441  
FXUS02 KWBC 090655  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
254 AM EDT TUE AUG 09 2022  
 
VALID 12Z FRI AUG 12 2022 - 12Z TUE AUG 16 2022  
 
...MONSOONAL MOISTURE/RAINFALL THREAT CONTINUES FOR THE SOUTHWEST  
AND INTERMOUNTAIN WEST/ROCKIES THIS WEEK, WITH SOME LOCALIZED  
HEAVY RAIN POSSIBLE FOR THE GULF COAST STATES AS WELL...  
 
...EXCESSIVE HEAT THREAT FROM THE INTERIOR NORTHWEST TO THE  
NORTH-CENTRAL PLAINS...  
 
   
..OVERVIEW
 
 
A FAIRLY STAGNANT TROUGH-RIDGE-TROUGH PATTERN IS FORECAST LATER  
THIS WEEK INTO EARLY NEXT WEEK ACROSS THE CONTIGUOUS U.S., AS  
SHORTWAVES DEEPEN AND THEN MAINTAIN A TROUGH IN THE EAST, AN UPPER  
LOW OFF THE WEST COAST LIFTS NORTHEASTWARD INTO BRITISH COLUMBIA,  
AND AN UPPER HIGH MEANDERS NEAR THE CENTRAL/SOUTHERN HIGH PLAINS.  
A COLD FRONT OR TWO APPROACHING THE GULF COAST AND STALLING WILL  
PROVIDE A FOCUS FOR MOISTURE AND RAIN/THUNDERSTORMS THERE AND  
LINGERING ACROSS MUCH OF FLORIDA INTO EARLY NEXT WEEK. MEANWHILE,  
PERSISTENT MONSOONAL MOISTURE LOOKS TO CONTINUE ACROSS THE  
SOUTHWEST AND EXPANDING INTO THE INTERMOUNTAIN WEST AND ROCKIES  
THIS WEEK INTO NEXT WEEK.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
WHILE MODEL GUIDANCE IS IN REASONABLY GOOD AGREEMENT WITH THE  
SYNOPTIC PATTERN, DIFFERENCES REMAIN ON THE SMALLER SCALE. MODELS  
CONTINUE TO WAFFLE REGARDING THE TIMING AND EVOLUTION OF THE UPPER  
LOW CENTERED JUST OFFSHORE THE PACIFIC NORTHWEST AS THE PERIOD  
BEGINS FRIDAY. THE GFS RUNS INDICATE A FASTER TRACK WITH THIS LOW  
AS IT COMES INTO SOUTHWESTERN CANADA, OPENS INTO A SHORTWAVE, AND  
MOVES EASTWARD THROUGH SOUTH-CENTRAL CANADA EARLY NEXT WEEK.  
PREFER A SOLUTION ON THE SLOWER SIDE OF THE FULL ENVELOPE OF  
GUIDANCE GIVEN MODEL TRENDS AND HISTORY. MEANWHILE, THE UPPER HIGH  
IN THE CENTRAL U.S. APPEARS WELL HANDLED IN THE MODELS, THOUGH  
THERE IS A FAIR AMOUNT OF UNCERTAINTY WITH THE ENERGETIC SHORTWAVE  
FEATURES ROUNDING THE RIDGE THIS WEEKEND AND BEYOND. THESE  
SHORTWAVES MAY SERVE TO SUPPRESS THE RIDGE ON THE NORTHEASTERN  
SIDE IN THE MIDWEST EARLY NEXT WEEK AS WELL AS PRODUCE SOME  
SHOWERS/STORMS/MCSS THAT HAVE LOW CONFIDENCE IN THE SPECIFICS AT  
THIS POINT. THEN THERE ARE SOME MODEL DIFFERENCES WITH  
DISTRIBUTION OF ENERGY OF THE TROUGH IN THE EAST, INCLUDING SOME  
MODELS INDICATING PERIODS OF A LOW CLOSING OFF WITHIN IT, BUT A  
COMPOSITE BLEND OF GUIDANCE AVERAGED OUT THESE DIFFERENCES. THE  
WPC MEDIUM RANGE FORECAST WAS THUS BASED ON A BLEND FAVORING THE  
ECMWF AND CMC BUT STILL INCLUDING THE GFS AND UKMET, AND  
TRANSITIONING TO A MODEL/MEAN (PARTICULARLY THE EC MEAN) BLEND  
LATER IN THE PERIOD FOR THE MASS FIELDS. FOR QPF, THE MAIN NOTABLE  
CHANGE TO THE NBM WAS TO INCREASE RAIN AMOUNTS AROUND THE MIDWEST  
INTO THE OHIO VALLEY WHERE MULTIPLE MODELS INDICATE THE POTENTIAL  
FOR STORMS, ALBEIT WITH TIMING AND PLACEMENT DIFFERENCES.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
MOISTURE STREAMING AHEAD OF A COUPLE OF COLD FRONTS MOVING INTO  
THE SOUTHEAST AND TOWARD THE GULF COAST LATE THIS WEEK WILL  
PRODUCE RAIN AND THUNDERSTORMS IN THOSE AREAS. THIS COULD CAUSE  
LOCALIZED FLOODING ISSUES SINCE STORMS SHOULD BE SLOW-MOVING AND  
MAY TRAIN OVER THE SAME AREAS. RAIN CHANCES ARE LIKELY TO CONTINUE  
ACROSS MUCH OF FLORIDA INTO EARLY NEXT WEEK AS THE FRONT STALLS.  
FARTHER NORTH, THE COLD FRONT SHOULD CLEAR OUT MOST RAINFALL FROM  
THE MID-ATLANTIC AND LIKELY THE NORTHEAST AS WELL, BUT DEPENDENT  
ON HOW CLOSE TO THE NEW ENGLAND COAST A LOW ALONG THE COLD FRONT  
SITS. SHORTWAVE IMPULSES ROUNDING THE RIDGE COULD LEAD TO RAIN AND  
STORMS ACROSS THE MIDWEST/UPPER GREAT LAKES INTO THE OHIO VALLEY  
THIS WEEKEND INTO EARLY NEXT WEEK, BUT WITH LOW CONFIDENCE ON THE  
SPECIFICS. MEANWHILE, MONSOONAL MOISTURE CONTINUES TO IMPACT THE  
SOUTHWEST INTO PARTS OF THE GREAT BASIN AND INTO THE ROCKIES WITH  
RAINFALL THROUGH THE MEDIUM RANGE PERIOD. SOME LOCALLY HEAVY  
TOTALS ARE POSSIBLE AND A SLIGHT RISK OF FLASH FLOODING HAS BEEN  
ADDED TO THE EXPERIMENTAL DAY 4 ERO.  
 
