361
FXUS02 KWBC 010643
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
243 AM EDT THU AUG 1 2024
VALID 12Z SUN AUG 04 2024 - 12Z THU AUG 08 2024
...HAZARDOUS HEAT THREATS TO FOCUS ACROSS THE SOUTHWEST AND BACK
INTO THE SOUTH-CENTRAL U.S. NEXT WEEK...
..OVERVIEW
UPPER RIDGING OVER THE WESTERN U.S. THIS WEEKEND WILL GRADUALLY
GET SUPPRESSED WITH TIME AND EXPAND EASTWARD BACK INTO PARTS OF THE
SOUTH-CENTRAL U.S. NEXT WEEK. THIS WILL PROMOTE HEAT THREATS
INITIALLY ACROSS THE SOUTHWEST BUT ALSO INTO THE CENTRAL PLAINS AND
SOUTHEAST. NORTHERN STREAM FLOW AND ENERGY DIGGING TO THE LEE OF
THE UPPER RIDGE WILL REINFORCE TROUGHING OVER THE UPPER MIDWEST TO
THE EAST THAT LASTS THROUGH THE MIDDLE OF NEXT WEEK. THE NATIONAL
HURRICANE CENTER IS ALSO MONITORING THE POTENTIAL FOR TROPICAL
DEVELOPMENT THAT COULD AFFECT THE EASTERN GULF COAST AND THE
SOUTHEAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT ON THE LARGE
SCALE PATTERN, BUT LOTS OF UNCERTAINTY IN THE DETAILS. THERE
REMAINS GROWING UNCERTAINTY IN THE TIMING AND AMPLITUDE OF ENERGIES
THROUGH THE NORTHERN TIER TO CARVE OUT A MIDWEST/EASTERN U.S. MEAN
UPPER TROUGH, ESPECIALLY LATER IN THE PERIOD. ALSO QUESTION ON THE
EXTENT AND STRENGTH OF THE UPPER RIDGE FROM THE SOUTHWEST INTO THE
CENTRAL PLAINS/SOUTHEAST.
MODELS AND ENSEMBLES CONTINUE TO FAVOR POSSIBLE TROPICAL
DEVELOPMENT NEAR/SOUTH OF FLORIDA THIS WEEKEND, AS HIGHLIGHTED IN
THE LATEST NHC OUTLOOK. THERE REMAINS A LOT OF UNCERTAINTY IN THE
EXACT TRACK, AND RESULTING RAINFALL FOOTPRINT, BUT THERE HAS BEEN
AN OVERWHELMING WESTWARD SHIFT IN THE GUIDANCE COMPARED TO 24 HOURS
AGO. MOST MODELS NOW SUGGEST SOMETHING WILL LIFT THROUGH THE FAR
EASTERN GULF OF MEXICO SUNDAY-MONDAY. WHAT HAPPENS WITH IT NEXT
WEEK IS EXTREMELY UNCERTAIN AND DEPENDENT ON POSSIBLE INTERACTIONS
WITH NORTHERN STREAM TROUGHING OVER THE EAST. MAJORITY OF GUIDANCE
SHOWS SOME SORT OF SLOWING/MEANDERING OF THIS SYSTEM NEAR THE
NORTHEAST GULF OR OVER FLORIDA, BUT THE NEW 00Z CMC CAME IN MUCH
MORE PROGRESSIVE TAKING IT NORTH THROUGH THE SOUTHEAST. THE GFS
ALSO CONTINUES TO BE A MUCH STRONGER OUTLIER WITH THE UKMET THE
FARTHEST WEST INTO THE CENTRAL GULF COAST REGION. EITHER WAY, THIS
SYSTEM WILL NEED TO BE WATCHED FOR POSSIBLE HEAVY RAINFALL IMPACTS
TO PARTS OF THE GULF COAST/FLORIDA AND THE SOUTHEAST.
THE WPC MEDIUM RANGE FORECAST SUITE USED A BLEND OF THE
OPERATIONAL MODELS FOR THE FIRST HALF OF THE PERIOD (MORE HEAVILY
WEIGHTED TOWARDS THE ECMWF AND CMC). LEANED MORE TOWARDS THE
ENSEMBLE MEANS DAYS 6 AND 7 TO ACCOUNT FOR NORTHERN STREAM
UNCERTAINTIES AND ALSO THE POSSIBLE TROPICAL DISTURBANCE.
