939  
FXUS02 KWBC 251856  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
255 PM EDT MON JUL 25 2022  
 
VALID 12Z THU JUL 28 2022 - 12Z MON AUG 01 2022  
 
...DANGEROUS HEAT WAVE OVER THE SOUTH-CENTRAL U.S. TO MODERATE BY  
MEDIUM RANGE, WHILE HEAT BUILDS ACROSS THE NORTHWEST INTO NEXT  
WEEKEND...  
 
...EXCESSIVE RAINFALL LIKELY FOR PARTS OF THE CENTRAL APPALACHIANS  
INTO SATURDAY, WITH HEAVY RAINFALL POSSIBLE ALSO EXTENDING AS FAR  
WEST AS THE CENTRAL/SOUTHERN ROCKIES...  
 
   
..OVERVIEW
 
 
A PERSISTENT RIDGE WILL BE PARKED OVER THE WESTERN U.S. THROUGH  
THE COURSE OF THE EXTEND PERIOD WHILE SOMEWHAT AMPLIFIED TROUGHING  
SLIDES ACROSS THE MIDWEST/OHIO VALLEY AND INTO THE NORTHEAST.  
SWELTERING HEAT WILL INCREASE/SPREAD ACROSS THE NORTHWEST U.S.  
WHILE PORTIONS OF THE SOUTH-CENTRAL PLAINS WILL EXPERIENCE MODEST  
RELIEF TO THE RECENT HOT TEMPERATURES THANKS TO A MEANDERING  
SURFACE FRONT. THIS FRONT WILL BE ALSO BE THE FOCUS FOR A  
MULTI-DAY, HEAVY RAIN EVENT. AREAS OF EXCESSIVE RAINFALL REMAINS  
LIKELY IN PLACES ALONG THIS BOUNDARY, PARTICULARLY THE CENTRAL  
APPALACHIANS, BUT ALSO FARTHER WEST INTO THE TENNESSEE/LOWER OHIO  
VALLEYS AND CENTRAL PLAINS. ADDITIONALLY, ENHANCED MONSOONAL  
MOISTURE LASTING FROM THE SHORT TO MEDIUM RANGE PERIOD WILL  
CONTINUE TO PROMOTE DAILY RISKS OF LOCALLY HEAVY SHOWERS AND  
STORMS THAT MAY PRODUCE INSTANCES OF FLASH FLOODING IN PARTS OF  
THE SOUTHWEST AND SOUTHERN/CENTRAL ROCKIES AND HIGH PLAINS.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE LATEST RUNS OF THE DETERMINISTIC AND ENSEMBLE MEANS REMAIN  
FAIRLY CLUSTERED WITH THE LARGE-SCALE PATTERN AND EVOLUTION OF THE  
EXPANSIVE RIDGE AND THE TROUGH DIGGING ACROSS THE UPPER  
MIDWEST/GREAT LAKES AROUND MIDWEEK AND SHIFTING INTO THE NORTHEAST  
BY THE WEEKEND. SOME MODEL DIFFERENCES REMAIN IN REGARDS TO THE  
DISTRIBUTION AND TIMING OF INDIVIDUAL ENERGIES WITHIN THE TROUGH  
BUT FALL WITHIN THE NORMAL DEGREE OF SPREAD. SATURDAY AND BEYOND  
THE TROUGH OVER THE NORTHEAST WILL BE REINFORCED AS MULTIPLE  
IMPULSES MOVE THROUGH. THE MAIN UPPER RIDGE AXIS ACROSS THE  
NORTHWEST SHOULD SHIFT EAST IN FAVOR OF A COUPLE OF WEAK  
SHORTWAVES ENTERING THE PACIFIC NORTHWEST BY AROUND  
SATURDAY-SUNDAY WITH VARYING DIFFERENCES IN THE DETAILS. THERE IS  
SOME INDICATION THAT A STRONGER SHORTWAVE MAY ADVANCE INTO THE  
NORTHWEST BY THE BEGINNING OF NEXT WEEK. THE WPC PREFERRED BLEND  
BEGAN WITH A GENERAL MODEL BLEND USING THE ECWMF/GFS/UKMET/CMC  
THAT TRANSITIONED TO THE ECWMF/GFS/CMC/EC ENSEMBLE MEAN/GEFS MEAN  
BEYOND DAY 5.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
A VAST PORTION OF THE SOUTH-CENTRAL U.S. HAS BEEN EXCESSIVELY HOT  
THIS SUMMER BUT TEMPERATURES ARE FORECAST TO TREND CLOSER TO  
NORMAL FOR LATE JULY AS A COLD FRONT SETTLES INTO THE REGION. IN  
CONTRAST, TEMPERATURES WILL CONTINUE TO RISE ACROSS MUCH OF THE  
NORTHWEST AND INTERIOR WEST AS THE UPPER RIDGE STRENGTHENS OVER  
THE WEST. MULTIPLE DAYS OF EXCESSIVE HEAT WILL OVERSPREAD THE  
NORTHWEST, WITH SOME LOCATIONS LIKELY TO SEE HIGHS AS MUCH AS  
10-20F ABOVE NORMAL. THIS EQUATES TO TEMPERATURES IN THE LOW TO  
MID 100S FOR THE COLUMBIA BASIN, WITH 90S EXPECTED TO REACH AS FAR  
WEST AS PORTLAND AND SEATTLE. SOME DAILY RECORDS FOR HIGHS/WARM  
LOWS COULD BE SET ACROSS INTERIOR PORTIONS OF THE NORTHWEST. THERE  
IS SOME FORECAST UNCERTAINTY WITH THE TIMING OF WHEN THE  
TEMPERATURES WILL MODERATE AGAIN, BUT CURRENT FORECASTS SHOW SOME  
LOWERING OF THE TEMPERATURES, THOUGH STILL ABOVE NORMAL, BY NEXT  
WEEKEND, WHILE TEMPERATURES OF ABOUT 10F ABOVE NORMAL SHIFT INTO  
THE NORTHERN PLAINS.  
 
