401  
FXUS02 KWBC 100658  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
257 AM EDT WED AUG 10 2022  
 
VALID 12Z SAT AUG 13 2022 - 12Z WED AUG 17 2022  
 
...MONSOONAL MOISTURE/RAINFALL THREAT CONTINUES FOR THE SOUTHWEST  
AND INTERMOUNTAIN WEST/ROCKIES...  
 
...EXCESSIVE HEAT THREAT ACROSS THE PLAINS, WITH WARMING  
TEMPERATURES IN THE NORTHWEST NEXT WEEK...  
 
   
..OVERVIEW
 
 
A FAIRLY STAGNANT TROUGH-RIDGE-TROUGH PATTERN IS FORECAST THIS  
WEEKEND 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 A WARM UPPER UPPER  
HIGH MEANDERS NEAR THE CENTRAL/SOUTHERN HIGH PLAINS. UPPER RIDGING  
IS FORECAST TO EXPAND INTO THE WEST BY TUESDAY-WEDNESDAY OF NEXT  
WEEK, INCREASING TEMPERATURES TO WELL ABOVE AVERAGE PARTICULARLY  
IN THE NORTHWEST. THE RIDGE ALOFT WILL ALSO CONTINUE TO SUPPORT  
MONSOONAL MOISTURE STREAMING INTO THE SOUTHWEST AND INTO THE  
INTERMOUNTAIN WEST AND ROCKIES THROUGH MUCH OF NEXT WEEK. A  
LINGERING FRONTAL BOUNDARY OVER FLORIDA WILL PROVIDE A FOCUS FOR  
RAINFALL THERE, WHILE POSSIBLE SHORTWAVE ENERGY ROUNDING THE RIDGE  
COULD LEAD TO ROUNDS OF SHOWERS/THUNDERSTORMS ACROSS THE  
MIDWEST/UPPER GREAT LAKES THIS WEEKEND, WITH RAIN CHANCES  
EXPANDING SOUTH AND EAST EARLY NEXT WEEK.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
MODEL GUIDANCE REMAINS STEADY IN INDICATING THE CENTRAL U.S. UPPER  
HIGH WILL SEPARATE THE EASTERN TROUGH AND A COMPACT UPPER LOW  
TRACKING ACROSS BRITISH COLUMBIA THIS WEEKEND (WHICH HAS FINALLY  
SHOWED BETTER AGREEMENT IN TRACK AND TIMING). LESS CERTAIN ASPECTS  
OF THE FORECAST INCLUDE SMALL-SCALE SHORTWAVES ROUNDING THE  
NORTHERN SIDE OF THE RIDGE, WHICH MAY NOT CAUSE CONSIDERABLE  
DIFFERENCES ON THE LARGER SCALE, BUT DO LEAD TO VARIETY IN  
PLACEMENT OF STORMS/POSSIBLE MCSS THAT DEVELOP IN AND AROUND THE  
MIDWEST IN THE NORTHWEST FLOW. THERE IS ALSO SOME VARIABILITY WITH  
THE DETAILS OF ENERGY DISTRIBUTION WITHIN THE EASTERN TROUGH, EVEN  
AS THE PERIOD BEGINS SATURDAY WITH THE 12Z ECMWF SHOWING A CLOSED  
LOW WITHIN THE TROUGH. THIS INITIAL ENERGY LOOKS TO LIFT NORTHEAST  
WHILE ADDITIONAL SHORTWAVES DIG TO MAINTAIN THE TROUGH THROUGH THE  
MIDDLE OF NEXT WEEK, WITH PERHAPS BETTER AGREEMENT FOR A CLOSED  
UPPER LOW TO FORM AROUND TUESDAY-WEDNESDAY AMONG DETERMINISTIC  
MODELS, BUT THE PLACEMENT OF THE UPPER LOW CENTER VARIES. AMONG  
12/18Z GUIDANCE THE ECMWF WAS THE FARTHEST NORTH INTO CANADA AND  
THE 12Z GFS WAS FARTHEST SOUTH OVER THE GREAT LAKES, WITH THE 12Z  
CMC LEANING SOUTH AS WELL WHILE THE 18Z GFS WAS IN BETWEEN. THE  
NEWER 00Z GUIDANCE TRENDED A BIT TOWARD THE SOUTHERN SIDE. DESPITE  
