483
FXUS62 KRAH 121701
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
100 PM EDT MON MAY 12 2025
SYNOPSIS
A SLOW MOVING UPPER LOW CENTERED OVER THE LOWER MISSISSIPPI
RIVER VALLEY WILL DRIFT NORTHEAST THROUGH THE MID SOUTH TO THE
CENTRAL APPALACHIANS THROUGH WEDNESDAY, BRINGING WET AND UNSETTLED
WEATHER TO THE REGION.
NEAR TERM /TODAY AND TONIGHT/
AS OF 954 AM MONDAY...
..A FLOOD WATCH IS IN EFFECT THROUGH TUESDAY MORNING
THE INHERITED FORECASTED IS ON TRACK THIS MORNING. THUS FAR, SHOWERS
(AND A FEW ISOLATED STORMS IN THE SOUTH) HAVE HAD FAIRLY LIMITED
RAINFALL RATES. A BAND OF ENHANCED REFLECTIVITY ASSOCIATED WITH A
WEAK MCV IS ENTERING THE SOUTHERN PIEDMONT AS OF THIS UPDATE. THIS
AREA DOES HAVE RELATIVELY LOWER FFG, SO SOME NEAR-TERM CONCERN MAY
BE THE URBAN AREAS OUT THIS WAY. HOWEVER, AS WE PROGRESS THROUGHOUT
TODAY EXPECT ADDITIONAL WAVES OF HEAVIER SHOWERS/STORMS TO MOVE
THROUGH ALL OF CENTRAL NC. HREF PROBABILITIES FOR EXCEEDING FFG OVER
VARIOUS TEMPORAL PERIODS (1,3,6 HR) ARE NEAR ZERO FOR MUCH OF OUR
AREA THROUGH TOMORROW. HOWEVER, WE DO EXPECT LOCALLY HIGHER AMOUNTS
(HREF LPMM FIELD SHOWS SWATHS OF POTENTIAL 3-4 INCHES THROUGH
TUESDAY MORNING). AS SUCH, THE CLASSIC URBAN AREAS WILL FAVOR FLASH
FLOOD POTENTIAL TODAY AND TONIGHT, ESPECIALLY WHERE/IF THESE HIGHER
TOTALS ARE REALIZED.
WHILE SPC ONLY HAS US OUTLINED IN GENERAL THUNDER, WE CAN'T FULLY
RULE OUT A QUICK SPIN UP TORNADO TODAY. WE'VE SEEN SOME WEAK
ROTATION IN A FEW CELLS ALREADY THIS MORNING OVER THE SOUTHERN
COASTAL PLAIN. EFFECTIVE SRH IS FORECAST TO RISE INTO THE 100 M2S2
RANGE AND MODEL-DERIVED HODOGRAPHS DO SO SOME HINTS OF LOW-LEVEL
CURVATURE POTENTIAL. COUPLED WITH LOW LCLS, THIS KIND OF SETUP
TRADITIONALLY HAS OCCASIONALLY LED TO A QUICK SPIN-UP TORNADO OR
FUNNEL CLOUD REPORT. OVERALL THOUGH, THE TORNADO CHANCES ARE QUITE
LOW TODAY.
THE BULK OF MODERATE TO HEAVY RAIN SHOULD LARGELY LIFT NORTH INTO VA
LATE TONIGHT THROUGH SUNRISE TUESDAY MORNING. HOWEVER, SCATTERED
SHOWER CHANCES WILL REMAIN POSSIBLE EVERYWHERE GIVEN THE PROXIMITY
TO THE CLOSED LOW AND THE RESIDUAL HIGHLY ANOMALOUS PWAT (150 TO 175
% OF NORMAL).
PREVIOUS DISCUSSION FROM 340 AM MONDAY...
