460
FXUS62 KCAE 181023
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
623 AM EDT THU JUN 18 2026
WHAT HAS CHANGED
POTENTIAL FOR STRONGER NON-THUNDERSTORM WINDS LATE
TONIGHT/EARLY FRIDAY IS ON THE INCREASE, BUT PLENTY OF
UNCERTAINTY REMAINS. THE POTENTIAL FOR A SWATH OF LOCALLY HEAVY
RAIN IN OR NEAR THE AREA HAS ALSO INCREASED.
KEY MESSAGES
- 1. GUSTY WINDS, HEAVY RAINFALL, AND SEVERE WEATHER ARE
POSSIBLE THIS AFTERNOON INTO FRIDAY.
- 2. A MORE TYPICAL SUMMER-LIKE PATTERN RETURNS FOR THE WEEKEND
INTO NEXT WEEK.
DISCUSSION
KEY MESSAGE 1: GUSTY WINDS, HEAVY RAINFALL, AND SEVERE WEATHER ARE
POSSIBLE THIS AFTERNOON INTO FRIDAY.
OVERVIEW: ACTIVE WEATHER IS LIKELY STARTING THIS AFTERNOON,
CONTINUING OVERNIGHT AND INTO FRIDAY AS THE REMNANTS OF ARTHUR
MOVE INTO THE REGION. ARTHUR AND ITS COUPLED UPPER WAVE CAN BE
SEEN ALONG/NEAR THE LA COASTLINE EARLY THIS MORNING, AND THIS
SHOULD CONTINUE TO GRADUALLY MOVE NORTHEASTWARD, MOVING INLAND
(AND WEAKENING) INTO THE LOWER MISSISSIPPI VALLEY AND INTO THE
GULF STATES. THE REMNANT LOW LEVEL CIRCULATION ASSOCIATED WITH
ARTHUR AND UPPER WAVE ARE EXPECTED TO DRIFT NORTHEASTWARD
THROUGH THE DAY, INCREASING DEEP MOISTURE ACROSS THE FA WITH
STRENGTHENING WIND FIELDS. A VERY MOIST AIRMASS BY THE AFTERNOON
HOURS SHOULD AID IN BRINGING SCATTERED SHOWER AND THUNDERSTORM
DEVELOPMENT, MAINLY IN THE CSRA, WHERE A COUPLE STRONG TO
SEVERE STORMS CANNOT BE RULED OUT. THIS THREAT IS EXPECTED TO
CONTINUE INTO THE EVENING WHERE A LOW TORNADO RISK COULD DEVELOP
MAINLY TOWARD THE CSRA, BUT CONFIDENCE IN THIS RISK
MATERIALIZING REMAINS RATHER LOW AT THE MOMENT. BY LATE THIS
EVENING, THE BULK OF MOISTURE IS EXPECTED TO OVERSPREAD THE
CWA, WITH SCATTERED TO WIDESPREAD SHOWERS AND STORMS MOVING IN,
CONTINUING INTO FRIDAY MORNING BEFORE COVERAGE MAY DECREASE A
BIT. THE MAIN RISK OVERNIGHT CONTINUES TO BE THE HEAVY RAIN
POTENTIAL WHERE PORTIONS OF THE CWA ARE IN A SLIGHT RISK (LEVEL
2 OUT OF 4) FOR EXCESSIVE RAINFALL. STRENGTHENING LOW LEVEL WIND
FIELDS THIS AFTERNOON AND A TIGHTENING SURFACE PRESSURE
GRADIENT SHOULD ALSO AID IN BRINGING 25-30 MPH WIND GUSTS, WHERE
ISOLATED GUSTS TOWARD 35-45 MPH CANNOT BE RULED OUT MAINLY INTO
THE OVERNIGHT PERIOD. CONDITIONS ARE EXPECTED TO GRADUALLY
IMPROVE FRIDAY MORNING BEFORE A COLD FRONT PUSHES THROUGH DURING
THE AFTERNOON/EVENING WITH ADDITIONAL SHOWER AND STORM CHANCES
THAT END BY THE LATE EVENING.
