296  
FXUS02 KWBC 260647  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
246 AM EDT FRI AUG 26 2022  
 
VALID 12Z MON AUG 29 2022 - 12Z FRI SEP 02 2022  
   
..OVERVIEW
 
 
ACROSS THE CONUS DURING THE PERIOD, THE MEAN FLOW IS EXPECTED TO  
TRANSITION FROM NEARLY ZONAL/FLAT FLOW TO A MORE AMPLIFIED PATTERN  
FEATURING TROUGHING OVER THE EASTERN PACIFIC AND EASTERN U.S. WITH  
A RIDGE EXTENDING THROUGH MUCH OF THE WESTERN U.S. THOUGH BY THE  
END OF NEXT WEEK, THERE ARE SIGNALS THAT TROUGHING MAY PUSH  
ONSHORE THE PACIFIC NORTHWEST. THE PRIMARY SYNOPTIC FORCING FOR  
RAINFALL WILL BE ALONG A PROGRESSIVE COLD FRONT THROUGH THE  
CENTRAL TO EASTERN U.S. NEXT WEEK AND THE GREATEST TEMPERATURE  
ANOMALIES WILL BE FOUND ACROSS THE INTERIOR WEST UNDERNEATH THE  
AMPLIFYING UPPER RIDGE.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
SHORTWAVE ENERGY MOVING ACROSS THE NORTHWEST THIS WEEKEND IS  
EXPECTED TO REACH THE NORTHERN PLAINS BY THE START OF THE MEDIUM  
RANGE PERIOD AND OVERALL, THE MOST RECENT DETERMINISTIC GUIDANCE  
HAS COME INTO BETTER AGREEMENT WITH ITS PROGRESSION AND AMPLITUDE.  
THE 18Z/12Z GFS SHOWED SOME DIFFERENCES IN THE SPEED AND  
MAGNITUDE, WITH THE 12Z GFS BEING SOMEWHAT AN OUTLIER COMPARED TO  
THE ECMWF AND UKMET, HAVING A SLOWER PROGRESSION AND EVENTUALLY  
CLOSING OFF A LOW THAT DRIFTS SOUTHWARD INTO THE PLAINS. THE 18Z  
(AND NEW 00Z) GFS RUNS ARE MORE IN LINE WITH THE ECMWF, BEING  
PROGRESSIVE ACROSS THE NORTHERN TIER. THAT ENERGY IS EXPECTED TO  
DEEPEN A TROUGH OVER THE GREAT LAKES AND PUSH A COLD FRONT THROUGH  
MUCH OF THE CENTRAL TO EASTERN U.S., REACHING THE SOUTHEAST AND  
GULF COAST LATER IN THE PERIOD. SPRAWLING CANADIAN HIGH PRESSURE  
IN ITS WAKE WILL BRING DRIER AND SEASONABLE TEMPERATURES TO  
PORTIONS OF THE CENTRAL/EASTERN CONUS. A WEAKNESS IN THE RIDGE  
OVER THE SOUTHERN PLAINS MAY LEAD TO A PERIOD OF UNSETTLED WEATHER  
WITH A WEAK SURFACE BOUNDARY IN PLACE INTERACTING WITH GULF  
MOISTURE AND THE AFOREMENTIONED FRONTAL BOUNDARY. THE GFS IS MORE  
BULLISH SHOWING THIS POTENTIAL FOR MORE WIDESPREAD PRECIPITATION  
COMPARED TO THE ECMWF WHICH SHUNTS ALL THE DEEPER MOISTURE WELL TO  
THE COAST. TOWARD THE END OF THE PERIOD, MODEL GUIDANCE IS SHOWING  
POTENTIAL FOR ANOTHER SHORTWAVE TROUGH TO APPROACH THE PACIFIC  
NORTHWEST, WITH THE TYPICAL TIMING BIASES SHOWING UP. AHEAD OF  
THAT FEATURE, THE UPPER RIDGE OVER THE SOUTHWEST IS FORECAST TO  
BUILD NORTHWARD AND STRENGTHEN.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
DEEPER MOISTURE POOLING ALONG AND AHEAD OF AN ADVANCING COLD FRONT  
ACROSS PORTIONS OF THE CENTRAL/EASTERN U.S. MAY LEAD TO POCKETS OF  
MODERATE TO LOCALLY HEAVY RAINFALL AT TIMES NEXT WEEK. ONE AREA OF  
FOCUS FOR HIGHER RAINFALL POTENTIAL IS ACROSS THE SOUTHERN/CENTRAL  
PLAINS WHERE INTERACTION WITH GULF MOISTURE MAY BOOST RAINFALL  
INTENSITY AND AMOUNTS. SHOWERS AND THUNDERSTORMS ARE ALSO LIKELY  
TO CONTINUE ACROSS PORTIONS OF THE SOUTH, INCLUDING THE GULF COAST  
AND FLORIDA PENINSULA WHERE LOCALLY HEAVY RAINFALL IS POSSIBLE,  
BUT LIKELY TO BE LOCALIZED/ISOLATED. ELSEWHERE, THE SOUTHWEST  
MONSOON ACTIVITY SHOULD SEE A REPRIEVE DURING THE PERIOD WITH THE  
BETTER MOISTURE SHUNTED OVER TO THE EAST. WITH UPPER RIDGING  
BUILDING OVER THE WEST, THE GREATEST TEMPERATURE ANOMALIES ARE  
EXPECTED OVER THE PACIFIC NORTHWEST INTO THE NORTHERN ROCKIES WITH  
DAYTIME HIGHS NEXT WEEK 10-15 DEGREES ABOVE NORMAL. A FEW PLACES  
COULD CHALLENGE DAILY RECORDS FOR HIGHS/WARM LOWS. ELSEWHERE,  
SLIGHTLY ABOVE NORMAL TEMPERATURES ARE FORECAST FOR THE  
MID-ATLANTIC AND NORTHEAST EARLY TO MID WEEK AHEAD OF THE  
APPROACHING COLD FRONT WHILE THE CENTRAL U.S. IS EXPECTED TO HAVE  
NEAR NORMAL READINGS FOR LATE AUGUST.  
 
TAYLOR/PUTNAM  
 
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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