621  
FXUS02 KWBC 040656  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
256 AM EDT MON JUL 04 2022  
 
VALID 12Z THU JUL 07 2022 - 12Z MON JUL 11 2022  
   
..OVERVIEW
 
 
A STRONG UPPER LEVEL HIGH OVER THE SOUTHERN TIER OF THE CONTIGUOUS  
U.S. WILL EXTEND RIDGING FARTHER NORTH INTO THE ROCKIES/HIGH  
PLAINS AND LEAD TO HOT TEMPERATURES ACROSS MUCH OF THE CENTRAL  
CONUS. SURROUNDING THIS MEAN RIDGE, A RELOADING UPPER LOW/TROUGH  
JUST OFF THE WEST COAST SHOULD PERSIST UNTIL EJECTING  
NORTHEASTWARD THIS WEEKEND ALONG THE U.S./CANADA BORDER, AND A  
MEAN TROUGH COVERING EASTERN CANADA AND THE NORTHEASTERN U.S. IS  
EXPECTED TO DEEPEN GRADUALLY OVER THE WEEKEND. A MEAN SURFACE  
FRONTAL BOUNDARY (POSSIBLY REINFORCED BY ONE OR MORE CANADIAN  
FRONTS) DRAPED FROM THE NORTH-CENTRAL PLAINS TO THE MID-ATLANTIC,  
COMBINED WITH SHORTWAVES EMBEDDED IN THE FLOW ALOFT, WILL LIKELY  
PRODUCE MULTIPLE EPISODES OF CONVECTION WITH LOCALLY HEAVY  
RAINFALL.  
 
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
MODEL AND ENSEMBLE GUIDANCE REMAINS IN GOOD AGREEMENT FOR THE  
LARGE SCALE EVOLUTION OF THE STRENGTHENING RIDGE IN BETWEEN THE  
TROUGHING FEATURES THAT SHOW LESS CERTAINTY WITH THE DETAILS.  
MODEL DIFFERENCES EARLY IN THE PERIOD AROUND THURSDAY-FRIDAY ARE  
MAINLY LIMITED TO MESOSCALE FEATURES, INCLUDING ENERGY IN THE  
CENTRAL U.S. THAT HAS SOME DIFFERENCES IN STRENGTH AND PLACEMENT  
AS IT ROUNDS THE UPPER HIGH. GFS RUNS HAVE BEEN AMONG THE  
STRONGEST BUT THE 18Z AND 00Z RUNS HAVE WEAKENED THE FEATURES  
SOMEWHAT AND APPEAR MORE CONSISTENT WITH OTHER GUIDANCE.  
UNFORTUNATELY IN THIS TYPE OF PATTERN, EVEN THE SMALLER SCALE  
FEATURES WILL HAVE CONSIDERABLE IMPLICATIONS FOR SENSIBLE WEATHER,  
INCLUDING FRONTAL POSITIONS AND RAINFALL AMOUNTS AND PLACEMENT, IN  
THIS CASE ACROSS THE ROCKIES INTO THE CENTRAL PLAINS/MISSISSIPPI  
VALLEY, WHILE OTHER VARIOUS SHORTWAVES EMBEDDED WITHIN THE EASTERN  
TROUGH ALSO PRESENT CHALLENGES FOR THE EAST. NEVERTHELESS A BLEND  
OF THE 12/18Z DETERMINISTIC GUIDANCE WORKED WELL FOR THE EARLY  
PART OF THE MEDIUM RANGE PERIOD GIVEN NO NOTABLE OUTLIERS AND  
LARGER SCALE AGREEMENT.  
 
BY THE WEEKEND INTO MONDAY, SOME SYNOPTIC SCALE DIFFERENCES BEGIN  
TO ARISE ESPECIALLY WITH THE WESTERN TROUGH, AS MULTIPLE IMPULSES  
EMBEDDED WITHIN THE TROUGH DIVERGE AND THE DIFFERENCES AMPLIFY  
DOWNSTREAM. MORE SPECIFICALLY, THE ENERGY DISTRIBUTION WITHIN THE  
TROUGH SHOWS MORE DIVISION 12Z SATURDAY IN THE 12Z ECMWF/UKMET  
COMPARED TO THE GFS AND CMC. THE 12Z ECMWF THUS ENDED UP CLOSING  
OFF AN UPPER LOW JUST OFFSHORE CALIFORNIA WHILE WEAKER ENERGY  
RACES EAST ACROSS SOUTHERN CANADA. MEANWHILE THE GFS RUNS SHOWED  
MORE POTENT ENERGY FORMING A COMPACT CLOSED LOW AS IT SHIFTS INTO  
SOUTH-CENTRAL CANADA, AND THE NEW 00Z CMC IS SIMILAR. THE NEWER  
00Z ECMWF DOES NOT CLOSE OFF A LOW LIKE THE 12Z RUN DID, ADDING  
EVIDENCE THAT THE 12Z EC MAY HAVE BEEN TOO AGGRESSIVE WITH ENERGY  
LEFT BEHIND IN THE PACIFIC. BUT INDIVIDUAL ENSEMBLE MEMBERS SHOW  
CONSIDERABLE DIFFERENCES WITH THE DEPTH AND TRACK OF THE TROUGH,  
SO AMPLE UNCERTAINTY REMAINS. THE WPC APPROACH DID NOT FAVOR THE  
12Z DETERMINISTIC EC BUT DID PREFER THE EC ENSEMBLE MEAN TO  
PROVIDE SOME HINT TOWARD A MORE AMPLIFIED TROUGH REMAINING  
OFFSHORE COMPARED TO THE GFS SUITE. THUS FOR THE LATTER PART OF  
THE MEDIUM RANGE PERIOD, TRANSITIONED PRETTY QUICKLY TO A BLEND  
FAVORING THE GEFS AND ESPECIALLY THE EC MEANS AS A COMPROMISE  
SOLUTION GIVEN THE SPREAD IN THE DETERMINISTIC MODELS.  
 