A NEARLY STATIONARY UPPER LEVEL LOW THAT HAS BEEN CHURNING OVER THE
MOUTH OF THE MISSISSIPPI THIS PAST WEEKEND, WILL FINALLY BEGIN TO
MOVE NORTH TOWARDS THE TENNESSEE VALLEY. WEAK INSITU CAD WILL HANG
ON ACROSS MUCH OF THE AREA, AHEAD OF THE ATTENDANT WARM FRONT AND
POTENTIAL WEAK TRIPLE POINT LOW FORECAST TO EXTEND ALONG THE SC-NC
STATE LINE BY DAYBREAK TUESDAY.
BENEATH INCREASING UPPER LEVEL DIFFLUENCE, A PLUME OF STRONG
SOUTHERLY MOISTURE TRANSPORT WILL SPREAD ACROSS THE AREA THROUGH
EARLY TUESDAY. THIS ANOMALOUS MOISTURE, COMBINED WITH DEEP LAYER
ASCENT, WILL SPAWN REPEATED ROUNDS OF SHOWERS AND THUNDERSTORMS THIS
MORNING THROUGH TONIGHT. THE SLOW PROGRESSION OF THIS SYSTEM AND
POTENTIAL FOR TRAINING CONVECTION RAISE CONCERNS FOR ISOLATED TO
WIDELY SCATTERED FLASH FLOODING, PARTICULARLY BY THE AFTERNOON AND
EVENING IN AREAS THAT EXPERIENCE MULTIPLE ROUNDS OF HEAVY CONVECTIVE
RAINFALL AS BL DEWPOINTS INCREASE 65-70 AND WEAK INSTABILITY
DEVELOPS.
RAINFALL AMOUNTS THROUGH TONIGHT ARE EXPECTED TO AVERAGE BETWEEN 1-
2" ACROSS CENTRAL NC, WITH LOCALIZED HEAVIER AMOUNTS OF 2-4"
POSSIBLE WHERE STORMS TRAIN. URBAN AREAS, POOR-DRAINAGE ROADS, AND
SMALL STREAMS WILL BE THE MOST SUSCEPTIBLE. SOME RIVER FLOODING IS
ALSO POSSIBLE, MAINLY ALONG THE HAW AND ROCKY RIVERS.
HIGHS RANGING FROM NEAR 70 ACROSS THE NORTHERN PIEDMONT TO MID 70S
ACROSS THE COASTAL PLAIN AND EASTERN SANDHILLS. LOWS IN THE LOWER TO
MID 60S.
SHORT TERM /TUESDAY AND TUESDAY NIGHT/
AS OF 420 AM MONDAY...
* SHOWERS/STORMS LIKELY
ON THE ERN PERIPHERY OF A MID/UPR-LEVEL CYCLONE THAT WILL MOVE
SLOWLY NEWD FROM THE MID-SOUTH TO THE OH VALLEY, A NEGATIVELY-TILTED
SHORTWAVE PERTURBATION, AND ASSOCIATED POCKET OF MINUS 12-15C
TEMPERATURES AND 20-40 METER HEIGHT FALLS AT 500 MB, WILL PIVOT NWD
ACROSS THE CAROLINAS ON TUE AND VIRGINIAS TUE NIGHT. THAT SHORTWAVE
PERTURBATION WILL BE PRECEDED BY A GENERALLY NORTH TO SOUTH-ORIENTED
BAND OF DEEP CONVECTION AND CONVECTIVELY-AMPLIFIED MID-LEVEL
VORTICITY, EMBEDDED WITHIN A PLUME OF TROPICAL MOISTURE
CHARACTERIZED BY PWS OF 1.5-1.75" AND 150-175% OF NORMAL, OVER ERN
NC AND NEAR AND JUST EAST OF RAH'S COASTAL PLAIN, AT THE START OF
THE PERIOD. THAT CONVECTIVE BAND AND DEEP MOIST AXIS WILL TRANSLATE
GENERALLY NWD ACROSS THE MIDDLE ATLANTIC THROUGH 12Z WED.
AT THE SURFACE, A TRIPLE SURFACE WAVE AND MOIST SECTOR WILL MIGRATE
NWD ACROSS THE CAROLINAS TUE AND W-CNTL VA TUE NIGHT.
