325
FXUS02 KWBC 110700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT SUN JUN 11 2023
VALID 12Z WED JUN 14 2023 - 12Z SUN JUN 18 2023
...HEAVY RAIN AND STRONG STORMS EXPECTED FROM THE CENTRAL PLAINS
TO THE MID-SOUTH, AND SUMMER HEAT BUILDS FROM TEXAS TO THE LOWER
MISSISSIPPI VALLEY...
..SYNOPTIC OVERVIEW
A RATHER BLOCKY UPPER LEVEL PATTERN APPEARS LIKELY TO REMAIN THE
CASE GOING INTO THE MIDDLE TO END OF THE WEEK, WITH A BROAD UPPER
LOW ANCHORED IN PLACE ACROSS SOUTHEASTERN CANADA AND NEW ENGLAND,
A TROUGH OVER WESTERN CANADA INTO THE NORTHWESTERN U.S., AND A
BUILDING UPPER RIDGE OVER THE GULF COAST REGION AND INTO CENTRAL
TEXAS. A WAVY FRONTAL BOUNDARY SITUATED OVER THE SOUTH-CENTRAL
U.S. ALONG WITH WEAK UPPER LEVEL SHORTWAVE DISTURBANCES IS LIKELY
TO RESULT IN MULTIPLE ROUNDS OF HEAVY SHOWERS AND THUNDERSTORMS
FROM THE CENTRAL PLAINS TO THE SOUTHEAST STATES, AND A HEAT WAVE
SOUTH OF THE BOUNDARY FROM CENTRAL TEXAS TO THE CENTRAL GULF
COAST. BY NEXT WEEKEND, ANOTHER COLD FRONT IS LIKELY TO DROP
SOUTH ACROSS THE PACIFIC NORTHWEST AND NORTHERN ROCKIES WITH
ADDITIONAL ROUNDS OF SHOWERS AND STORMS.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE 00Z MODEL GUIDANCE SUITE INITIALLY HAS A VERY GOOD OVERALL
DEPICTION OF THE SYNOPTIC SCALE PATTERN ACROSS THE CONTINENTAL
U.S. ON WEDNESDAY, AND THEREFORE A MULTI-DETERMINISTIC MODEL BLEND
SUFFICES AS A STARTING POINT IN THE FORECAST PROCESS. THE GFS AND
TO A SLIGHTLY LESSER DEGREE THE GEFS MEAN ARE MORE AMPLIFIED WITH
THE SHORTWAVE TRACKING ACROSS THE DEEP SOUTH GOING INTO THURSDAY,
AND THIS SOLUTION HAS THE AXIS OF HEAVIEST RAINFALL SOUTH OF THE
MULTI-MODEL CONSENSUS. MORE NOTABLE DIFFERENCES BECOME APPARENT
WITH THE NEXT SHORTWAVE TROUGH BUILDING IN ACROSS THE NORTHWESTERN
U.S., WITH THE GFS BEING CONSIDERABLY STRONGER AND THE CMC QUITE
WEAK WITH IT, SO THE ECMWF SERVES AS A GOOD MIDDLE GROUND SOLUTION
GOING INTO NEXT WEEKEND ACROSS THIS REGION. THERE ARE ALSO
CONSIDERABLE DIFFERENCES REGARDING THE EXTENT OF A RIDGE AXIS
ACROSS THE CENTRAL U.S. BY NEXT SUNDAY, AND OVERALL FORECAST
CONFIDENCE IS BELOW AVERAGE BY THAT TIME WITH SIGNIFICANT FORECAST
CHANGES POSSIBLE IN THE DAYS AHEAD. THE ENSEMBLE MEANS ACCOUNTED
FOR ABOUT HALF OF THE FORECAST BLEND BY NEXT WEEKEND.
..WEATHER/HAZARDS HIGHLIGHTS
THE MAIN FOCUS FOR HEAVY RAINFALL IS EXPECTED ACROSS PORTIONS OF
THE DEEP SOUTH AND INTO SOUTH CAROLINA FOR THE WEDNESDAY AND
THURSDAY TIME PERIOD, 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.
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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