632
FXUS02 KWBC 300646
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
246 AM EDT TUE JUL 30 2024
VALID 12Z FRI AUG 02 2024 - 12Z TUE AUG 06 2024
...HAZARDOUS HEAT FROM THE SOUTH-CENTRAL PLAINS EASTWARD BECOMING
MORE SUPPRESSED WITH TIME WHILE BUILDING OVER THE NORTHWEST LATER
THIS WEEK...
..OVERVIEW
A BROAD UPPER RIDGE STRETCHED FROM THE WEST TO THE SOUTHEAST AS
THE PERIOD BEGINS FRIDAY WILL FOCUS IN THE WEST BY THIS WEEKEND AND
BEYOND AS THE SOUTHEAST PORTION GETS SUPPRESSED BY TROUGHING OVER
THE EAST LATER THIS WEEK. THIS WILL PROMOTE SOME LINGERING HEAT
ACROSS THE SOUTH-CENTRAL U.S. INTO THE SOUTHEAST FRIDAY, BUT
BUILDING AND LINGERING HEAT OVER THE WEST. NORTHERN STREAM FLOW
WILL GENERALLY MAINTAIN SHALLOW TROUGHING OVER THE EAST INTO NEXT
WEEK AS THE WESTERN RIDGE STARTS TO BUILD BACK INTO THE CENTRAL
U.S. LATE PERIOD. THE NATIONAL HURRICANE CENTER IS ALSO MONITORING
THE POTENTIAL FOR TROPICAL DEVELOPMENT THAT COULD AT LEAST COME
CLOSE TO AFFECTING LOCATIONS NEAR THE SOUTHEASTERN COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MOST GUIDANCE AGREES FAIRLY WELL FOR THE LARGE SCALE PATTERN BUT
STILL DISPLAYS IMPORTANT DIFFERENCES FOR SOME DETAILS. TIMING OF A
SHORTWAVE INTO THE GREAT LAKES/NORTHEAST ON FRIDAY HAS IMPROVED
COMPARED TO RECENT DAYS, BUT THERE IS UNCERTAINTY REGARDING
AMPLITUDE AND TIMING OF ADDITIONAL ENERGY THROUGH THE REGION THIS
WEEKEND INTO EARLY NEXT WEEK. THE RIDGE OVER THE WEST SHOULD BE
SUFFICIENTLY STRONG TO PREVENT ANY MAJOR INTRUSIONS, BUT GUIDANCE
STRUGGLES ON POSSIBLE ENERGY SLIDING INTO THE NORTHWEST AND OVER
THE TOP OF THE RIDGE ON SUNDAY WHICH COULD AFFECT ITS OVERALL
STRENGTH/NORTHWARD EXTENT BY EARLY NEXT WEEK.
MOST GUIDANCE CONTINUES TO SUPPORT THE IDEA OF POSSIBLE TROPICAL
DEVELOPMENT IN THE ATLANTIC, AS HIGHLIGHTED IN THE NATIONAL
HURRICANE CENTER OUTLOOK, BUT A LOT OF LINGERING UNCERTAINTY IN THE
EXACT TRACK. GUIDANCE AND ENSEMBLES SEEM TO BE TRENDING TOWARDS A
MORE EASTERLY TRACK, AS THE ECMWF HAS BEEN SHOWING THE PAST DAY OR
TWO. QUESTIONS ON ITS SPEED OFF THE SOUTHEAST COAST THOUGH LATE
PERIOD, WITH THE CMC THE QUICKEST TO RACE IT NORTHEASTWARD AWAY
FROM THE MID-ATLANTIC. LATEST OPERATIONAL GFS RUNS REMAIN FAIRLY
ILL- DEFINED WITH ANY POSSIBLE SYSTEM, THOUGH MAYBE MORE SO
BRINGING THE TROPICAL WAVE MORE INTO THE GULF VERY LATE PERIOD.
WPC FORECAST USED A BLEND OF THE OPERATIONAL GUIDANCE FOR THE
FIRST HALF OF THE PERIOD AMIDST SUFFICIENT MODEL AGREEMENT.
INCREASED THE ENSEMBLE MEANS TO 50 PERCENT OF THE BLEND BY THE END
OF THE PERIOD TO HELP MITIGATE DIFFERENCES. THE OPERATIONAL MODEL
HALF LEANED MORE HEAVILY TOWARDS THE ECMWF WHICH SHOWS THE BEST
SUPPORT FOR WPC/NHC PREFERENCES ON THE POTENTIAL TROPICAL SYSTEM.