THE AFOREMENTIONED BAND OF DEEP CONVECTION AND MAIN FOCUS FOR FLASH
FLOODING, ONGOING IN OR NEAR THE COASTAL PLAIN AT THE START OF THE
PERIOD, WILL GRADUALLY EDGE NEWD AND OUT OF RAH'S AREA BY MID-
MORNING. IN ITS WAKE, PARTIAL CLEARING MAY RESULT FROM ERN SC NWD
AND INTO SRN AND CNTL NC, AS A MID-LEVEL DRY SLOT BRIEFLY STREAMS
NWD ACROSS THE REGION. ASSOCIATED POCKETS OF RELATIVELY MAXIMIZED
INSOLATION AND DIABATIC HEATING WILL PROBABLY CONTRIBUTE TO WARMING
INTO THE UPR 70S-LWR 80S OVER THE SANDHILLS AND PARTS OF THE COASTAL
PLAIN AND NE PIEDMONT, WITH GENERALLY MID-UPR 70S ELSEWHERE. WHEN
COMBINED WITH SEASONABLY RICH LOW-LEVEL MOISTURE AND COOL
TEMPERATURES ALOFT, MODERATE INSTABILITY OF 1000-2000 J/KG WILL
RESULT. THAT HEATING WILL ERODE ANY WEAK CONVECTIVE INHIBITION
PRESENT IN THE MORNING, WITH LOW LCLS AND LFCS THAT WILL ALL FAVOR
THE REDEVELOPMENT OF NUMEROUS SHOWERS/STORMS THROUGH THE DAY,
PARTICULARLY GIVEN BACKGROUND FORCING FOR ASCENT ACCOMPANYING THE
NEGATIVELY-TILTED SHORTWAVE PERTURBATION. 15-25 KTS OF 0-1 KM BULK
SHEAR AND SLIGHTLY BACKED SURFACE FLOW AHEAD OF THE TRIPLE
POINT/TROUGH WILL YIELD CLOCKWISE-CURVED AND SOMEWHAT ELONGATED
HODOGRAPHS IN THE LOWEST 2-3 KM, WITH ASSOCIATED EFFECTIVE HELICITY
VALUES UP TO 100-150 M2/S2. ASSOCIATED LOW-LEVEL SHEAR PROFILES,
BENEATH MODEST SSWLY MID-LEVEL FLOW OF 20-30 KTS, WILL PROBABLY
PROMOTE MOSTLY WEAK LOW-LEVEL ROTATION IN EVEN SHALLOW, CELLS (MINI-
SUPERCELLS). A CONDITIONAL RISK OF A WEAK SPIN-UP CANNOT BE RULED
OUT WHERE INSTABILITY AND LOW-LEVEL SHEAR MAY LOCALLY MAXIMIZE.
THAT CONVECTION MAY LINGER NUMEROUS IN COVERAGE ESPECIALLY ACROSS
THE NE PIEDMONT AND NRN COASTAL PLAIN TUE EVENING, BUT OTHERWISE
DIMINISH IN COVERAGE AND INTENSITY OVERNIGHT, WITH LOW TEMPERATURES
MOSTLY IN THE LWR-MID 60S.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
AS OF 445 AM MONDAY...
* LINGERING SHOWERS/STORMS WED-WED NIGHT, THEN MAINLY DRY UNTIL
LATE FRI
* TURNING HOT, WITH SCATTERED, POSSIBLY STRONG-SEVERE CONVECTION FRI-
SAT
A MID-LEVEL CYCLONE OVER THE OH VALLEY AT THE START OF THE PERIOD
WILL BECOME AN OPEN WAVE TROUGH WHILE WEAKENING AND LIFTING NEWD
ACROSS THE LWR GREAT LAKES AND MIDDLE ATLANTIC THROUGH THU NIGHT.
PROGRESSIVE SHORTWAVE RIDGING WILL MIGRATE FROM THE MS VALLEY TO THE
MIDDLE AND SOUTH ATLANTIC THROUGH THE SAME TIME, THEN OFFSHORE.