VERY WARM TO HOT TEMPERATURES AROUND 10-15F ABOVE AVERAGE, THOUGH  
NOT QUITE TO RECORD-BREAKING LEVELS, ARE FORECAST ACROSS INTERIOR  
PORTIONS OF THE NORTHWEST AND INTO THE NORTHERN/CENTRAL PLAINS  
THROUGH THE LATTER PART OF THE WEEK, AND LASTING ACROSS THE  
CENTRAL PLAINS AND PARTS OF THE MID-MISSISSIPPI VALLEY THIS  
WEEKEND INTO EARLY NEXT WEEK. A SLIGHT SOUTHERN SHIFT IS EXPECTED  
WITH TIME, LEADING TO HIGHS NEARING/REACHING 100F FORECAST EARLY  
NEXT WEEK IN THE CENTRAL/SOUTHERN PLAINS. FARTHER EAST, BELOW  
NORMAL HIGHS ARE POSSIBLE IN THE EAST-CENTRAL U.S. BEHIND THE COLD  
FRONT, WITH THE MOST PERSISTENT COOLER THAN AVERAGE WEATHER IN THE  
OHIO AND TENNESSEE VALLEYS. GIVEN THE RAINFALL AND CLOUDINESS OVER  
THE SOUTHWEST AND GREAT BASIN, HIGHS ARE LIKELY TO BE SEVERAL  
DEGREES BELOW NORMAL THERE THROUGH EARLY NEXT WEEK.  
 
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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