896  
FXUS02 KWBC 201900  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT TUE SEP 20 2022  
 
VALID 12Z FRI SEP 23 2022 - 12Z TUE SEP 27 2022  
   
..OVERVIEW
 
 
THE MEDIUM RANGE PERIOD BEGINS LATE THIS WEEK WITH AN UPPER HIGH  
OVER THE SOUTH-CENTRAL U.S. PROMOTING WARM TEMPERATURES WELL INTO  
THE 90S, WHILE A COOL SURFACE HIGH LEADS TO BELOW NORMAL  
TEMPERATURES IN PARTS OF THE EAST-CENTRAL U.S. THE PATTERN SETTLES  
INTO A WESTERN RIDGE AND EASTERN TROUGH OVERALL PATTERN FOR THE  
EARLY PART OF NEXT WEEK, KEEPING THE WEST GENERALLY DRY WHILE  
FRONTAL SYSTEMS BRING SOME RAIN TO THE EAST-CENTRAL U.S. TO THE  
EAST COAST.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
RECENT MODEL GUIDANCE HAS REMAINED IN GOOD AGREEMENT FOR THE LARGE  
SCALE PATTERN, AS MOST IMPACTFUL SYSTEMS ARE ON THE SYNOPTIC SCALE  
AND THUS HAVE GREATER PREDICTABILITY. OVERALL A COMPOSITE BLEND OF  
THE DETERMINISTIC MODELS (SPECIFICALLY THE 06Z GFS AND 00Z ECMWF,  
CMC, AND UKMET) WORKED WELL FOR THE FRONTS/PRESSURES FORECAST,  
WITH SOME INCLUSION OF THE GEFS AND EC ENSEMBLE MEANS BY DAYS 6/7  
TO REDUCE DETAIL DIFFERENCES BETWEEN INDIVIDUAL MODELS. THE 13Z  
NATIONAL BLEND OF MODELS WAS USED HEAVILY FOR QPF AND TEMPERATURES  
ETC. FORECASTS, THOUGH WITH SOME ENHANCEMENTS PARTICULARLY TO  
EXPAND SOME LIGHT QPF AMOUNTS. FRONTAL BOUNDARIES TRACKING ACROSS  
THE CENTRAL AND EASTERN U.S. AND THE ASSOCIATED QPF EARLY NEXT  
WEEK SHOW SOME WAFFLING IN TIMING AND PLACEMENT FOR SOME MINOR  
DIFFERENCES FROM CONTINUITY.  
 
MODEL GUIDANCE IS AGREEABLE WITH THE TRACK OF HURRICANE FIONA NEAR  
THE CANADIAN MARITIMES EVEN AS IT TRANSITIONS TO A DEEP  
EXTRATROPICAL LOW DURING THE MEDIUM RANGE PERIOD. WPC AND THE  
NATIONAL HURRICANE CENTER WILL ALSO CONTINUE TO MONITOR THE  
TROPICS REGARDING INVEST 98L, WHICH IS LIKELY TO FORM INTO A  
TROPICAL CYCLONE IN THE CARIBBEAN PER THE NHC TROPICAL WEATHER  
OUTLOOK. BROADLY, GFS RUNS INDICATE A STRONGER TROPICAL SYSTEM BY  
EARLY NEXT WEEK AND A MORE NORTHEASTERLY TRACK COMPARED TO THE 00Z  
ECMWF AND CMC RUNS AND MOST 00Z EC ENSEMBLE MEMBERS (GEFS MEMBERS  
WERE MORE DIFFUSE IN PLACEMENT). LEANED AWAY FROM THESE  
NORTHEASTERLY GFS RUNS AT THIS POINT, THOUGH THE NEW 12Z ECMWF IS  
NOW ACTUALLY CLOSER TO THE GFS. THERE IS STILL AMPLE UNCERTAINTY  
AS THE TRACK WILL DEPEND ON MULTIPLE FACTORS INCLUDING THE EXACT  
TROUGH POSITION TO THE NORTH. STAY TUNED FOR FORECAST UPDATES OVER  
THE NEXT SEVERAL DAYS AS THIS SYSTEM COULD EVENTUALLY BE IMPACTFUL.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
A SHORTWAVE TROUGH TRACKING ACROSS THE NORTH-CENTRAL U.S. WILL  
COMBINE WITH ENERGY FROM NORTHERN CANADA TO DEEPEN A TROUGH WITH  
ITS AXIS IN THE EAST-CENTRAL U.S. FOR THE EARLY PART OF NEXT WEEK.  
THIS TROUGH AND A COUPLE OF FRONTAL SYSTEMS AT THE SURFACE SHOULD  
HELP PRODUCE SOME INCREASING RAINFALL CHANCES ACROSS THE UPPER  
MIDWEST/GREAT LAKES AND TOWARD THE OHIO VALLEY LATE WEEK INTO THE  
WEEKEND, SHIFTING INTO THE EASTERN SEABOARD BY LATER SUNDAY INTO  
MONDAY-TUESDAY NEAR THE FRONTAL SYSTEM, WITH SOME LAKE ENHANCED  
RAINFALL BEHIND IT. THE WESTERN U.S. SHOULD SEE GENERALLY DRY  
CONDITIONS DURING THE MEDIUM RANGE PERIOD AFTER A WET SHORT RANGE  
TIMEFRAME. SHOWERS AND STORMS ARE POSSIBLE ACROSS THE FLORIDA  
PENINSULA AND MAY INCREASE IN COVERAGE BY AROUND TUESDAY AND  
BEYOND AS THERE IS POTENTIAL FOR TROPICAL MOISTURE STREAMING IN.  
 
A BROAD COOL SURFACE HIGH WILL LEAD TO BELOW NORMAL TEMPERATURES  
FROM THE NORTHERN HALF OF THE MISSISSIPPI VALLEY INTO THE OHIO  
VALLEY, GREAT LAKES, AND MID-ATLANTIC/NORTHEAST ON FRIDAY, WITH  
COOLER THAN NORMAL TEMPERATURES REMAINING ACROSS THE EAST ON  
SATURDAY. MEANWHILE AN UPPER HIGH CENTERED IN TEXAS FRIDAY WILL  
PRODUCE CONTINUED WARMTH FOR THE SOUTHERN PLAINS AND LOWER  
MISSISSIPPI VALLEY THROUGH THE WEEKEND, WITH HIGHS IN THE 90S AND  
PERHAPS ISOLATED 100S, WHICH ARE 10-15F ABOVE AVERAGE. AS UPPER  
RIDGING DEVELOPS IN THE WEST, WARMER THAN AVERAGE TEMPERATURES BY  
AROUND 5-10F ARE FORECAST FOR THE FIRST PART OF NEXT WEEK,  
BRINGING THE DESERT SOUTHWEST TEMPERATURES WELL INTO THE 100S.  
 
TATE  
 
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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