697  
FXUS02 KWBC 130608  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
207 AM EDT SAT AUG 13 2022  
 
VALID 12Z TUE AUG 16 2022 - 12Z SAT AUG 20 2022  
 
...MONSOONAL MOISTURE/RAINFALL THREAT CONTINUES FOR THE SOUTHWEST  
AND SOUTH-CENTRAL GREAT BASIN/ROCKIES NEXT WEEK...  
 
...HEAVY RAIN/FLASH FLOODING POSSIBLE ACROSS THE MID-LOWER  
MISSISSIPPI VALLEY TUESDAY-THURSDAY...  
 
...EXCESSIVE HEAT THREAT ACROSS THE SOUTH CENTRAL PLAINS TO  
REFOCUS IN ERNEST OVER INTERIOR CALIFORNIA AND BROADLY ACROSS THE  
NORTHWEST NEXT WEEK...  
 
...THE NATIONAL HURRICANE CENTER IS MONITORRING A TROPICAL  
DISTURBANCE OVER THE NORTHWEST GULF OF MEXICO...  
 
   
..OVERVIEW
 
 
THE PROSPECT FOR AN AMPLIFIED UPPER FLOW PATTERN OVER THE NATION  
REMAINS ON TAP FOR NEXT WEEK. THIS PATTERN 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 AND SOUTH-CENTRAL  
GREAT BASIN/ROCKIES NEXT WEEK. THE DOWNSTREAM DIGGING OF  
SHORTWAVES/HEIGHT FALLS TO THE LEE OF THE RIDGE WILL PERIODICALLY  
REINFORCE UPPER DIFFLUENT FLOW OVER THE 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.  
 
THE NATIONAL HURRICANE CENTER (NHC) IS ALSO NOW MONITORRING A  
TROPICAL DISTURBANCE OVER THE NORTHWEST GULF OF MEXICO FOR ANY  
SIGNS OF DEVELOPMENT. A MAIN THREAT BY MEDIUM RANGE TIME SCALES  
MAY BE FOR SLOW TRACKING AND DEEP TROPICAL MOISTURE FUELING HEAVY  
RAINFALL/RUNOFF ISSUES UP THE RIO GRANDE VALLEY AND ACROSS  
NORTHERN MEXICO ALONG WITH ANY SUBSEQUENT MOISTURE INFLUENCE INTO  
THE MONSOONAL FETCH INTO THE SOUTHWEST, ALL CONTINGENT ON  
UNCERTAIN DEVELOPMENT.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
WHILE THE MID-LARGER SCALE PATTERN EVOLUTION FOR NEXT WEEK SEEMS  
WELL DEPICTED BY GUIDANCE THROUGH MEDIUM RANGE TIME SCALES, FLOW  
EMBEDDED SYSTEMS OFFER INCREASED FORECAST SPREAD. THIS COMBINED  
WITH UNCERTAINTY WITH THE FUTURE EVOLUTION OF A TROPICAL  
DISTURBANCE OVER THE NORTHERN GULF OF MEXICO LOWERS OVERALL  
PREDICTABILITY TO NO BETTER THAN AVERAGE OVERALL. ACCORDINGLY, THE  
WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A  
COMPOSITE BLEND OF THE 01 UTC NATIONAL BLEND OF MODELS, THE 18 UTC  
GEFS MEAN, THE 12 UTC ECMWF ENSEMBLE MEAN AND CLOSEST MATCHING  
MODEL GUIDANCE A LA THE 12 UTC ECMWF/UKMET FOR TUESDAY/WEDNESDAY.  
OPTED TO SWITCH PREFERENCE TO JUST THE NBM AND GEFS/ECMWF ENSEMBLE  
MEANS THURSDAY-NEXT SATURDAY ANID GROWING DETAIL UNCERTAINTIES TO  
MAXIMIZE WPC PRODUCT CONTINUITY. TAGRETED FORECASTER ADJUSTMENTS  
TO 01 UTC NBM QPF GUIDANCE WERE APPLIED TO INCREASE RAINFALL SOME  
OVER NC TUESDAY CONSIDERING AVAILABLE MOISTURE. THE NBM LOOKED  
MORE SIGNIFICANTLY TOO LIGHT WITH CONVECTIVE RAINFALL OVER THE  
UPPER MIDWEST/GREAT LAKES THURSDAY-NEXT SATURDAY GIVEN DYNAMIC  
UPPER SUPPORT AND FRONTAL PASSAGE. THE 01 UTC NBM ALONG WITH  
LATEST MODEL AND ENSEMBLE GUIDANCE TRENDED LESS WET WITH MONSOONAL  
FLOW FOR THE WEST/ROCKIES. HESITANCE TO MAKE SUCH A CONTINUITY  
SHIFT FOR QUITE A WET AND PROTRACTED MONSOONAL PATTERN WAS  
COMPENSATED BY BLENDING IN SOME WETTER WPC DAYSHIFT QPF CONTINUITY  
ACROSS THE SOUTHWEST AND SOUTH-CENTRAL GREAT BASIN.  
   
..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. WPC EXPERIMENTAL SLIGHT RISKS OF  
EXCESSIVE RAINFALL ARE IN PLACE FOR THE SOUTH-CENTRAL ROCKIES FOR  
EARLY-MID NEXT WEEK, WHERE THERE IS A VIABLE GUIDANCE SIGNAL FOR  
HEAVY CONVECTIVE RAINFALL ROOTED BY DIGGING SHORTWAVE ENERGY/UPPER  
DIFFLUENCE AND TERRAIN LIFT.  
 
THERE ARE INCREASING CHANCES FOR ORGANIZED CLUSTERS OF CONVECTION  
WITH HEAVY DOWNPOURS TO SPREAD THROUGH EASTERN PORTIONS OF THE  
CENTRAL/SOUTHERN PLAINS AND ESPECIALLY INTO THE MID-LOWER  
MISSISSIPPI VALLEY AS NEXT WEEK PROGRESSES. THERE IS A WPC SLIGHT  
RISK OF EXCESSIVE RAINFALL IS IN EFFECT FOR CENTRAL-SOUTHERN  
MISSOURI AND NORTHERN ARKANSAS TUESDAY INTO WEDNESDAY. ELSEWHERE,  
THE GULF COAST AND INTO FLORIDA COULD SEE SCATTERED STORMS WITH A  
MOIST AIRMASS AND FRONTAL BOUNDARIES. A WAVY SURFACE FRONT  
EXPECTED TO TRACK ACROSS THE MID-ATLANTIC TO THE NORTHEAST TO  
FOCUS SOME ORGANIZED RAINS. A MULTI-DAY RAIN EVENT MAY OCCUR 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 DEVELOPING COASTAL LOW. THERE REMAINS SOME UNCERTAINTY  
WITH THE EXACT TRACK OF THIS MODERATE LOW GIVEN CONNECTION TO A  
MAIN UPPER LOW INLAND.  
 
AS THE UPPER RIDGE EXPANDS OVER THE WEST/NORTHWEST NEXT WEEK,  
EXPECT A HEAT WAVE WITH DAYTIME AND OVERNIGHT TEMPERATURE 10-20F  
ABOVE NORMAL. THESE TEMPERATURES ARE LIKELY TO PRODUCE SOME LOCAL  
RECORD VALUES, ESPECIALLY FOR HOT OVERNIGHT CONDITIONS. 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  
SOUTH-CENTRAL GREAT BASIN/ROCKIES, HIGHS ARE LIKELY TO REMAIN  
SEVERAL DEGREES BELOW NORMAL.  
 
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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