582  
FXUS02 KWBC 200700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM 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 NEW ENGLAND 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 WILL SUPPORT AT LEAST A COUPLE FRONTAL SYSTEMS THAT SHOULD  
ERODE SOME OF THIS HEAT FROM THE NORTH OVER THE COURSE OF THE  
PERIOD. EXPECT THESE FRONTS AND EMBEDDED WAVES TO PRODUCE EPISODES  
OF 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 MAY EXTEND BEYOND THE MEDIUM RANGE PERIOD  
PER THE CLIMATE PREDICTION CENTER WEEK 2 FORECAST. MONSOONAL  
MOISTURE OVER THE SOUTHWEST/SOUTHERN ROCKIES WILL 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
 
 
COMPARED TO 24 HOURS AGO, THE GUIDANCE APPEARS TO BE MAKING SOME  
PROGRESS IN RESOLVING DETAILS WITHIN WHAT HAS GENERALLY BEEN A  
MORE AGREEABLE AND CONSISTENT LARGE SCALE EVOLUTION, BUT WITH SOME  
SPREAD PERSISTING. THERE ARE STILL ISSUES WITH SPECIFICS OF  
NORTHERN TIER FLOW FROM THE START OF THE PERIOD, AFFECTING  
WAVE/FRONTAL DETAILS. AMONG 12Z/18Z SOLUTIONS THE 18Z GFS SEEMED  
LESS APPEALING THAN MOST DUE TO ITS SHORTWAVE AMPLITUDE AROUND  
SATURDAY-EARLY SUNDAY (FAVORABLY CORRECTED IN THE NEW 00Z RUN),  
WHILE 12Z UKMET SPECIFICS BECAME MORE QUESTIONABLE TOWARD THE END  
OF ITS RUN LATE WEEKEND/EARLY MONDAY (STILL QUESTIONABLY SHARP  
WITH ITS GREAT LAKES SHORTWAVE BY MONDAY IN THE NEW 00Z RUN).  
UPSTREAM THERE IS STILL A MODERATE AMOUNT OF SPREAD FOR ENERGY  
LIKELY TO AMPLIFY OVER CENTRAL CANADA INTO THE NORTHERN TIER U.S.  
AS UPPER RIDGING BUILDS INTO THE NORTHEASTERN PACIFIC AND WESTERN  
CANADA. THE NEW 00Z UKMET BECOMES A FAST EXTREME WITH ITS SYSTEM  
BY LATE MONDAY. AN AVERAGE AMONG LATEST MODELS AND ENSEMBLE MEANS  
CONTINUES TO PROVIDE THE MOST STEADY SOLUTION FOR THE UPPER TROUGH  
AND ASSOCIATED SURFACE SYSTEM/FRONT. SOME GFS RUNS HAVE BEEN  
SOMEWHAT MORE EAGER TO EXTEND WESTERN CANADA TROUGHING INTO THE  
NORTHWEST U.S. BUT DO EVENTUALLY BUILD A DECENT AMOUNT OF RIDGING  
INTO THE NORTHWEST AS REFLECTED BY RECENT CONSENSUS.  
 
THE LATEST FORECAST STARTED WITH A 12Z/18Z MODEL BLEND FOR THE  
FIRST PART OF THE PERIOD TO REFLECT THE MOST COMMON ELEMENTS OF  
GUIDANCE WHILE DOWNPLAYING THE LESS CONFIDENT DETAILS FROM  
INDIVIDUAL SOLUTIONS. THE BLEND TRANSITIONED TO ABOUT HALF  
MODELS/HALF ENSEMBLE MEANS BY DAYS 6-7 TUESDAY-WEDNESDAY TO YIELD  
THE DESIRED COMPROMISE FOR THE CENTRAL CANADA INTO NORTHERN U.S.  
SYSTEM AT THAT TIME AND OTHERWISE ACCOUNT FOR INCREASING DETAIL  
UNCERTAINTY.  
   
..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. THERE WILL BE 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. VERY  
WARM LOWS WILL PROVIDE LITTLE NIGHTTIME RELIEF. THIS HEAT WAVE  
SHOULD BRING SCATTERED RECORDS FOR HIGHS AND WARM LOWS. A COLD  
FRONT MOVING INTO THE CENTRAL/EASTERN U.S. WILL 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. 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. 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 OVER THE PAST  
DAY, FROM THE MIDWEST AND LOWER GREAT LAKES 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.  
 
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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