952
FXUS62 KCAE 271739
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
139 PM EDT SAT JUN 27 2026
WHAT HAS CHANGED
A LOW END SEVERE THREAT IS POSSIBLE BOTH TODAY AND SUNDAY WITH
SCATTERED CONVECTION. AVIATION DISCUSSION UPDATED FOR 18Z TAFS.
KEY MESSAGES
- 1. SCATTERED AFTERNOON SHOWERS AND STORMS EACH DAY THROUGH
MONDAY. ISOLATED SEVERE STORMS POSSIBLE TODAY AND SUNDAY.
- 2. PROLONGED HOT PATTERN EXPECTED WITH DANGEROUS HEAT POSSIBLE
THIS WEEKEND AND A SIGNAL FOR A MORE IMPACTFUL, INTENSE HEAT
EVENT BY THE END OF NEXT WEEK.
DISCUSSION
KEY MESSAGE 1: SCATTERED AFTERNOON SHOWERS AND STORMS EACH DAY
THROUGH MONDAY. ISOLATED SEVERE STORMS POSSIBLE TODAY AND
SUNDAY.
AS UPPER-LEVEL RIDGING BEGINS TO BUILD INTO THE REGION NEXT
WEEK, A COUPLE OF WEAK SHORTWAVES ARE EXPECTED TO PASS NEARBY
TODAY AND SUNDAY. DEW POINTS INTO THE LOW TO MID 70S, PWATS
AROUND 2.0", AND STRONG SURFACE HEATING WILL PROMOTE ROBUST
DESTABILIZATION EACH AFTERNOON THIS WEEKEND, WITH SIMILAR
CONDITIONS POSSIBLE AGAIN ON MONDAY. IN THIS MOISTURE RICH
ENVIRONMENT WITH MLCAPE VALUES BETWEEN 1500-2000 J/KG, ONLY
SUBTLE FORCING IS NEEDED TO INITIATE SHOWERS AND THUNDERSTORMS.
A FEW STORMS MAY BECOME STRONG TO SEVERE, AS STEEP LOW-LEVEL
LAPSE RATES AND MODEST LOW-LEVEL SHEAR SUPPORT STORM CLUSTERING
CAPABLE OF PRODUCING DAMAGING WIND GUSTS.
ANOTHER ROUND OF CONVECTION IS POSSIBLE ON SUNDAY AS AN UPPER-
LEVEL RIDGE STRENGTHENS OVER THE LOWER MS VALLEY. THIS PATTERN
WILL PLACE THE AREA BENEATH NORTHWESTERLY FLOW, ALLOWING
CONVECTION TO PROPAGATE DOWNSTREAM FROM THE RIDGE AXIS. DEEPER
BOUNDAY LAYER MIXING IS EXPECTED TOMORROW AFTERNOON, RESULTING
IN INVERTED-V SOUNDINGS AND DCAPE VALUES BETWEEN 700-1000 J/KG,
WHICH WOULD FAVOR STRONG DOWNDRAFT AND DAMAGING WINDS. THE
EXTENT OF SUNDAYS CONVECTIVE THREAT WILL DEPEND IN PART ON HOW
TODAYS CONVECTION EVOLVES. THE LATEST CAMS SUGGEST A WEAKENING
MCS MAY MOVE ACROSS NEIGHBORING FAS SUNDAY MIDDAY. WHILE THE
SYSTEM IS EXPECT TO WEAKEN AS IT APPROACHES, IT COULD STILL
PROVIDE SUFFICIENT FORCING FOR A FEW STRONGER STORMS,
PARTICULARLY IF IT ARRIVES DURING PEAK HEATING. SPC HAS JUST PUT
MUCH OF THE NORTH AND EASTERN PORTIONS OF THE CWA IN A MARGINAL
(LEVEL 1) RISK FOR SEVERE WEATHER TOMORROW.
LINGERING MOISTURE IS EXPECTED TO BRING ANOTHER
AFTERNOON/EVENING WITH SCATTERED SHOWERS AND STORMS MONDAY.
HOWEVER, THERE IS LESS CONFIDENCE FOR ANY ISOLATED STRONG TO
SEVERE STORMS.
KEY MESSAGE 2: PROLONGED HOT PATTERN EXPECTED WITH DANGEROUS
HEAT POSSIBLE THIS WEEKEND AND A SIGNAL FOR A MORE IMPACTFUL,
INTENSE HEAT EVENT BY THE END OF NEXT WEEK.
THE PRIMARY STORY OVER THE NEXT 7-10 DAYS WILL BE A PROLONGED
STRETCH OF HOT AND HUMID CONDITIONS. A STRENGTHENING UPPER-LEVEL
RIDGE WILL BECOME ESTABLISHED OVER THE LOWER MS VALLEY THIS
WEEKEND BEFORE GRADUALLY EXPANDING EASTWARD. BY THE MIDDLE OF
NEXT WEEK, MOST DETERMINISTIC AND ENSEMBLE GUIDANCE PLACES THE
CENTER OF THE CLOSED RIDGE OVER THE EASTERN CONUS, SUPPORTING
AFTERNOON HIGHS IN THE MID TO UPPER 90S WITH DEW POINTS IN THE
LOW TO MID 70S. HEAT INDICES ARE ARE EXPECTED TO RANGE BETWEEN
100-105F TODAY AND TOMORROW, ALTHOUGH SCATTERED AFTERNOON
CONVECTION COULD PROVIDE LOCALIZED RELIEF.