HEAVY RAINFALL: THE PRIMARY THREAT FROM THIS SYSTEM REMAINS TO
BE THE HEAVY RAINFALL POTENTIAL AS VERY EFFICIENT RAIN RATES ARE
LIKELY DUE IN PART TO THE HIGH PWAT VALUES, ESPECIALLY LATE
THIS EVENING AND INTO FRIDAY MORNING. SPEAKING OF HIGH PWAT
VALUES, THEY ARE EXPECTED TO INCREASE TOWARD 2" BY EARLY THIS
AFTERNOON, BEFORE SURGING TOWARD 2.20-2.40" DURING THE EVENING
AND OVERNIGHT PERIOD. AS THIS MOISTURE INCREASES WITH THE
APPROACHING UPPER WAVE AND REMNANT LOW LEVEL CIRCULATION, IVT
VALUES REACH TOWARD THE NAEFS 99TH TO 99.5TH PERCENTILE. THIS IS
MOSTLY THANKS TO A SLIGHT SHIFT IN A FEW HIGH-RES AND GLOBAL
MODELS KEEPING THE LOW TO MID LEVEL CORE OF THE SYSTEM A BIT
MORE INTACT, LEADING TO A 35-55 KT LLJ OVERSPREADING THE AREA
THIS EVENING AND OVERNIGHT. SOME GUIDANCE INDICATES THIS LLJ
COULD BE EVEN STRONGER. FOR EXAMPLE, THE ECMWF AND NAM 3K MODELS
SHOW A 70 KT LLJ. THIS INCREASING LLJ COUPLED WITH THE
AFOREMENTIONED PWAT'S, WARM CLOUD LAYER DEPTHS EXCEEDING 14,000
FT, AND ELEVATED INSTABILITY SETS THE STAGE FOR EFFICIENT RAIN
RATES. IN TERMS OF TOTALS, THE LATEST MEAN HREF AND REFS
SOLUTIONS CONTINUE TO SUPPORT A WIDESPREAD 0.75-1.25" ACROSS
THE FA. WHEN TAKING A LOOK AT THE LPMM PRODUCT FROM EACH SUITE
AND INDIVIDUAL 00Z CAM'S SPOTS OF 2-3.5" ARE SEEN WHERE
TRAINING OCCURS WITH THE EXPECTED RATES. THIS SEEMS REASONABLE
CONSIDERING THE LLJ MAY ENHANCE THE EFFICIENCY OF THIS RAINFALL
MORE THAN PREVIOUSLY DISCUSSED. THE LOCATION OF THIS POTENTIAL
POCKET OF HEAVY RAIN IS TOO DIFFICULT TO PIN DOWN, BUT RECENT
GUIDANCE INDICATES A POCKET IN OR VERY NEAR THE FORECAST AREA
IS VERY MUCH A POSSIBILITY. WITH THE HEAVIER AMOUNTS BEING
RATHER ISOLATED, DON'T THINK A FLOOD WATCH IS WARRANTED, BUT A
FEW INSTANCES OF NUISANCE OR FLASH FLOODING ARE POSSIBLE IN THE
LOCATIONS THAT RECEIVE THE HEAVIEST RAIN.
SEVERE WEATHER: THE WHOLE FA IS OUTLINED IN SPC'S MARGINAL RISK
(LEVEL L OUT OF 5) FOR SEVERE WEATHER TODAY. AT LEAST MODEST
HEATING IN AN INCREASINGLY MOIST AIRMASS IS EXPECTED TO YIELD
MLCAPE VALUES NEAR 1200-1700 J/KG WITH INCREASING DEEP LAYER
SHEAR AS THE REMNANT SURFACE CIRCULATION AND UPPER WAVE NEAR.
INCREASED MIXING IN THE AFTERNOON ALSO IS EXPECTED TO YIELD
DCAPE VALUES NEAR 700-1000 J/KG WITH TEI VALUES NEARING 25.
ISOLATED TO SCATTERED STORMS IN THE AFTERNOON ARE EXPECTED TO
BRING THE MAIN RISK OF STRONG TO DAMAGING WIND GUSTS FROM PRECIP
LOADED DOWNDRAFTS, BUT ALSO FROM POSSIBLE COLD POOL
CONSOLIDATION IN ANY CLUSTER. THERE REMAINS A LOW END TORNADO
RISK THAT MAY DEVELOP MAINLY NEAR THE CSRA DURING THE EVENING
INTO THE EARLY OVERNIGHT HOURS. NEAR SURFACE WINDS ARE EXPECTED
TO BACK A BIT AS THE REMNANT SURFACE CIRCULATION NEARS AND THE
AFOREMENTIONED LLJ MOVES IN. MODELED SOUNDINGS INDICATE 0-1KM
BULK SHEAR SHOULD INCREASE TOWARD 25-30 KTS DURING THE EVENING
WITH 0-1KM SRH NEARING 125-200 M^2/S^2 AND THIS IS FURTHER
SUPPORTED IN THE 00Z MEAN HREF SOLUTION. THIS RISK CONTINUES TO
BE CONDITIONAL HOWEVER ON THE AMOUNT OF LOW LEVEL INSTABILITY
THAT CAN REMAIN IN PLACE DURING THE EVENING. THE SEVERE WEATHER
RISK IS EXPECTED TO GRADUALLY DIMINISH OVERNIGHT WITH THE
PROBABILITY FOR CONVECTION TO BECOME ELEVATED INCREASING.
