584  
FXUS02 KWBC 110700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT THU AUG 11 2022  
 
VALID 12Z SUN AUG 14 2022 - 12Z THU AUG 18 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
 
 
THE MEDIUM RANGE PERIOD WILL BEGIN SUNDAY WITH A CONTINUED  
TROUGH-RIDGE-TROUGH PATTERN ACROSS THE LOWER 48. AS NEXT WEEK  
PROGRESSES, THERE SHOULD BE A TREND TOWARD THE UPPER HIGH/RIDGE  
EXPANDING INTO THE WEST, LEADING TO WELL ABOVE AVERAGE  
TEMPERATURES IN THE NORTHWEST. THE RIDGE ALOFT WITH EMBEDDED  
SHORTWAVE ENERGY WILL ALSO CONTINUE TO SUPPORT MONSOONAL MOISTURE  
STREAMING INTO THE SOUTHWEST, INTERMOUNTAIN WEST, AND ROCKIES  
THROUGH THE WEEK, WITH RAIN EVENTUALLY SPREADING INTO PORTIONS OF  
THE PLAINS AND MISSISSIPPI VALLEY. MEANWHILE THE TROUGH ACROSS THE  
EAST MAY DEEPEN AND CLOSE OFF AN UPPER LOW AROUND MIDWEEK, WHICH  
COULD CAUSE MULTIPLE DAYS OF RAINFALL IN THE NORTHEAST, BUT  
DEPENDENT ON THE POSITION OF THE UPPER LOW AND THE ASSOCIATED  
SURFACE LOW/FRONTS, WHICH REMAIN UNCERTAIN AT THIS POINT.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
MODEL GUIDANCE REMAINS AGREEABLE FOR AN UPPER HIGH OVER THE  
CENTRAL/SOUTHERN HIGH PLAINS TO SLOWLY RETROGRADE AND EXPAND  
RIDGING INFLUENCE INTO THE WESTERN U.S., OVERTAKING THE EARLY WEEK  
WEAK TROUGHING THERE. SOME SMALL-SCALE SHORTWAVES EMBEDDED WITHIN  
THE BROAD RIDGE SHOW SOME VARIABILITY AS THEY MOVE THROUGH THE  
INTERIOR WEST, BUT NOTHING TOO SIGNIFICANT ON THE LARGE SCALE.  
FARTHER EAST, MODELS HAVE PERSISTENTLY INDICATED TROUGHING ACROSS  
THE EASTERN THIRD OF THE U.S. THROUGH MUCH OF NEXT WEEK. BUT THE  
DETAILS REMAIN INCONSISTENT FROM MODEL CYCLE TO MODEL CYCLE,  
PARTICULARLY BY TUESDAY-THURSDAY. IN GENERAL, GUIDANCE INDICATES  
THAT AN UPPER LOW COULD CLOSE OFF WITHIN THE TROUGH AROUND MIDWEEK  
BUT WITH DIFFERING PLACEMENT. THE 12/18Z MODEL CYCLE THAT WAS  
AVAILABLE FOR THE WPC FORECAST SHOWED AN UPPER LOW CENTER FARTHER  
SOUTH THAN PREVIOUS RUNS, AS WELL AS A DEEPER SURFACE LOW. THIS  
ALLOWED MORE MORE QPF FARTHER INLAND IN THE NORTHEAST COMPARED TO  
THE PREVIOUS CYCLE AS DEEP MOISTURE WRAPS AROUND THE LOW. WPC'S  
FORECAST TRENDED UPWARD FROM CONTINUITY BUT NOT AS HIGH AS THE NBM  
GIVEN THE RUN-TO-RUN UNCERTAINTY. THE NEWER 00Z MODELS HAVE  
GENERALLY BACKED OFF A BIT, SHOWING A WEAKER SURFACE LOW AND A  
FARTHER NORTH UPPER LOW, LEADING TO LESS RAINFALL OVERALL, THOUGH  
STILL INDICATING SOME HEAVY AMOUNTS IN NEW ENGLAND (LESS IN NEW  
YORK AND THE MID-ATLANTIC). THE WPC FORECAST USED A MULTI-MODEL  
DETERMINISTIC BLEND FOR THE EARLY PART OF THE MEDIUM RANGE  
FORECAST, INCORPORATING SOME GEFS AND EC ENSEMBLE MEANS INTO THE  
BLEND DAYS 5-7, SO AS NOT TO GO ALL IN FOR THE SOUTHERN TREND OF  
THE UPPER LOW IN THE 12/18Z CYCLE.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
PARTS 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. SLIGHT RISKS OF EXCESSIVE RAINFALL ARE IN PLACE FOR  
PORTIONS OF THE DESERT SOUTHWEST ON SUNDAY AND THE CENTRAL ROCKIES  
ON MONDAY, WHERE CURRENT FORECASTS SHOW THE BEST CHANCES FOR HEAVY  
RAINFALL. HEAVY RAIN AMOUNTS LOOK TO CONTINUE THROUGH MIDWEEK IN  
THE CENTRAL ROCKIES. THERE ARE INCREASING CHANCES FOR RAINFALL TO  
SPREAD INTO THE CENTRAL AND SOUTHERN PARTS OF THE PLAINS AND  
MISSISSIPPI VALLEY AS THE WEEK PROGRESSES. ELSEWHERE, THE GULF  
COAST AND INTO FLORIDA COULD SEE SCATTERED STORMS WITH A MOIST  
AIRMASS AND A COUPLE OF FRONTAL BOUNDARIES. THEN AS A SURFACE LOW  
IS CURRENTLY FORECAST TO TRACK ACROSS THE OHIO VALLEY THROUGH THE  
MID-ATLANTIC TOWARD THE NORTHEAST, RAIN IS FORECAST FOR THOSE  
AREAS, BUT THE TRACK OF THE SURFACE LOW (AND UPPER LOW) HAVE  
VARIED QUITE A BIT IN MODEL GUIDANCE SO THERE IS LOW CONFIDENCE IN  
RAINFALL PLACEMENT AND AMOUNTS.  
 
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.  
 
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  
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page