364  
FXUS02 KWBC 030701  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT SUN JUL 03 2022  
 
VALID 12Z WED JUL 06 2022 - 12Z SUN JUL 10 2022  
   
..OVERVIEW
 
 
EXPECT THE CENTER OF A STRONG UPPER LEVEL RIDGE/HIGH TO DRIFT  
SLOWLY WESTWARD ACROSS THE SOUTHERN TIER OF THE CONTIGUOUS U.S.  
FOR THE LATTER PART OF THIS WEEK INTO THE WEEKEND, WHILE PRODUCING  
RIDGING FARTHER NORTH INTO THE ROCKIES/HIGH PLAINS AND LEADING TO  
HOT TEMPERATURES ACROSS MUCH OF THE CENTRAL CONUS. SURROUNDING THE  
MEAN RIDGE, A RELOADING UPPER LOW/TROUGH JUST OFF THE WEST COAST  
WILL PERSIST UNTIL EJECTING NORTHEASTWARD BY THE WEEKEND WHILE  
LEADING ENERGY SHOULD FLOW ACROSS THE NORTHERN TIER AND FEED INTO  
A BROAD MEAN TROUGH COVERING EASTERN CANADA AND THE NORTHEASTERN  
U.S. THIS FLOW PATTERN IS FAIRLY TYPICAL FOR SUMMER, WITH THE  
LARGE SCALE FEATURES JUST A LITTLE STRONGER THAN THE  
CLIMATOLOGICAL AVERAGE. 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 GUIDANCE REMAINS IN GOOD AGREEMENT FOR THE LARGE SCALE  
PATTERN OF AN EAST PACIFIC LOW TRACKING INTO THE NORTHWEST LATE IN  
THE WEEK, RELOADING TROUGHING OVER THE NORTHEAST, AND  
STRENGTHENING RIDGING IN BETWEEN. SIGNIFICANT DIFFERENCES ON THE  
LARGE SCALE DO NOT REALLY ARISE UNTIL NEXT WEEKEND; WHILE GUIDANCE  
IS MORE AGREEABLE IN RECENT CYCLES FOR AT LEAST SOME ENERGY AND  
TROUGHING TO COME ONSHORE INTO THE NORTHWEST FROM THE EASTERN  
PACIFIC AROUND SATURDAY, MODELS DIFFER REGARDING ITS EVOLUTION AS  
IT TRACKS EASTWARD OVER THE WEEKEND, HOW MUCH ENERGY/TROUGHING IS  
LEFT BEHIND IN THE PACIFIC, AS WELL AS THE FLOW UPSTREAM. THE MAIN  
OUTLIER WITH AT LEAST THE LATTER APPEARED TO BE THE 12Z GFS THAT  
SHOWED AN UPPER LOW FARTHER SOUTH IN THE PACIFIC COMPARED TO OTHER  
GUIDANCE INDICATING THE LOW WOULD BE NEAR THE GULF OF ALASKA.  
 
