486  
FXUS02 KWBC 181902  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
301 PM EDT THU AUG 18 2022  
 
VALID 12Z SUN AUG 21 2022 - 12Z THU AUG 25 2022  
 
...MONSOONAL RAINFALL THREAT FOR THE SOUTHWEST AND SOUTH-CENTRAL  
GREAT BASIN/ROCKIES TO RELAX EARLY NEXT WEEK AS A SIGNIFICANT  
EXCESSIVE RAINFALL/FLASH FLOODING THREAT SETTLES INTO THE SOUTHERN  
PLAINS/LOWER MISSISSIPPI VALLEY...  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE LATEST GUIDANCE AND ENSEMBLES ARE MAINTAINING A GOOD GRASP ON  
THE SYNOPTIC PATTERN, THE MAGNITUDE AND EVOLUTION OVER THE CONUS  
THROUGH THE EXTENDED PERIODS. THE ECWMF HAS TRENDED CLOSER TOWARD  
THE GFS SOLUTION FROM ITS PREVIOUS CYCLE. THE WPC MEDIUM RANGE  
PRODUCT SUITE WAS PRIMARILY DERIVED FROM A A COMBINATION OF THE  
ECWMF/GFS/CMC/UKMET THROUGH DAYS 3-5 (SUNDAY-TUESDAY) WITH  
INCREASING WEIGHTS OF THE EC ENSEMBLE AND GEFS MEAN THROUGH THE  
END OF THE FORECAST PERIOD.  
   
..PATTERN OVERVIEW AND WEATHER/HAZARDS HIGHLIGHTS
 
 
THE WIDESPREAD HEAVY TO EXTREME RAINFALL ACROSS THE SOUTHWEST AND  
SOUTH-CENTRAL GREAT BASIN/ROCKIES IS EXPECTED TO RELAX AFTER THE  
WEEKEND.; WHILE THERE WILL BE LINGERING MOISTURE AND INSTABILITY  
OVER THE REGION, THE THREAT FOR EXCESSIVE RAINFALL WILL LESSEN.  
THE FOCUS FOR SUBSTANTIAL HEAVY RAIN WILL SHIFT TO THE SOUTHERN  
PLAINS INTO THE LOWER MISSISSIPPI VALLEY FOR SEVERAL DAYS AS  
MOISTURE AND INSTABILITY POOL WITH RETURN FLOW INTO SLOW  
MOVING/WAVY FRONTS IN FAVORABLE UPPER FLOW AS UPPER TROUGH  
ENERGIES EJECT OUT FROM THE WEST/ROCKIES. THERE IS GENERAL  
CONSENSUS FOR THE HEAVIEST QPF TO ALIGN OVER EASTERN PORTIONS OF  
TEXAS AND SOUTHERN OKLAHOMA, WITH THE AXIS SPANNING FROM THE TEXAS  
PANHANDLE, SOUTHWARD TO TEXAS HILL COUNTRY AND EAST TOWARD CENTRAL  
MISSISSIPPI. ONCE AGAIN THE LATEST SOLUTIONS CONTINUED TO PREFER  
THE SOUTHERN PLACEMENT OF THE QPF. WPC HAS EXPERIMENTAL DAY 4/5  
SLIGHT RISKS FOR EXCESSIVE RAINFALL SPANNING FROM EASTERN NEW  
MEXICO THROUGH OKLAHOMA AND TEXAS INTO THE LOWER MISSISSIPPI  
VALLEY FROM SUNDAY INTO TUESDAY; SMALL ADJUSTMENTS WERE MADE TO  
EXPAND THE SLIGHT RISK AREAS TO REFLECT THE LATEST WPC QPF AND  
MODEL TRENDS.  
 
FURTHER EAST ALONG THIS WAVY, SLOW-MOVING FRONT SHOWERS AND  
THUNDERSTORMS WILL LINGER ACROSS THE DEEP SOUTH, SOUTHEAST AND THE  
MID-ATLANTIC THROUGH THE END OF THE EXTENDED PERIOD. THERE MAY BE  
LOCAL AREAS THAT RECEIVE MODERATE TO HEAVY DOWNPOURS. ACROSS THE  
GREAT LAKES AND OHIO VALLEY SHOWERS AND THUNDERSTORMS WILL  
GINGERLY SPREAD EAST/NORTHEAST AS THE THE UPPER TROUGH AND SURFACE  
FRONTAL WEAKENS AND DECAYS. SLOW CELL MOTIONS/INSTABILITY NEAR THE  
CLOSED FEATURE OFFER POTENTIAL FOR LOCAL DOWNPOURS WITH RUNOFF  
ISSUES.  
 
AN ENERGETIC PACIFIC UPPER TROUGH AND ASSOCIATED FRONTAL SYSTEM  
WITH LIMITED SUMMER RAINFALL POTENTIAL IS FORECAST TO MOVE INLAND  
ACROSS THE PACIFIC NORTHWEST EARLY NEXT WEEK, BUT ACTIVITY MAY  
BECOME MORE ORGANIZED INTO FAVORED TERRAIN DOWNSTREAM OVER THE  
NORTHERN GREAT BASIN/ROCKIES THROUGH NEXT MIDWEEK.  
 
CAMPBELL  
 
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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