504  
FXUS02 KWBC 190702  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
259 AM EDT TUE JUL 19 2022  
 
VALID 12Z FRI JUL 22 2022 - 12Z TUE JUL 26 2022  
 
...DANGEROUS HEAT TO PERSIST OVER THE CENTRAL U.S. THROUGH EARLY  
NEXT WEEK...  
   
..OVERVIEW
 
 
GUIDANCE SHOWS THE AXIS OF A STRONG UPPER RIDGE STRETCHING ACROSS  
MUCH OF THE SOUTH-CENTRAL U.S. DURING THE PERIOD, ALBEIT WITH SOME  
UNCERTAINTY OVER EXACTLY WHERE THE HIGHEST HEIGHTS WILL BE ON A  
DAY-TO-DAY BASIS. THIS RIDGE WILL KEEP HOT AND HUMID WEATHER OVER  
THE CENTRAL/SOUTHERN PLAINS FOR A MAJORITY OF THE PERIOD. SOME  
SOUTHERN LOCATIONS COULD SEE READINGS APPROACH OR BREAK DAILY  
RECORDS FOR HIGHS AND VERY WARM NIGHTTIME LOWS. WITH SOMEWHAT LESS  
EXTREME ANOMALIES, AREAS FROM THE TENNESSEE/OHIO VALLEYS THROUGH  
THE MID-ATLANTIC AND NEW ENGLAND WILL EXPERIENCE MULTIPLE HOT DAYS  
AS WELL. THE WEST SHOULD SEE MODERATE TEMPERATURES RELATIVE TO  
NORMAL LATE WEEK THROUGH THE WEEKEND WITH THE APPROACH/EJECTION OF  
EASTERN PACIFIC UPPER TROUGH ENERGY, FOLLOWED BY HIGHER READINGS  
OVER THE NORTHWEST EARLY NEXT WEEK. THE INITIAL PACIFIC ENERGY AND  
OTHER FEATURES ACROSS SOUTHERN CANADA AND THE NORTHERN TIER U.S.  
WILL FLOW AROUND THE RIDGE AND FEED INTO A BROAD NORTHEASTERN  
U.S./EASTERN CANADA MEAN TROUGH, SUPPORTING ONE OR MORE  
WAVES/FRONTAL SYSTEMS AND EPISODES OF SHOWERS AND THUNDERSTORMS  
FROM THE NORTHERN TIER INTO THE EAST. MONSOONAL MOISTURE OVER THE  
SOUTHWEST/SOUTHERN ROCKIES WILL PROMOTE DAILY CHANCES OF SHOWERS  
AND STORMS, SOME OF WHICH COULD LEAD TO FLASH FLOODING. THIS  
ACTIVITY MAY INCREASE IN COVERAGE AND INTENSITY DURING THE WEEKEND  
AND EARLY NEXT WEEK.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
MODELS AND ENSEMBLES CONTINUE TO AGREE WITH THE LARGE SCALE  
PATTERN OF SOUTH-CENTRAL U.S. RIDGING AND PROGRESSIVE FLOW ACROSS  
THE NORTHERN TIER U.S. AND SOUTHERN CANADA. HOWEVER THE GUIDANCE  
HAS BEEN VARIABLE FOR DETAILS WITHIN THE NORTHERN STREAM FLOW, THE  
DAY-TO-DAY SPECIFICS OF EXACTLY WHERE STRONGEST RIDGING WILL BE  
(AFFECTING SPECIFICS OF THE SOUTHWEST MONSOON), AND LATE PERIOD  
FLOW DETAILS OVER THE NORTHWEST.  
 
