTRAL U.S.  
TO THE EAST THIS WEEKEND. A STRONG COLD FRONT ACROSS THE MIDWEST  
AND EAST THIS WEEKEND WILL RESULT IN INCREASED CHANCES FOR HEAVY  
RAINFALL AND SEVERE WEATHER ALONG AND AHEAD OF IT. A NORTHWARD  
SURGE OF TROPICAL MOISTURE WILL ALSO INCREASE RAIN/THUNDERSTORM  
CHANCES ACROSS FLORIDA THIS WEEKEND. TROUGHING BACK INTO THE WEST  
SUNDAY/MONDAY SHOULD DIG INTO THE SOUTH-CENTRAL U.S. EARLY NEXT  
WEEK AS UPPER RIDGING BUILDS INTO THE SOUTHWEST AND FLORIDA AND  
FLATTER FLOW RIDES OVERTOP OVER THE NORTHERN TIER OF THE LOWER 48.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A  
COMPOSITE BLEND OF REASONABLY WELL CLUSTERED GUIDANCE FOR THE  
WEEKEND IN A PATTERN WITH AVERAGE TO ABOVE AVERAGE PREDICTABILITY  
BEYOND SMALLER SCALE DETAILS. MODEL SYSTEM TIMING/AMPLITUDE  
DIFFERENCES BECOME MORE PROBLEMATIC THROUGH EARLY-MID NEXT WEEK  
WITH THE ECMWF TRACKING CLOSEST TO THE COMPATIBLE GEFS/ECMWF  
ENSEMBLE MEANS. THE MOST SIGNIFICANT WPC PRODUCT CONTINUITY CHANGE  
INTO EARLY NEXT WEEK WAS TO PROMOTE A MORE ORGANIZED AND SOUTHWARD  
SHIFTED HEAVY QPF THREAT FOCUS OVER THE SOUTHERN PLAINS AND LOWER  
MS VALLEY DUE TO THE SIGNAL FOR A NOW MORE LIKELY DEVELOPMENT OF  
SUPPORTING UPPER TROUGHING AND SURFACE SYSTEM DEVELOPMENT IN A  
MOIST AND UNSTABLE ENVIRONMENT. THE RESULTANT WPC QPF IS HEAVIER  
THAN NBM 4.0.  
 
   
..WEATHER/THREAT HIGHLIGHTS
 
 
THE RELENTLESS HEAT ACROSS THE SOUTHERN PLAINS/LOWER MISSISSIPPI  
VALLEY SHOULD FINALLY BREAK BY THIS WEEKEND THOUGH RECORD HEAT  
CONTINUES INTO SATURDAY ACROSS THE EAST. NUMEROUS DAILY RECORDS  
COULD BE MET OR EXCEEDED ON SATURDAY ACROSS THE APPALACHIANS,  
MID-ATLANTIC, AND NORTHEAST WITH A FEW LINGERING RECORDS ACROSS  
FAR SOUTHERN REGIONS IN TEXAS/LOUISIANA. A STRONG COLD FRONT WILL  
SPREAD RAIN AND THUNDERSTORMS THROUGH THE MISSISSIPPI VALLEY/OHIO  
VALLEY ON SATURDAY AND INTO THE EAST ON SUNDAY. HEAVY RAINFALL AS  
WELL AS SEVERE WEATHER IS POSSIBLE ALONG THIS BOUNDARY GIVEN ABOVE  
NORMAL MOISTURE AND INSTABILITY PRESENT. FLOODING AND FLASH  
FLOODING COULD BE AN ISSUE AS WELL, PARTICULARLY IN PLACES THAT  
MAY BE SENSITIVE TO ADDITIONAL RAINFALL GIVEN WET ANTECEDENT  
CONDITIONS. LEAD SOUTHERN STREAM IMPULSE ENERGY MAY ALSO FOCUS  
HEAVY RAINFALL AREAS ACROSS PARTS OF THE SOUTH, ESPECIALLY THE  
GULF COAST, AS TROPICAL MOISTURE SURGING NORTHWARD ALLOWS FOR  
HEAVY RAINFALL ACROSS THE FLORIDA PENINSULA THIS WEEKEND. TO THE  
WEST, UNSEASONABLY COOL TEMPERATURES WILL MOVE FROM THE ROCKIES  
INTO THE NORTH-CENTRAL U.S., LOWERING SNOW LEVELS ACROSS THE  
ROCKIES SATURDAY AND SUNDAY. THE NEXT SYSTEM DIGGING INTO THE  
SOUTH-CENTRAL U.S. INTO 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. THE NORTHWEST SHOULD REMAIN FAIRLY  
DRY, THOUGH WITH SOME LIGHT PRECIPITATION ACCOMPANYING FRONTAL  
BOUNDARIES. THE SOUTHERN HALF OF THE WEST SHOULD SEE A SLIGHT  
WARMING TREND EXPAND FROM WEST TO EAST MONDAY THROUGH WEDNESDAY  
WHILE MEAN TROUGHING KEEPS TEMPEARTURES NEAR OR COOLER THAN NORMAL  
EAST OF THE ROCKIES.  
 
SCHICHTEL/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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