MONDAY AND TUESDAY WILL SERVE AS TRANSITION DAYS AS A DEEP
WESTERN US TROUGH AMPLIFIES THE DOWNSTREAM RIDGE TO NEAR THE
99.5TH PERCENTILE OF THE NAEFS CLIMATOLOGY. TEMPERATURES WILL
REMAIN HOT, GENERALLY IN THE MID TO UPPER 90S, BUT STRENGTHENING
SURFACE HIGH PRESSURE OVER THE NORTHEAST SHOULD ADVECT SLIGHTLY
DRIER AIR MIDWEEK. LOWER DEW POINTS COMBINED WITH DEEPER
AFTERNOON MIXING AND LOW-LEVEL SUBSIDENCE BENEATH THE RIDGE
SHOULD ALLOW HEAT INDICES TO BACK OFF A BIT AND BE CLOSER TO THE
UPPER 90S TO AROUND 100 DEGREES WHILE ALSO SUPPRESSING ANY
CONVECTIVE DEVELOPMENT THROUGH MUCH OF THE WORK WEEK.
BY LATE WEEK, AND INTO THE HOLIDAY WEEKEND, GUIDANCE CONTINUES
TO MAINTAIN A STRONG UPPER RIDGE, WITH 850-MB TEMPERATURES
APPROACHING OR EXCEEDING 20C. THIS PATTERN FAVORS TEMPERATURES
INCREASING AGAIN, WITH HIGHS CLIMBING INTO THE UPPER 90S AND
POTENTIALLY 100 DEGREES, ESPECIALLY ON FRIDAY AND SATURDAY.
HUMIDITY IS ALSO LIKELY TO INCREASE RESULTING IN HEAT INDICES
THAT COULD EXCEED 105 DEGREES AND POTENTIALLY REACH OUR HEAT
ADVISORY CRITERIA. HOWEVER, AFTERNOON CONVECTION COULD LOCALLY
TEMPER MAX VALUES, BUT CONFIDENCE REMAINS TOO LOW IN COVERAGE TO
SIGNIFICANTLY ALTER THE HEAT FORECAST. BE SURE TO TAKE HEAT
SAFETY PRECAUTIONS AND MONITOR CHILDREN, THE ELDERLY, AND PETS.
ONE LAST THING TO NOTE, AS OF THIS MORNING, NHC PUT OUT A 20%
CHANCE FOR CYCLONE FORMATION OVER THE NEXT 7 DAYS JUST OFF THE
SC COAST. CONFIDENCE REMAINS LOW, AS ENSEMBLE GUIDANCE CONTINUES
TO SHOW CONSIDERABLE SPREAD ON DEVELOPMENT AND TRACK. HOWEVER,
ANY SYSTEM COULD ALTER THE EXPECTED HEAT PATTERN HEADING INTO
THE INDEPENDENCE DAY HOLIDAY, MAKING THIS FEATURE WORTH
MONITORING OVER THE COMING DAYS.
AVIATION /18Z SATURDAY THROUGH THURSDAY/
VFR CONDITIONS LIKELY INTO THIS EVENING WITH SCATTERED STORMS
EXPECTED TO PERIODICALLY IMPACT SITES.
UNSETTLED WEATHER IS FORECAST TO CONTINUE TODAY WITH ANOTHER
ROUND OF SHOWERS AND THUNDERSTORMS DEVELOPING CURRENTLY. THESE
STORMS ARE GENERALLY EXPECTED TO REMAIN RELATIVELY TAME IN THE
NEXT HOUR OR TWO BUT AS CONVECTION BECOMES A BIT MORE
WIDESPREAD, EXPECT A STRONG STORM OR TWO TO POTENTIALLY GIVE A
TAF SITE A WIND GUST EXCEEDING 30 KNOTS. HARD TO PINPOINT WHEN
AND WHERE THE STORMS ARE MOST LIKELY AT THIS POINT SO HAVE A
GENERIC PROB30 GROUP IN THROUGH THIS EVENING. THIS MAY NEED TO
BE AMENDED LATER TO ACCOUNT FOR ANY WIDESPREAD STORMS NEAR A
SITE. AS WE GET THROUGH THIS EVENING, THINGS SHOULD GENERALLY
CLEAR UP AFTER 00Z-02Z AS THE SUN SETS. DEBRIS CLOUDINESS IS
LIKELY TO HANG AROUND FOR SEVERAL HOURS BEFORE CLEARING UP
OVERNIGHT. LOOK FOR CLEAR SKIES INTO TOMORROW MORNING BEFORE
CUMULUS DEVELOPS AGAIN BY LATE MORNING. WINDS THROUGH THE PERIOD
SHOULD OSCILLATE BETWEEN LIGHT AND VARIABLE AND SOUTHWESTERLY
BETWEEN 6 AND 12 KNOTS.
EXTENDED AVIATION OUTLOOK...DIURNAL CONVECTION AND ASSOCIATED
RESTRICTIONS REMAIN POSSIBLE SUNDAY AND INTO THE EARLY WEEK
BEFORE SLIGHTLY DRIER AIR LIMITS RAIN CHANCES LATER IN THE WEEK.
BRIEF MORNING VSBY/CIG RESTRICTIONS ALSO POSSIBLE INTO EARLY
NEXT WEEK.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
DISCUSSION...ND
AVIATION...PL
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