GUIDANCE STILL APPEARS TO BE TRYING TO CONVERGE UPON AN  
INTERMEDIATE SOLUTION FOR THE SHORTWAVE TRACKING OUT OF THE  
NORTHWEST AS OF FRIDAY. OTHERWISE CONFIDENCE REMAINS LOW FOR  
NEARBY SOUTHERN CANADA ENERGY, WITH DIFFERENCES LEADING TO  
INCONSISTENCY FOR FRONTAL/WAVE DETAILS BETWEEN THE NORTHERN PLAINS  
AND NORTHEASTERN U.S. MODELS/MEANS ARE STARTING TO SHOW A  
SHORTWAVE CROSSING THE GULF OF ALASKA AROUND FRIDAY-SATURDAY AND  
THEN PROGRESSING THROUGH WESTERN/CENTRAL CANADA. THIS FEATURE  
WOULD BRING ANOTHER FRONT INTO THE NORTHERN TIER EARLY NEXT WEEK.  
AN AVERAGE OF THE 12Z GFS/ECMWF/CMC AND 18Z GEFS/12Z ECMWF MEANS  
LOOKED GOOD FOR DEPICTING THIS EVOLUTION, WITH THE ECMWF/CMC  
RUNNING A LITTLE AHEAD OF THE OTHER SOLUTIONS. THE 18Z GFS SEEMED  
TOO AMPLIFIED WITH ITS UPPER TROUGH. NEW 00Z GFS/CMC RUNS APPEAR  
TO FIT WELL WITH THE PREFERENCE BY EARLY DAY 7 TUESDAY. MEANWHILE  
GUIDANCE INCREASINGLY DIVERGES FOR NORTHWEST U.S. FLOW BY LATE IN  
THE PERIOD, DEMONSTRATED BY THE NEW 00Z GFS BRINGING A COMPACT  
UPPER LOW INTO THE NORTHERN GREAT BASIN VERSUS LATEST ECMWF/CMC  
RUNS BUILDING A STRONGER RIDGE. AT THE VERY LEAST, EVEN THE GEFS  
MEAN IS NOT VERY SUPPORTIVE OF 00Z GFS SPECIFICS BY NEXT TUESDAY,  
WITH THE 18Z GFS RIDGE MORE REPRESENTATIVE. TELECONNECTIONS  
RELATIVE TO THE RIDGE THAT BUILDS OVER THE NORTHEASTERN PACIFIC  
KEEP THE DOOR OPEN FOR A LITTLE RESIDUAL TROUGHING OVER THE  
NORTHWEST WHILE MAJORITY CLUSTERING LEANS MORE TOWARD A RIDGE--BUT  
NOT AS STRONG AS THE 12Z ECMWF/CMC. THE 00Z CMC HAS TRENDED  
SOMEWHAT WEAKER WITH ITS WESTERN RIDGE.  
 
THE UPDATED FORECAST STARTED WITH A 12Z MODEL COMPOSITE EARLY IN  
THE PERIOD AND THEN TRANSITIONED TO 50-60 PERCENT TOTAL ENSEMBLE  
MEAN WEIGHT BY DAYS 6-7 MONDAY-TUESDAY. THIS APPROACH PROVIDED  
REASONABLE CONTINUITY FOR THE SHORTWAVE EJECTING FROM THE  
NORTHWEST EARLY IN THE PERIOD AND THEN INCREASINGLY ACCOUNTED FOR  
DETAIL UNCERTAINTIES WITHIN THE MORE AGREEABLE MEAN PATTERN  
MID-LATE PERIOD--LEANING SOMEWHAT MORE TO UPPER RIDGING OVER THE  
WEST BY NEXT TUESDAY AND REFLECTING THE PREFERRED AVERAGE FOR THE  
SYSTEM MOVING THROUGH WESTERN/CENTRAL CANADA.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
CONTINUE TO EXPECT MOST OF THE GREATEST TEMPERATURE ANOMALIES TO  
BE OVER AND NEAR THE CENTRAL PLAINS THROUGH THE PERIOD, WITH  
MULTIPLE DAYS OF HIGHS 10-15F ABOVE NORMAL. SOME OF THE HEAT MAY  
ALSO EXTEND INTO PARTS OF THE TENNESSEE VALLEY. BY SUNDAY-MONDAY A  
COLD FRONT MAY SUPPRESS THE HEAT OVER THE NORTH-CENTRAL PLAINS.  
TYPICALLY HOTTER SOUTHERN PLAINS LOCATIONS WILL SEE LESS EXTREME  
ANOMALIES BUT OVERALL THERE WILL BE A BROAD AREA WITH HIGHS  
REACHING OR EXCEEDING 100F FOR HIGHS, WHILE VERY WARM LOWS IN THE  
UPPER 70S TO LOW 80S WILL PROVIDE LITTLE NIGHTTIME RELIEF. THIS  
HEAT WAVE SHOULD BRING SCATTERED RECORDS, MOST LIKELY OVER THE  
SOUTHERN PLAINS TO LOWER/MID MISSISSIPPI VALLEY.  
 
