997
FXUS02 KWBC 060659
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT TUE AUG 6 2024
VALID 12Z FRI AUG 09 2024 - 12Z TUE AUG 13 2024
...HEAVY RAIN AND FLASH FLOODING THREAT ASSOCIATED WITH DEBBY EXPECTED
TO SPREAD UP THE EAST COAST TOWARD NEW ENGLAND LATE THIS WEEK...
...EXCESSIVE HEAT LINGERS OVER PORTIONS OF TEXAS AND THE CENTRAL
GULF COAST FRIDAY INTO THIS WEEKEND...
..OVERVIEW
THE LATEST NATIONAL HURRICANE CENTER FORECAST TRACK FOR DEBBY
TAKES IT UP THE CAROLINAS FRIDAY AND THEN ALONG THE NORTHEASTERN
SEABOARD THIS WEEKEND WHERE THERE IS THE THREAT FOR ADDITIONAL HEAVY
RAINFALL. 00Z MODEL GUIDANCE CONTINUES TO DEPICT FRONTAL
INTERACTION OF TROPICAL MOISTURE, WITH HEAVY RAIN, ASSOCIATED WITH
DEBBY OVER THE MID-ATLANTIC AND NORTHEAST.
UPPER RIDGING CENTERED OVER TEXAS WILL MAINTAIN MONSOONAL FLOW
OVER THE SOUTHWEST THROUGH THIS WEEKEND WITH HEAT CONCERNS
PERSISTING FROM TEXAS TO THE CENTRAL GULF COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE FOCUS OF HEAVY RAINFALL ASSOCIATED WITH DEBBY AS IT BEGINS TO
EJECT NORTH FROM THE CAROLINA COAST ON FRIDAY AND THE ASSOCIATED
MOISTURE INTERACTING WITH A STALLED FRONTAL BOUNDARY OVER THE
NORTHEASTERN SEABOARD IS THE MAJOR FORECAST CONCERN FOR THE
MEDIUM- RANGE PERIOD. THE ECMWF FAVORS A FARTHER INLAND TRACK OF
THE HEAVY RAIN, WITH THE 00Z RUN FOCUSING ON THE EASTERN SLOPES OF
THE CENTRAL APPALACHIANS AND THE EASTERN GREAT LAKES ON FRIDAY
BEFORE SHIFTING OVER NEW ENGLAND ON SATURDAY. THE CMC HAS BEEN
CLOSER TO THE COAST AND THE GFS REMAINS A SIGNIFICANT OUTLIER,
MAINTAINING REMNANTS OF DEBBY OVER GA INTO FRIDAY A FEW STATES
SOUTH OF THE 00Z CONSENSUS. THE 00Z UKMET DID NOT ARRIVE IN TIME
FOR EVALUATION FOR THIS DISCUSSION.
ELSEWHERE, MODEL SOLUTIONS AGREE RATHER WELL EVEN INTO DAY 7. THE
WPC MEDIUM-RANGE FORECASTS WERE DERIVED BASED ON 50% FROM THE 12Z
ECMWF, 20% FROM THE 12Z CMC AND THE REMAINING FROM THE 12Z
UKMET/18Z GFS AND/OR THE 12Z ECENS AND 18Z GEFS MEANS. THE QPF IS
GENERALLY A BLEND OF THE 01Z NBM AND THE 12Z ECMWF. THE 00Z ECMWF
CONTINUES THE INLAND TRACK OF HEAVY QPF ON FRIDAY OVER THE EAST.
DATA FROM THE 18Z GFS WAS MINIMIZED ACROSS THE SOUTHEAST ON DAY 4
DUE TO THE AFOREMENTIONED SLOW PROGRESSION OF DEBBY.
..WEATHER/HAZARDS HIGHLIGHTS
GIVEN VARIABILITY OF GUIDANCE ON THE INTERACTION OF TROPICAL
MOISTURE FROM DEBBY AND A FRONTAL ZONE NEAR THE NORTHEASTERN
SEABOARD, A BROAD SLIGHT RISK WAS MAINTAINED FOR THE DAY 4 ERO
(THOUGH NORTHERN MAINE WAS REMOVED). A TARGETED MODERATE RISK IS
LIKELY TO BE NEEDED EVENTUALLY, BUT NOT UNTIL GREATER MODEL
CONSENSUS ON WHERE THAT TARGETED AREA SHOULD BE DRAWN.
A SLIGHT RISK WAS INTRODUCED FOR THE DAY 5 ERO IN NEW ENGLAND GIVEN
TIMING OF HEAVY QPF MOVING THROUGH SATURDAY IN RECENT ECMWF
SOLUTIONS.
MONSOONAL MOISTURE ON THE WESTERN SIDE OF THE RIDGE WILL KEEP A
WET AND UNSETTLED PATTERN IN PLACE FROM THE FOUR CORNERS REGION
NORTHWARD INTO THE ROCKIES/HIGH PLAINS THROUGH THIS WEEKEND .
MARGINAL EROS ARE IN EFFECT FOR PARTS OF THE SOUTHWEST/FOUR
CORNERS (ESPECIALLY THE SENSITIVE SLOT CANYONS IN SOUTHERN UTAH)
THROUGH THE NORTHERN HIGH PLAINS THURSDAY WITH A SLIGHT RISK
MAINTAINED FOR THE NEW DAY 4 OVER NORTHERN NM/SOUTHERN CO WHERE
HIGHER QPF IS NOTED.
ABOVE SEASONAL NORMAL TEMPERATURES ACROSS THE SOUTHERN TIER ARE
FORECAST TO CONTINUE FRIDAY AND THIS WEEKEND, MAINLY OVER TEXAS TO
THE CENTRAL GULF COAST. BELOW NORMAL TEMPERATURES OVER CENTRAL
U.S. PERSISTS BEHIND A COLD FRONT FRIDAY INTO THE WEEKEND BEFORE
TRENDING TOWARD NORMAL.
JACKSON
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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