739  
FXUS02 KWBC 121912  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
311 PM EDT FRI AUG 12 2022  
 
VALID 12Z MON AUG 15 2022 - 12Z FRI AUG 19 2022  
 
...MONSOONAL MOISTURE/RAINFALL THREAT CONTINUES FOR THE SOUTHWEST  
AND INTERMOUNTAIN WEST/ROCKIES...  
 
...HEAVY RAIN/FLASH FLOODING POSSIBLE ACROSS PORTIONS OF THE  
CENTRAL PLAINS/MIDDLE MISSISSIPPI VALLEY NEXT TUESDAY/WEDNESDAY...  
 
...EXCESSIVE HEAT THREAT ACROSS THE SOUTH-CENTRAL U.S. AND  
NORTHWEST NEXT WEEK...  
 
   
..OVERVIEW
 
 
AN AMPLIFIED UPPER FLOW PATTERN FOR NEXT WEEK WILL FEATURE TROUGHS  
OVER THE NORTHEAST PACIFIC AND EAST-CENTRAL U.S. SANDWICHED AROUND  
A RIDGE OVER THE WEST. THE RIDGE WILL BUILD NORTHWARD THROUGH THE  
NORTHWEST AND WESTERN CANADA, LEADING TO A THREAT OF EXCESSIVE  
HEAT, AS THE NORTHEAST PACIFIC TROUGH SHIFTS SLOWLY EASTWARD  
TOWARD THE COASTLINE. THE RIDGE AND EMBEDDED SHORTWAVE IMPULSES  
WILL ALSO CONTINUE TO SUPPORT WIDESPREAD MONSOONAL MOISTURE  
STREAMING UNDERNEATH INTO A WET AND UNSETTLED SOUTHWEST,  
INTERMOUNTAIN WEST, AND ROCKIES THROUGH NEXT WEEK. THE DOWNSTREAM  
DIGGING OF SHORTWAVES/HEIGHT FALLS TO THE LEE OF THE RIDGE WILL  
PERIODICALLY REINFORCE UPPER DIFFLUENT FLOW OVER A HOT  
SOUTH-CENTRAL U.S. BEFORE FEEDING INTO A SLOW TO DISLODGE  
EAST-NORTHEAST U.S. CLOSED LOW. THIS LOW ALONG WITH MODEST COASTAL  
LOW DEVELOPMENT SHOULD SUPPORT MULTIPLE DAYS OF RAINFALL IN THE  
NORTHEAST AND ALLOW A BREAK FROM SUMMER TEMPERATURES DOWN THROUGH  
ROUGHLY THE EASTERN HALF OF THE NATION AS A COOLING FRONT SETTLES  
FAR DOWN THROUGH THE EAST-CENTRAL U.S. TO THE SOUTH TO PROVIDE A  
MULTI-DAY FOCUS FOR CONVECTION WITH LOCALLY HEAVY RAINS.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE OVERALL SYNOPTIC PATTERN WAS CAPTURED REASONABLY WELL BY THE  
CURRENT GUIDANCE WITH SOME AREAS OF UNCERTAINTY. THE  
TROUGH-RIDGE-TROUGH SETUP WILL TILT FARTHER WEST AS THE CENTRAL  
CONUS RIDGE EXPANDS AND LIFTS INTO THE NORTHWEST. THIS WAS  
RESOLVED FAIRLY WELL BY THE SUITE OF DETERMINISTIC GUIDANCE  
THROUGH DAY 5 BEFORE THE 00Z EC INTRODUCES AN ANOMALOUS SHORTWAVE  
TROUGH OVER THE CALIFORNIA COAST ON DAYS 5 AND 6, PROMPTING A MORE  
ENSEMBLE-CENTRIC APPROACH THROUGH THE REST OF NEXT WEEK. A GENERAL  
MODEL BLEND OF DETERMINISTIC EC/GFS/UKMET/CMC BEING USED AND THE  
00Z EC/UKMET BEING FAVORED WITH GREATER WEIGHTING DUE TO THEIR  
EMPHASIS ON AN IMPACTFUL SHORTWAVE IMPULSE ROTATING THROUGH THE  
CENTRAL PLAINS. THIS SAME BLEND WAS CONTINUED THROUGH DAY 4 BEFORE  
BEING DILUTED A BIT WITH THE 00Z EC/CMCE AND 06Z GEFS TO HELP  
SIGNAL A CLOSED LOW IN THE EAST THAT WAS MISSING IN THE 00Z EC.  
ENSEMBLES AND THE 06Z GFS WERE USED ON DAY 6 BEFORE ENDING WITH  
00Z ECE FAVORED ENSEMBLE BLEND ON DAY 7. GEFS 06Z GEFS MEMBERS  
STRUGGLED TO AGREE WITH THE REST OF THE 00Z/06Z GUIDANCE WITH  
RESPECT TO THE EASTERN TROUGH EARLY NEXT WEEK AND THE  
EAST-NORTHEASTERN PACIFIC TROUGH LATER IN NEXT WEEK, AS IT WAS  
GENERALLY A BIT DEEPER.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
PORTIONS OF THE WEST HAVE SEEN PERSISTENT MONSOONAL MOISTURE OVER  
THE PAST COUPLE OF MONTHS, AND NEXT WEEK WILL CONTINUE THAT  
PATTERN AS ANOMALOUSLY HIGH MOISTURE STREAMS INTO THE SOUTHWEST,  
GREAT BASIN, AND ROCKIES IN CONJUNCTION WITH SMALL-SCALE SHORTWAVE  
ENERGY TO PRODUCE RAIN AND THUNDERSTORMS, PARTICULARLY IN THE  
AFTERNOON AND EVENING HOURS. COLLABORATED WPC EXPERIMENTAL SLIGHT  
RISKS OF EXCESSIVE RAINFALL ARE IN PLACE FOR THE CENTRAL ROCKIES  
FOR EARLY NEXT WEEK, WHERE THERE IS A VIABLE GUIDANCE SIGNAL FOR  
HEAVY CONVECTIVE RAINFALL ROOTED BY DIGGING SHORTWAVE ENERGY/UPPER  
DIFFLUENCE AND TERRAIN LIFT. THE HEAVY RAIN FOCUS LOOKS TO SHIFT  
SLOWLY SOUTHWARD MID-LATER NEXT WEEK INTO THE SOUTHERN ROCKIES.  
 
