485  
FXUS02 KWBC 262035  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
434 PM EDT TUE JUL 26 2022  
 
VALID 12Z FRI JUL 29 2022 - 12Z TUE AUG 02 2022  
 
...DANGEROUS HEAT WAVE TO FOCUS OVER OF THE NORTHWEST/GREAT BASIN  
THROUGH THE WEEKEND, BUT STILL LINGERS OVER THE SOUTH...  
 
...EXCESSIVE RAINFALL LIKELY ACROSS PARTS OF THE SOUTH-CENTRAL  
HIGH PLAINS THROUGH FRIDAY, WITH HEAVY RAIN THREATS STRETCHING  
FROM THE SOUTHWEST TO THE SOUTHERN MID-ATLANTIC INTO NEXT WEEK...  
 
   
..OVERVIEW
 
 
IT REMAINS THE CASE THAT 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., WITH HIGH  
HEAT THEN SET TO SPREAD TO THE NORTH-CENTRAL STATES. HEAT SHOULD  
ALSO LINGER IN PARTICULAR OVER THE SOUTHERN PLAINS AND LOWER  
MISSISSIPPI VALLEY TO THE SOUTH OF A WAVY QUASI-STATIONARY FRONT.  
THIS IMPORTANT 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. WPC  
ISSUES AN EXPERIMENTAL DAYS 4/5 EXCESSIVE RAINFALL OUTLOOK (ERO).  
AN ELONGATED SLIGHT RISK AREA FOR EXCESSIVE RAINFALL HAS BEEN  
ISSUED FOR THIS BROAD AREA GIVEN POTENTIAL FOR CELL  
TRAINING/REPEAT ACTIVITY FUELED BY DEEP MOISTURE AND INSTABILITY.  
ADDITIONALLY, ENHANCED MONSOONAL MOISTURE PERSISTING WELL INTO THE  
MEDIUM RANGE PERIOD WILL CONTINUE TO PROMOTE A DAILY THREAT OF  
LOCALLY HEAVY SHOWERS AND STORMS THAT MAY PRODUCE INSTANCES OF  
FLASH FLOODING IN PARTS OF THE SOUTHWEST, THE SOUTHERN/CENTRAL  
ROCKIES AND ESPECIALLY THE SOUTH-CENTRAL HIGH PLAINS WHERE A  
MODERATE RISK AREA FOR EXCESSIVE RAINFALL HAS BEEN ISSUED THROUGH  
FRIDAY GIVEN FAVORABLE FLOW AND LONGEVITY. ALL THESE THREATS AND  
MORE ARE ALSO HIGHLIGHTED IN THE WPC DAY 3-7 HAZARDS OUTLOOK  
PRODUCT.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
DETERMINISTIC MODELS 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  
SOME IMPLICATIONS FOR EXCESSIVE HEAT DETAILS IN THAT REGION. THE  
GFS AND UKMET HAVE BEEN THE QUICKEST TO BRING THIS ENERGY ONSHORE,  
WHILE THE ENSEMBLE MEANS SUPPORT SOMETHING A LITTLE SLOWER, NOW A  
BIT MORE IN LINE WITH THE ECMWF, SOME RUNS OF THE CANADIAN AND  
CLIMATOLOGY. 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 MEDIUM RANGE PRODUCT SUITE MAINLY UTILIZED A BLEND OF THE  
SEEMINGLY REASONABLE AND OVERALL COMPATIBLE  
GFS/ECMWF/UKMET/CANADIAN MODELS FRIDAY/SATURDAY, SWITCHING TO THE  
GEFS/ECMWF ENSEMBLE MEANS THEREAFTER TO MITIGATE GROWING SMALLER  
SCALE EMBEDDED SYSTEM VARIANCE. THIS MAINTAINS GOOD WPC PRODUCT  
CONTINUITY THAT IS GENERALLY IN LINE WITH 13 UTC NATIONAL BLEND OF  
MODELS GUIDANCE.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
HEAT HEADLINES EXPAND INTO THE NORTHWEST/GREAT BASIN 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. 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 CLOSER 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. AS STATED EARLIER, 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 REMAINS IN PLACE FOR 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/SCHICHTEL  
 
HAZARDS:  
- HEAVY RAIN ACROSS PORTIONS OF NORTHERN NEW MEXICO AND SOUTHERN  
COLORADO, ACROSS THE CENTRAL PLAINS, THE MID-MISSISSIPPI VALLEY,  
THE TENNESSEE VALLEY, AND INTO THE SOUTHERN APPALACHIANS, FRI-SAT,  
JUL 29-JUL 30.  
- HEAVY RAIN ACROSS PORTIONS OF HIGHER ELEVATIONS OF ARIZONA INTO  
WESTERN NEW MEXICO, FRI-TUE, JUL 29-AUG 2.  
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL TO SOUTHERN  
APPALACHIANS, THE OHIO VALLEY, AND THE TENNESSEE VALLEY, SUN-MON,  
JUL 31-AUG 1.  
- HEAVY RAIN ACROSS PORTIONS OF THE MID-ATLANTIC, FRI-MON, JUL  
29-AUG 1.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE NORTHERN  
PLAINS.  
- EXCESSIVE HEAT ACROSS PORTIONS OF CALIFORNIA INTO THE GREAT  
BASIN, THE PACIFIC NORTHWEST, AND WESTERN MONTANA, FRI-SUN, JUL  
29-JUL 31.  
- EXCESSIVE HEAT ACROSS THE COASTAL PLAINS OF THE CAROLINAS INTO  
SOUTHEASTERN VIRGINIA, FRI, JUL 29.  
- EXCESSIVE HEAT ACROSS SOUTHERN/EASTERN TEXAS AND INTO THE LOWER  
MISSISSIPPI VALLEY, FRI, JUL 29, AND MON-TUE, AUG 1-AUG 2.  
- EXCESSIVE HEAT ACROSS THE MID-MISSISSIPPI VALLEY, MON-TUE, AUG  
1-AUG 2.  
 
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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