878
FXUS62 KCHS 020248
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1048 PM EDT FRI MAY 1 2026
WHAT HAS CHANGED
TIDE LEVELS HAVE DROPPED BELOW MINOR FLOOD CRITERIA IN THE
CHARLESTON HARBOR, SO THE COASTAL FLOOD ADVISORY WAS ALLOWED TO
EXPIRE.
KEY MESSAGES
- 1) A WIDESPREAD, SIGNIFICANT RAINFALL EVENT WILL OCCUR ACROSS
THE SOUTH CAROLINA LOWCOUNTRY AND SOUTHEAST GEORGIA THROUGH
SATURDAY.
- 2) MINOR COASTAL FLOODING POSSIBLE WITH THE SATURDAY EVENING
HIGH TIDE ALONG THE LOWER SOUTH CAROLINA COAST.
DISCUSSION
KEY MESSAGE 1: A WIDESPREAD, SIGNIFICANT RAINFALL EVENT
WILL OCCUR ACROSS THE SOUTH CAROLINA LOWCOUNTRY AND SOUTHEAST
GEORGIA THROUGH SATURDAY.
THE FORECAST PHILOSOPHY FOR TONIGHT INTO SATURDAY HAS NOT
CHANGED SIGNIFICANTLY. CYCLOGENESIS IS EXPECTED TO INITIATE OFF
THE SOUTH CAROLINA/GEORGIA COAST OVERNIGHT AS A POTENT MID-
LEVEL DISTURBANCE OVER TEXAS PROPAGATES TO THE EAST. ISENTROPIC
ASCENT IS FORECAST TO STEADILY STRENGTHEN OVERNIGHT AS A WELL-
DEFINED 850 HPA FRONT LOCATED OVER SOUTHERN PORTIONS OF ALABAMA
AND GEORGIA JUMPS NORTH AND A SOUTHERLY LOW-LEVEL JET NUDGES IN
FROM THE SOUTHWEST. THIS SHOULD RESULT IN A STEADY INCREASE IN
SHOWERS/TSTMS OVERNIGHT WITH THE GREATEST COVERAGE POISED TO
SETUP ACROSS THE INTERIOR PRIOR TO DAYBREAK CLOSER TO THE 850
HPA FRONT AND AXIS OF STRONGEST 850-700 HPA FRONTOGENESIS. RAIN
WILL CONTINUE TO EXPAND AND SPREAD EAST THROUGH THE MORNING
HOURS AS THE STRONGEST DEEP-LAYERED FORCING FOR ASCENT SWINGS
THROUGH WITH THE APPROACHING DISTURBANCE AND UPPER DIFLUENCE
ASSOCIATED WITH A DUAL-JET STRUCTURE BETWEEN THE POLAR AND
SUBTROPICAL JETS PEAKS. THERE COULD BE A PERIOD OF ENHANCED
ELEVATED INSTABILITY WHERE SOME NEGATIVE EPV ALIGNS WITH AT
LEAST TWO BANDS OF STRONG MID-LEVEL FRONTOGENESIS, SO ISOLATED
TO SCATTERED EMBEDDED TSTMS ARE STILL POSSIBLE (ESPECIALLY
SOUTHEAST GEORGIA INTO SOUTH COASTAL SOUTH CAROLINA) DESPITE THE
LACK OF ANY MEANINGFUL SURFACE-BASED INSTABILITY. RAIN CHANCES
WILL BEGIN TO QUICKLY DIMINISH FROM WEST-EAST BY MID-AFTERNOON
AS THE UPPER DISTURBANCE PASSES OFFSHORE AND LOW PRESSURE
QUICKLY EXISTS THE AREA. DRY CONDITIONS SHOULD PREVAIL SUNDAY
EVENING AND LINGER INTO THE OVERNIGHT HOURS. POPS TONIGHT RANGE
FROM 50-100% (LOWEST ALONG THE MIDDLE GEORGIA COAST) WITH 100%
POPS EVERYWHERE FOR SATURDAY.
