629
FXUS02 KWBC 111901
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SUN JUN 11 2023
VALID 12Z WED JUN 14 2023 - 12Z SUN JUN 18 2023
...HEAVY RAIN AND STRONG THUNDERSTORM THREAT FROM THE CENTRAL
PLAINS/MID-SOUTH TO THE SOUTHEAST OVERTOP A BUILDING HEATWAVE DOME
FROM TEXAS TO THE LOWER MISSISSIPPI VALLEY THIS WEEK...
..SYNOPTIC OVERVIEW
THE ONGOING BLOCKY PATTERN OVER THE NATION HAS PROVEN SLOW TO
DISLODGE, BUT WILL TRANSITION THIS WEEK. THIS IS EXPECTED AS UPPER
TROUGH ENERGIES SPLIT/EXIT THE SOUTHWEST AND WITH THE GRADUAL
EJECTION OF A NEW ENGLAND CLOSED LOW POSITION AS UPPER TROUGHING
WORKS FROM WESTERN CANADA AND THE NORTHWESTERN U.S. TO
MID-CONTINENT, LEADING TO SEVERAL LEAD ROUNDS OF SHOWERS AND
THUDERSTORMS ACROSS THAT BROAD AREA. A WARMING UPPER RIDGE WILL
BUILD OVER TEXAS AND THE GULF COAST REGION. A WAVY FRONTAL DRAPE
OVERTOP THE RIDGE FROM THE SOUTH-CENTRAL U.S. TO THE SOUTHEAST
ALONG WITH EJECTING SOUTHERN STREAM UPPER LEVEL SHORTWAVE
DISTURBANCES ARE LIKELY TO RESULT IN MULTIPLE ROUNDS OF HEAVY
SHOWERS AND THUNDERSTORMS FROM THE CENTRAL PLAINS TO THE SOUTHEAST
STATES AS AN EXCESSIVE HEAT THREAT TAKES HOLD SOUTH OF THE FRONT
FROM TEXAS TO THE CENTRAL GULF COAST.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
COMPOSITE BLEND OF REASONABLY WELL CLUSTERED GUIDANCE FROM THE 06
UTC GFS AND 00 UTC CANADIAN/UKMET AND SUPPORTIVE GEFS/ECMWF
ENSEMBLE MEAN GUIDANCE ALONG WITH 13 UTC NATIONAL BLEND OF MODELS
FOR THE COMING WEEK IN AN OVERALL PATTERN WITH SEEMINGLY ABOVE
NORMAL TO AVERAGE PREDICTABILITY. THE 00 UTC ECMWF SEEMS AN
OUTLIER PROGRESSIVE RUN FROM THE NORTHEAST PACIFIC TO
MID-CONTINENT COMPARED TO PRIOR ECMWF RUNS AND THE AFOREMENTIONED
COMPOSITE BLEND, BUT THE LATEST 12 UTC RUN HAS TRENDED A BIT BACK
INTO THE FOLD.
..WEATHER/HAZARDS HIGHLIGHTS
THE MAIN FOCUS FOR HEAVY RAINFALL IS EXPECTED ACROSS PORTIONS OF
THE SOUTH/SOUTHEAST MID-LATER WEEK, WHERE AN AXIS OF 1-2+ INCH
RAINFALL TOTALS WITH LOCALLY HIGHER AMOUNTS IS LIKELY GIVEN
POTENTIAL FOR SLOW CELL MOTIONS AND CONVECTIVE TRAINING. THERE
HAS BEEN A RECENT TREND OVER THE PAST 24 HOURS FOR THE AXIS OF
HEAVIEST RAINFALL TO BE MORE TOWARDS THE SOUTH COMPARED TO EARLIER
FORECASTS, AND ALSO A SLIGHT REDUCTION IN THE MAGNITUDE OF THE
EXPECTED RAINFALL. MOISTURE ADVECTION FROM THE GULF OF MEXICO
WILL INTERSECT A QUASI-STATIONARY/WARM FRONTAL BOUNDARY AND
SHORTWAVE ENERGY ALOFT WILL ALSO AID IN ASCENT. A FEW MESOSCALE
CONVECTIVE COMPLEXES ARE LIKELY TO DEVELOP NEAR THIS BOUNDARY AND
RESULT IN HIGHER RAINFALL RATES THAT COULD RESULT IN SOME
INSTANCES OF FLASH FLOODING, AND THUS A SLIGHT RISK OF EXCESSIVE
RAINFALL IS PLANNED FOR THE NEW DAY 4 ERO FROM NORTHERN ALABAMA TO
CENTRAL SOUTH CAROLINA WHERE DETERMINISTIC AND ENSEMBLE GUIDANCE,
ALONG WITH THE NBM, HAS THE MOST CONCENTRATED SIGNAL FOR HIGHER
QPF. ELSEWHERE, SOME SHOWERS ARE LIKELY FROM THE GREAT LAKES TO
THE NORTHEAST AS MOISTURE PIVOTS AROUND THE UPPER LEVEL LOW. FOR
THE DAY 5 PERIOD, PATCHY AREAS OF HEAVY RAIN ARE POSSIBLE ACROSS
PORTIONS OF THE CENTRAL AND NORTHERN PLAINS, BUT THE LACK OF MODEL
AGREEMENT PRECLUDES ANYTHING HIGHER THAN A MARGINAL RISK AT THIS
TIME.
IN TERMS OF TEMPERATURES, THE MAIN STORY THAT WILL MAKE HEADLINES
WILL BE THE PERSISTENT HEAT AND HUMIDITY ACROSS MUCH OF TEXAS AND
INTO SOUTHERN PORTIONS OF THE DEEP SOUTH STATES, WITH THE HOTTEST
WEATHER OF THE SEASON EXPECTED THUS FAR. WIDESPREAD MID-UPPER 90S
ARE LIKELY FROM NORTHERN FLORIDA TO LOUISIANA, AND 100-110 DEGREES
FOR MUCH OF CENTRAL AND ESPECIALLY SOUTHERN TEXAS AWAY FROM THE
COASTAL AREAS. SOME HEAT INDICES ON THE ORDER OF 110-120 DEGREES
ARE POSSIBLE ACROSS PORTIONS OF DEEP SOUTH TEXAS FOR THE MIDDLE TO
END OF THE WEEK WITH DEWPOINTS WELL INTO THE 70S. THIS HEAT WAVE
WILL LIKELY HAVE SOME STAYING POWER BEYOND NEXT SATURDAY BASED ON
THE LATEST FORECASTS FROM THE CLIMATE PREDICTION CENTER.
ELSEWHERE, EXPECT SLIGHTLY COOLER CONDITIONS COMPARED TO AVERAGE
ACROSS MUCH OF THE SOUTHWEST TO THE CENTRAL ROCKIES, AND ALSO FOR
MUCH OF THE EASTERN U.S. FOR THE MIDDLE OF THE WEEK, AND THEN A
GRADUAL WARMING TREND GOING INTO THURSDAY AND BEYOND.
SCHICHTEL/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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES 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
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