OVER THE WEST, MONSOONAL MOISTURE AND ASSOCIATED DIURNALLY FAVORED  
SHOWERS/STORMS WITH LOCALLY HEAVY RAINFALL MAY KEEP PARTS OF THE  
FOUR CORNERS/GREAT BASIN REGION WITHIN A FEW DEGREES ON EITHER  
SIDE OF NORMAL DURING THROUGH THE PERIOD. THERE IS A GENERAL  
SIGNAL IN THE GUIDANCE THAT RAINFALL SHOULD INCREASE IN COVERAGE  
AND INTENSITY DURING THE WEEKEND AND EARLY NEXT WEEK BUT WITH  
CONSIDERABLE UNCERTAINTY OVER THE SPECIFICS. THE INITIAL SHORTWAVE  
EJECTING FROM THE NORTHWEST AND THEN LINGERING WEAK TROUGH ENERGY  
SHOULD KEEP THAT REGION NEAR OR A TAD BELOW NORMAL THROUGH THE  
WEEKEND. THE MAJORITY SCENARIO OF SOME DEGREE OF UPPER RIDGING  
BUILDING INTO THE NORTHWEST BY NEXT TUESDAY SHOULD LEAD TO A  
WARMING TREND, WITH SOME HIGHS POSSIBLY REACHING UP TO 10-15F  
ABOVE NORMAL.  
 
THE COMBINATION OF SHORTWAVES ALOFT AND SURFACE WAVES/FRONTS WILL  
LIKELY PRODUCE ONE OR MORE EPISODES OF SHOWERS AND STORMS FROM THE  
NORTHERN TIER STATES INTO THE EAST DURING THE PERIOD, WITH SOME  
HEAVY RAINFALL POSSIBLE. CURRENTLY THE BEST SIGNAL FOR ENHANCED  
RAINFALL EXTENDS FROM THE MIDWEST THROUGH THE LOWER GREAT LAKES  
INTO THE MID-ATLANTIC, BUT RECENT GUIDANCE INCONSISTENCY WITH  
IMPORTANT DETAILS AT THE SURFACE AND ALOFT TEMPER CONFIDENCE IN  
THE SPECIFICS FOR NOW. THE MID-ATLANTIC AND NORTHEAST WILL BE ON  
THE VERY WARM TO HOT SIDE FROM LATE WEEK THROUGH THE WEEKEND, WITH  
SOME LOCATIONS POSSIBLY SEEING MORE CONSECUTIVE DAYS OF PLUS 5-10F  
OR SO ANOMALIES FOR HIGHS THAN PREVIOUSLY EXPERIENCED SO FAR THIS  
SUMMER. TEMPERATURES SHOULD TREND CLOSER TO NORMAL FROM NORTH TO  
SOUTH BY EARLY NEXT WEEK AS A COUPLE FRONTS ARRIVE. PERSISTENT  
MOISTURE WILL ALLOW FOR MULTIPLE EPISODES OF SHOWERS/THUNDERSTORMS  
OVER THE SOUTHEAST/FLORIDA AND CENTRAL GULF COAST REGION. BEST  
ORGANIZATION MAY BE LATE THIS WEEK. HIGHS SHOULD STAY NEAR NORMAL  
OVER THE SOUTHEAST.  
 
RAUSCH/KEBEDE  
 
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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