296  
FXUS02 KWBC 131906  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
305 PM EDT TUE SEP 13 2022  
 
VALID 12Z FRI SEP 16 2022 - 12Z TUE SEP 20 2022  
   
..OVERVIEW
 
 
THE MEDIUM RANGE PERIOD BEGINS FRIDAY WITH BROAD UPPER TROUGHING  
WITH EMBEDDED SHORTWAVES ACROSS MUCH OF THE WESTERN TO  
NORTH-CENTRAL U.S., WHILE WARM RIDGING IS IN PLACE OVER THE  
EAST-CENTRAL CONUS. THE TROUGHING OVER THE WEST IS FORECAST TO  
DEEPEN/SHARPEN BY THE WEEKEND INTO EARLY NEXT WEEK, THOUGH WITH  
SOME LINGERING MODEL DIFFERENCES IN THE PLACEMENT/TIMING. THIS  
WILL LEAD TO COOLER TEMPERATURES AND SOME PRECIPITATION COMING  
INTO THE WEST. FARTHER EAST, ROUNDS OF RAIN ARE POSSIBLE ALONG THE  
NORTHERN TIER WITH PROGRESSIVE SHORTWAVES AND FRONTAL BOUNDARIES  
PASSING THROUGH, WHILE A MEANDERING FRONT SHOULD CONTINUE TO ALLOW  
FOR SCATTERED THUNDERSTORMS ACROSS FLORIDA AND THE GULF COAST.  
TEMPERATURES SHOULD BE ABOVE NORMAL UNDERNEATH RIDGING IN THE  
CENTRAL U.S. AND EVENTUALLY INTO THE EAST.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE GENERAL TREND FOR THE PAST FEW MODEL CYCLES KEEPS THE ECWMF  
FASTER/MORE PROGRESSIVE WITH LESS POTENTIAL FOR A ROUNDED AND  
PERSISTENT CLOSED LOW, THE GFS REMAINS A LITTLE SLOWER BUT COUPLES  
WELL WITH THE EC/GEFS MEANS WHILE THE CMC AND UKMET FALL BETWEEN  
THE GFS AND EC SOLUTIONS. SOME MODEL DIFFERENCES PERSIST WITH  
TIMING OF THE TROUGH'S MOVEMENT EASTWARD AND ITS POTENTIAL FOR A  
CLOSED LOW. ALSO, SOME OF THE SOLUTIONS CONTINUE TO DEPICT TYPHOON  
MERBOK MERGING/ABSORBING AS IT RECURVES INTO THE ADVANCING GULF OF  
ALASKA TROUGH JUST PRIOR TO THE EXTENDED PERIOD, WHICH ADDS TO  
MODEL DIFFERENCES ON THE TIMING AND PLACEMENT OF FEATURES  
DOWNSTREAM, PARTICULARLY WHERE RIDGING SETS UP DEPENDENT ON HOW  
FAR EAST THE TROUGH PUSHES INLAND. THE PREFERRED WPC BLEND  
UTILIZED THE DETERMINISTIC 00Z ECMWF, CMC, AND UKMET AND 06/00Z  
GFS EARLY ON, REDUCING THE FASTER EC AND SLOWER GFS WHILE  
INCREASING THE WEIGHTING OF THE GEFS AND EC ENSEMBLE MEANS. THIS  
APPROACH HELPED MAINTAIN CONTINUITY FROM THE OVERNIGHT FORECAST.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
LIGHT TO MODERATE PRECIPITATION MAY SPREAD ACROSS PORTIONS OF THE  
NORTHWEST, NORTHERN CALIFORNIA, INTERIOR WEST, GREAT BASIN AND  
INTO THE NORTHERN ROCKIES INTO EARLY NEXT WEEK THANKS TO  
APPROACHING UPPER-LEVEL TROUGHING AND FRONTAL SYSTEMS TREKKING  
ACROSS THE WEST. TEMPERATURES ALOFT WILL COOL IN THE COMING DAYS  
WITH THIS TROUGHING, SO SOME OF THE HIGHEST PEAKS ACROSS THE  
NORTHWEST AND THE ROCKIES MAY CHANGE OVER TO SNOW; ADDITIONALLY,  
REACHING THE SIERRA NEVADA RANGE BY SUNDAY. THERE IS ALSO AN  
INCREASED SIGNAL FOR SHOWERS AND THUNDERSTORMS TO FIRE UP ACROSS  
THE FOUR CORNERS REGION MONDAY AND TUESDAY. THIS IS IN RESPONSE TO  
TROPICAL MOISTURE ADVECTING INTO THE SOUTHWEST FROM A SYSTEM THAT  
MAY BECOME TROPICAL, AS IT TRACKS NEAT BAJA CALIFORNIA. ACROSS THE  
GULF AND SOUTHEAST A QUASI-STATIONARY FRONT WILL REMAIN DRAPED FOR  
SEVERAL DAYS, PROVIDING A FOCUS FOR MULTIPLE ROUNDS OF CONVECTIVE  
DEVELOPMENT. THE HEAVIEST RAIN CONTINUES TO BE FORECAST OFFSHORE  
OF THE GEORGIA/CAROLINA COASTS AND THE GULF COAST, BUT SOME  
RAINFALL COULD SNEAK ONSHORE FROM SOUTHERN TEXAS TO THE NORTH  
CAROLINA OUTER BANKS. THERE MAY BE PERIODS OF MODERATE TO HEAVY  
RAINFALL ACROSS FLORIDA. FOR THE NORTHERN TIER OF THE CONUS, A  
PAIR OF FRONTS ALONG WITH IMPULSES OF SHORTWAVE ENERGY MAY  
GENERATE ROUNDS OF RAINFALL THROUGH THE EXTENDED FORECAST THAT MAY  
REACH THE NORTHEAST BY EARLY NEXT WEEK. THERE IS SOME SIGNAL FOR  
INTERMITTENT DURATIONS OF HIGHER INTENSITY/HEAVY RAINFALL, HOWEVER  
THE CONFIDENCE FOR EXCESSIVE RAINFALL OR LOCALIZED FLASH FLOODING  
IS NOT THAT HIGH.  
 
