899  
FXUS02 KWBC 201850  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
249 PM EDT WED JUL 20 2022  
 
VALID 12Z SAT JUL 23 2022 - 12Z WED JUL 27 2022  
 
...DANGEROUS HEAT OVER THE CENTRAL U.S. TO PERSIST OVER SOME AREAS  
WHILE BECOMING SLIGHTLY LESS PRONOUNCED NEXT WEEK...  
 
...HEAT WAVE OVER THE MID-ATLANTIC AND PARTS OF THE NORTHEAST  
LIKELY TO PEAK THIS WEEKEND...  
   
..HEAT EXPECTED TO BUILD OVER THE NORTHWEST NEXT WEEK
 
 
   
..OVERVIEW
 
 
MOST OF THE PERIOD WILL FEATURE STRONG UPPER RIDGING THAT EXTENDS  
ACROSS MOST OF THE SOUTH-CENTRAL U.S., WITH SOME DAY-TO-DAY  
VARIATION IN WHERE INDIVIDUAL HIGH CENTERS MAY BE. HEAT ASSOCIATED  
WITH THIS RIDGE WILL BE MOST EXPANSIVE AND ANOMALOUS DURING THE  
WEEKEND WHEN LOCATIONS FROM THE CENTRAL PLAINS THROUGH THE  
NORTHERN HALF OR TWO-THIRDS OF THE EAST SHOULD SEE HIGHS 10-15F  
ABOVE NORMAL. FLAT TO BROADLY CYCLONIC FLOW ACROSS THE NORTHERN  
TIER SHOULD SUPPORT AT LEAST A COUPLE FRONTAL SYSTEMS THAT SHOULD  
ERODE SOME OF THIS HEAT FROM THE NORTH OVER THE COURSE OF THE  
PERIOD, WHILE ALSO PRODUCING LOCALLY HEAVY SHOWERS AND  
THUNDERSTORMS, WHICH ARE MOST LIKELY FROM THE MIDWEST INTO THE  
EAST. MEANWHILE THE NORTHWEST WILL SEE WEAK UPPER TROUGHING GIVE  
WAY TO A STRENGTHENING RIDGE, BEGINNING A STRETCH OF HEAT THAT  
SHOULD EXTEND BEYOND THE MEDIUM RANGE PERIOD PER THE CLIMATE  
PREDICTION CENTER WEEK 2 FORECAST. MONSOONAL MOISTURE IS LIKELY TO  
INCREASE EARLY NEXT WEEK OVER THE SOUTHWEST/SOUTHERN ROCKIES AND  
PROMOTE DAILY CHANCES OF SHOWERS AND STORMS THAT MAY PRODUCE SOME  
INSTANCES OF FLASH FLOODING. THERE IS A CONTINUED SIGNAL THAT THE  
PATTERN EVOLUTION WILL SUPPORT GREATER COVERAGE AND INTENSITY OF  
RAINFALL FROM THE WEEKEND INTO NEXT WEEK RELATIVE TO THE SHORT  
RANGE TIME FRAME.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
MODEL GUIDANCE IS QUITE AGREEABLE WITH THE OVERALL PATTERN OF THE  
SOUTHERN TIER BEING DOMINATED BY UPPER RIDGING AND KEEPING THE  
STORM TRACK OVER THE NORTHERN TIER. INDIVIDUAL UPPER HIGHS  
EMBEDDED WITHIN THE RIDGE THAT VARY SLIGHTLY BETWEEN MODELS IN  
TERMS OF POSITION AND STRENGTH SHOULD NOT HAVE PARTICULAR SENSIBLE  
WEATHER DIFFERENCES. SOME SPREAD REMAINS WITH THE MORE ACTIVE  
NORTHERN TIER FLOW, HOWEVER, PARTICULARLY WITH THE SMALLER SCALE  
SHORTWAVES AND THE ASSOCIATED SURFACE WAVE/FRONTAL DETAILS. THE  
00Z UKMET BECOMES A FAST OUTLIER WITH A SHORTWAVE OVER  
SOUTH-CENTRAL CANADA COMING IN BEHIND A JAMES BAY UPPER LOW ON  
MONDAY, AND IS SLIGHTLY DEEPER WITH TROUGHING INTO THE GREAT LAKES  
AS WELL. MOST OTHER GUIDANCE LOOKS WITHIN REASON THROUGH EARLY-MID  
NEXT WEEK WITH THE NORTHERN TIER FLOW PATTERN, THOUGH NOTED THAT  
THE 06Z GFS APPEARED BETTER CLUSTERED WITH CONSENSUS AND THE  
ENSEMBLE MEANS COMPARED TO THE 00Z GFS. GUIDANCE HAS ALSO  
CONVERGED REASONABLY WELL ON A SOLUTION FOR RIDGING ACROSS THE  
NORTHWEST BY MIDWEEK NEXT WEEK, THOUGH OCCASIONAL GFS RUNS HAVE  
BEEN SOMEWHAT MORE EAGER TO EXTEND WESTERN CANADA TROUGHING THERE.  
THE WPC FORECAST BLEND WAS BASED ON MAINLY THE 00Z ECMWF, 06Z GFS,  
AND 00Z CMC EARLY, AND THEN INTRODUCING AND INCREASING THE  
PROPORTION OF THE GEFS AND EC ENSEMBLE MEANS TO AROUND 30 PERCENT  
BY THE END OF THE PERIOD AMID INCREASING BUT STILL SOMEWHAT MINOR  
MODEL SPREAD. THIS APPROACH LED TO GENERALLY GOOD CONTINUITY FROM  
THE PREVIOUS FORECAST.  
   
