957  
FXUS02 KWBC 260707  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
307 AM EDT TUE JUL 26 2022  
 
VALID 12Z FRI JUL 29 2022 - 12Z TUE AUG 02 2022  
 
...DANGEROUS HEAT WAVE CONTINUES ACROSS PARTS OF THE NORTHWEST  
THROUGH THE WEEKEND...  
 
...EXCESSIVE RAINFALL LIKELY ACROSS PARTS OF THE CENTRAL HIGH  
PLAINS ON FRIDAY, WITH HEAVY RAIN THREATS STRETCHING FROM THE  
SOUTHWEST TO THE SOUTHERN MID-ATLANTIC INTO NEXT WEEK...  
 
   
..OVERVIEW
 
 
AN UPPER LEVEL RIDGE WILL BE PARKED OVER THE SOUTHERN AND WESTERN  
PARTS OF THE COUNTRY THROUGH MUCH OF THE PERIOD WHILE SOMEWHAT  
AMPLIFIED TROUGHING SLIDES ACROSS THE MIDWEST/OHIO VALLEY AND INTO  
THE NORTHEAST. DANGEROUS HEAT WILL CONTINUE INTO NEXT WEEKEND  
ACROSS THE NORTHWEST U.S. WHILE PORTIONS OF THE SOUTH-CENTRAL  
PLAINS SHOULD FINALLY SEE A PERIOD OF MODEST RELIEF TO THE RECENT  
HEAT WAVE THANKS TO A MEANDERING SURFACE FRONT. THIS  
QUASI-STATIONARY FRONT WILL ALSO BE THE FOCUS FOR A MULTI-DAY,  
HEAVY RAIN EVENT FROM THE SOUTH-CENTRAL PLAINS TO THE SOUTHERN  
MID-ATLANTIC WITH EXCESSIVE RAINFALL LIKELY IN SOME PLACES.  
ADDITIONALLY, ENHANCED MONSOONAL MOISTURE PERSISTING INTO THE  
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 ESPECIALLY THE  
SOUTHERN/CENTRAL ROCKIES AND HIGH PLAINS.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE LATEST RUNS OF THE DETERMINISTIC AND ENSEMBLE MEANS REMAIN  
FAIRLY WELL CLUSTERED WITH THE LARGE-SCALE PATTERN AND EVOLUTION  
OF THE EXPANSIVE RIDGE AND THE TROUGH DIGGING ACROSS THE  
MIDWEST/GREAT LAKES AND INTO THE NORTHEAST. SOME MODEL DIFFERENCES  
REMAIN IN REGARDS TO THE DISTRIBUTION AND TIMING OF INDIVIDUAL  
ENERGIES WITHIN THE TROUGH BUT FOR THE MOST PART THESE DIFFERENCES  
FALL WITHIN THE NORMAL DEGREE OF SPREAD. SATURDAY AND BEYOND THE  
TROUGH OVER THE NORTHEAST WILL BE REINFORCED AS MULTIPLE IMPULSES  
MOVE THROUGH AND THE GUIDANCE CONTINUES TO OFFER PLENTY OF  
UNCERTAINTY IN THE DETAILS. OUT WEST, THERE ARE LINGERING  
QUESTIONS IN THE TIMING OF A SHORTWAVE ENTERING THE NORTHWEST,  
WHICH WOULD HAVE IMPLICATIONS FOR EARLY PERIOD EXCESSIVE HEAT IN  
THAT REGION AND HOW LONG IT STICKS AROUND. GFS AND UKMET ARE THE  
QUICKEST TO BRING THIS ENERGY ONSHORE, WHILE THE ENSEMBLE MEANS  
SUPPORT SOMETHING A LITTLE SLOWER LIKE THE ECMWF AND CMC. THE  
MODELS SUGGEST THE OVERALL PATTERN MAY BECOME MORE AMPLIFIED BY  
THE MIDDLE OF NEXT WEEK WITH TROUGHING OVER THE WEST AND EAST  
SANDWICHING A BUILDING HEAT DOME OVER THE FOUR CORNERS AND INTO  
THE PLAINS.  
 
