996
FXUS62 KCAE 041153
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
753 AM EDT MON MAY 4 2026
WHAT HAS CHANGED
CONFIDENCE INCREASING IN PERIODS OF MODERATE TO HEAVY RAIN LATE
WEDNESDAY AND THURSDAY. AVIATION DISCUSSION UPDATED FOR 12Z
TAFS.
KEY MESSAGES
- 1. PERIODS OF MODERATE TO HEAVY RAINFALL ARE EXPECTED DURING
THE MID WEEK WITH THE POTENTIAL SEVERE WEATHER.
- 2. RAIN CHANCES PICK BACK UP LATE WEEK AND INTO THE WEEKEND
DISCUSSION
KEY MESSAGE 1: PERIODS OF MODERATE TO HEAVY RAINFALL ARE
EXPECTED DURING THE MID WEEK WITH THE POTENTIAL SEVERE WEATHER.
SUMMARY: THE RAINFALL FORECAST REMAINS ON TRACK FOR MID-WEEK AS
AN UPPER LEVEL TROUGH DIGS INTO THE CENTRAL US, PHASES WITH
SOUTHERN STREAM ENERGY, AND SHIFTS EASTWARD. THE ASSOCIATED
SURFACE COLD FRONT WILL WORK INTO THE SOUTHEAST ON THURSDAY.
MODELS CONTINUE TO SHOW AGREEMENT IN OVERALL SYNOPTIC PATTERN
DESPITE DIFFERENCES IN THE TIMING OF THE FRONT AND OTHER
DETAILS. THIS INCREASES CONFIDENCE IN PERIODS OF MODERATE TO
HEAVY RAINFALL BUT LEAVES THE THREAT OF SEVERE WEATHER
UNCERTAIN.
RAINFALL: ROBUST MOISTURE TRANSPORT IS EXPECTED AHEAD OF THIS
FRONT WITH PWAT VALUES REACHING THE NAEFS 99TH PERCENTILE BY
THURSDAY MORNING AND IVT AT THE CLIMATOLOGICAL MAXIMUM. AS
SYNOPTIC SCALE LIFT MOVES OVER THE REGION LATE WEDNESDAY INTO
EARLY THURSDAY, SCATTERED SHOWERS AND STORMS SHOULD DEVELOP.
COVERAGE WILL LIKELY INCREASE THURSDAY MORNING AS MOISTURE
TRANSPORT AND SURFACE CONVERGENCE AHEAD OF THE FRONT PEAKS. THIS
ACTIVITY COULD BRING PERIODS OF MODERATE TO HEAVY RAIN AS
FORECAST SOUNDINGS THURSDAY MORNING DEPICT DEEP MOISTURE, A
LONG/SKINNY CAPE PROFILE, AND A 30- 40 KT LLJ. WITH THE
ANTECEDENT DRY CONDITIONS, THE OVERALL FLASH FLOODING RISK IS
EXPECTED TO BE ON THE LOW SIDE. THE FRONT WILL SHIFT EAST LATE
THURSDAY BRINGING AN END TO RAIN FROM WEST TO EAST. GUSTY WINDS
WILL ALSO BE POSSIBLE THURSDAY AND A LAKE WIND ADVISORY MAY BE
NEEDED.
SEVERE THREAT: THE THREAT OF SEVERE WEATHER WILL BE LARGELY
DEPENDENT ON THE TIMING OF THE FRONT. SOME OF THE TIMING
DIFFERENCES STEM FROM THE PROGRESSION OF THE UPPER TROUGH AND
THE INTERACTION WITH A CUT-OFF LOW TO THE WEST. THERE IS ALSO
SOME UNCERTAINTY IN THE DEGREE OF DESTABILIZATION THROUGH THE
DAY WITH WIDESPREAD RAIN AND CLOUD COVER ANTICIPATED. THAT SAID,
ECMWF EFI VALUES FOR CAPE- SHEAR COMBO STILL RANGE FROM 0.6 TO
0.8 INDICATING SOME POTENTIAL FOR DEEP SHEAR TO LINE UP WITH
MODERATE INSTABILITY. NCAR ML/AI SEVERE PROBABILITIES HAVE
REMAINED CONSISTENT INDICATING A POTENTIAL THREAT OF SEVERE
WEATHER, PARTICULARLY TO OUR EAST WHERE INSTABILITY MAY BE
HIGHER AND TO THE NORTH IN THE MID-ATLANTIC STATES WHERE THE
DYNAMICS WILL BE STRONGER AS THE TROUGH LIFTS.
KEY MESSAGE 2: RAIN CHANCES PICK BACK UP LATE WEEK AND INTO THE
WEEKEND
GLOBAL ENSEMBLES TEND TO FAVOR A SOMEWHAT PERSISTENT SYNOPTIC
PATTERN THROUGH THE WEEKEND WITH ANOTHER TROUGH DIGGING INTO THE
CENTRAL US THEN SHIFTING EAST. HOWEVER A LARGE SPREAD IN 500 MB
HEIGHTS INDICATE MUCH MORE UNCERTAINTY IN THE FORECAST COMPARED
TO THE MID- WEEK SYSTEM. MEAN PWAT VALUES FROM THE GEFS AND
ECMWF ENSEMBLE RISE BACK ABOVE 1 INCH BY EARLY NEXT WEEK. NEAR
NORMAL MOISTURE AND UPPER LEVEL TROUGHING OVER THE REGION
SUPPORTS A CHANCE OF RAIN NEAR THE END OF THE FORECAST PERIOD.
AVIATION /12Z MONDAY THROUGH FRIDAY/
VFR CONDITIONS WILL PREVAIL THROUGH 12Z TUESDAY.
SATELLITE IMAGERY SHOWS MAINLY CLEAR SKIES IN PLACE OVER THE
AREA THIS MORNING. WINDS ARE GENERALLY LIGHT/CALM AT ALL
TERMINALS. WHILE A DRY AIRMASS HAS LIMITED FOG FORMATION, THERE
IS LIGHT PATCHY FOG IN SOME RIVER VALLEYS.
WINDS ALONG THE BACK SIDE OF ATLANTIC HIGH PRESSURE WILL
INCREASE FROM THE SOUTH-SOUTHWEST TO 5-10 KT DURING THE LATE
MORNING AND AFTERNOON HOURS TODAY. WHILE THEY SHOULD DIMINISH
WITH THE LOSS OF DAYTIME HEATING THIS EVENING, THEY MAY NOT
FULLY DECOUPLE. THIN CIRRUS SHOULD BEGIN SPREADING OVER THE AREA
THIS AFTERNOON, POTENTIALLY INCREASING IN THICKNESS/COVERAGE
TOWARD THIS EVENING AND OVERNIGHT, BUT WILL HAVE NO IMPACT TO
AVIATION INTERESTS.
EXTENDED AVIATION OUTLOOK...DRIER CONDITIONS ARE EXPECTED
THROUGH TUESDAY, THEN A MIDWEEK SYSTEM BRINGS A CHANCE FOR
RESTRICTIONS ONCE AGAIN.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
DISCUSSION...CJR
AVIATION...JAQ
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