303  
FXUS02 KWBC 211910  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
310 PM EDT WED SEP 21 2022  
 
VALID 12Z SAT SEP 24 2022 - 12Z WED SEP 28 2022  
 
...DANGEROUS FIONA FORECAST TO SLAM TOWARD THE CANADIAN MARITIMES  
SATURDAY WITH TRANSITION FROM HURRICANE TO A DEEP EXTRATROPICAL  
STORM...  
   
..PATTERN OVERVIEW
 
 
GUIDANCE AGREES TO BUILD AN AMPLIFIED/WARMING WESTERN NORTH  
AMERICAN UPPER RIDGE THIS WEEKEND INTO NEXT WEEK WITH THE DECAY OF  
A HOT RIDGE OVER THE SOUTHERN TIER U.S.. THIS TRANSITION WOULD  
ALLOW ENERGETIC MID-LATITUDE AND NORTHERN STREAM SHORTWAVE TROUGHS  
TO MORE ROBUSTLY DIG DOWNSTREAM TO CARVE OUT AN AMPLIFIED  
EAST-CENTRAL NORTH AMERICAN UPPER TROUGH TO FOCUS COOLER/UNSETTLED  
WEATHER AND POSSIBLY OFFER SOME CONNECTION TO TROPICAL LATTUDES TO  
MONITOR BY MID-LATER NEXT WEEK.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
MODEL GUIDANCE REMAINS AGREEABLE WITH THE TRACK OF HURRICANE FIONA  
TOWARD THE CANADIAN MARITIMES EVEN AS IT TRANSITIONS TO A VERY  
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. THE 00Z EC WAS A BIT MORE PROGRESSIVE THAN THE 00Z GFS  
WITH THE COLD FRONT MOVING TOWARD THE GULF COAST NEXT SUNDAY INTO  
MONDAY. THE LATEST 00Z ECMWF/GFS RUNS WERE AWFULLY BULLISH WITH  
THE DEPTH AND TRACK OF THE TROPICAL SYSTEM MOVING THROUGH THE  
CARIBBEAN AND GULF NEXT WEEK. THE GFS HAS TRENDED CLOSER TOWARD  
THE BASIN OF THE GULF OF MEXICO WHILE THE EC TRACK HAS TRENDED  
CLOSER TO WESTERN CUBA BY NEXT WEDNESDAY WITH SEVERAL INCHES OF  
QPF FORECAST BY BOTH MODELS. ENSEMBLES ARE MUCH MORE RESERVED WITH  
QPF MAXIMA ASSOCIATED WITH THIS SYSTEM. ENOUGH UNCERTAINTY  
SURROUNDS THIS SYSTEM AND THE INTERACTION OF IT'S ASSOCIATED  
MOISTURE WITH AN APPROACHING COLD FRONT TO TAMP DOWN NBM QPF  
MAXIMA OVER SOUTHERN FLORIDA AND EFFECTIVELY PRESERVE WPC  
CONTINUITY THROUGH THE MIDDLE OF NEXT WEEK.  
   
..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 FROM THE GREAT LAKES  
TO THE OHIO VALLEY INTO THE WEEKEND, SHIFTING INTO THE EASTERN  
SEABOARD BY LATER SUNDAY INTO MONDAY 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. 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. HOWEVER, OPTED TO  
TARGET A DECENT DECREASE IN FLORIDA RAINFALL AMOUNTS COMPARED TO  
THE NBM IN THIS TIME WINDOW FOR NOW GIVEN THE UNCERTAINTY WITH  
FUELING TROPICAL INFLUENCES.  
 
A LINGERING UPPER RIDGE WILL FAVOR CONTINUED WARMTH FOR THE  
SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY THROUGH THE WEEKEND  
PRIOR TO MODERATING FRONTAL PASSAGES DOWN ACROSS MUCH OF THE  
CENTRAL AND EASTERN U.S., 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.  
 
SCHICHTEL/KEBEDE  
 
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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