459
FXUS02 KWBC 061919
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
319 PM 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 FOR
THE INTERIOR MID-ATLANTIC INTO NEW ENGLAND LATE THIS WEEK...
...EXCESSIVE HEAT LINGERS OVER PORTIONS OF TEXAS AND THE CENTRAL
GULF COAST FRIDAY INTO THIS WEEKEND...
..OVERVIEW
TROPICAL STORM DEBBY WILL LIFT THROUGH THE EAST COAST AT THE START
OF THE MEDIUM RANGE PERIOD, EVENTUALLY COMPLETING EXTRATROPICAL
TRANSITION INTO NEW ENGLAND AND MERGING WITH THE BAROCLINIC ZONE TO
THE NORTH. THE INFLUX OF TROPICAL MOISTURE WILL SET THE STAGE FOR
HEAVY RAINFALL THAT MAY BE EXACERBATED BY THE IN SITU FRONTAL
BOUNDARY FROM THE MID-ATLANTIC NORTHWARD INTO THE NORTHEAST, MAINLY
ALONG THE I-81 CORRIDOR TO NORTHERN PARTS OF THE I-87/91
CORRIDORS.
UPSTREAM OVER THE WEST AND CENTRAL STATES, 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. TROUGHING INTO THE NORTHWEST WILL LINGER
THROUGH THE PERIOD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
FOR DEBBY, THE 15Z NHC FORECAST FAVORED THE QUICKER SOLUTIONS ONCE
DEBBY STARTS TO GET PICKED UP BY TROUGHING MOVING THROUGH THE
GREAT LAKES. THIS WAS NEARER TO THE 00Z ECMWF AND SOMEWHAT THE 06Z
GFS, WITH A BIT QUICKER TREND NOTICED IN SOME OF THE 12Z GUIDANCE.
UPSTREAM, A CONSENSUS OF THE ECMWF/GFS DETERMINISTIC AND ENSEMBLE
GUIDANCE SUFFICED AS DIFFERENCES WERE GENERALLY WITH THE NOISE AT
THE ~D5 TIME RANGE, BUT MOSTLY SHOWED GOOD AGREEMENT OVERALL.
LARGEST CHANGES WERE WITH THE QPF FROM THE NBM, WHICH WAS STILL
MOSTLY BASED ON OLDER/SLOWER GUIDANCE. QUICKENED THE PACE OF THE
RAINFALL UP THE EAST COAST BUT AMOUNTS WERE GENERALLY ON PAR.
..WEATHER/HAZARDS HIGHLIGHTS
FOR FRIDAY, IN COORDINATION WITH THE OFFICES FROM THE MID-ATLANTIC
NORTHWARD, RAISED THE ERO LEVEL TO MODERATE FROM ROUGHLY THE
MASON-DIXON LINE NORTHWARD AND NORTHEASTWARD INTO NORTHERN NEW
ENGLAND. MUCH OF VA HAS SEEN WELL BELOW NORMAL RAINFALL AND
WIDESPREAD EXCESSIVE RAINFALL MAY NOT BE REALIZED, BUT WILL
CONTINUE TO SEE FUTURE QPF TRENDS IN AMOUNTS/RATES. FARTHER NORTH,
FFG VALUES ARE LOWER AND THE AREAS ARE MORE SUSCEPTIBLE TO
FLOODING, PARTLY CONTINGENT UPON SHORT TERM RAINFALL. BY SATURDAY,
RAINFALL WILL BE ON ITS WAY OUT OF THE NORTHEAST AND MAINTAINED
THE SLIGHT RISK FOR PARTS OF THE NORTHEAST. THESE FOCUS FOR THE
RAINFALL IMPACTS IS THROUGH THE INTERIOR, THOUGH EVERYONE WILL SEE
RAINFALL AS THE LARGE MOISTURE PLUME LIFTS NORTHWARD/NORTHEASTWARD
IRRESPECTIVE OF THE TROPICAL CLASSIFICATION.
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 FRIDAY WITH A SLIGHT RISK MAINTAINED 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 (HIGHS ONLY IN THE 60S/70S
EAST OF THE ROCKIES INTO THE NORTHERN/CENTRAL PLAINS) INTO THE
WEEKEND BEFORE TRENDING TOWARD NORMAL.
FRACASSO/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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