THE DIFFERENCES, NO MODELS SEEMED QUESTIONABLE ENOUGH TO BE CALLED  
OUTLIERS. THUS THE WPC FORECAST WAS BASED ON AN INITIAL BLEND OF  
THE 18Z GFS AND 12Z ECMWF/UKMET/CMC, WITH THE BLEND SERVING TO  
SMOOTH OUT THE SMALL SCALE DIFFERENCES. GRADUALLY INCORPORATED THE  
EC AND GEFS ENSEMBLE MEANS DAY 5-7, WHICH WERE AGREEABLE, TO TRY  
TO PRODUCE A MIDDLE GROUND FORECAST. THE MAIN CHANGE TO THE  
PREVIOUS WPC FORECAST WAS REGARDING TIMING OF A COLD FRONT  
TRACKING EASTWARD THROUGH THE GREAT LAKES TO NORTHEAST AS THE  
EASTERN TROUGH SEEMS TO SHARPEN UP, WHILE THE MAIN CHANGE TO THE  
QPF FROM THE NATIONAL BLEND OF MODELS WAS TO INCREASE COVERAGE OF  
QPF IN THE EAST-CENTRAL U.S. GIVEN SHORTWAVE ENERGY COULD CAUSE  
SHOWERS AND STORMS THERE.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
PARTS OF THE WEST HAVE SEEN PERSISTENT MONSOONAL MOISTURE OVER THE  
PAST COUPLE OF MONTHS, AND THE REST OF THIS WEEK AND INTO NEXT  
WEEK WILL CONTINUE THAT PATTERN. IN FACT, NOTABLE MOISTURE  
ANOMALIES ARE FORECAST TO STREAM INTO PARTS OF THE GREAT BASIN AND  
THE ROCKIES AND PRODUCE RAIN AND THUNDERSTORMS. RAIN TOTALS MAY  
INCREASE BY MONDAY-TUESDAY FOR THE NORTHERN/CENTRAL ROCKIES IN  
PARTICULAR. MEANWHILE, A MOIST AIRMASS AND A LINGERING FRONTAL  
BOUNDARY WILL CAUSE SHOWERS AND THUNDERSTORMS ACROSS THE FLORIDA  
PENINSULA INTO EARLY NEXT WEEK. FARTHER NORTH, SHORTWAVE IMPULSES  
ROUNDING THE RIDGE COULD LEAD TO RAIN AND STORMS ACROSS THE  
MIDWEST/UPPER GREAT LAKES INTO THE OHIO VALLEY THIS WEEKEND, BUT  
WITH LOW CONFIDENCE ON THE SPECIFICS. THEN RAIN CHANCES COULD  
INCREASE FOR THE OHIO VALLEY TO APPALACHIANS AND THE EAST COAST  
EARLY NEXT WEEK ALONG A COLD FRONT, BUT THE DETAILS REMAIN  
UNCERTAIN THERE AS WELL.  
 
VERY WARM TO HOT TEMPERATURES AROUND 10-15F ABOVE AVERAGE, THOUGH  
MAINLY NOT TO RECORD-BREAKING LEVELS, ARE FORECAST ACROSS THE  
NORTHERN AND ESPECIALLY THE CENTRAL PLAINS OVER THE WEEKEND, WITH  
SOME GRADUAL MODERATION AND SHIFT SOUTHWARD THROUGH THE WORKWEEK,  
THOUGH HIGHS COULD STILL REACH 100F IN THE SOUTHERN PLAINS. AS THE  
UPPER RIDGE EXPANDS INTO THE NORTHWEST, THIS WILL WARM UP  
TEMPERATURES THERE AND CAUSE HIGHS 10-20F ABOVE NORMAL BY  
TUESDAY-WEDNESDAY. MEANWHILE, 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 TOWARD THE MID-ATLANTIC. GIVEN THE RAINFALL AND CLOUDINESS  
OVER THE SOUTHWEST AND GREAT BASIN INTO THE ROCKIES, HIGHS ARE  
LIKELY TO BE SEVERAL DEGREES BELOW NORMAL THERE THROUGH MUCH OF  
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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