448
FXUS02 KWBC 241853
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
252 PM EDT THU AUG 24 2023
VALID 12Z SUN AUG 27 2023 - 12Z THU AUG 31 2023
***HOT AND HUMID CONDITIONS WILL PERSIST FOR THE GULF COAST REGION
THROUGH EARLY NEXT WEEK WITH SOME PLACES LIKELY RECORDING THE
WARMEST AUGUST ON RECORD***
..SYNOPTIC OVERVIEW
RELIEF FROM ONGOING RECORD-BREAKING HEAT WAVE WILL FINALLY ARRIVE
THIS WEEKEND FOR MUCH OF THE CENTRAL U.S. AS THE UPPER LEVEL RIDGE
IS SUPPRESSED TO THE SOUTHWEST. HOT AND HUMID CONDITIONS WILL
LINGER LONGER ALONG THE GULF COAST, LASTING THROUGH MONDAY, AND
MULTIPLE DAILY RECORD HIGH MAX AND MIN TEMPERATURES WILL BE
POSSIBLE. UPPER LEVEL TROUGHING WILL STRENGTHEN OVER THE EASTERN
HALF OF THE NATION, DRIVING SEVERAL FRONTAL SYSTEMS THAT WILL
CREATE A HEAVY RAINFALL THREAT IN PARTS OF THE CENTRAL HIGH
PLAINS, MID-MISSISSIPPI VALLEY, AND THE CAROLINAS. RAIN WILL ALSO
RETURN TO THE PACIFIC NORTHWEST MID-NEXT WEEK AS AN UPPER LEVEL
LOW MOVES ONSHORE. THE NATIONAL HURRICANE CENTER IS ALSO
MONITORING A DISTURBANCE IN THE CARIBBEAN THAT MAY BRING HEAVY
RAINFALL TO PARTS OF THE SOUTHEAST LATE NEXT WEEK.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE REMAINS IN GOOD AGREEMENT ON THE SYNOPTIC PATTERN
OVER THE PERIOD, ESPECIALLY THE ENSEMBLE MEANS. SLIGHT DIFFERENCES
IN THE POSITIONS AND TRACKS OF LOW PRESSURE SYSTEMS APPEAR IN THE
DETERMINISTIC SOLUTIONS, BUT ARE RELATIVELY MINOR. A PURE
DETERMINISTIC MODEL BLEND WITH NEARLY EVEN AMOUNTS OF THE
CMC/GFS/ECMWF/UKMET WAS USED FOR THE FIRST HALF OF THE PERIOD TO
PRODUCE A MIDDLE OF THE ROAD SOLUTION, AND ENSEMBLE MEANS WERE
BLENDED WITH THE DETERMINISTIC GFS/ECMWF FOR THE SECOND HALF OF
THE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
SHOWERS AND THUNDERSTORMS ARE EXPECTED TO BE PREVALENT FROM
EASTERN COLORADO AND EXTENDING INTO PORTIONS OF EASTERN NEW MEXICO
AND NORTHWESTERN TEXAS SUNDAY AND INTO MONDAY AS A COUPLE OF
CONVECTIVE COMPLEXES ARE LIKELY TO DEVELOP. A MARGINAL RISK OF
EXCESSIVE RAINFALL IS IN EFFECT FOR BOTH OF THESE DAYS WHERE SOME
SLOW MOVING STORMS COULD DEVELOP AND PRODUCE LOCALIZED INSTANCES
OF FLOODING. IN THE EAST, A STALLED FRONTAL BOUNDARY ALONG THE
SOUTHEAST AND GULF COASTS AND AN APPROACHING COLD FRONT FROM THE
NORTH WILL CREATE RAIN CHANCES EARLY NEXT WEEK IN THE
MID-MISSISSIPPI VALLEY ON SUNDAY AND IN THE CAROLINAS SUNDAY AND
MONDAY. THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL IN EFFECT
FOR THESE AREAS AS WELL.
THE NATIONAL HURRICANE CENTER IS MONITORING THE POTENTIAL
DEVELOPMENT OF A TROPICAL SYSTEM THAT COULD BRING A HEAVY RAIN
THREAT TO PARTS OF THE SOUTHEAST MID-NEXT WEEK. THERE IS STILL A
SIGNIFICANT AMOUNT OF UNCERTAINTY CONCERNING THE HEAVY RAINFALL
POTENTIAL, BUT WE WILL BE MONITORING THE SITUATION CLOSELY.
TROPICAL MOISTURE AHEAD OF THE SYSTEM WILL REACH SOUTH FLORIDA ON
MONDAY, AND THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN
EFFECT. THE RAINFALL THREAT IS FORECAST TO SPREAD NORTH THROUGH
MID-WEEK.
ELSEWHERE, SHOWERS AND A FEW STORMS ARE LIKELY FROM THE GREAT
LAKES TO NEW ENGLAND FOR THE FIRST HALF OF THE WEEK, AND
WASHINGTON STATE MAY ALSO GET SOME BENEFICIAL RAINFALL BY TUESDAY
AND WEDNESDAY AS A FRONTAL SYSTEM MOVES ONSHORE.
ALTHOUGH THE HEATWAVE WILL HAVE CONCLUDED ACROSS THE MIDWEST AND
OHIO VALLEY, IT WILL STILL BE QUITE HOT AND UNCOMFORTABLE FROM
TEXAS TO SOUTH CAROLINA THIS WEEKEND, WITH WIDESPREAD 100+ DEGREE
HIGHS EXPECTED ON SUNDAY. THIS MAY ESTABLISH ADDITIONAL DAILY
RECORD HIGHS AND PROBABLY SECURE THE HOTTEST AUGUST ON RECORD FOR
MANY GULF COAST AND SOUTHERN CITIES. THE HEAT FINALLY ABATES A
LITTLE ACROSS THE GULF COAST REGION GOING INTO TUESDAY AND
WEDNESDAY WITH NEAR TO JUST ABOVE NORMAL HIGHS EXPECTED.
UNFORTUNATELY, HEAT IS FORECAST TO BUILD AGAIN ACROSS THE LOWER
ELEVATIONS OF THE DESERT SOUTHWEST WITH SOME 110S LIKELY BY THE
WEEKEND AND EARLY NEXT WEEK, BUT THIS SHOULD ALSO ABATE SOME BY
WEDNESDAY AND BEYOND.
DOLAN/HAMRICK
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, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES ARE AT:
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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