MEANWHILE, YET ANOTHER CLOSED AND CUTOFF LOW WILL DEVELOP ACROSS THE
NRN PLAINS AND NRN MS VALLEY AND DRIFT SLOWLY EWD ACROSS THE GREAT
LAKES AND SRN ON/QC THROUGH THE WEEKEND.
AT THE SURFACE, A TROUGH WILL LINGER OVER THE MIDDLE ATLANTIC AND
CAROLINAS THROUGHOUT THE PERIOD, WITH A WEAK COLD FRONTAL PASSAGE IN
CNTL NC POSSIBLE LATE SAT INTO EARLY SUN.
ABOVE AVERAGE PROBABILITIES OF CONVECTION WILL LINGER WITH THE
SLOWLY EXITING MID/UPR-LEVEL TROUGH AND CYCLONIC FLOW ALOFT MID-
WEEK, FOLLOWED BY A MAINLY DRY THU-INTO AT LEAST EARLY FRI, BENEATH
SHORTWAVE RIDGING AND RISING HEIGHTS ALOFT. CONVECTIVE CHANCES WILL
THEN INCREASE LATE FRI, AND ESPECIALLY FRI NIGHT, AS FALLING HEIGHTS
AND FORCING FOR ASCENT, ACCOMPANYING THE CUTOFF LOW OVER THE GREAT
LAKES, GLANCE THE SRN MIDDLE ATLANTIC. A BELT OF SEASONABLY STRONG,
35-45 KTS OF MID-LEVEL AT ITS BASE AND INTO PARTS OF THE SRN MIDDLE
ATLANTIC WOULD FAVOR ORGANIZED STORMS AND RISK OF SEVERE.
IT WILL OTHERWISE TURN WARMER, TO HOT PARTICULARLY FRI, WHEN
FORECAST TEMPERATURES WILL BE IN THE UPR 80S TO LWR 90S, AND WITH
HEAT INDEX VALUES IN THE UPR 90S TO NEAR 100 MAINLY IN THE SANDHILLS
AND SRN-CNTL COASTAL PLAIN.
AVIATION /18Z MONDAY THROUGH SATURDAY/
AS OF 1255 PM MONDAY...
MVFR TO IFR CONDITIONS WILL CONTINUE OVER THE NEXT 24 HOURS AS
ADDITIONAL ROUNDS OF MODERATE TO HEAVY RAIN MOVES ACROSS CENTRAL NC.
BRIEF DROPS TO LIFR WILL BE POSSIBLE AT ANY TERMINAL WITH ANY
HEAVIER DOWNPOUR. AS WE PIVOT TO THE OVERNIGHT PERIOD, EXPECT
CEILINGS TO GENERALLY TREND TO THE IFR/LIFR RANGE AS ADDITIONAL
SHOWERS/ISOLATED STORMS MOVE ACROSS THE AREA.
A BRIEF LIFT TO MVFR APPEARS LIKELY LATE IN THE 24 HR TAF PERIOD AT
ALL SITES (WITH KFAY POSSIBLY GOING VFR EARLY TUESDAY AFTERNOON).
HOWEVER, ADDITIONAL SCATTERED SHOWERS AND STORMS WILL BE POSSIBLE
THROUGH WEDNESDAY MORNING (HIGHEST CHANCES FOR STORMS WOULD BE AT
KFAY/KRWI AND MAYBE KRDU FROM LATE TUESDAY MORNING THROUGH THE
EVENING HOURS).
AFTER 18Z TUESDAY: DIURNALLY DRIVEN SCATTERED SHOWERS AND
THUNDERSTORMS WILL CONTINUE TUESDAY AFTERNOON THROUGH LATE WEEK.
EARLY MORNING STRATUS AND/OR FOG (IFR TO LIFR) WILL BE LIKELY.
RAH WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH FROM LATE TONIGHT THROUGH TUESDAY MORNING FOR
NCZ007>011-021>028-038>043-073>078-083>086-088-089.
SYNOPSIS...BADGETT
NEAR TERM...LUCHETTI/CBL
SHORT TERM...MWS
LONG TERM...MWS
AVIATION...LUCHETTI/CBL
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