189
FXUS62 KCAE 191810
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
210 PM EDT SAT SEP 19 2026
WHAT HAS CHANGED
MINIMAL CHANGE TO KEY MESSAGES. AVIATION DISCUSSION UPDATED FOR
18Z TAFS.
KEY MESSAGES
- 1. ABOVE AVERAGE TEMPERATURES AND INCREASED CHANCES FOR
SHOWERS AND STORMS CONTINUE INTO EARLY NEXT WEEK.
- 2. COOLER AND DRIER AIR RETURNS BY THE MIDDLE OF NEXT WEEK
BUT FORECAST UNCERTAINTY REMAINS.
DISCUSSION
KEY MESSAGE 1: ABOVE AVERAGE TEMPERATURES AND INCREASED CHANCES
FOR SHOWERS AND STORMS CONTINUE INTO EARLY NEXT WEEK.
A DIFFUSE FRONTAL BOUNDARY HAS SANK NEAR THE PEE DEE EARLY THIS
AFTERNOON, CHARACTERIZED BY A VERY SUBTLE WIND SHIFT AND
SLIGHTLY ENHANCED MOISTURE CONVERGENCE. AS TEMPERATURES CONTINUE
TO WARM TOWARD THE LOW TO MID 90S AND SURFACE DEWPOINTS REMAIN
IN THE UPPER 60S TO LOWER 70S, AROUND 1500-2500 J/KG OF MLCAPE
SHOULD DEVELOP. OVERALL FORCING REMAINS WEAK AND DUE TO THIS,
BOTH THE 12Z HREF AND REFS KEEP DIURNALLY DRIVEN CONVECTION
FAIRLY ISOLATED TO WIDELY SCATTERED (MAINLY AFTER 19-21Z).
OVERALL, THE SEVERE RISK WITH ANY STORM THIS AFTERNOON AND
EVENING IS LOW, BUT A FEW EFFICIENT DOWNPOURS WILL BE POSSIBLE
AND PERHAPS SOME GUSTY WINDS IN THE STRONGEST STORMS.
THIS CHANCE FOR ISOLATED TO SCATTERED DIURNAL CONVECTION
CONTINUES SUNDAY AND INTO EARLY NEXT WEEK, WHERE COVERAGE HAS
TRENDED SLIGHTLY HIGHER ON TUESDAY. SLIGHTLY ABOVE NORMAL
TEMPERATURES AND PWAT'S REMAINING ABOVE 1.75" WILL LIKELY DRIVE
SEASONABLE INSTABILITY, BUT WITH WEAK FORCING, ACTIVITY SUNDAY
AND MONDAY WILL LIKELY BE MORE DIURNALLY DRIVEN. COME TUESDAY,
THE UPPER AIR PATTERN BEGINS TO SHIFT WITH THE MID LEVEL LOW
CURRENTLY OVER THE FAR EASTERN GULF, DRIFTING NORTHWARD ALONG
THE EASTERN SEABOARD. THIS FEATURE ALONG WITH DEVELOPING
TROUGHING MOVING IN FROM THE MIDWEST COULD BRING INCREASED
SYNOPTIC FORCING, AIDING IN INCREASING COVERAGE OF
SHOWERS/STORMS. OVERALL, THE SEVERE WEATHER RISK THROUGH THE
EARLY WEEK IS ON THE LOWER END, BUT CANNOT RULE OUT PERIODS OF
HEAVY RAINFALL, ESPECIALLY INTO TUESDAY.
KEY MESSAGE 2: COOLER AND DRIER AIR RETURNS BY THE MIDDLE OF
NEXT WEEK BUT FORECAST UNCERTAINTY REMAINS.
