512  
FXUS02 KWBC 170700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
259 AM 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  
MID-LATE WEEK WILL LIKELY SHIFT SOMEWHAT EASTWARD BY THE WEEKEND.  
THE PERSISTENCE OF RIDGING OVER OR NEAR THE CENTRAL/SOUTHERN  
PLAINS WILL KEEP HOT TEMPERATURES OVER THAT REGION AND INTO PARTS  
OF THE MISSISSIPPI VALLEY THROUGH THE PERIOD. SOUTHERN AREAS WILL  
SEE THE BEST POTENTIAL FOR SOME DAILY RECORDS FOR HIGHS AND/OR  
VERY WARM 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
 
 
THE LATEST MODELS AND ENSEMBLES CONTINUE TO AGREE FOR THE  
LARGEST-SCALE ASPECTS OF THE MEAN PATTERN AND ITS GENERAL  
EVOLUTION, AND TO A REASONABLE DEGREE FOR THE DOMINANT FEATURES  
MID-LATE WEEK: THE FOUR CORNERS RIDGE AND THE UPPER GREAT LAKES  
INTO EASTERN CANADA SYSTEM THAT BRINGS A COLD FRONT FROM THE  
MIDWEST/PLAINS INTO THE EAST. HOWEVER SIGNIFICANT MODEL SPREAD  
PERSISTS FOR HOW INITIAL PACIFIC TROUGH ENERGY WILL EJECT AND THE  
SPECIFICS OF ANY RESIDUAL PACIFIC ENERGY, AS WELL AS FOR THE  
CHARACTER OF FEATURES ACROSS THE NORTHEASTERN PACIFIC THROUGH  
SOUTHERN CANADA/NORTHERN TIER U.S. THESE ISSUES LOWER CONFIDENCE  
IN FRONTAL/WAVE DETAILS BEHIND THE SYSTEM/FRONT REACHING THE EAST  
LATE THIS WEEK. IN ADDITION, 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 UPDATED FORECAST BASED ON 12Z/18Z GUIDANCE STARTED WITH AN  
OPERATIONAL MODEL BLEND DAYS 3-4 WEDNESDAY-THURSDAY FOLLOWED BY A  
FAIRLY RAPID INCREASE OF THE 18Z GEFS/12Z ECMWF MEANS SO THAT THE  
MEANS REACHED 50-60 PERCENT TOTAL WEIGHT BY NEXT WEEKEND. THIS  
REFLECTS THE DECENT CLUSTERING FOR PRIMARY FEATURES EARLY AND THEN  
ACCOUNTS FOR THE INCREASING DIVERGENCE IN DETAILS.  
DIFFERENCES/CHANGES IN THE SOUTHERN CANADA/NORTHERN TIER STREAM  
CONTINUE TO AFFECT SPECIFICS OF LOW PRESSURE REACHING EASTERN  
CANADA BY FRIDAY BUT WITH LESS IMPACT ON THE TRAILING FRONT.  
MODELS STILL VARY CONSIDERABLY FOR TIMING/AMPLITUDE OF THE FEATURE  
EJECTING FROM THE EASTERN PACIFIC AND TRACKING AROUND THE RIDGE,  
THOUGH THERE IS MODEST IMPROVEMENT. LATELY THE GFS/ECMWF HAVE BEEN  
SOMEWHAT FASTER THAN THE UKMET/CMC. THE NEW 00Z UKMET HAS TRENDED  
CLOSER TO THE GFS/ECMWF BUT BECOMES QUITE AMPLIFIED VERSUS OTHER  
GUIDANCE AS THE SHORTWAVE TRACKS INLAND. THE NEW 00Z ECMWF HAS  
TRENDED SLOWER, HIGHLIGHTING THE CONTINUED UNCERTAINTY.  
MODEL/ENSEMBLE SPREAD YIELDS LOW CONFIDENCE IN DETAILS OF OTHER  
SOUTHERN CANADA/NORTHERN TIER U.S. SHORTWAVES AS WELL. AN  
INTERMEDIATE SOLUTION, CLOSEST TO AN AVERAGE OF THE 12Z  
ECMWF/ECMWF MEAN AND 18Z GEFS MEAN, PROVIDES GOOD CONTINUITY FOR  
THE WEEKEND POSITION AND SHAPE OF THE SOUTHERN TIER RIDGE. GFS  
RUNS HAVE TENDED TO CENTER THE RIDGE A LITTLE FARTHER EAST BUT THE  
18Z AND NEW 00Z RUNS ARE CLOSER TO PREFERENCE THAN SOME EARLIER  
RUNS. THE PREFERRED SOLUTION WOULD SUPPORT SOMEWHAT MORE OF AN  
INCREASE IN WESTERN MONSOONAL MOISTURE THAN DEPICTED IN THE GFS BY  
LATE IN THE PERIOD.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
THE CENTRAL U.S. WILL BE THE FOCUS FOR THE MOST ANOMALOUSLY HOT  
WEATHER DURING THE PERIOD, WITH EACH DAY LIKELY FEATURING SOME  
AREAS WITH HIGHS REACHING 10-15F ABOVE NORMAL AND A FAIRLY BROAD  
AREA OF TRIPLE DIGIT READINGS. SUCH ANOMALIES SHOULD PERSIST OVER  
THE SOUTH-CENTRAL PLAINS MOST OF THE PERIOD WHILE LOCATIONS UP  
INTO THE NORTH-CENTRAL PLAINS MAY SEE SIMILAR DEPARTURES FROM  
NORMAL THURSDAY-SATURDAY. THE NORTHERN EXTENT OF HEAT EACH DAY  
WILL DEPEND ON LOWER-CONFIDENCE FRONTAL/WAVE DETAILS. THE BEST  
POTENTIAL FOR SOME DAILY RECORD HIGHS AND WARM LOWS WILL BE OVER  
SOUTHERN AREAS. 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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