..WEATHER/HAZARDS HIGHLIGHTS
 
 
THIS WEEKEND WILL SEE THE BROADEST COVERAGE OF HOT TEMPERATURES TO  
THE EAST OF THE ROCKIES, WITH MANY AREAS FROM THE CENTRAL PLAINS  
THROUGH THE MID-ATLANTIC/NEW ENGLAND SEEING HIGHS 10-15F ABOVE  
NORMAL ON ONE OR BOTH DAYS. THE PLAINS FORECAST HAS BEEN  
CONSISTENT WHILE GUIDANCE FOR THE MID-ATLANTIC/NEW ENGLAND HAS  
BEEN TRENDING INCREMENTALLY HIGHER LATELY. FORECASTS SHOW A FAIRLY  
BROAD AREA OF 100+F HIGHS OVER THE CENTRAL/SOUTHERN PLAINS AND  
POSSIBLY EXTENDING INTO PARTS OF THE MISSISSIPPI VALLEY, AND AREAS  
ALONG THE EAST COAST COULD REACH THE MID 90S TO AROUND 100. HEAT  
INDICES COULD BE 105-110F IN MANY AREAS, AND VERY WARM LOWS WILL  
PROVIDE LITTLE NIGHTTIME RELIEF. THIS HEAT WAVE SHOULD BRING  
SCATTERED DAILY RECORDS FOR HIGHS AND WARM LOWS AS WELL. A COLD  
FRONT MOVING INTO THE CENTRAL/EASTERN U.S. SHOULD BEGIN TO ERODE  
THE NORTHERN PERIPHERY OF THE HEAT LATER IN THE WEEKEND AND  
CONTINUING SOUTHWARD NEXT WEEK, LIKELY LEADING TO HIGHS MODERATING  
TO 5-10F ABOVE NORMAL OVER THE SOUTH-CENTRAL PLAINS/TENNESSEE  
VALLEY BY MIDWEEK AND NEAR NORMAL FARTHER NORTHWARD. ADDITIONALLY,  
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  
SEVERE WEATHER AND HEAVY RAINFALL POSSIBLE. EVEN WITH  
DIFFERENCES/CONTINUITY CHANGES FOR SOME DETAILS AT THE SURFACE AND  
ALOFT, THE GENERAL GUIDANCE SIGNALS FOR HIGHEST RAINFALL TOTALS  
HAVE BEEN FAIRLY CONSISTENT FOR THE PAST FEW MODEL CYCLES, SHOWING  
ENHANCED RAINFALL ACROSS THE MIDWEST AND GREAT LAKES AND  
EAST/SOUTHEAST TOWARD THE EAST COAST. SOME ADJUSTMENTS ARE STILL  
POSSIBLE AS IMPORTANT SMALLER SCALE FEATURES GET BETTER RESOLVED.  
 
OVER THE WEST, EXPECT PERSISTENT MONSOONAL MOISTURE AND VARIOUS  
SHORTWAVE IMPULSES TO SUPPORT DIURNALLY FAVORED SHOWERS/STORMS  
WITH SOME LOCALLY HEAVY RAINFALL OVER THE FOUR CORNERS/GREAT BASIN  
REGION THROUGH THE PERIOD. GUIDANCE CONTINUES TO SUGGEST THAT THE  
PATTERN EVOLUTION WILL LEAD TO GREATER COVERAGE AND INTENSITY OF  
RAINFALL DURING THE WEEKEND AND NEXT WEEK RELATIVE TO THE SHORT  
RANGE PERIOD. POTENTIAL EXISTS FOR SOME OF THIS MOISTURE TO  
INTERACT WITH THE FRONTS THAT REACH THE CENTRAL PLAINS (ONE DURING  
SUNDAY-MONDAY AND ANOTHER AROUND WEDNESDAY). MEANWHILE THERE IS  
BETTER AGREEMENT TODAY THAT UPPER RIDGING SHOULD BUILD INTO THE  
NORTHWEST DURING THE EARLY-MIDDLE PART OF NEXT WEEK, ALBEIT STILL  
WITH A LITTLE TIMING UNCERTAINTY. SOME LOCATIONS IN THE REGION  
SHOULD SEE HIGHS REACH UP TO 10-15F OR SO ABOVE NORMAL AND A FEW  
DAILY RECORDS FOR HIGHS/WARM LOWS COULD BE POSSIBLE.  
 
TATE/RAUSCH  
 
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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