598
FXUS62 KCAE 090632
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
232 AM EDT FRI OCT 9 2026
WHAT HAS CHANGED
HURRICANE ISAIAS STRENGTHENS AND TURNS NORTHWARD TOWARD THE GULF
COAST. AVIATION DISCUSSION UPDATED FOR 06Z TAFS.
KEY MESSAGES
- 1. AN ACTIVE WEEKEND AHEAD AS HURRICANE ISAIAS MOVES INLAND TO
OUR WEST. CONFIDENCE IN THE EXTENT OF IMPACTS INCREASING WITH
PERIODS OF HEAVY RAIN BRINGING AN ISOLATED FLOODING THREAT.
ISOLATED TORNADOES ARE POSSIBLE ON SATURDAY NIGHT AS WELL.
DISCUSSION
KEY MESSAGE 1: AN ACTIVE WEEKEND AHEAD AS HURRICANE ISAIAS
MOVES INLAND TO OUR WEST. CONFIDENCE IN THE EXTENT OF IMPACTS
INCREASING WITH PERIODS OF HEAVY RAIN BRINGING AN ISOLATED
FLOODING THREAT. ISOLATED TORNADOES ARE POSSIBLE ON SATURDAY
NIGHT AS WELL.
OVERVIEW: MODERATE TO HEAVY RAINFALL IS LIKELY AS HURRICANE
ISAIAS PASSES TO OUR WEST ON SATURDAY AND INTO SATURDAY NIGHT.
OVERALL, THE FORECAST HAS NOT CHANGED SIGNIFICANTLY SINCE
YESTERDAY AFTERNOON. THE 00Z SUITE OF GUIDANCE IS FAIRLY SIMILAR
TO YESTERDAY'S 12Z SUITE. ISAIAS IS BEGINNING TO ACCELERATE TO
THE NORTHEAST AS IT INTERACTS WITH THE BACKGROUND SYNOPTIC
ENVIRONMENT SURROUNDING IT. THE HURRICANE IS COMPACT AND
INTENSE, BUT IT IS EXPANDING IN SIZE. HIGH CIRRUS IS OVERHEAD
AND WILL CONTINUE TO GROW IN THICKNESS AS THE HURRICANE
APPROACHES THE FLORIDA/ALABAMA COASTLINE THIS AFTERNOON. THESE
CLOUDS WILL CONTINUE TO KEEP TEMPERATURES COOLER THAN THEY WOULD
BE OTHERWISE. MOISTURE ADVECTION WILL BE RELATIVELY QUICK THIS
EVENING WITH PWS RISING FROM WHERE THEY ARE CURRENTLY WHICH IS
AROUND 0.8" TO WELL OVER 2" BY SATURDAY MORNING.
RAINFALL IS EXPECTED TO ACCOMPANY THIS & SHOULD BEGIN SOMETIME
AFTER MIDNIGHT TONIGHT. FORCING THIS RAINFALL WILL BE A
COMBINATION OF STRONG MOISTURE TRANSPORT & ISENTROPIC ASCENT
ATOP AN IN-SITU WEDGE ACROSS THE AREA. IT DOESN'T HURT THAT
SYNOPTIC SCALE LIFT SHOULD BE PRETTY GOOD AS WELL AS THE RIGHT-
ENTRANCE REGION OF AN UPPER LEVEL JET STREAK PUSHES NORTHWARD
INTO THE MID-ATLANTIC. THE QUESTION REMAINS JUST HOW MUCH RAIN
WE GET AND HOW/WHEN THE RAIN ENDS & BEGINS AGAIN SATURDAY
EVENING. THERE IS SOME GUIDANCE (ESPECIALLY THE RRFS BUT SOME
OTHER MODELS TOO) THAT MAINTAIN THE IDEA THAT A MORE FOCUSED
AREA OF CONVECTION WILL DEVELOP ALONG THE COAST OF SC DUE TO A
COASTAL LOW THAT DEVELOPS ALONG THE WEDGE BOUNDARY. THIS WOULD
THEN FOCUS A BRANCH OF MOISTURE TRANSPORT MORE ALONG THAT
BOUNDARY AND LESS SO PUSHING INTO ISAIAS' OVERALL CIRCULATION.
WHILE THE PRESENCE OF A STRONG COASTAL THERMAL GRADIENT WILL
LIKELY RESULT IN ENHANCED PRECIPITATION TOTALS IN THE COASTAL
PLAIN, IT SEEMS UNLIKELY THAT IT WILL LIMIT OUR OVERALL RAIN
TOTALS LIKE RRFS IS SHOWING. THE GUIDANCE HAS TENDED TO SHIFT
THE MOST ROBUST MOISTURE TRANSPORT SLIGHTLY EAST OVER THE LAST
24H, MAKING THIS FORECASTER THINK THAT 1-3" OF RAINFALL IS THE
MOST LIKELY OUTCOME ACROSS THE AREA. THERE COULD BE LOCALLY
HIGHER TOTALS ESPECIALLY IN THE COASTAL PLAIN OR WESTERN
MIDLANDS/CSRA - BOTH THE AREA CLOSER TO THAT COASTAL THERMAL
GRADIENT AND THE BETTER MOISTURE TRANSPORT. BUT FOR NOW,
GUIDANCE RIGHT NOW IS IN GOOD AGREEMENT ON THAT 1-3" RAINFALL
TOTAL.
