831
FXUS02 KWBC 200641
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
241 AM EDT TUE AUG 20 2024
VALID 12Z FRI AUG 23 2024 - 12Z TUE AUG 27 2024
..HAZARDOUS HEAT TO PERSIST FOR THE SOUTHERN PLAINS
..OVERVIEW
AN AMPLIFIED UPPER PATTERN WILL BE HIGHLIGHTED BY A CENTRAL CONUS
RIDGE CENTERED OVER THE SOUTHERN PLAINS, WITH TROUGHING OVER THE
NORTHEAST INTO THIS WEEKEND AND A LOW MOVING OVER THE NORTHWEST
THEN NORTH-CENTRAL U.S. WITH CYCLOGENESIS INTO NEXT WEEK. THIS
PATTERN OFFERS A HAZARDOUS HEAT EMINATING FROM TEXAS, MOIST
MONSOONAL FLOW LINGERING OVER THE SOUTHWEST/FOUR CORNERS, COOLER
SURFACE HIGH PRESSURE ALONG THE EASTERN SEABOARD, AND TROPICAL
MOISTURE LURKING NEAR THE GULF COAST AND ACROSS FLORIDA.
..GUIDANCE/PREDICTABILITY ASSESSMENT
DIFFERENCES LINGER WITH THE HANDLING OF DEEP EASTERN PACIFIC UPPER
TROUGH/LOW ENERGY INLAND INTO THE WEST/NORTHWEST BY THIS WEEKEND.
THE 18 UTC GFS HAS BEEN THE LATEST MODEL TO FAVOR A SOLUTION ON THE
MORE PROGRESSIVE SIDE OF GUIDANCE, WHILE MOST OTHER GUIDANCE HAS
BEEN TRENDING SLOWER WITH RECENT RUNS. STILL PREFER TO FAVOR A
SLOWER SOLUTION AND THAT TREND AGAIN SEEMS SUPPORTED BY LATEST 00
UTC GUIDANCE. 18 UTC GFS OUTLIER RUNS IN PARTICULAR HAVE BEEN MUCH
MORE PROGRESSIVE THAN 12/00 UTC GFS RUNS OVER THE PAST FEW DAYS.
A COMPOSITE OF COMPATIBLE 12 UTC GFS/UKMET/ECMWF/CANADIAN MODEL
GUIDANCE WAS USED TO DERIVE THE WPC MEDIUM RANGE PRODUCT SUITE FOR
FRIDAY INTO SUNDAY IN CONJUCTURE WITH THE 01 UTC NATIONAL BLEND OF
MODELS. FORECAST UNCERTAINTY GROWS INTO NEXT WEEK, BUT THE 12 UTC
GFS/ECMWF BEST OFFER A REASONABLY SLOW PATTERN PROGRESSION WHILE
MAINTAINING SYSTEM CONTINUITY, AMPLITUDE AND FOCUS THROUGH THE
NORTHWEST AND ONWARD TO THE NORTH-CENTRAL U.S. AT THESE TIMES.
..WEATHER/HAZARDS HIGHLIGHTS
UPPER TROUGH AMPLIFICATION PROXIMITY ALONG/OFF THE WEST COAST
PORTENDS A COOLER AND WETTER PATTERN FOR THE NORTHWEST LATER THIS
WEEK. RAINS AND SPOTTY HIGH ELEVATION MOUNTAIN SNOWS MAY WORK
INLAND ACROSS THE NORTH-CENTRAL INTERMOUNTAIN WEST/ROCKIES THIS
WEEKEND INTO EARLY NEXT WEEK DEPENDENT ON THE UNCERTAIN
TRACK/TIMING OF SUPPORTING BUT LIKELY AMPLIFIED UPPER TROUGH/LOW
EJECTION. RAINS/CONVECTION MAY ALSO CONSOLIDATE DOWNSTREAM OVER THE
NORTH-CENTRAL U.S. EARLY NEXT WEEK GIVEN POSSIBLE MODERATE
CYCLOGENESIS/FRONTOGENESIS FOR FOCUS IN THIS SCENARIO.
MEANWHILE, A MONSOONAL CONVECTIVE PATTERN WILL LINGER BUT
GRADUALLY EASE OVER THE SOUTHWEST/FOUR CORNERS STATES FRIDAY INTO
SATURDAY WITH MOIST SOUTHERLY FLOW WEST OF A SLOW TO DISLODGE UPPER
RIDGE AXIS CENTERED OVER THE SOUTHERN PLAINS. SOME MOISTURE MAY BE
PULLED NORTHWARD INTO THE NORTHERN INTERMOUNTAIN WEST/ROCKIES INTO
SATURDAY CONTINGENT AND IN ADVANCE OF POSSIBLE PACIFIC UPPER
TROUGH/LOW TRANSLATION TOWARD THAT REGION. THE WPC DAY 4/5
EXCESSIVE RAINFALL OUTLOOKS (EROS) FOR FRIDAY/SATURDAY SHOW
ELONGATED MARGINAL RISKS AREAS. LOCAL STORMS WITH EMBEDDED HEAVY
RAIN COULD CAUSE FLASH FLOODING, PARTICULARLY IN VULNERABLE AREAS.
UPPER RIDGING FOCUS OVER THE SOUTH-CENTRAL U.S. WILL SUPPORT 5-15
DEGREE ABOVE NORMAL TEMPERATURES. HIGHS WELL INTO THE 100S IN MUCH
OF TEXAS IN PARTICULAR COULD SET DAILY RECORDS AND HIGH DEWPOINTS
SHOULD PRODUCE HEAT INDICES LIKELY ABOVE 110 DEGREES. LOW
TEMPERATURES IN THE UPPER 70S TO LOW 80S WILL EXACERBATE HEAT
STRESS AND COULD SET RECORDS FOR WARM MINIMUM TEMPERATURES.
EXPERIMENTAL HEATRISK CONTINUES TO INDICATE MAJOR TO EXTREME
IMPACTS FROM THIS HEAT. THIS WILL BE IN CONTRAST TO COOLING
CONDITIONS INTO THE WEST/NORTHWEST AND ALSO OVER THE CENTRAL TO
EASTERN U.S. UNDER THE INFLUENCE OF DAMMED SURFACE HIGH PRESSURE.
SOME RECORD COOL OVERNIGHT TEMPERATURE VALUES ARE POSSIBLE OVER THE
EAST IN THIS PATTERN INTO LATER WEEK, BUT EXPECT SUMMER HEAT TO
THEN STEADILY RETURN WITH SPREAD ACROSS THE CENTRAL-EASTERN U.S..
ELSEWHERE, A TRAILING FRONT STALLING ACROSS FLORIDA WILL MAINTAIN
PERIODIC RAIN/THUNDERSTORM CHANCES THERE AND INTO SOUTHEAST U.S.
COASTAL AREAS LATER WEEK INTO NEXT WEEK. MOIST FLOW AND PATTERN
LONGEVITY MAY LEAD TO POSSIBLE FLOODING ISSUES, ESPECIALLY IF HEAVY
RAIN FALLS IN URBAN AREAS. A WPC DAY5/SATURDAY ERO MARIGINAL RISK
AREA WAS INTRODUCED FOR SOUTH FLORIDA GIVEN A GROWING SIGNAL.
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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