070  
FXUS02 KWBC 241848  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
248 PM 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 BUILDS ACROSS THE NORTHWEST THROUGH  
THE WEEK...  
 
...HEAVY TO EXCESSIVE RAINFALL LIKELY IN PARTS OF THE  
CENTRAL/SOUTHERN ROCKIES AND HIGH PLAINS AS WELL AS THE  
OHIO/TENNESSEE VALLEYS 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 MEANDERING ACROSS  
THE EASTERN/CENTRAL U.S. SHOULD FINALLY BRING SOME MODEST RELIEF  
TO THE HEAT ACROSS THE SOUTH-CENTRAL PLAINS, BUT EXCESSIVE HEAT  
ACROSS THE NORTHWEST COULD CONTINUE THROUGH THE END OF THE WEEK. A  
MULTI-DAY PERIOD OF HEAVY TO EXCESSIVE RAINFALL REMAINS LIKELY IN  
PLACES ALONG THIS BOUNDARY, PARTICULARLY THE CENTRAL APPALACHIANS  
INTO THE TENNESSEE/LOWER OHIO VALLEYS. 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 MODEL AND ENSEMBLE GUIDANCE REMAINS IN GOOD AGREEMENT  
WITH THE LARGE SCALE PATTERN OF 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  
SHIFTING INTO THE NORTHEAST BY NEXT FRIDAY-SATURDAY. THERE ARE  
SOME MODEL DIFFERENCES REGARDING THE DISTRIBUTION OF ENERGY WITHIN  
THE TROUGH, ESPECIALLY ONCE AN ADDITIONAL SHORTWAVE OR TWO DROPS  
INTO THE WESTERN SIDE BEHIND THE MAIN UPPER LOW AROUND FRIDAY, BUT  
MOST DIFFERENCES ARE WELL WITHIN REASON FOR A MEDIUM RANGE  
FORECAST. THE FIRST HALF OF THE WPC FORECAST USED A BLEND OF THE  
00/06Z DETERMINISTIC GUIDANCE SINCE THERE WAS GOOD AGREEMENT  
OVERALL.  
 
MODELS (PARTICULARLY THE ECMWF AND GFS RUNS) AGREE REASONABLY WELL  
THAT TROUGHING ACROSS THE NORTHEASTERN QUADRANT OF THE U.S. SHOULD  
LINGER BUT DEAMPLIFY INTO NEXT WEEKEND AS THE UPPER LOW SHIFTS  
NORTHEASTWARD WELL INTO CANADA, WITH SOME MINOR VARIATIONS FROM  
MODEL TO MODEL. HOWEVER, SOMEWHAT MORE IMPACTFUL DIFFERENCES ARISE  
LATE THIS WEEK INTO THE WEEKEND UPSTREAM WITH FLOW APPROACHING AND  
MOVING THROUGH THE NORTHWEST, WHICH HAS IMPLICATIONS FOR THE HEAT  
WAVE THERE. GFS RUNS HAVE PERSISTENTLY SHOWN A SHORTWAVE TRACKING  
THROUGH THE PACIFIC NORTHWEST TOWARD THE NORTHERN ROCKIES OVER THE  
WEEKEND, WHILE ECMWF RUNS TAKE THAT PACIFIC ENERGY AND SPLIT OFF A  
SMALL UPPER LOW LINGERING OVER THE PACIFIC, LEADING TO RIDGING  
REMAINING OVER THE NORTHWEST. CMC RUNS ARE PERHAPS MORE LIKE THE  
GFS BUT WITH AN UPPER HIGH EXTENDING MUCH FARTHER WEST INTO THE  
PACIFIC SOUTH OF THE MAIN FLOW WITH THE EMBEDDED SHORTWAVES.  
THOUGH THESE DIFFERENCES ARE RELATIVELY SMALL SCALE FOR A DAY 6-7  
FORECAST, THEY COULD HAVE IMPLICATIONS FOR THE TEMPERATURE  
FORECASTS IN THE NORTHWEST GIVEN THEY AFFECT IF THE RIDGE  
PERSISTS. THE WPC FORECAST ATTEMPTS A MIDDLE GROUND APPROACH WITH  
THE SHORTWAVE NOT MOVING THROUGH AS FAST AS THE GFS RUNS, BUT NOT  
LINGERING IT OFFSHORE LIKE THE ECMWF EITHER--FAVORED THE ENSEMBLE  
MEANS FOR THE TIMING/TRACK OF THIS FEATURE. THUS THE WPC FORECAST  
USED HALF DETERMINISTIC MODELS/HALF ENSEMBLE MEANS BY DAY 7. THIS  
MAINTAINED GOOD CONTINUITY WITH THE PREVIOUS FORECAST.  
 
   
..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. 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 COULD  
BE SET ACROSS INTERIOR PORTIONS OF THE NORTHWEST. THERE IS SOME  
FORECAST UNCERTAINTY WITH THE TIMING OF WHEN THE HOT TEMPERATURES  
THERE WILL MODERATE, 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.  
 
THE LATEST GUIDANCE CONTINUES TO SUGGEST INCREASING POTENTIAL FOR  
A MULTIPLE DAY PERIOD OF HEAVY TO POSSIBLY EXCESSIVE RAINFALL  
INITIALLY ALONG A WARM FRONT DRAPED FROM THE MID-ATLANTIC TO THE  
MIDDLE MISSISSIPPI VALLEY, BUT THEN AGAIN AS THE NEXT FRONT  
SETTLES INTO THE 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 OHIO AND  
TENNESSEE VALLEYS 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, WHILE ADDITIONAL ROUNDS  
OF CONVECTION CONTINUE TO AFFECT THE TENNESSEE VALLEY.  
 
PERSISTENT MONSOONAL MOISTURE WILL 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, AS INDICATED BY THE DAY 4 ERO. THE MOISTURE PLUME  
IS ALSO EXPECTED TO STREAM INTO THE CENTRAL PLAINS FRONT,  
ENHANCING 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).  
 
TATE/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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