WITH THE FRONTAL BOUNDARY BOUNDARY TAKING UP RESIDENCE ACROSS THE  
SOUTH-CENTRAL STATES AND PROVIDING A FOCUS FOR CONVECTION, MUCH OF  
THIS REGION ALONG WITH THE PARTS OF THE MID-ATLANTIC WILL HAVE  
MULTIPLE DAYS OF SHOWERS AND THUNDERSTORMS. THERE WILL BE AREAS  
THAT WILL SEE REPEATED ROUNDS OF MODERATE TO EXCESSIVE RAINFALL  
THAT WILL INCREASE THE RISK THE FOR LOCALIZED FLASH FLOODING,  
ESPECIALLY ACROSS THE MISSISSIPPI/TENNESSEE VALLEYS AND INTO THE  
CENTRAL APPALACHIANS. THE DAYS 4 AND 5 EXPERIMENTAL EROS HAVE  
EXPANSIVE SLIGHT RISKS DEPICTED ALONG THIS BOUNDARY FROM THE  
CENTRAL APPALACHIANS TO THE CENTRAL PLAINS. A MODERATE RISK WAS  
IDENTIFIED ACROSS PORTIONS OF WEST VIRGINIA AND FAR EASTERN  
KENTUCKY ON THE DAY 4 ERO, WHICH COVERS THE POTENTIAL FOR  
CONTINUED HEAVY RAINFALL OVER AN ALREADY SOGGY AREA LIKELY TO  
RECEIVE HEAVY RAINFALL IN THE SHORT RANGE AS WELL. ACTIVITY ALONG  
THIS BOUNDARY MAY SINK SLIGHTLY SOUTHWARD WITH TIME, CONTINUING  
THROUGH NEXT WEEKEND FOR SOME REGIONS IN ESPECIALLY THE TENNESSEE  
VALLEY. GIVEN SEVERAL DAYS OF RAINFALL OVER THE SAME AREA, THIS  
LIKELY WILL RAISE CONCERNS FOR FLOODING AS FLASH FLOODING.  
RAINFALL SHOULD SLIDE ACROSS PORTIONS OF THE NORTHEAST AHEAD OF A  
MORE PROGRESSIVE COLD FRONT ON THURSDAY, THOUGH LINGER ACROSS  
PORTIONS OF THE SOUTHERN MID-ATLANTIC FOR A COUPLE OF DAYS.  
 
PERSISTENT MONSOONAL MOISTURE WILL CONTINUE TO SUPPORT DIURNALLY  
FAVORED SHOWERS/STORMS WITH SOME LOCALLY HEAVY RAINFALL OVER THE  
FOUR CORNERS STATES THROUGH THIS WEEK. ACROSS PARTS OF ARIZONA IN  
PARTICULAR, ANOMALOUS MOISTURE LINGERING OVER LIKELY WET SOIL FROM  
ACTIVITY IN THE SHORT RANGE PERIOD COULD LEAD TO ADDITIONAL FLASH  
FLOODING THERE, WITH ANOTHER UPTICK EXPECTED ON FRIDAY AND  
PROMPTING THE INTRODUCTION OF A SLIGHT RISK ON THE DAY 5 ERO. THE  
MOISTURE PLUME IS ALSO EXPECTED TO INTERACT WITH THE CENTRAL  
PLAINS FRONT, ENHANCING RAINFALL TOTALS FARTHER NORTH AND EAST  
INTO NEW MEXICO AND COLORADO MIDWEEK, WITH INCREASING POTENTIAL  
FOR FLOODING AND FLASH FLOODING. SLIGHT RISKS REMAIN IN PLACE FOR  
THE DAYS 4 AND 5 EROS IN THIS AREA.  
 
CAMPBELL/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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