221  
FXUS02 KWBC 250700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
259 AM 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 THURSDAY, WITH HEAVY RAINFALL POSSIBLE ALSO EXTENDING AS FAR  
WEST AS THE CENTRAL/SOUTHERN ROCKIES...  
 
   
..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,  
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 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 AND TIMING OF  
ENERGY WITHIN THE TROUGH, BUT MOST DIFFERENCES ARE WELL WITHIN  
REASON FOR A MEDIUM RANGE FORECAST. THE FIRST HALF OF THE WPC  
FORECAST WAS ABLE TO UTILIZE A BLEND OF THE LATEST DETERMINISTIC  
GUIDANCE.  
 
BEYOND DAY 5/SATURDAY, MODELS AGREE REASONABLY WELL THAT TROUGHING  
MAY LINGER ACROSS THE NORTHEAST INTO NEXT WEEKEND, JUST IN A MUCH  
LESS AMPLIFIED FASHION, AS VARIOUS SHORTWAVES ACT TO REINFORCE THE  
TROUGH. 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. A STRONGER SHORTWAVE MAY MOVE INTO THE  
NORTHWEST AGAIN EARLY NEXT WEEK. GIVEN THE INCREASED  
UNCERTAINTIES, THE WPC BLEND TRANSITIONED TOWARDS MAJORITY  
ENSEMBLE MEANS TO HELP MITIGATE THE DIFFERENCES. THIS APPROACH  
MAINTAINS GOOD CONTINUITY WITH THE PREVIOUS FORECAST AS WELL.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
THE SOUTH-CENTRAL U.S. HAS SEEN PROLONGED EXCESSIVE HEAT IN RECENT  
WEEKS, AND THIS IS FORECAST TO FINALLY MODERATE BACK TOWARDS  
NORMAL TEMPERATURES BY THE START OF THE MEDIUM RANGE PERIOD AS A  
COLD FRONT SETTLES ACROSS THE SOUTH-CENTRAL U.S.. MEANWHILE, A  
BUILDING UPPER RIDGE OVER THE NORTHWEST THIS WEEK WILL BRING  
MULTIPLE DAYS OF EXCESSIVE HEAT, 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.  
 
THE LATEST GUIDANCE CONTINUES TO SUGGEST INCREASING POTENTIAL FOR  
A MULTIPLE DAY PERIOD OF HEAVY TO POSSIBLY EXCESSIVE RAINFALL  
INITIALLY ALONG A FRONT DROPPING INTO THE MID-ATLANTIC AND  
EXTENDING BACK INTO THE MIDDLE MISSISSIPPI VALLEY 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 EXPANSIVE  
SLIGHT RISKS DEPICTED ALONG THIS BOUNDARY FROM THE CENTRAL  
APPALACHIANS TO THE CENTRAL PLAINS. A MODERATE RISK WAS INTRODUCED  
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.  
 
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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