757  
FXUS02 KWBC 220715  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
315 AM EDT MON SEP 22 2025  
 
VALID 12Z THU SEP 25 2025 - 12Z MON SEP 29 2025  
   
..HEAVY RAIN THREAT FOR PORTIONS OF THE EASTERN U.S. LATE WEEK
 
 
   
..OVERVIEW
 
 
AN AMPLIFIED TROUGH/CLOSED LOW WILL MOVE SLOWLY FROM THE MIDWEST  
ON THURSDAY TO THE EAST BY THE WEEKEND, WITH SOME ENERGY MEANDERING  
OVER THE SOUTHEAST. THE ASSOCIATED COLD FRONT WILL FOCUS  
POTENTIALLY HEAVY RAINFALL FROM THE GULF COAST/SOUTHEAST INTO THE  
APPALACHIANS AND THE MID-ATLANTIC MAINLY THURSDAY AND FRIDAY.  
MEANWHILE, PACIFIC MOISTURE AHEAD OF ANOTHER CUTOFF LOW NEAR THE  
CALIFORNIA COAST COULD LEAD TO DAILY RAIN CHANCES OVER SOUTHERN  
CALIFORNIA INTO THE SOUTHWEST AS IT DRIFTS SOUTHEASTWARD. AN UPPER  
LEVEL RIDGE IN BETWEEN THESE TWO SYSTEMS WILL ALLOW FOR ABOVE  
NORMAL TEMPERATURES MUCH OF THE PERIOD FROM THE INTERIOR WEST TO  
THE NORTHERN PLAINS.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
THE LATEST NUMERICAL GUIDANCE REMAINS IN RELATIVELY GOOD AGREEMENT  
WITH THE LARGE SCALE PATTERN THROUGH THE MEDIUM RANGE PERIOD. WITH  
THE EASTERN TROUGH/UPPER LOW, THE CMC WAS NOTABLY FASTER AS EARLY  
AS DAY 3 WITH THE UKMET ALSO SLIGHTLY FASTER, PARTICULARLY BY DAY  
5. OTHERWISE, A BLEND OF THE GFS AND ECMWF WAS REASONABLE FOR MUCH  
OF THE PERIOD. THE GFS WAS STRONGER WITH HOLDING A CLOSED LOW OVER  
THE SOUTHEAST NEXT WEEKEND, BUT THERE IS CONSENSUS THAT SOME SORT  
OF WEAK ENERGY MAY BE LEFT BEHIND AS THE NORTHERN STREAM ENERGY  
EXITS THE NORTHEAST. GOOD AGREEMENT IN THE MODELS WITH THE UPPER  
LOW OVER CALIFORNIA THAT DRIFTS INTO THE SOUTHWEST. THE GREATEST  
UNCERTAINTY IS THE LATTER HALF OF THE PERIOD WITH SHORTWAVES MOVING  
THROUGH THE NORTHWEST.  
 
THE WPC FORECAST TODAY WAS BASED ON A BLEND OF THE ECMWF WITH THE  
GFS AND UKMET FOR DAYS 3 AND 4 AND THE ECMWF WITH THE ENSEMBLE  
MEANS BEYOND. OVERALL, THIS MAINTAINS GOOD AGREEMENT WITH THE  
PREVIOUS WPC FORECAST AS WELL.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
WIDESPREAD RAIN AND CONVECTION WILL FOCUS ALONG AND AHEAD OF A  
COLD FRONT AS IT SLOWLY MOVES INTO THE EAST LATER THIS WEEK.  
ANOMALOUS MOISTURE AND AMPLE INSTABILITY WILL BE IN PLACE,  
WARRANTING BROAD MARGINAL RISKS ON THE DAYS 4 AND 5 (THURSDAY-  
FRIDAY) ERO STRETCHED FROM THE GULF COAST TO THE MID- ATLANTIC. DRY  
ANTECEDENT CONDITIONS MAY LIMIT THE OVERALL FLOOD THREAT, BUT  
THERE CONTINUES TO BE ENOUGH OF A HEAVY RAINFALL SIGNAL FOR THE  
MORE VULNERABLE SOUTHERN APPALACHIANS REGION ON THURSDAY WHERE A  
SLIGHT RISK IS HIGHLIGHTED IN THE ERO. ADDITIONAL SLIGHT RISK  
UPGRADES ARE NOT OUT OF THE QUESTION WITHIN THE BROADER MARGINAL  
RISKS, AND WILL BE REEVALUATED WITH FUTURE ISSUANCES SHOULD THE  
GUIDANCE SHOW BETTER CONSENSUS. RAINFALL MAY LINGER ACROSS THE  
NORTHEAST AND THE IMMEDIATE EAST COAST THIS WEEKEND AS WELL.  
 
MEANWHILE, PACIFIC MOISTURE AHEAD OF AN UPPER LOW NEAR CALIFORNIA  
WILL RESULT IN INCREASING RAINFALL CHANCES ACROSS MUCH OF THE  
SOUTHWEST INTO SOUTHERN CALIFORNIA. MOISTURE ANOMALIES 2 TO 3  
STANDARD DEVIATIONS ABOVE NORMAL AND SUFFICIENT INSTABILITY WILL  
RESULT IN AT LEAST A LOCALIZED FLASH FLOOD THREAT, PARTICULARLY FOR  
VULNERABLE BURN SCAR AREAS. THIS ENTIRE REGION IS HIGHLIGHTED WITH  
A MARGINAL RISK FOR BOTH THURSDAY AND FRIDAY'S EROS. A MORE  
TARGETED SLIGHT RISK WAS ADDED ON BOTH DAYS ACROSS SOUTHEAST  
ARIZONA WHERE QPF AMOUNTS LOOK GREATEST. THIS ACTIVITY WILL  
CONTINUE INTO THE WEEKEND AS THE UPPER LOW DROPS SLOWLY SOUTH AND  
EASTWARD THROUGH THE REGION.  
 
A RIDGE AXIS WILL BUILD FROM THE FOUR CORNERS STATES INTO THE WEST  
WITH THE MOST ANOMALOUSLY WARM TEMPERATURES EXPECTED FROM THE  
NORTHWEST INTO THE NORTHERN ROCKIES AND PLAINS WHICH MAY HOLD MUCH  
OF THE PERIOD. THE DESERT SOUTHWEST SHOULD ALSO SEE TEMPERATURES  
REACHING OR EXCEEDING 100F, MAINLY INTO THURSDAY BEFORE THE RIDGE  
SHIFTS EAST. EXPECT NEAR TO BELOW NORMAL TEMPERATURES FOR THE  
CENTRAL U.S. AND MIDWEST UNDER THE LARGE UPPER TROUGH/LOW. AS THE  
LOW DRIFTS EASTWARD, TEMPERATURES WILL COOL ACROSS THE EAST 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 FORECAST (QPF), EXCESSIVE RAINFALL  
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT  
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:  
 
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  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW  
 

 
 
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