641  
FXUS02 KWBC 171849  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
249 PM EDT SUN JUL 17 2022  
 
VALID 12Z WED JUL 20 2022 - 12Z SUN JUL 24 2022  
 
...DANGEROUS HEAT TO PERSIST OVER MUCH OF THE CENTRAL U.S. MIDWEEK  
THROUGH THE WEEKEND...  
   
..OVERVIEW
 
 
A STRONG UPPER RIDGE CENTERED OVER THE FOUR CORNERS REGION IS  
EXPECTED TO SHIFT TOWARD THE MID-MS AND DEEP SOUTH BY THE WEEKEND,  
WHICH WILL KEEP THE PERSISTENT HOT AND HUMID WEATHER OVER THE  
CENTRAL/SOUTHERN PLAINS IN PLACE THROUGH THE PERIOD. SOUTHERN  
AREAS WILL SEE THE BEST POTENTIAL FOR READINGS TO APPROACH OR  
BREAK DAILY RECORDS FOR HIGHS AND VERY WARM NIGHTTIME LOWS.  
MEANWHILE THE WEST SHOULD MODERATE AFTER MIDWEEK WITH THE APPROACH  
OF A PACIFIC TROUGH TOWARD THE WEST COAST AND THEN THE EASTWARD  
SHIFT OF THE RIDGE. FLOW AROUND THE RIDGE WILL CARRY SHORTWAVES  
THAT WILL FEED INTO THE NORTHEASTERN U.S. MEAN TROUGH WHICH MAY  
TREND A LITTLE FLATTER/BROADER BY THE WEEKEND, PRODUCING EPISODES  
OF SHOWERS AND THUNDERSTORMS FROM THE NORTHERN TIER INTO THE EAST.  
MONSOONAL MOISTURE OVER THE SOUTHWEST/SOUTHERN ROCKIES WILL  
PROMOTE DAILY CHANCES OF SHOWERS AND STORMS, SOME OF WHICH COULD  
LEAD TO FLASH FLOODING. THE PATTERN ADJUSTMENT LATE IN THE PERIOD  
MAY SUPPORT AN INCREASE OF THIS ACTIVITY.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THIS CYCLE OF MODEL GUIDANCE CONTINUED TO SHOW FAIRLY HIGH  
AGREEMENT AND PREDICTABILITY IN THE LARGE SCALE PATTERN AND ITS  
EVOLUTION WITH SOME OF THE MAJOR SYNOPTIC FEATURES INCLUDING THE  
FOUR CORNERS RIDGE, UPPER GREAT LAKES INTO EASTERN CANADA SYSTEM.  
THE LARGEST MODEL DIFFERENCES REMAIN FOCUSED ON THE  
WESTERN/NORTHWESTERN U.S. ENERGY COMING IN AND ITS PROGRESSION  
THROUGH THE NORTHERN ROCKIES AND NORTHERN PLAINS, WHICH THE GFS  
APPEARS TO BE FAST AND AGGRESSIVE WITH SHOWING. MEANWHILE, THE CMC  
IS ON THE SLOWER SIDE OF THE MODEL SPREAD, AT LEAST THROUGH DAY 4  
THEN BEGINS TO PROGRESS THE ENERGY EASTWARD. A SOLUTION TOWARD  
CONSENSUS, SIMILAR TO THE ECMWF, WAS PREFERRED THOUGH  
ACKNOWLEDGING THE LOWER CONFIDENCE IN THE DETAILS/TIMING WITH THE  
SPECIFIC SHORTWAVES COMING THROUGH THE FLOW AND HOW THIS  
TRANSLATES ACROSS THE NORTHERN TIER. BY NEXT WEEKEND THE QUESTION  
MARKS OVER WEST COAST TROUGH DETAILS AND CHARACTER OF THE  
EASTWARD-SHIFTING UPPER RIDGE COMBINE TO AFFECT THE FORECAST OF  
HOW MUCH SOUTHERLY FLOW ALOFT WILL DEVELOP TO ENHANCE THE  
MONSOONAL MOISTURE OVER THE WEST. THE FORECAST BLEND WAS COMPOSED  
OF NEAR EQUAL WEIGHTS OF THE 00Z ECMWF/UKMET/CMC AND 06Z GFS FOR  
DAYS 3-5 FOLLOWED BY NEAR 50 PERCENT OF ECENS/GEFS MEANS AND THE  
LATEST DETERMINISTIC ECMWF AND GFS. THIS ACCOUNTED FOR THE  
INCREASING MODEL SPREAD LATER IN THE FORECAST SPREAD WHILE  
MAINTAINING CONTINUITY.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
THE HOT AND HUMID WEATHER WILL BE FOCUSED ON THE CENTRAL U.S.  
WHERE DAILY HIGHS ARE EXPECTED TO BE BETWEEN 5 AND 15 DEGREES  
ABOVE NORMAL WITH MANY AREAS SEEING CONSECUTIVE DAYS ABOVE 100 FOR  
HIGHS. LITTLE NIGHTTIME RELIEF IS EXPECTED WITH VERY WARM LOWS IN  
THE UPPER 70S TO LOWER 80S. THIS HEATWAVE WILL LIKELY BRING  
SCATTERED RECORDS, MOST LIKELY OVER THE SOUTHERN PLAINS TO  
LOWER/MID MS VALLEY. THE NORTHERN EXTENT OF HEAT EACH DAY WILL  
DEPEND ON LOWER-CONFIDENCE FRONTAL/WAVE DETAILS BUT SOME POTENTIAL  
FOR ABOVE NORMAL TEMPERATURES TO EXTEND INTO THE NORTHERN TIER OF  
THE CENTRAL/EASTERN U.S. MID TO LATE WEEK.  
 