   
..SENSIBLE WEATHER AND HAZARDS
 
 
SCATTERED SHOWERS AND STORMS ARE LIKELY ACROSS MUCH OF THE U.S.  
FROM THE ROCKIES EASTWARD AT TIMES THIS WEEK INTO EARLY NEXT WEEK,  
WITH ENHANCED TOTALS IN THE VICINITY OF A COUPLE OF FRONTAL  
BOUNDARIES STRETCHING GENERALLY WEST TO EAST ACROSS THE NORTHERN  
HALF OF THE COUNTRY. NORTHWESTERLY FLOW ALOFT AND ABUNDANT  
MOISTURE AND INSTABILITY WILL CREATE A FAVORABLE PATTERN FOR  
MESOSCALE CONVECTIVE SYSTEMS AND HIGH RAINFALL RATES WITHIN A  
BROAD AREA FROM THE NORTHERN PLAINS/MIDWEST/UPPER GREAT LAKES INTO  
THE OHIO VALLEY AND APPALACHIANS TO THE EAST COAST. AREAS OF  
EXCESSIVE RAINFALL/FLASH FLOODING ARE CERTAINLY POSSIBLE THROUGH  
THE WEEKEND, BUT CONSIDERABLE UNCERTAINTY WITH THE PLACEMENT OF  
HEAVY RAIN AMOUNTS PRECLUDES DELINEATING SLIGHT RISK AREAS IN THE  
EXPERIMENTAL DAY 4-5 EXCESSIVE RAINFALL OUTLOOK AT THIS POINT.  
SCATTERED THUNDERSTORMS ARE ALSO LIKELY IN THE SOUTHEAST THROUGH  
THE WEEK, AND THE CURRENT FORECAST SHOWS THE EASTERN PART OF THE  
MAIN FRONT SINKING SOUTHWARD FROM MEANDERING OVER THE MID-ATLANTIC  
INTO THE CAROLINAS AND EVENTUALLY THE GULF COAST BY NEXT WEEKEND,  
LEADING TO MORE FOCUSED RAINFALL IN THE SOUTHEAST AND CLEARING FOR  
THE NORTHEAST BEHIND THE FRONT. AT THE SAME TIME A FRONTAL SYSTEM  
EMERGING INTO THE NORTHERN PLAINS NEXT WEEKEND MAY PROVIDE ADDED  
CONVECTIVE FOCUS OVER THAT REGION ONCE AGAIN. MEANWHILE MONSOONAL  
MOISTURE COULD PERSIST THROUGH MUCH OF THE WEEK WITH MOIST  
SOUTHWESTERLY FLOW/EMBEDDED SHORTWAVES LEADING TO MAINLY DIURNALLY  
DRIVEN SHOWERS AND STORMS OVER THE FOUR CORNERS STATES. THE  
SOUTHERN PLAINS AND CALIFORNIA INTO THE GREAT BASIN SHOULD BE THE  
MOST CONSISTENTLY DRY AREAS DURING THE PERIOD.  
 
HOT WEATHER IS EXPECTED TO CONTINUE ACROSS THE SOUTHERN HALF OF  
THE PLAINS/MISSISSIPPI VALLEY UNDERNEATH THE UPPER RIDGE/HIGH,  
WITH HIGH TEMPERATURES APPROACHING OR EXCEEDING 100F (ABOUT 5-15F  
ABOVE AVERAGE). THE HIGHEST HEAT INDEX VALUES COULD STRETCH  
TOWARDS THE MIDDLE MISSISSIPPI AND OHIO VALLEYS WHERE HIGH  
HUMIDITY WILL CONTRIBUTE. THERE COULD BE SOME DAILY RECORDS SET  
ESPECIALLY FOR WARM LOWS ACROSS THE SOUTH-CENTRAL TO SOUTHEASTERN  
U.S. THROUGH EARLY NEXT WEEK. ABOVE NORMAL TEMPERATURES ARE ALSO  
FORECAST TO SPREAD ACROSS THE NORTHERN ROCKIES TO NORTHERN PLAINS  
LATE WEEK AND INCREASE OVER THE WEEKEND, BEFORE POSSIBLY  
MODERATING BY MONDAY DEPENDING ON THE SPECIFICS OF A FRONT.  
MEANWHILE, THE WEST COAST COULD SEE COOLER THAN NORMAL CONDITIONS  
LATE WEEK BEFORE MODERATING CLOSER TO AVERAGE, WHILE THE DESERT  
SOUTHWEST SHOULD SEE NEAR NORMAL TEMPERATURES BECOMING A FEW  
DEGREES ABOVE AVERAGE. PARTS OF THE EAST MAY SEE SLIGHTLY BELOW  
NORMAL TEMPERATURES SPREADING SOUTH THIS WEEKEND INTO MONDAY  
BEHIND A COLD FRONT.  
 
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  
 

 
 

 
 
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