279
FXUS62 KCAE 080512
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
112 AM EDT THU OCT 8 2026
WHAT HAS CHANGED
UPDATES RELATED TO HURRICANE ISAIAS. AVIATION DISCUSSION
UPDATED FOR 06Z TAFS.
KEY MESSAGES
- 1. AN ACTIVE WEEKEND AHEAD AS TROPICAL STORM ISAIAS MOVES INLAND
TO OUR WEST. CONFIDENCE IN THE EXTENT OF IMPACTS IS INCREASING BUT
REMAINS LOWER THAN NORMAL.
DISCUSSION
KEY MESSAGE 1: AN ACTIVE WEEKEND AHEAD AS TROPICAL STORM ISAIAS
MOVES INLAND TO OUR WEST. CONFIDENCE IN THE EXTENT OF IMPACTS IS
INCREASING BUT REMAINS LOWER THAN NORMAL.
OVERVIEW: MODERATE, TO AT TIMES, HEAVY RAINFALL APPEARS LIKELY AS
HURRICANE ISAIAS PASSES TO OUR WEST ON SATURDAY AND INTO SATURDAY
NIGHT. BREEZY, COOLISH, AND CLOUDY CONDITIONS ARE EXPECTED
OTHERWISE.
DISCUSSION: HURRICANE ISAIAS HAS DEVELOPED IN THE SOUTH-CENTRAL GULF
AS OF THE 11P 10/7 ADVISORY. GUIDANCE CONTINUES TO BE IN FAIRLY GOOD
AGREEMENT ON IT INTENSIFYING QUICKLY OVER THE NEXT 24-36 HOURS AS IT
TREKS NORTHEASTWARD AND BEGINS INTERACTING WITH AN UPPER LEVEL
TROUGH PUSHING EASTWARD OUT OF TEXAS. THERE IS STILL SOME SPREAD
BETWEEN THE AI & PHYSICS-BASED MODELS ON HOW FAR EAST ISAIAS
EVENTUALLY MAKES LANDFALL. THE IMPACTS TO THE MIDLANDS AND CSRA
ARE EXPECTED TO BE RELATIVELY UNCHANGED BASED ON WHICH PATH IT
EVENTUALLY TAKES.
ISAIAS WILL OVERSPREAD THE AREA WITH WIDESPREAD HIGH CLOUD COVER
OVER THE NEXT COUPLE OF DAYS AS THE SYSTEM INTERACTS WITH A REMNANT
TROUGH OVER TEXAS. THIS TROUGH WILL CONTINUE TO SHIFT THE ISAIAS
NORTHEASTWARD AND EVENTUALLY NORTHWARD AS THE NORTHERN/SOUTHERN
STREAM OF THE JET STREAK MERGE OVER THE MID-ATLANTIC AND EVERYTHING
GRADUALLY AMPLIFIES. THE RIGHT ENTRANCE REGION OF THIS UPPER LEVEL
JET STREAK IS FORECAST TO OVERSPREAD MUCH OF THE SOUTHEASTERN CONUS
BY FRIDAY AFTERNOON, HELPING MOISTURE ADVECTION TO BEGIN GOING TO
OUR SOUTH. AS ISAIAS MOVE NORTHWARD, IT WILL BEGIN INTERACTING WITH
THE OVERALL SYNOPTIC PATTERN & IS EXPECTED TO EXPAND IN SIZE,
PUSHING UP AGAINST A LOW-LEVEL HIGH PRESSURE SYSTEM & DEVELOP A
STRONG EASTERLY BRANCH OF THE LOW-LEVEL JET. THIS FEATURE, IN SOME
FORM OR FASHION, IS EXPECTED TO OVERSPREAD THE AREA DURING THE DAY
ON SATURDAY. AS IT DOES SO, SIGNIFICANT PWS ON THE ORDER OF 2-2.5
STANDARD DEVIATIONS ABOVE NORMAL (2.2"+) WILL OVERSPREAD THE
REGION.
THE SYNOPTIC PATTERN ASSOCIATED WITH THIS, FEATURING HIGH PWS, A
BROAD ENTRANCE REGION OF AN UPPER LEVEL JET, ONSHORE 850 HPA FLOW
ATOP A STRONG SURFACE HIGH PRESSURE, SHOULD FAVOR WIDESPREAD AND
HEAVY RAINFALL ON SATURDAY. HOWEVER, GUIDANCE IS FAIRLY BEARISH ON
OVERALL RAINFALL TOTALS. PART OF THIS DERIVES FROM SOME GUIDANCE
WANTING TO DEVELOP A SORT OF COASTAL LOW OR MORE FOCUSED TROUGH
ALONG THE LARGER SCALE IN-SITU WEDGE BOUNDARY THAT WILL BE IN
PLACE ALONG THE COAST. IT IS NOT ENTIRELY CLEAR WHY THIS
DEVELOPS; THE EXTRA-TROPICAL TRANSITION OF ISAIAS WILL BE WELL
TO THE WEST OF THIS BOUNDARY. THIS SETUP SHOULD NOT YIELD A
COASTAL LOW, BUT IN SOME MODEL SCENARIOS, A WEAK ONE DEVELOPS
AND FOCUSES MOISTURE TRANSPORT VECTORS MUCH MORE IN THE COASTAL
PLAIN AND NEARER TO THE BOUNDARY ALONG THE COAST AS OPPOSED TO
BEING MORE IN-LINE & ATTACHED TO ISAIAS' MOVEMENT. THIS PLAYS A
ROLE IN HOW MUCH RAIN WE MAY RECEIVE, AS WE WILL NEED
ISENTROPIC LIFT AND WARM ADVECTION TO BE THE PRIMARY FORCING
MECHANISMS FOR RAIN DEVELOPMENT ACROSS OUR AREA.