WITH TROUGHING OVER THE WEST, COOLER TEMPERATURES CAN BE EXPECTED  
WITH SOME LOCATIONS' DAILY MAXIMUMS DIPPING TO BELOW AVERAGE.  
HIGHS OF 10-15F BELOW AVERAGE MAY BE COMMON IN THE WEST COAST  
STATES INTO THE INTERMOUNTAIN WEST, WITH EVEN COOLER READINGS  
CURRENTLY FORECAST CENTERED OVER NORTHERN CALIFORNIA ON SUNDAY.  
LIKEWISE, WITH RIDGING OVER THE CENTRAL/EASTERN U.S. TEMPERATURES  
WILL REMAIN NEAR SEASONAL UP TO 10-15F WARMER THAN AVERAGE (WITH  
ACTUAL TEMPERATURES WELL INTO THE 90S) CENTERED IN THE CENTRAL  
PLAINS/MIDDLE MISSISSIPPI VALLEY FOR THIS WEEKEND INTO EARLY NEXT  
WEEK, AND WARMER THAN NORMAL CONDITIONS COULD STRETCH INTO THE  
MIDWEST/GREAT LAKES TO EASTERN U.S. WITH TIME.  
 
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  
 
HAZARDS:  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE SOUTHERN  
PLAINS.  
- EXCESSIVE HEAT ACROSS PORTIONS OF THE CENTRAL PLAINS, THE MIDDLE  
MISSISSIPPI VALLEY, THE LOWER  
MISSISSIPPI VALLEY, AND THE SOUTHERN PLAINS, SAT-TUE, SEP 17-SEP  
20.  
 
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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