THERE ARE OTHER POTENTIAL HAZARDS AT PLAY WITH THIS EVENT.
TORNADOES ARE CERTAINLY POSSIBLE IN THIS EVENT, ESPECIALLY ON
SATURDAY NIGHT. AS ISAIAS' CIRCULATION LIFTS NORTHWARD, THE
AFORMENTIONED THERMAL GRADIENT IS EXPECTED TO LIFT NORTHWARD AS
WELL. THE TIMING OF THIS SHOULD BE SUCH THAT IT OCCURS AS THE
BEST MOISTURE TRANSPORT APPROACHES, WHICH COULD CREATE A
SCENARIO ON SATURDAY NIGHT THAT WE SEE LOW-TOPPED SUPERCELLS
DEVELOP IN A HIGHLY SHEARED ENVIRONMENT. LCLS WILL BE QUITE LOW,
AND WE TYPICALLY DON'T NEED MUCH MORE THAN A SURFACE DEWPOINT OF
70F TO HAVE SOME TROPICAL TORS DEVELOP. THE RRFS AND HRRR HAVE
BOTH SHOWN SIGNS OF DEVELOPING THE NECESSARY CONVECTION AS WELL
AS PUSHING SUFFICIENT LOW-LEVEL CAPE INTO THE AREA ON SATURDAY
NIGHT. SPC HAS PLACED THE AREA IN A SLIGHT RISK, DRIVEN BY A
TORNADO THREAT. HAVE MULTIPLE WAYS TO RECEIVE WARNINGS ON
SATURDAY NIGHT!
WINDS ARE THE OTHER "THREAT" BUT IT WON'T REALLY BE MUCH OF A
THREAT. IT SHOULD JUST BE BREEZY ACROSS THE AREA, WITH GUSTS OF
25-35 MPH POSSIBLE ESPECIALLY SATURDAY MORNING AND EARLY
AFTERNOON. A LAKE WIND ADVISORY HAS BEEN HOISTED FOR AREA LAKES,
BEGINNING 5A SATURDAY AND RUNNING THROUGH 2P SATURDAY. ISAIAS
SHOULD QUICKLY MOVE NORTHEASTWARD AND OUT OF THE AREA BY SUNDAY
AFTERNOON. WARM AND DRY CONDITIONS ARE EXPECTED FOR THE
REMAINDER OF THE PERIOD.
AVIATION /06Z FRIDAY THROUGH TUESDAY/
VFR CONDITIONS EXPECTED THROUGHOUT THE FORECAST PERIOD.
HIGH LEVEL CLOUDS CONTINUE OVER THE AREA OVERNIGHT AND INTO THE
DAY FRIDAY. THESE CLOUDS ARE FORECAST TO GRADUALLY LOWER THROUGH
THE DAY, PARTICULARLY LATE IN THE TAF PERIOD. SOME GUIDANCE IS
INDICATING THE POTENTIAL FOR MVFR CEILINGS OVER THE AUGUSTA
TERMINALS AT THE TAIL END OF THE PERIOD. RAIN CHANCES SHOULD
HOLD OFF UNTIL AFTER 06Z TOMORROW. HOWEVER, CAN'T RULE OUT SOME
SHOWER ACTIVITY REACHING AGS OR DNL LATE. LIGHT AND VARIABLE TO
CALM WINDS OVERNIGHT PICK UP OUT OF THE NORTHEAST AFTER ABOUT
16Z, WITH GUSTS TO AROUND 15 KTS POSSIBLE. WINDS ARE THEN
FORECAST TO INCREASE AFTER ABOUT 00Z, GUSTING TO 20 KTS, AS
PRESSURE GRADIENTS BEGIN TO TIGHTEN.
EXTENDED AVIATION OUTLOOK...THE THREAT OF RESTRICTIONS AND
RAINFALL INCREASES EARLY SATURDAY MORNING AS TROPICAL MOISTURE
SURGES INTO THE SOUTHEAST WITH ISAIAS. STRONG GUSTY
NORTHEASTERLY WINDS LIKELY THROUGHOUT SATURDAY AND SUNDAY ALONG
WITH PERIODS OF HEAVY RAIN AND LIFR CONDITIONS.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
DISCUSSION...PL
AVIATION...29
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