917
FXUS62 KRAH 120827
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
427 AM 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 340 AM MONDAY...
..A FLOOD WATCH IS IN EFFECT THROUGH TUESDAY MORNING
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 REMAIN
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 TRAINING CONVECTIVE BANDS LINE UP. 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 415 PM SUNDAY...
SHOWER COVERAGE WILL DECREASE SOMEWHAT ON WEDNESDAY AS THE LOW LIFTS
FURTHER NORTH, SO CAPPED POPS AT LIKELY, AGAIN HIGHEST IN THE NE.
AGAIN A FEW STORMS CAN'T BE RULED OUT WITH WEAK TO MODERATE
DESTABILIZATION, BUT NOT EXPECTING ANYTHING SEVERE AS THE MID-LEVEL
FLOW WILL BE EVEN MORE DIMINISHED BY THIS POINT. FORECAST HIGHS ARE
MID-70S TO LOWER-80S. DRIER AIR FROM NW FLOW ALOFT SHOULD REALLY
BEGIN TO MOVE IN ON WEDNESDAY NIGHT AS THE MID-LEVEL TROUGH FINALLY
PUSHES TO OUR EAST. LOWS SHOULD BE IN THE UPPER-50S TO MID-60S.
MID-LEVEL RIDGING WILL BUILD TO OUR WEST ON THURSDAY AND MOVE
OVERHEAD ON THURSDAY NIGHT, GETTING REPLACED BY FAST ZONAL FLOW
ACROSS CENTRAL NC ON FRIDAY AND SATURDAY AS THE RIDGE FLATTENS. THUS
WIDESPREAD UPPER FORCING WILL BE LACKING, AND WE WILL INSTEAD MOSTLY
RELY ON DAYTIME HEATING AND BOUNDARY LAYER DESTABILIZATION FOR
AFTERNOON/EVENING SHOWERS AND STORMS, ALONG WITH POSSIBLE MCS'S FROM
THE MIDWEST TRACKING NEAR OUR REGION. HOWEVER, THESE MCS'S ARE
IMPOSSIBLE TO PINPOINT WITH ANY SPECIFICITY THIS FAR OUT. SO POPS
ARE ONLY IN THE SLIGHT TO LOW CHANCE RANGE EACH DAY, INCREASING A
BIT TO CHANCE EVERYWHERE ON SATURDAY. MODERATE DESTABILIZATION WILL
BE POSSIBLE, PERHAPS EVEN STRONG (2000-3000+ J/KG OF CAPE) ON FRIDAY
ACCORDING TO LATEST GUIDANCE. SO A FEW STRONG TO SEVERE STORMS CAN'T
BE RULED OUT EACH DAY. TEMPERATURES WILL ALSO BE ON THE INCREASE,
WITH HIGHS IN THE MID-TO-UPPER-80S ON THURSDAY AND UPPER-80S TO MID-
90S ON FRIDAY, THEN DECREASING A BIT TO MID-80S TO LOWER-90S ON
SATURDAY WITH BETTER CONVECTION CHANCES. DEW POINTS WILL RISE TO THE
UPPER-60S AND POSSIBLY LOWER-70S ON FRIDAY AND SATURDAY, SO HEAT
INDICES WILL BE A CONCERN BOTH DAYS, ESPECIALLY ON FRIDAY WHEN THEY
COULD REACH THE MID-90S TO 100 IN THE SOUTH AND EAST. CONFIDENCE IN
THE OVERALL PATTERN IS QUITE LOW BY SUNDAY AS THE ECMWF AND MANY OF
ITS ENSEMBLES DRY US OUT BEHIND A COLD FRONT, WHILE THE GFS/GEFS AND
SLOWER WITH THE FRONT, THUS KEEPING US WARM AND WET. FOR NOW JUST
CONTINUE THE SLOW DECREASING TREND IN TEMPERATURES, WITH POPS IN THE
SLIGHT CHANCE RANGE.
AVIATION /06Z MONDAY THROUGH FRIDAY/
AS OF 220 AM MONDAY...
THROUGH 06Z TUESDAY: CONDITIONS WILL CONTINUE TO DETERIORATE WITH
CEILINGS LOWERING TO LIFR TO IFR THROUGH DAYBREAK AS WIDESPREAD
SHOWERS AND RAIN OVERSPREAD THE AREA FROM THE SOUTH. ADDITIONALLY,
BEFORE THE RAIN MOVES IN, A PERIOD OF PATCHY FOG IS POSSIBLE, WITH
VSBYS POTENTIALLY DROPPING TO LESS THAN A MILE AT TIMES.
EXPECT LITTLE TO NO IMPROVEMENT THROUGH THE FORECAST PERIOD AS
WIDESPREAD SHOWERS AND ISOLATED THUNDERSTORMS WILL CONTINUE TO
REDEVELOP ACROSS THE AREA THROUGH TONIGHT. RESTRICTIONS SHOULD
REMAIN PREDOMINATELY IFR THROUGH THE EVENING, BEFORE POTENTIALLY
LOWERING TO LIFR TONIGHT/EARLY TUESDAY.
AFTER 06Z TUESDAY: BANDS OF MODERATE TO HEAVY RAIN AND IFR
CONDITIONS WILL MORE-OR-LESS CONTINUE THROUGH TUESDAY MORNING.
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...CBL
SHORT TERM...MWS
LONG TERM...DANCO
AVIATION...CBL/BADGETT
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