554  
FXUS02 KWBC 120658  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
257 AM 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...  
 
...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 INPULSES  
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 MID-LARGER SCALE PATTERN EVOLUTION FOR NEXT WEEK SEEMS WELL  
DEPICTED BY GUIDANCE THROUGH MEDIUM RANGE TIME SCALES. MODEL  
FORECASTS OF FLOW EMBEDDED SYSTEMS AND AFFECTS OVERALL SEEM  
DECENTLY CLUSTERED MONDAY/TUESDAY TO PROVIDE MAX DETAIL CONSISTENT  
WITH AN AMPLIFIED PATTERN WITH ABOVE NORMAL PREDICTABILITY. A  
COMPOSITE OF THE GFS/ECMWF/UKMET AND CANADIAN SEEMS TO PROVIDE A  
GOOD FORECAST BASIS ALONG WITH THE 01 UTC NATIONAL BLEND OF MODELS  
(NBM). GROWING SMALL-MID SCALE SYSTEM VARIANCE MID-LATER NEXT WEEK  
LED TO TRANSITION TO A BLEND OF THE GEFS/ECMWF ENSEMBLE MEANS  
ALONG WITH MOST COMPATIBLE MODEL GUIDANCE OF THE 12 UTC GFS/ECMWF  
ALONG WITH THE NBM. THE 12 UTC GEFS WAS MORE IN LINE WITH THIS  
SOLUTION THAN THE LESS AMPLIFIED PATTERNS OF THE 18 UTC GFS AND 12  
UTC CANADIAN AT THESE LONGER TIME FRAMES. THE LATEST 00 UTC  
GFS/CANADIAN HAVE TRENDED MORE AMPLIFIED AND IN LINE WITH THE  
AFOREMENTIONED PREFERED COMPOSITE, BOLSTERING FORECAST CONFIDENCE.  
NBM QPF FORECASTS SEEMS REASONABLE AND CONSISTENT WITH THE PATTERN  
(IF NOT DETAILS) SO NO SIGNIFICANT FORECASTER MODIFICATIONS WERE  
APPLIED FOR THE WPC FORECAST PACKAGE.  
   
..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. 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, ORGAINZED  
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.  
 
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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