401
FXUS62 KCAE 201224
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
824 AM EDT WED MAY 20 2026
WHAT HAS CHANGED
12Z AVIATION UPDATE.
KEY MESSAGES
- 1. ABOVE NORMAL TEMPERATURES LIKELY THROUGH THURSDAY; SOME
UNCERTAINTY IN TEMPERATURES THIS WEEKEND.
- 2. RAIN CHANCES INCREASE LATE WEEK ONWARD.
DISCUSSION
KEY MESSAGE 1: ABOVE NORMAL TEMPERATURES LIKELY THROUGH THURSDAY;
SOME UNCERTAINTY IN TEMPERATURES THIS WEEKEND.
STRONG UPPER RIDGE EXPECTED TO PERSIST OVER THE EASTERN CONUS INTO
THE UPCOMING WEEKEND. THIS WILL GENERALLY BRING ABOVE NORMAL
TEMPERATURES TO THE FORECAST AREA OVER THE NEXT SEVERAL DAYS,
HOWEVER HEAT INDICES ARE EXPECTED TO REMAIN WELL BELOW ANY HEADLINE
CRITERIA. WITH THAT IN MIND, THERE IS SOME UNCERTAINTY REGARDING
TEMPERATURES PARTICULARLY FRIDAY AND SATURDAY, AS THERE REMAINS SOME
POTENTIAL FOR WEAK COLD AIR DAMMING OVER MAINLY THE NORTHERN HALF OF
THE FORECAST AREA. THE LATEST ROUND OF MODEL GUIDANCE CONTINUES TO
DEPICT SOME RIDGING OF SURFACE HIGH PRESSURE SOUTH ALONG THE EASTERN
APPALACHIANS WITH STRENGTHENING SOUTHWEST FLOW ALOFT. DEPENDING ON
THE STRENGTH OF THIS WEDGE, IT IS POSSIBLE THAT TEMPERATURES WILL BE
SEVERAL DEGREES COOLER THAN BLENDED GUIDANCE CURRENTLY ADVERTISES.
TEMPERATURES ON FRIDAY WERE THEREFORE ADJUSTED A FEW DEGREES COOLER,
ESPECIALLY IMPACTING THE NORTHERN PORTION OF THE FORECAST AREA. IT
REMAINS TO BE SEEN WHETHER THESE CONDITIONS WILL LINGER FOR SEVERAL
DAYS OR NOT, BUT THE BLOCKING PATTERN IN PLACE DOES INDICATE THE
POTENTIAL IS THERE. IT WAS ALSO NOTED THAT THE NBM AND LREF
INTERQUARTILE RANGES FOR HIGH TEMPS FRIDAY INTO EARLY NEXT WEEK ARE
5-8 DEGREES F DEPENDING ON THE MODEL, FURTHER SUPPORTING LOWER
CONFIDENCE IN THE HIGH TEMPERATURE FORECAST OVER THE HOLIDAY WEEKEND.
KEY MESSAGE 2: RAIN CHANCES INCREASE LATE WEEK ONWARD.
DRY CONDITIONS PERSIST TODAY WITH THE RIDGE OVERHEAD AND HIGH
PRESSURE OFFSHORE. EXPECT JUST SOME FAIR WEATHER CU WITH THE PEAK
HEATING OF THE DAY. THE UPPER LOW OFFSHORE UNDER THE RIDGE HAS
CREATED A BLOCKING PATTERN WHICH IS KEEPING CONDITIONS STAGNANT.
THERE LOOKS TO BE A SLIGHT SHIFT EASTWARD OF THE LARGE SCALE PATTERN
IN THE COMING DAYS, WITH THE POTENTIAL FOR WEAK CAD CONDITIONS TO
DEVELOP. IVT WILL BE INCREASING ACROSS THE DEEP SOUTH INTO THE TN
VALLEY, HOWEVER IT STILL LOOKS LIKE THE BEST MOISTURE WILL REMAIN TO
OUR WEST, THOUGH POTENTIALLY AS CLOSE AS THE UPSTATE. EVEN SO,
PERSISTENT SOUTHWEST FLOW ALOFT AND THE POTENTIAL FOR SOME
OVERRUNNING SHOULD LEAD TO INCREASED MOISTURE OVER THE SOUTHEAST
FROM THURSDAY THROUGH MEMORIAL DAY. THERE REMAINS DISCREPANCIES
BETWEEN THE ECENS AND NAEFS FORECAST PWAT VALUES, WITH THE EC
GENERALLY SHOWING BETTER MOISTURE FOR OUR FORECAST AREA. INITIALLY,
IT APPEARS THE BEST CHANCE OF RAIN WILL BE FRIDAY INTO SATURDAY WHEN
THE WEDGE DEVELOPS. ADDITIONAL PERIODS OF INCREASED RAIN POTENTIAL
ARE THEN EXPECTED INTO EARLY NEXT WEEK, AS A FEW SHORTWAVES MOVE
THROUGH THE LARGER SCALE FLOW AND PROVIDE ADDITIONAL UPPER SUPPORT.
IT STILL APPEARS QPFS SHOULD BE FAIRLY MODEST GIVEN LIMITED
MOISTURE TRANSPORT AND THE OVERALL UPPER RIDGE STILL IN PLACE.
NBM PROBABILITIES OF GREATER THAN 0.5" THROUGH 00Z MONDAY RANGE
FROM 80% WEST OF THE I-20 CORRIDOR TO ABOUT 60% NEAR THE I-95
CORRIDOR. THESE VALUES THEN DROP TO 65% AND 35% RESPECTIVELY
WHEN LOOKING AT POTENTIAL OF GREATER THAN 1".
AVIATION /12Z WEDNESDAY THROUGH SUNDAY/
PREDOMINANTLY VFR WITH BRIEF MORNING RESTRICTIONS.
A VERY SIMILAR SYNOPTIC PATTERN IS IN PLACE WITH HIGH PRESSURE
OFFSHORE AND SOUTHERLY FLOW LEADING TO CONTINUED LINGERING LOW
LEVEL MOISTURE IN PLACE. AS A RESULT, WITH MODELS GENERALLY
SUPPORTIVE OF BRIEF RESTRICTIONS DURING THE EARLY MORNING PERIOD
AND WHICH FAVORS A PERSISTENCE FORECAST. ANY LOW CLOUDS OR FOG
IS EXPECTED TO DISSIPATE SHORTLY AFTER SUNRISE WITH SOUTHERLY
WINDS AROUND 5 KNOTS AND A FEW CUMULUS AROUND 6KFT. AN ISOLATED
SHOWER COULD POP UP THIS AFTERNOON BUT IMPACTS TO TERMINALS ARE
UNLIKELY.
EXTENDED AVIATION OUTLOOK...INCREASED MOISTURE MAY RESULT IN
BRIEF RESTRICTIONS AT THE TERMINALS DUE TO LOW CLOUDS AND/OR FOG
EACH DAY THIS WEEK. RAIN CHANCES INCREASE TOMORROW AND INTO
THIS WEEKEND.
CAE WATCHES/WARNINGS/ADVISORIES
SC...NONE.
GA...NONE.
DISCUSSION...96
AVIATION...EC
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