THE WPC BLEND UTILIZED A BLEND OF THE DETERMINISTIC MODELS THROUGH  
DAY 4, WITH INCREASING INFLUENCE FROM THE ENSEMBLE MEANS  
THEREAFTER, ALONG WITH SMALLER PORTIONS OF THE ECMWF AND CMC FOR A  
LITTLE ADDED SYSTEM DEFINITION. THIS MAINTAINS GOOD CONTINUITY  
WITH THE PREVIOUS WPC FORECAST AS WELL.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
HEAT HEADLINES WILL SHIFT TO THE NORTHWEST DURING THE MEDIUM RANGE  
PERIOD AS TEMPERATURES SHOULD FINALLY MODERATE MORE TOWARDS NORMAL  
(FOR LATE JULY AT LEAST) FOR THE RECENTLY HEAT STRICKEN  
SOUTH-CENTRAL U.S.. MEANWHILE, EXCESSIVE HEAT WILL CONTINUE INTO  
THE WEEKEND ACROSS THE NORTHWEST WITH HIGHS IN THE LOW TO MID 100S  
FOR THE COLUMBIA BASIN, AND EVEN 90S EXPECTED AS FAR WEST AS  
PORTLAND AND SEATTLE. THESE MUCH ABOVE NORMAL TEMPERATURES  
COMBINED WITH LITTLE TO NO RELIEF OVERNIGHT FROM THE HEAT, COULD  
CREATE A DANGEROUS HEAT THREAT FOR MANY ACROSS THE REGION. SOME  
DAILY RECORDS FOR HIGHS/WARM LOWS COULD ALSO 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 SUGGEST BY EARLY NEXT WEEK  
TEMPERATURES COULD ONCE AGAIN BOUNCE BACK TO NORMAL AS THE RIDGE  
SHIFTS INTO THE NORTHERN PLAINS. A BUILDING HEAT DOME OVER THE  
CENTRAL PART OF THE NATION BY AROUND NEXT TUESDAY, MAY ONCE AGAIN  
BRING ANOTHER PERIOD OF ABOVE NORMAL HEAT TO MUCH OF THE PLAINS  
STATES.  
 
A QUASI-STATIONARY BOUNDARY DRAPED FROM THE SOUTH-CENTRAL PLAINS  
TO THE SOUTHERN MID-ATLANTIC WILL CONTINUE TO FOCUS A THREAT FOR  
HEAVY TO EXCESSIVE RAINFALL WITH SOME AREAS LIKELY TO SEE REPEATED  
ROUNDS OF HEAVY RAINFALL INCREASING THE RISK THE FOR LOCALIZED  
FLASH FLOODING. THE DAYS 4 AND 5 EXPERIMENTAL EROS HAVE EXPANSIVE  
SLIGHT RISKS DEPICTED ALONG THIS BOUNDARY FROM THE CENTRAL  
APPALACHIANS/SOUTHERN MID-ATLANTIC TO THE CENTRAL PLAINS. ACTIVITY  
ALONG THIS BOUNDARY MAY SINK SLIGHTLY SOUTHWARD WITH TIME,  
CONTINUING THROUGH NEXT WEEKEND FOR SOME REGIONS IN ESPECIALLY THE  
TENNESSEE VALLEY. MEANWHILE, PERSISTENT MONSOONAL MOISTURE WILL  
CONTINUE TO SUPPORT DIURNALLY FAVORED SHOWERS/STORMS WITH SOME  
LOCALLY HEAVY TO EXCESSIVE RAINFALL OVER A VERY SOGGY FOUR CORNERS  
REGION INTO THE MIDDLE OF NEXT WEEK. MODELS SHOW INCREASING  
POTENTIAL THAT THIS MOISTURE PLUME MAY INTERACT WITH THE CENTRAL  
PLAINS FRONT, ENHANCING RAINFALL TOTALS FARTHER NORTH AND EAST  
INTO PARTS OF THE CENTRAL AND SOUTHERN ROCKIES AND HIGH PLAINS. A  
MODERATE RISK WAS INTRODUCED ON THE DAY 4 ERO FROM FAR NORTHEAST  
NEW MEXICO, SOUTHEAST COLORADO, AND INTO FAR WESTERN KANSAS IN A  
REGION LIKELY TO RECEIVE VERY HEAVY RAINFALL AT THE END OF THE  
SHORT RANGE PERIOD AS WELL.  
 
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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