..WEATHER/HAZARDS HIGHLIGHTS
THE MAIN FOCUS FOR HEAVY RAINFALL THREATS DURING THE PERIOD WILL
LIKELY BE ASSOCIATED WITH WHATEVER BECOMES OF A TROPICAL
DISTURBANCE LIKELY TO AFFECT PARTS OF FLORIDA AND THE SOUTHEAST.
GUIDANCE THIS CYCLE SHOWED A DRASTIC SHIFT TOWARDS HEAVY RAINFALL
POTENTIAL FOR MUCH OF THE NORTHERN TO CENTRAL PARTS OF THE STATE.
THE DAYS 4 AND 5 EXCESSIVE RAINFALL OUTLOOKS COVERING SUNDAY-MONDAY
SHOW SLIGHT RISK UPGRADES ACROSS THIS REGION, WITH A BROADER
MARGINAL COVERING MUCH OF THE STATE TO ACCOUNT FOR THE LINGERING
UNCERTAINTY. IT IS LIKELY THESE AREAS WILL NEED TO BE MODIFIED AS
WE GET CLOSER IN TIME, BUT FOR NOW, THIS SEEMED THE MOST PLAUSIBLE
SOLUTION COVERING THE BETTER MODEL TRACK CONSENSUS. HEAVY RAINFALL
ACROSS FLORIDA MAY LINGER INTO NEXT WEEK WITH POSSIBLE EXTENSION
INTO PARTS OF THE SOUTHEAST DEPENDENT ON TRACK OF THIS SYSTEM.
ELSEWHERE, A FRONT EXITING THE NORTHEAST ON SUNDAY MAY BRING A
PERIOD OF LOCALLY HEAVY RAINFALL, WHICH CONTINUES TO BE COVERED IN
THE DAY 4 ERO. TO THE WEST, MODELS SHOW A POTENTIAL MESOSCALE
SYSTEM RIDING THE TOP OF THE RIDGE INTO THE UPPER MIDWEST EARLY
NEXT WEEK. A MARGINAL RISK ON THE DAY 4 ERO STRETCHES FROM THE
NORTHERN HIGH PLAINS EASTWARD, BUT DID INCLUDE A SMALL SLIGHT RISK
ACROSS PARTS OF CENTRAL MINNESOTA AND WISCONSIN ON THE DAY 5 ERO
GIVEN AMPLE MOISTURE, INSTABILITY, AND SOME SOIL SENSITIVITY. SOME
RAIN WILL CONTINUE EAST INTO THE OHIO VALLEY AND NORTHEAST MIDDLE
OF NEXT WEEK.
MONSOONAL MOISTURE ON THE WESTERN SIDE OF THE RIDGE SHOULD
CONTINUE A WET AND UNSETTLED PATTERN STRETCHING FROM THE FOUR
CORNERS REGION NORTHWARD INTO THE ROCKIES/HIGH PLAINS MOST OF THE
PERIOD. MARGINAL RISKS ON THE ERO CONTINUE ACROSS PARTS OF THE
SOUTHWEST/FOUR CORNERS SUNDAY AND MONDAY.
MUCH OF THE WEST COAST SHOULD BE MODESTLY ABOVE NORMAL MUCH OF THE
PERIOD, BUT THE GREATEST THREAT FOR HAZARDOUS HEAT WILL BE ACROSS
PARTS OF SOUTHERN CALIFORNIA AND THE DESERT SOUTHWEST THIS WEEKEND
INTO EARLY NEXT WEEK, WITH DAYTIME HIGHS EXCEEDING 110F LIKELY.
ABOVE NORMAL TEMPERATURES ACROSS THE CENTRAL U.S. SHOULD SLOWLY
SINK SOUTH AND EASTWARD WITH TIME. THIS EQUATES TO MODERATE TO
MAJOR HEATRISK ACROSS THE SOUTH-CENTRAL TO SOUTHEAST U.S.., WITH
SOME LOCALIZED EXTREME ACROSS PARTS OF THE CENTRAL GULF COAST
STATES. NORTHERN TIER SHOULD REMAIN NEAR TO BELOW NORMAL THROUGH
THE PERIOD AS WEAK SHORTWAVE ENERGIES MOVE THROUGH.
SANTORELLI
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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