REGARDLESS OF THE MAGNITUDE, A RAINY DAY DOES LOOK TO BE ON TAP
ON SATURDAY. WE SHOULD SEE RAIN OVERSPREAD THE AREA IN THE
MORNING AND LAST IN WAVES THROUGH AT LEAST SATURDAY
EVENING/OVERNIGHT AS THE BEST WARM ADVECTION AND ONSHORE LOW-
LEVEL FLOW SHIFTS NORTHWARD. OVERALL TOTALS, AS MENTIONED
BEFORE, ARE UNCERTAIN. GUIDANCE IS NOT TIGHTLY CLUSTERED AROUND
A SOLUTION, WITH LREF MEMBERS PRESENTING A FAIRLY LARGE SPREAD
AMONGST GUIDANCE. OF NOTE IS THE LONG RIGHT-SHIFT IN THE
DISTRIBUTION OF ENSEMBLE SOLUTIONS, INDICATING STILL THE
POTENTIAL FOR HEAVY RAINFALL (3"+) ON SATURDAY. HOWEVER, THE
MAJORITY OF MEMBERS SUGGEST THAT 1"-3" OF RAINFALL IS MOST
LIKELY ACROSS THE AREA, WITH THE HEAVIEST TOTALS EXPECTED IN THE
EASTERN MIDLANDS. AS WITH ANY TROPICAL CYCLONE, A TORNADO
THREAT APPEARS POSSIBLE, ESPECIALLY IF THE AFOREMENTIONED FRONT
CAN SHIFT TO OUR NORTH. WE'LL LIKELY NEED 70F+ SURFACE DEWPOINTS
TO HELP ANY CIRCULATION MAKE IT TO THE SURFACE. THERE WILL BE
PLENTY OF SHEAR IN PLACE, SO IF WE CAN GET CONVECTION SOUTH OF
THIS BOUNDARY ON SATURDAY NIGHT A TORNADO THREAT COULD
MATERIALIZE. EMPHASIS ON COULD THERE, AS CONFIDENCE ISN'T TOO
HIGH IN GETTING CONVECTION SOUTH OF THE STRONG WARM ADVECTION
REGIME EARLIER IN SATURDAY.
ISAIAS LOOKS TO REMAIN WELL WEST OF THE REGION, AND ITS GREATEST
IMPACTS ARE FORECAST TO REMAIN THERE AS WELL. HOWEVER, THAT
DOESN'T MEAN THAT WE WON'T SEE IMPACTS HERE LOCALLY. KEEP AN EYE
ON THE FORECAST OVER THE NEXT COUPLE OF DAYS!
AVIATION /06Z THURSDAY THROUGH MONDAY/
EXPECT PREDOMINANTLY VFR CONDITIONS WITH SOME PATCHY FOG
POSSIBLE EARLY THIS MORNING.
SURFACE HIGH PRESSURE OVER THE AREA WILL KEEP WINDS LIGHT AND
VARIABLE THROUGHOUT MUCH OF THE 24 HOUR TAF PERIOD, WITH CALM
WINDS OVERNIGHT. RECENT SATELLITE OBS SHOW HIGH CLOUDS CREEPING
INTO THE AREA FROM THE SOUTHWEST AND WILL INCREASE THROUGH
TODAY.
ALTHOUGH THE DRY AIR MASS AND INCREASING HIGH CLOUDS TONIGHT
SHOULD INHIBIT THE OVERALL THREAT OF WIDESPREAD DENSE FOG, CALM
CONDITIONS MAY SUPPORT A PATCHY, DENSE FOG THREAT FOR PORTIONS
OF THE SOUTHERN FA AND FOR AREAS ALONG RIVERS. CURRENTLY, TEMPS
AND DEW POINTS ARE RUNNING A COUPLE DEGREES BELOW AND ABOVE MOST
GUIDANCE, RESPECTIVELY, SO IT SEEMS REASONABLE TO ADD TEMPOS
FOR MVFR WITH BR FOR A COUPLE OF HOURS AT AIK, CAE, AND CUB
AROUND SUNRISE. AGS AND OGB WOULD STILL BE THE MOST LIKELY TO BE
IMPACTED BY ANY FOG THAT DEVELOPS AND KEPT RESTRICTIONS IN
TEMPOS FOR VIS APPROACHING IFR FOR A COUPLE OF HOURS AROUND
SUNRISE.
EXTENDED AVIATION OUTLOOK...THE THREAT OF
RESTRICTIONS AND RAINFALL INCREASES LATE WEEK AND INTO THE
WEEKEND AS TROPICAL MOISTURE SURGES INTO THE SOUTHEAST WITH
ISAIAS.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
DISCUSSION...PL
AVIATION...SF
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