..WEATHER/HAZARDS HIGHLIGHTS
A GENERALLY WET AND UNSETTLED PATTERN IS LIKELY FROM THE OHIO
VALLEY TO THE EASTERN SEABOARD INTO THIS WEEKEND WITH AMPLE
MOISTURE AND INSTABILITY IN PLACE WHILE A SLOW MOVING UPPER TROUGH
AND SURFACE/FRONTAL SYSTEMS ALL SUPPORT AREAS OF SHOWERS AND
THUNDERSTORMS. THE DAYS 4-5 EXCESSIVE RAINFALL OUTLOOKS COVERING
FRIDAY-SATURDAY NIGHT SHOW FAIRLY BROAD MARGINAL RISKS ACROSS PARTS
OF THE OHIO VALLEY AND THE NORTHEAST/MID-ATLANTIC. LATEST GUIDANCE
CONTINUES TO SHOW POTENTIAL FOR EMBEDDED MESOSCALE SYSTEMS TO
PRODUCE LOCALLY HEAVY RAINFALL ACROSS PARTS OF THE ABOVE AREAS.
HOWEVER THERE IS STILL A LOT OF SPREAD FOR LOCATION OF HEAVIEST
ACTIVITY, PLUS DEPENDENCE ON STILL- UNCERTAIN SHORTER TERM RAINFALL
AND RESULTING SOIL SENSITIVITY. PARTS OF THE NORTH- CENTRAL U.S.
TO THE EASTERN THIRD OF THE COUNTRY SHOULD REMAIN GENERALLY
UNSETTLED INTO EARLY NEXT WEEK WITH GENERAL MEAN TROUGHING LIKELY
TO PERSIST. LOCATIONS NEAR FLORIDA AND THE SOUTHEASTERN COAST
SHOULD MONITOR LATEST FORECASTS REGARDING POSSIBLE TROPICAL
DEVELOPMENT DURING THE WEEKEND/EARLY NEXT WEEK TIME FRAME.
ELSEWHERE, MONSOONAL CONVECTION OVER THE SOUTHWEST CONTINUES TO
SUPPORT MARGINAL RISK AREAS ON THE DAYS 4 AND 5 EROS. CHANCES FOR
CONVECTION MAY EXPAND NORTHEASTWARD WITH TIME DEPENDING ON THE
SHAPE OF THE SOUTHERN ROCKIES/PLAINS RIDGE AND UPPER LEVEL ENERGY
ROTATING AROUND ITS WESTERN PERIPHERY. FROM THE WEEKEND INTO EARLY
NEXT WEEK, FLOW BETWEEN THE UPPER RIDGE AND A WEAK TROUGH SETTING
UP OFF THE WEST COAST MAY SUPPORT A NORTHWESTWARD/NORTHWARD
EXPANSION OF SCATTERED CONVECTION.
THE HEAT WAVE OVER THE CENTRAL PLAINS EARLY THIS WEEK SHOULD WANE
BY THE START OF THE MEDIUM RANGE PERIOD WITH AN INCOMING FRONT, BUT
HEAT WILL CONTINUE ACROSS THE SOUTHEAST THROUGH FRIDAY OR SATURDAY
WITH WARM OVERNIGHT TEMPERATURES ONLY EXACERBATING HEAT STRESS IN
THAT REGION. MEANWHILE, HAZARDOUS HEAT THREATS WILL INCREASE OVER
MUCH OF THE WEST, WITH LOWER ELEVATIONS SEEING 100F+ HIGH
TEMPERATURES, AND SCATTERED DAILY RECORD HIGHS ARE POSSIBLE AND
APPEAR MOST LIKELY OVER THE INTERIOR NORTHWEST ON FRIDAY- SATURDAY.
SHORTER BURSTS OF ABOVE NORMAL TEMPERATURES ARE ALSO LIKELY FOR
THE MIDWEST TO OHIO VALLEY TO THE MID- ATLANTIC/NORTHEAST LATE THIS
WEEK, WITH PERHAPS SOME MODERATION NEXT WEEKEND AFTER COLD FRONTS
PASS THROUGH. HEAT MAY EXPAND BACK INTO THE NORTHERN-CENTRAL PLAINS
EARLY NEXT WEEK.
SANTORELLI
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 FORECAST (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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