808  
FXUS02 KWBC 240700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT SUN JUL 24 2022  
 
VALID 12Z WED JUL 27 2022 - 12Z SUN JUL 31 2022  
 
...DANGEROUS HEAT WAVE OVER THE SOUTH-CENTRAL U.S. TO MODERATE  
SOME BY MIDWEEK, WHILE HEAT ALSO BUILDS ACROSS THE NORTHWEST INTO  
NEXT WEEKEND...  
 
...HEAVY TO EXCESSIVE RAINFALL LIKELY IN PARTS OF THE  
CENTRAL/SOUTHERN ROCKIES AS WELL AS THE TENNESSEE VALLEY AND  
CENTRAL APPALACHIANS...  
 
   
..OVERVIEW
 
 
A WEST-EAST ORIENTED RIDGE WILL PERSIST ACROSS THE SOUTHERN AND  
WESTERN U.S. THROUGH NEXT WEEKEND AS SOMEWHAT AMPLIFIED TROUGHING  
SLIDES ACROSS THE MIDWEST/OHIO VALLEY AND INTO THE NORTHEAST. THIS  
ENERGY/FLOW PATTERN AS WELL AS A SURFACE FRONT SETTLING INTO THE  
EAST-CENTRAL U.S. SHOULD FINALLY BRING SOME MODEST RELIEF TO THE  
HEAT ACROSS THE SOUTH-CENTRAL PLAINS WITH EXCESSIVE HEAT ACROSS  
THE NORTHWEST CONTINUING INTO NEXT WEEKEND. THE POTENTIAL FOR A  
MULTI-DAY PERIOD OF HEAVY TO EXCESSIVE RAINFALL IS INCREASING IN  
PLACES ALONG THIS BOUNDARY FROM ESPECIALLY THE CENTRAL  
APPALACHIANS INTO THE TENNESSEE/LOWER OHIO VALLEYS. ADDITIONALLY,  
ENHANCED MONSOONAL MOISTURE 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.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
ON THE LARGE SCALE, THE LATEST MODEL AND ENSEMBLE GUIDANCE REMAINS  
IN AGREEMENT WITH THE OVERALL PATTERN SHOWING EXPANSIVE AND  
PERSISTENT RIDGING FROM THE NORTHWEST TO THE SOUTHERN HALF OF THE  
U.S., WITH A MORE CONSOLIDATED TROUGH (STEMMING FROM A SOUTHERN  
CANADA UPPER LOW) DIGGING ACROSS THE UPPER MIDWEST/GREAT LAKES  
AROUND MIDWEEK AND INTO THE NORTHEAST BY NEXT FRIDAY-SATURDAY.  
WITHIN THIS NORTHERN STREAM ENERGY THERE ARE SOME DIFFERENCES IN  
GUIDANCE WITH THE SMALLER SCALE DETAILS, WITH MOST DIFFERENCES  
WELL WITHIN REASON FOR A MEDIUM RANGE FORECAST. THE PATTERN ACROSS  
THE NORTHERN TIER BECOMES A LITTLE MORE MESSY AND UNCERTAIN BY  
DAYS 6-7, MOSTLY RELATED TO ADDITIONAL SHORTWAVE ENERGY DROPPING  
INTO CENTRAL CANADA BEHIND THE DEPARTING LARGER UPPER LOW EARLIER  
IN THE PERIOD, AND ALSO ADDIITONAL WEAK ENERGY ENTERING THE  
PACIFIC NORTHWEST. GIVEN GOOD AGREEMENT, THE WPC FORECAST WAS  
BASED ON A BLEND OF THE DETERMINISTIC GUIDANCE THROUGH DAY 5,  
THROUGH TRANSITIONED TO MOVE WEIGHTING ON THE ENSEMBLE MEANS BY 6  
AND 7 TO SMOOTH OUT THE VARIABILITY IN THE DETERMINISTIC  
SOLUTIONS. THIS MAINTAINS GOOD CONTINUITY WITH THE PREVIOUS WPC  
FORECAST, WITH ONLY TYPICAL SMALL SHIFTS IN FRONTS AND QPF BASED  
ON THE MOST RECENT GUIDANCE, ALTHOUGH MODELS HAVE SHOWN A NOTABLE  
INCREASE IN QPF AMOUNTS ALONG THE MAIN FRONTAL BOUNDARY FROM THE  
CENTRAL HIGH PLAINS ALL THE WAY INTO THE CENTRAL APPALACHIANS.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
THE SOUTH-CENTRAL U.S. HAS SEEN PROLONGED EXCESSIVE HEAT IN RECENT  
WEEKS, AND THIS IS FORECAST TO LAST INTO THE BEGINNING OF THE  
MEDIUM RANGE PERIOD FOR THE SOUTHERN HALF OF THE PLAINS AND  
MISSISSIPPI VALLEY. WIDESPREAD TEMPERATURES NEAR OR ABOVE 100  
DEGREES (WITH HIGHER HEAT INDICES) WILL CONTINUE IN THIS REGION  
THROUGH AT LEAST WEDNESDAY. THE NEXT FRONT THAT REACHES THE  
NORTHERN PLAINS EARLY NEXT WEEK LOOKS TO BRING MODERATELY BELOW  
NORMAL HIGHS TO THE NORTHERN-CENTRAL PLAINS WEDNESDAY-THURSDAY,  
AND SHOULD HAVE A STRONG ENOUGH SOUTHWARD PUSH TO FINALLY BRING  
SOME MODERATING TEMPERATURES BACK TOWARDS NORMAL FOR THE SOUTHERN  
PLAINS AS WELL FOR THE LATTER HALF OF THE WEEK. MEANWHILE, A  
BUILDING UPPER RIDGE OVER THE NORTHWEST THIS WEEK WILL BRING  
MULTIPLE DAYS OF HOT WEATHER, WITH SOME LOCATIONS LIKELY TO SEE  
HIGHS AS MUCH AS 10-20F ABOVE NORMAL. THIS EQUATES TO HIGHS IN THE  
LOW TO MID 100S FOR THE COLUMBIA BASIN, AND 90S ARE EXPECTED TO  
REACH AS FAR WEST AS PORTLAND AND SEATTLE. SOME DAILY RECORDS FOR  
HIGHS/WARM LOWS WILL BE POSSIBLE ACROSS INTERIOR PORTIONS OF THE  
NORTHWEST.  
 
