908
FXUS02 KWBC 051900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MON AUG 5 2024
VALID 12Z THU AUG 08 2024 - 12Z MON AUG 12 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 CONTINUES FOR PORTIONS OF TEXAS AND CENTRAL GULF
COAST THURSDAY INTO THIS WEEKEND...
..OVERVIEW
THE NATIONAL HURRICANE CENTER FORECAST TRACK FOR DEBBY TAKES IT UP
THE EASTERN SEABOARD THURSDAY INTO THIS WEEKEND WHERE THERE IS THE
THREAT FOR HEAVY RAINFALL ALONG WITH GUSTY WINDS. LATEST MODEL
GUIDANCE HAS TRENDED TOWARD GREATER FRONTAL INTERACTION OF
TROPICAL MOISTURE ASSOCIATED WITH DEBBY LEADING TO INCREASING
HEAVY RAIN POTENTIALS UP TOWARD NEW ENGLAND. UPPER RIDGING
CENTERED NEAR THE FOUR CORNERS WILL MAINTAIN MONSOONAL FLOW OVER
THE SOUTHWEST THROUGH THIS WEEKEND WITH HEAT CONCERNS SHIFTING
SOUTH AHEAD OF THE RIDGE, OVER TEXAS TO THE CENTRAL GULF COAST
(AREAS WEST OF DEBBY'S CLOUD COVER).
..GUIDANCE/PREDICTABILITY ASSESSMENT
FOCUS AREAS IN THE SYNOPTIC PATTERN LATTER HALF OF THE WEEK AREA
THE TRACK OF DEBBY AND THE ASSOCIATED EASTERN CONUS TROUGH ALONG
WITH TROUGHING OVER THE NORTHERN TIER OF STATES. THE LATEST NHC
TRACK CONTINUES TO FAVOR THE ECMWF AND A WEAKER EASTERN CONUS
TROUGH THAT ALLOWS DEBBY TO TRACK UP THE EASTERN SEABOARD LATE THIS
WEEK AFTER STALLING NEAR THE SOUTHEAST COAST. THAT SAID, SITUATIONS
LIKE THIS WITH WEAK STEERING FLOW ALOFT MEANS MODEL GUIDANCE
TYPICALLY STRUGGLES. THE OUTLIER WITH THE DEBBY TRACK REMAINS THE
GFS WHICH HAS A STRONGER EASTERN TROUGH AND KEEPS DEBBY BELOW IT,
CAUSING MEANDERING OVER THE SOUTHEAST, WHILE THE 00Z CONSENSUS IS
FOR A SLOW TREK UP THE EASTERN SEABOARD. HOWEVER, THE GFS
RETROGRADES MORE THAN ITS ENSEMBLE MEAN AND THE 12Z GRAPHCAST AI
RUN OFF THE GFS INITIALIZATION IS IN LINE WITH THE NON-GFS 00Z
CONSENSUS. THE MODEL PREFERENCE WAS HEDGED IN THE DIRECTION OF THE
ECMWF, THE 12Z UKMET AND THEN INCREASINGLY IN THE ECENS AND GEFS
MEANS.
..WEATHER/HAZARDS HIGHLIGHTS
SLOW MOTION TO DEBBY RAISES THE THREAT FOR EXTREME RAINFALL TO
CONTINUE IN THE SOUTHEAST THURSDAY. A DAY 4 MODERATE RISK FOR
EXCESSIVE RAINFALL REMAINS FOR EASTERN SC INTO SOUTHERN NC. GIVEN
THE EJECTION NORTH OF DEBBY/PERHAPS ITS REMNANTS, AN EXPANSIVE
SLIGHT RISK IS INTRODUCED OVER MUCH OF THE EASTERN SEABOARD FOR THE
DAY 5 ERO. A SURGE OF TROPICAL MOISTURE AHEAD OF DEBBY INTO A
FRONTAL BOUNDARY OVER THE NORTHEAST FAVORS A PRE SETUP WITH
ADDITIONAL RAINFALL STRETCHED NORTHEASTWARD ACROSS THE MID-
ATLANTIC AND NORTHEAST.
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 MUCH OF THE EXTENDED
PERIOD. MARGINAL RISKS FOR EXCESSIVE RAIN 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 DAY 4 OVER NORTHERN NM/SOUTHERN
CO WHERE HIGHER QPF IS NOTED. WILL NEED TO MONITOR THE NEED FOR A
SLIGHT INTRODUCTION ON DAY 5 WITH CONTINUED ANOMALOUS MOISTURE
INFLUX OVER THE WEST.
ABOVE SEASONAL NORMAL TEMPERATURES ACROSS THE SOUTHWEST AND
SOUTHERN PLAINS ON WEDNESDAY ARE FORECAST TO TREND TOWARD NORMAL
INTO THE WEEKEND AS THE RIDGE SUPPRESSES SOUTH UNDER TROUGHING
ALONG THE CANADIAN BORDER. HAZARDOUS HEAT IS LIKELY FOR TEXAS AND
LOWER MISSISSIPPI VALLEY/CENTRAL GULF COAST LATE THIS WEEK INTO THE
WEEKEND. EXPERIMENTAL HEATRISK VALUES ARE GENERALLY MAJOR FOR MUCH
OF THIS REGION WITH EXTREME FOR THE CENTRAL GULF COAST AREA. MUCH
OF THE CENTRAL U.S. WILL COOL OFF IN THE WAKE OF A COLD FRONT
MIDWEEK.
KONG/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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