THERE IS BETTER AGREEMENT THAT TROUGHING FROM THE MIDWEST WILL
GENERALLY SHIFT EASTWARD THROUGH THE WEEK, WITH THE
AFOREMENTIONED MID LEVEL LOW CONTINUING TO GLIDE NORTHWARD,
EVENTUALLY GENERATING A SURFACE RESPONSE OFF THE EAST COAST. THE
MAIN SURFACE FEATURE OF NOTE WILL BE THE ROBUST AREA OF HIGH
PRESSURE THAT BUILDS INTO THE QUEBEC, RIDGING DOWN INTO THE MID-
ATLANTIC DURING THE MID TO LATE WEEK. THIS HIGH IS EXPECTED TO
BE NEAR THE NAEFS CLIMATOLOGICAL MAX. GENEROUS UNCERTAINTY
REMAINS IN THE DEGREE OF SURFACE RIDGING THAT REACHES THE CWA,
WHICH IS DISPLAYED WELL ACROSS THE SPREAD OF ENSEMBLE MEMBERSHIP
IN LREF CLUSTERS. THE DEGREE OF MOISTURE ADVECTION ATOP THE
POTENTIAL SURFACE WEDGE WILL LIKELY BE MODULATED BY THE TIMING
AND STRENGTH OF THE TROUGHING MENTIONED ABOVE. THE LATEST ECMWF
RUN KEEPS THE TROUGH A BIT WEAKER AND SLOWER, KEEPING A BIT MORE
SOUTHWESTERLY FLOW ALOFT WITH INCREASED MOISTURE OVERRIDING THE
SURFACE WEDGE, WHILE THE GFS AND NAM ARE FAVORING A STRONGER
TROUGH, MORE NORTHWESTERLY TO NORTHERLY FLOW ALOFT, AND THUS
DRIER AIR ATOP THE WEDGE. THE EOF PATTERNS FROM THE LREF CLUSTER
ANALYSIS REALLY HIGHLIGHT THE IMPORTANCE THE STRENGTH AND
TIMING OF TROUGHING WILL HAVE ON POTENTIAL CAD CONDITIONS. DUE
TO THE UNCERTAINTY THAT REMAINS, THERE IS FAIRLY LOW CONFIDENCE
WEDNESDAY INTO THE LATE WEEK IN TERMS OF TEMPERATURES AND POP'S.
THE POTENTIAL FOR BELOW NORMAL TEMPERATURES EXISTS, BUT NEARLY
10 DEGREE IQR RANGES REMAIN DURING THIS PERIOD. WIDESPREAD
PRECIPITATION SEEMS FAIRLY LOW, BUT IF MOIST ISENTROPIC LIFT CAN
RIDE OVER THE POTENTIAL WEDGE, CANNOT RULE OUT TYPICAL CAD
CONDITIONS WITH LIGHT STRATIFORM RAIN OR DRIZZLE, ACTING TO
REINFORCE THE WEDGE.
AVIATION /18Z SATURDAY THROUGH THURSDAY/
MID AND UPPER LEVEL CLOUD COVER EARLIER THIS MORNING HAS THINNED
OUT, GIVING WAY TO SCATTERED AND AGITATED CU WITH HEATING EARLY
THIS AFTERNOON. ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS
DEVELOPING AGAIN THIS AFTERNOON NECESSITATES MAINTAINING PROB30
GROUPS FROM 20-02Z ACROSS CAE, CUB, AND OGB, AND 21-03Z ACROSS
AGS, DNL, AND AIK, WITH GREATER COVERAGE POSSIBLE ACROSS THE
LATTER 3 TERMINALS. RECENT GFS-MOS AND LAMP GUIDANCE HAS SHOWN
CONSISTENCY IN RECENT RUNS IN DEVELOPING LOW CIGS AND POSSIBLE
VIS RESTRICTIONS BY 08-09Z SUNDAY, PARTICULARLY ACROSS THE
WESTERN HALF OF THE FA PER 12Z HREF GUIDANCE. HAVE INCLUDED
TEMPO GROUPS FOR 09-13Z FOR THE POTENTIAL FOR IFR CONDITIONS
WITH SCT CLOUDS BELOW 1000FT AT ALL TERMINALS, AS WELL AS
POTENTIAL FOR IFR VIS DOWN 1-2 SM AT MORE FOG-PRONE AIK, AGS,
AND OGB TERMINALS. WILL CONTINUE TO MONITOR LATER NEAR TERM
GUIDANCE AND ADJUST THESE VALUES AS NECESSARY, ESPECIALLY
FOLLOWING RAINFALL WITH CONVECTION THIS AFTERNOON AND EVENING.
ANY LOW CIGS AND/OR VIS SHOULD LIFT/IMPROVE BY LATE MORNING
TOMORROW WITH HEATING.
EXTENDED AVIATION OUTLOOK...CHANCES FOR SHOWERS AND/OR THUNDERSTORMS
WILL CONTINUE THROUGH EARLY NEXT WEEK. MORNING CIG/VSBY
RESTRICTIONS ARE POSSIBLE AS WELL.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
DISCUSSION...DH
AVIATION...SF
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