THE LATEST GUIDANCE CONTINUES TO SUGGEST INCREASING POTENTIAL FOR  
A MULITPLE DAY PERIOD OF HEAVY TO POSSIBLE EXCESSIVE RAINFALL  
ALONG INTIALLY A WARM FRONT DRAPED FROM THE MID-ATLANTIC TO THE  
MIDDLE MISSISSIPPI VALLEY, BUT THEN AGAIN AS THE NEXT FRONT  
THROUGH THE PLAINS SETTLES INTO MID-SOUTH AND CENTRAL PLAINS.  
SUFFICIENT MOISTURE AND INSTABILITY POOLED ALONG THIS BOUNDARY AS  
IT BECOMES QUASI-STATIONARY SHOULD SUPPORT ROUNDS OF HEAVY  
RAINFALL AND CONVECTION ACROSS SOME OF THE SAME REGIONS OVER  
MULTIPLE DAYS. THE DAYS 4 AND 5 EXPERIMENTAL EROS HAVE EXPANDED  
THE SLIGHT RISKS ACROSS THE CENTRAL APPALACHIANS AND BACK INTO THE  
TENNESSEE VALLEY AND PARTS OF THE MIDDLE MISSISSIPPI VALLEY. HEAVY  
RAINFALL WILL EXPAND INTO THE SOUTHERN MID-ATLANTIC AND THE  
CENTRAL PLAINS LATER IN THE WEEK AS WELL.  
 
PERSISTENT MONSOONAL MOISTURE WILL SUPPORT DIURNALLY FAVORED  
SHOWERS/STORMS WITH SOME LOCALLY HEAVY RAINFALL OVER THE FOUR  
CORNERS/GREAT BASIN REGION THROUGH NEXT WEEK. A SLIGHT RISK OF  
EXCESSIVE RAINFALL ON THE DAY 4 ERO WAS INTRODUCED ACROSS A GOOD  
PORTION OF CENTRAL AND EASTERN ARIZONA AS THAT ANOMALOUS MOISTURE  
STAYS PUT OVER LIKELY WET SOIL FROM ACTIVITY IN THE SHORT RANGE  
PERIOD. SOME OF THIS MOISTURE IS ALSO EXPECTED TO INTERACT WITH  
THE CENTRAL PLAINS FRONT TO ENHANCE RAINFALL TOTALS FARTHER NORTH  
AND EAST INTO NEW MEXICO AND COLORADO MIDWEEK, WITH POTENTIAL FOR  
FLASH FLOODING AS WELL (AND THE PRESENCE OF A SLIGHT RISK ON BOTH  
THE DAYS 4 AND 5 ERO).  
 
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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