HOWEVER, SMALLER SCALE FEATURES REMAIN CONSIDERABLY UNCERTAIN  
THROUGH THE PERIOD. ONE SUCH MESOSCALE FEATURE IS SHORTWAVE ENERGY  
THAT LOOKS TO BE SOMEWHERE NEAR BAJA CALIFORNIA/NORTHERN  
MEXICO/SOUTHERN ARIZONA AS THE PERIOD BEGINS WEDNESDAY MORNING AND  
TRACKS NORTH-NORTHEAST THURSDAY-FRIDAY, POSSIBLY SLIGHTLY  
DISRUPTING THE BROAD UPPER HIGH AT TIMES. UNFORTUNATELY THE  
FEATURE IS SMALL ENOUGH TO HAVE FAIRLY LOW PREDICTABILITY. GFS  
RUNS HAVE TYPICALLY BEEN STRONGER WITH THIS FEATURE WITH THE ECMWF  
AMONG THE WEAKEST, WHILE THE 12Z CMC WAS STRONGER THAN THE NEWER  
00Z CMC, AND THE UKMET WAS ON THE STRONGER SIDE BUT THE FARTHEST  
WEST IN TRACK WEST OF THE RIDGE. THE FEATURE WILL BE VERY  
IMPORTANT WITH RESPECT TO THE RAINFALL FORECAST OVER THE  
SOUTHWEST/ROCKIES AND THEN THE CONVECTIVE FORECAST AS THIS ENERGY  
BECOMES EMBEDDED IN THE SOUTHERN FRINGE OF THE WESTERLIES AND  
INTERACTS WITH THE SURFACE FRONT TO THE EAST OF THE ROCKIES, SO  
THIS IS ONE ASPECT OF THE FORECAST THAT LEADS TO UNCERTAINTY IN  
THE DETAILS OF SENSIBLE WEATHER. ADDITIONALLY, SHORTWAVE SPECIFICS  
AROUND THE NORTHERN PERIPHERY OF THE CONUS RIDGE AND INTO THE  
EASTERN CANADA/NORTHEAST U.S. MEAN TROUGH VARY CONSIDERABLY  
BETWEEN MODELS AND THUS CONFIDENCE IS LOW FOR THESE FEATURES AND  
FOR SURFACE FRONT/WAVE DETAILS. IT WILL LIKELY TAKE UNTIL THE  
SHORT RANGE PERIOD TO RESOLVE THESE DETAILS, AND EVEN THEN SOME  
ASPECTS OF THE FORECAST MAY HAVE VERY SHORT LEAD TIME GIVEN HOW  
CHALLENGING IT CAN BE FOR MODELS TO LATCH ONTO MESOSCALE FEATURES  
THAT WILL MATTER GREATLY FOR QPF PLACEMENT AND AMOUNTS. CONTINUE  
TO MONITOR THE FORECAST FOR UPDATES GOING FORWARD. OVERALL, THE  
WPC FORECAST UTILIZED A BLEND OF THE 12Z/18Z DETERMINISTIC MODELS  
FOR THE EARLY PART OF THE PERIOD, WITH SOME INCLUSION OF THE GEFS  
AND EC ENSEMBLE MEANS LATER ON AS DIFFERENCES INCREASE.  
 
   
..SENSIBLE WEATHER AND HAZARDS
 
 
SCATTERED SHOWERS AND STORMS ARE LIKELY ACROSS MUCH OF THE U.S.  
FROM THE ROCKIES EASTWARD AT TIMES THIS 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 END OF THE WEEK, 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 BY NEXT WEEKEND, LEADING TO MORE FOCUSED RAINFALL IN THE  
SOUTHEAST AND CLEARING FOR THE NORTHEAST BEHIND THE FRONT.  
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.  
 
THE GREATEST CONCERN FOR TEMPERATURES IS WITH THE HEAT EXPECTED TO  
BUILD ACROSS THE CENTRAL U.S. IN RESPONSE TO A STRENGTHENING UPPER  
LEVEL RIDGE. HIGHS OF 10-15 DEGREES ABOVE NORMAL ARE LIKELY OVER  
THE CENTRAL PLAINS TO MIDDLE MISSISSIPPI VALLEY AT LEAST DURING  
WEDNESDAY-THURSDAY, EQUATING TO TEMPERATURES IN THE MID 90S TO LOW  
100S. A SOUTHWARD-DRIFTING SURFACE FRONT AND ASSOCIATED CONVECTION  
COULD ERODE THIS HEAT SOMEWHAT TOWARD THE END OF THE WEEK. HOWEVER  
WARMER THAN AVERAGE TEMPERATURES SHOULD BUILD INTO THE NORTHERN  
ROCKIES/HIGH PLAINS LATE IN THE WEEK, LEADING TO SOME HOT READINGS  
OF UP TO 10-15F ABOVE NORMAL FOR THE WEEKEND. SOUTHERN PLAINS  
LOCATIONS WILL SEE HOT TEMPERATURES THROUGH THE PERIOD BUT WITH  
LESS EXTREME ANOMALIES. MEANWHILE THE WEST WILL SEE COOLER THAN  
NORMAL HIGHS THROUGH AT LEAST MIDWEEK DUE TO THE INITIAL EASTERN  
PACIFIC UPPER TROUGH AND LEADING MOISTURE OVER THE FOUR CORNERS  
STATES. THEN TEMPERATURES SHOULD MODERATE CLOSER TO NORMAL, AND  
EVEN ABOVE NORMAL IN THE DESERT SOUTHWEST AND CALIFORNIA BY FRIDAY  
AND INTO THE WEEKEND. THE EAST IS LIKELY TO BE NEAR AVERAGE  
TEMPERATURE-WISE, WITH A TREND TOWARD COOLING SLIGHTLY BY THE  
WEEKEND.  
 
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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