THERE ARE INCREASING CHANCES FOR ORGANIZED CLUSTERS OF CONVECTION  
WITH HEAVY DOWNPOURS TO SPREAD THROUGH PARTS OF THE  
CENTRAL/SOUTHERN PLAINS AND MID-LOWER MISSISSIPPI VALLEY AS THE  
WEEK PROGRESSES. A SLIGHT RISK OF EXCESSIVE RAINFALL IS IN EFFECT  
FOR PARTS OF CENTRAL-SOUTHEASTERN MISSOURI NEXT TUESDAY.  
ELSEWHERE, THE GULF COAST AND INTO FLORIDA COULD SEE SCATTERED  
STORMS WITH A MOIST AIRMASS AND FRONTAL BOUNDARIES. THEN AS A  
SURFACE LOW IS CURRENTLY FORECAST TO TRACK ACROSS THE OHIO VALLEY  
THROUGH THE MID-ATLANTIC TO THE NORTHEAST, ORGANIZED RAINS ARE  
FORECAST FOR THOSE AREAS. THERE'S INCREASING CONFIDENCE IN A  
MULTI-DAY RAIN EVENT OCCURRING FOR MUCH OF THE COASTAL NORTHEAST,  
FROM NEW JERSEY UP TO MAINE THROUGH MID-WEEK UNDER CLOSED UPPER  
LOW INFLUENCE AND WITH NEAR SHORE TRACK OF A COASTAL FRONTAL LOW.  
 
VERY WARM TO HOT TEMPERATURES AROUND 10-15F ABOVE AVERAGE, THOUGH  
MAINLY NOT TO RECORD-BREAKING LEVELS, ARE FORECAST ACROSS THE  
CENTRAL PLAINS SUNDAY INTO MONDAY, WITH A GRADUALLY MODERATING  
TREND TUESDAY ONWARD YIELDING BELOW NORMAL HIGHS. AS THE UPPER  
RIDGE EXPANDS INTO THE NORTHWEST, THIS WILL WARM UP TEMPERATURES  
THERE AND CAUSE HIGHS 10-20F ABOVE NORMAL FOR TUESDAY-THURSDAY.  
MEANWHILE, BELOW NORMAL HIGHS ARE EXPECTED 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.  
 
KEBEDE/SCHICHTEL  
 
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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