292
FXUS02 KWBC 301900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM 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 WEST/NORTHWEST...
..OVERVIEW
AMPLE UPPER RIDGING STRETCHING 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 AND
ENERGIES DIGGING TO THE LEE OF THE BUILDING UPPER RIDGE OVER THE
WEST WILL REINFORCE UPPER TROUGHING OVER THE EAST INTO NEXT WEEK.
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
LASTEST GUIDANCE MOSTLY AGREES FAIRLY WELL FOR THE LARGE SCALE
PATTERN, BUT STILL DISPLAYS IMPORTANT DIFFERENCES. THERE IS
UNCERTAINTY REGARDING AMPLITUDE AND TIMING OF ENERGIES TO CARVE OUT
A MIDWEST/EASTERN U.S. MEAN UPPER TROUGH THIS WEEKEND INTO EARLY
NEXT WEEK. PREFER A SOLUTION CLOSEST TO THE 00 UTC ECMWF AND ECMWF
ENSEMBLES THAT DEPICT A SLIGHTLY MORE AMPLIFIED AND LESS
PROGRESSIVE FEATURE THAT SEEMS MORE LIKELY GIVEN UPSTREAM UPPER
RIDGE AMPLITUDE OVER THE HOT WEST. THIS ACTS TO FOCUS ASSOCIATED
HEAVY RAINFALL THREATS FARTHER TO THE SOUTH THAN EARLIER GUIDANCE.
THE RIDGE OVER THE WEST SHOULD BE SUFFICIENTLY STRONG TO PREVENT
ANY MAJOR INTRUSIONS FROM UPSTREAM, 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 UP THROUGH THE BAHAMAS AND UP OFF THE SOUTHEAST
U.S., MORE IN LINE WITH AS THE ECMWF HAS BEEN SHOWING THE PAST DAY
OR TWO. 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.
THE WPC MEDIUM RANGE FORECAST SUITE WAS MAINLY DERIVED WITH THE
IDEA TO SHIFT COMPOSITE/NBM GUIDANCE TOWARD THE 00 UTC ECMWF/ECMWF
ENSEMBLE MEAN THAT SHOW THE BEST SUPPORT FOR WPC/NHC PREFERENCES
ON THE POTENTIAL TROPICAL SYSTEM AS WELL AS FOR A MORE AMPLIFIED
AND SLOW TO PROGRESS WESTERN U.S. UPPER RIDGE AND MIDWES/EASTERN
U.S. UPPER TROUGH COUPLET.
..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 AND DAY 5 EXCESSIVE RAINFALL OUTLOOKS
CENTERED ON FRIDAY AND SATURDAY SHOW BROAD MARGINAL RISKS FROM THE
OHIO VALLEY/APPALACHIANS AND THE MID-ATLANTIC INTO THE NORTHEAST.
THESE RISK AREAS HAVE BEEN SUPRESSED SOUTHWARD FROM CONTINUITY
GIVEN FLOW AMPLITUDE AND SLOWED PROGRESSION. 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. A DAY 5/SATURDAY
MARGINAL RISK AREA WAS ADDED FOR SOUTHEAST FLORIDA TO DENOTE THE
UNCERTAIN RAINFALL THREAT GIVEN PROXIMITY.
ELSEWHERE, MONSOONAL CONVECTION OVER THE SOUTHWEST CONTINUES TO
SUPPORT MARGINAL RISK AREAS ON THE DAYS 4 AND 5 EROS. THE DAY
4/FRIDAY RISK AREA WAS EXPANDED WESTWARD THROUGH SOUTHEAST
CALIFORNIA GIVEN SOILS/TERRAIN AND AN EASTERLY WAVE. 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/SCHICHTEL
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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