OVER THE WEST, MONSOONAL MOISTURE AND ASSOCIATED DIURNALLY FAVORED  
SHOWERS/STORMS WITH LOCALLY HEAVY RAINFALL MAY KEEP PARTS OF THE  
FOUR CORNERS/GREAT BASIN REGION CLOSE TO NORMAL FOR HIGHS THROUGH  
THE PERIOD. THE EASTWARD SHIFT OF UPPER RIDGING LATE IN THE PERIOD  
MAY LEAD TO AN INCREASE OF MOISTURE/RAINFALL NEXT WEEKEND. OTHER  
PARTS OF THE WEST INLAND FROM THE PACIFIC COAST SHOULD START THE  
PERIOD UP TO 5-10F ABOVE NORMAL FOR HIGHS BUT THEN DECLINE MORE  
TOWARD NORMAL AS AN UPPER LOW/SHORTWAVE EJECT FROM THE PACIFIC.  
LOCALLY HEAVY RAINFALL WILL BE POSSIBLE WITH A FAIRLY VIGOROUS  
SYSTEM FORECAST TO TRACK FROM THE UPPER GREAT LAKES THROUGH  
EASTERN CANADA/NORTHEAST U.S. MID-LATE WEEK. UNCERTAIN SPECIFICS  
OF ENERGY EJECTING FROM THE PACIFIC, AS WELL AS SEPARATE FEATURES  
WITHIN SOUTHERN CANADA/NORTHERN U.S. FLOW, MAY PLAY A ROLE IN  
CONVECTIVE DETAILS ALONG A TRAILING FRONT THAT SHOULD AFFECT  
NORTHERN AREAS AFTER MIDWEEK. THE MID-ATLANTIC AND NORTHEAST WILL  
BE ON THE VERY WARM TO HOT SIDE, WITH SOME LOCATIONS POSSIBLY  
SEEING MORE CONSECUTIVE DAYS OF PLUS 5-10F ANOMALIES FOR HIGHS  
THAN PREVIOUSLY EXPERIENCED SO FAR THIS SUMMER. THE FRONT REACHING  
THE EAST COAST BY FRIDAY COULD LEAD TO A BRIEF AND SLIGHT DIP IN  
TEMPERATURES BEFORE IT WEAKENS DURING THE WEEKEND. PERSISTENT  
MOISTURE WILL ALLOW FOR MULTIPLE EPISODES OF SHOWERS/THUNDERSTORMS  
OVER THE SOUTHEAST/FLORIDA AND CENTRAL GULF COAST REGION.  
TEMPERATURES SHOULD BE NEAR NORMAL OVER THOSE AREAS.  
 
RAUSCH/TAYLOR  
 
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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