STORM TOTAL RAINFALL AMOUNTS OF 1-2" THROUGH SATURDAY EVENING
STILL LOOK ON TRACK. 01/13Z NBM PROBABILITIES ARE AS FOLLOWS:
* PROB FOR >1": 85-95% (HIGHEST INLAND)
* PROB FOR >2": 25-55% (HIGHEST FAR INTERIOR SOUTHEAST GEORGIA)
* PROB FOR >3": 5-20% (HIGHEST FAR INTERIOR SOUTHEAST GEORGIA)
THIS REPRESENTS A SOLID MUCH NEEDED RAINFALL GIVEN THE CURRENT
DROUGHT SITUATION, BUT IT ALSO LOOKS LIKE RAINFALL RATES WILL BE
LOW ENOUGH TO KEEP THE THREAT OF FLASH FLOODING VERY LOW. THERE
COULD STILL BE SOME MINOR FLOODING ISSUES IN LOW-LYING AND POOR
DRAINAGE AREAS ACROSS THE CHARLESTON AND SAVANNAH METRO AREAS
AS POCKETS OF PERIODIC MODERATE TO LOCALLY HEAVY RAIN MOVE
THROUGH.
KEY MESSAGE 2: MINOR COASTAL FLOODING POSSIBLE WITH THE
SATURDAY EVENING HIGH TIDE ALONG THE LOWER SOUTH CAROLINA
COAST.
ASTRONOMICAL TIDE LEVELS WILL PEAK TONIGHT WITH THE FULL MOON.
COASTAL FLOODING THREAT IS A BIT MORE MARGINAL FOR SATURDAY
EVENING SINCE THE WINDS WILL TIP TO A MORE NNW DIRECTION WHICH
SHOULD BRING DOWN THE ANOMALIES. WE WOULD NEED +1.1 FT TO REACH
THE 7.0 FT MINOR COASTAL FLOOD THRESHOLD, WHICH MAY BE A STRETCH
BASED ON THAT WIND FORECAST.
AVIATION /02Z SATURDAY THROUGH WEDNESDAY/
KCHS/KJZI/KSAV: WIDESPREAD IFR CONDITIONS ARE EXPECTED TO
OVERSPREAD THE AREA TONIGHT AS LOW PRESSURE BEGINS TO ORGANIZE
OFFSHORE. CIGS COULD EVEN APPROACH AIRFIELD MINIMUMS AT TIMES
OVERNIGHT INTO SATURDAY MORNING. THE HEAVIEST RAINS ARE POISED
TO IMPACT ALL THREE TERMINALS BETWEEN SUNRISE AND LATE MORNING,
WITH A CHANCE FOR SOME ELEVATED TSTMS. PROB30 FROM 13-17Z WAS
MAINTAINED AT ALL SITES TO HIGHLIGHT THIS POTENTIAL. WHILE
RAINFALL SHOULD BEGIN TO TAPER OFF BY MID-AFTERNOON, LOW CLOUDS
LOOK TO HANG AROUND THROUGH THE END OF THE VALID TAF CYCLE (00Z
SUNDAY).
EXTENDED AVIATION OUTLOOK: EXPECT IMPROVING CONDITIONS SATURDAY
EVENING; OTHERWISE, THERE ARE NO CONCERNS THROUGH TUESDAY.
MARINE
A BRIEF PERIOD OF MARGINAL SMALL CRAFT ADVISORY CONDITIONS IS
POSSIBLE OVER THE SC NEARSHORE AND GA OFFSHORE WATERS SATURDAY
AFTERNOON INTO SATURDAY NIGHT AS SURFACE LOW PRESSURE DEVELOPS
ALONG THE SC COAST. AT THE MOMENT, WE ONLY HAVE A FEW HRS OF 25
KT WIND GUSTS, AND SEAS POSSIBLY REACHING 6 FT OVER FAR OUTER
PORTIONS, SO AN ADVISORY WOULD BE VERY MARGINAL.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
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