WIND GUSTS: AS MENTIONED IN THE OVERVIEW, INCREASING WIND
PROFILES WITH A TIGHTENING SURFACE PRESSURE GRADIENT ARE
EXPECTED TO YIELD WIND GUSTS TO 25-30 MPH THROUGH THE AFTERNOON
AND INTO THE EVENING HOURS TODAY. OVERNIGHT GETS A LITTLE MORE
INTERESTING IN REGARDS TO THE POTENTIAL FOR STRONGER WIND GUSTS.
AS MENTIONED EARLIER, A STRONG LLJ IS EXPECTED TO MOVE OVER THE
AREA AS THE REMNANTS OF ARTHUR MOVE INTO THE REGION.
THE 18Z AND 00Z SUITE OF MODEL SOLUTIONS SHOE THAT THE CORE OF
THIS SYSTEM STAYS INTACT OR POTENTIALLY REDEVELOPS OVER THE
AREA. AS SUCH DETERMINISTIC SOLUTIONS INDICATE 30-45 MPH GUSTS,
WITH SOME HIGHER GUSTS POSSIBLE, COULD OCCUR IN THE EASTERN
PORTIONS OF THE FORECAST AREA. THE CAMS ARE GENERALLY ON THE
LOWER END OF THAT SPECTRUM. HREF AND REFS PROBABILITIES OF OVER
40 MPH HAVE INCREASED TO GENERALLY 30-40% IN AREAS SOUTH AND
EAST OF I-20. THE TIMING OF THESE GUSTS LOOK TO BE EARLY FRIDAY
MORNING, SO THERE IS A BIG QUESTION MARK WHETHER THE STRONG LLJ
WINDS ARE ABLE TO MIX DOWN. REGARDLESS, IT IS WORTH PAYING
ATTENTION TO THIS POTENTIAL AND WE'LL CONTINUE TO EVALUATE THIS
THREAT TODAY AND TONIGHT.
KEY MESSAGE 2: A MORE TYPICAL SUMMER-LIKE PATTERN RETURNS FOR
THE WEEKEND INTO NEXT WEEK.
AFTER THE REMNANTS OF ARTHUR MOVE OUT OF THE AREA, MORE ZONAL
FLOW IS EXPECTED TO SETTLE OVER THE REGION. MULTIPLE
DISTURBANCES ARE FORECAST TO MOVE THROUGH THE GENERAL FLOW,
BRINGING A MORE SUMMER-LIKE PATTERN OF DIURNAL THUNDERSTORM
CHANCES AS WE HEAD INTO THE WEEK AHEAD.
AVIATION /12Z THURSDAY THROUGH MONDAY/
CEILING RESTRICTIONS THIS MORNING AND EXPECTED AGAIN TONIGHT.
INCREASING RAIN AND THUNDERSTORMS CHANCES THIS AFTERNOON THROUGH
TONIGHT.
AN AREA OF MVFR/IFR STRATUS HAS SPREAD INTO THE FORECAST AREA
EARLY THIS MORNING KEEPING RESTRICTIONS IN THE TAFS THROUGH
MID-MORNING. GUSTS WILL PICK UP OUT OF THE SW AROUND 20 KTS AT
OR SHORTLY AFTER 14Z.
A SURFACE LOW WILL LIFT INTO THE SOUTHEAST TODAY AND TONIGHT
LEADING TO STRONG MOISTURE ADVECTION AND STRONG LOW LEVEL WINDS.
SURFACE WINDS WILL GUST FROM 20 TO 25 KTS THIS AFTERNOON. A 40
TO 50 KT LLJ WILL MOVE INTO THE AREA TONIGHT. WINDS WILL STAY
UP AROUND 10 KTS THROUGH THE NIGHT WITH GUSTS FROM 20 TO 30 KTS
KTS POSSIBLE FROM 06 TO 12Z.
SHOWERS AND THUNDERSTORMS BECOME INCREASINGLY LIKELY AFTER 21Z.
RAIN SHOULD MOVE FROM WEST TO EAST WITH AGS, DNL AND AIK MOST
LIKELY TO SEE RAINFALL AND REDUCED VISIBILITIES BEFORE 00Z. THE
HEAVIER RAIN IS MORE LIKELY AFTER 00Z WHEN THE LLJ AND STRONG
MOISTURE ADVECTION MOVES OVER THE REGION. PERIODS OF HEAVY RAIN
AND RESTRICTIONS WILL BE POSSIBLE THROUGH 12Z FRIDAY.
EXTENDED AVIATION OUTLOOK...A FRONT MOVES THROUGH DURING THE DAY
FRIDAY, KEEPING SHOWERS AND STORMS IN THE FORECAST. DIURNALLY
DRIVEN CONVECTION CAN BE ANTICIPATED HEADING INTO THE WEEKEND.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
DISCUSSION...29
AVIATION...CJR
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