326
FXUS62 KRAH 111810
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
210 PM EDT TUE AUG 11 2026
WHAT HAS CHANGED
* TWO ROUNDS OF CONVECTION WILL BE POSSIBLE THIS AFTERNOON/EVENING
AND AGAIN LATE TONIGHT. CONFIDENCE IS GREATEST, ALTHOUGH STILL
QUITE LOW, ACROSS THE PIEDMONT FOR DAMAGING WIND GUSTS TO
OCCUR LATER THIS AFTERNOON.
KEY MESSAGES
AS OF 200 PM TUESDAY...
1) HEAT ADVISORY IN EFFECT UNTIL 8 PM TONIGHT FOR THE SOUTHERN
COASTAL PLAIN.
2) CONDITIONAL RISK FOR A LINE OF DAMAGING STRAIGHT-LINE WIND GUSTS
FOR THIS AFTERNOON WITHIN A COMPLEX AND EVOLVING FORECAST.
3) THE HEAT AND HUMIDITY WILL CONTINUE INTO LATE WEEK, WITH DAILY
AFTERNOON CHANCES FOR ISOLATED THUNDERSTORMS.
DISCUSSION
AS OF 200 PM TUESDAY...
KEY MESSAGE 1... HEAT ADVISORY IN EFFECT UNTIL 8 PM TONIGHT FOR THE
SOUTHERN COASTAL PLAIN.
CENTRAL NC HAS BEEN VOID OF MID/HIGH CLOUDS FROM THE WAVES OF MCS'S
RIPPLING THROUGH THE OHIO VALLEY AND MID-ATLANTIC. ALTHOUGH FLOW
JUST ABOVE THE SURFACE HAS BEEN NORTH-NORTHWESTERLY VIA REGIONAL VWP
DATA AND 12Z RAOB'S EARLIER THIS MORNING, A PERSISTENT SURFACE
TROUGH DRAPED FROM CENTRAL VA INTO THE WESTERN PIEDMONT WEST OF CLT
HAS ALLOWED GENERALLY WESTERLY FLOW TO CONTINUE AT THE SURFACE. 12Z
RAOB DATA ALSO SHOWS A 6-12M INCREASE IN MORNING LOW-LVL THICKNESSES
WHICH WILL SUPPORT 2 TO 4 DEGREE INCREASE IN AFTERNOON TEMPS
COMPARED TO YESTERDAY, YIELDING HIGHS IN THE MID/UPPER 90S.
IN COMBINATION WITH DEW POINTS REMAINING IN THE MID 70S THROUGH PEAK
HEATING ACROSS THE EASTERN SANDHILLS AND SOUTHERN COASTAL PLAIN,
SEVERAL HOURS OF HEAT INDEX VALUES OF > 105 ARE EXPECTED. ELSEWHERE,
A SLIGHT REDUCTION IN DEW POINTS INTO THE UPPER 60S WILL CURB HEAT
INDICES A BIT AND RANGE FROM AROUND 100 IN THE TRIAD UP TO 105.
WITHIN THE COMPLEX FORECAST PATTERN, THERE ARE MANY FAILURE MODES
FOR WED IN TERMS OF DANGEROUS HEAT. THE LINGERING CLOUD COVER FROM
UPSTREAM MCS ACTIVITY OVER THE MID-ATLANTIC WILL BE MORE PROBABLE
OVER THE CAROLINAS ON WED AND COULD TEMPER HIGHS BY A FEW DEGREES
AND PREVENT REACHING THE THERMODYNAMIC POTENTIAL THROUGH THE
AFTERNOON. THIS FACTOR ALONG WITH THE LOCATIONS OF OUTFLOW
BOUNDARIES FROM CONVECTION EXPECTED LATER TODAY WILL LIKELY KEEP
TEMP/DEW POINT FORECAST CONFIDENCE LOW UNTIL LATER TONIGHT WHEN THE
DUSTS SETTLES.
KEY MESSAGE 2... CONDITIONAL RISK FOR A LINE OF DAMAGING STRAIGHT-
LINE WIND GUSTS FOR THIS AFTERNOON WITHIN A COMPLEX AND EVOLVING
FORECAST.
REGIONAL SATELLITE AND SURFACE OBSERVATIONS SHOW A SLOWLY MOVING
OUTFLOW BOUNDARY LAID OUT NORTHWEST TO SOUTHEAST ACROSS EASTERN KY
INTO NORTHWEST NC, WITH SOME DEEPENING CU EXTENDING INTO THE EASTERN
PIEDMONT. AN UPSTREAM MCS AND ASSOCIATED OUTFLOW BOUNDARY IS NOTED
DIVING SOUTH ALONG THE STRONG THETA-E GRADIENT WITH 2000-3000 MLCAPE
SOUTH AND WEST OF THE FRONTAL BOUNDARY INTO CENTRAL NC.
ADDITIONALLY, MID-LVL WATER VAPOR IMAGERY SHOWS A BELT OF DRIER AIR
OVER THE TN VALLEY EXTENDING INTO NC, WHICH WILL WORK TO ENHANCE
DOWNDRAFTS THROUGH DIABATIC COOLING. DCAPE VALUES OF 1000-1300 J/KG
IS MORE THAN SUFFICIENT TO STRONGLY ENHANCE OUTFLOWS WHERE STORMS
GROUP TOGETHER AND FORM COMMON COLD POOLS. CENTRAL NC WILL BE ON THE
SOUTHERN FLANK OF ENHANCED WEST-NORTHWEST MID-LVL WINDS WITH AROUND
15-30 KTS TO WORK WITH (GREATEST NORTH AND EAST OF THE TRIANGLE).
THE ENVIRONMENT IS PRIMED FOR STRONG WINDS OVER THE FORECAST AREA
WITH CLUSTERS/SWATHS OF 50-70 MPH POSSIBLE, HOWEVER THE THREAT IS
ENTIRELY CONDITIONAL. WITH THE LACK OF ANY SYNOPTIC FORCING FOR
ASCENT AS MCV'S WILL LIKELY TRACK NORTH OF THE AREA ACROSS VA. WE
WILL HAVE TO RELY ON OUTFLOW BOUNDARIES FROM PRIOR STORMS (UPSTREAM
MCS ACTIVITY OR DEVELOPING SHOWERS/STORMS ACROSS THE EASTERN SLOPES
OF THE APPALACHIANS) TO SPARK MORE SCATTERED TO LOCALLY NUMEROUS
SHOWERS/STORMS. THERE IS A POTENTIAL FOR CONVECTIVE TEMPERATURES TO
BE REACHED ANYWHERE WITHIN CENTRAL NC, HOWEVER, SEVERAL DEGREES
WARMER AIR-TEMPERATURES COMPARED TO THE PAST FEW DAYS WITH SIMILAR
DEW POINTS WILL LIMIT 0-3 MLCAPE TO ONLY AROUND 100 J/KG (COMPARED
TO 125-150+ J/KG OVER THE PAST SEVERAL DAYS) WITH THE ADDED
DIFFICULTY OF DRY AIR ENTRAINMENT TO OVERCOME FROM INITIAL
CONVECTIVE ATTEMPTS. FORECAST SPC MESOANALYSIS DATA DOES SHOW HINTS
OF 125-175 0-3KM MLCAPE DEVELOPING AROUND AND EAST OF CLT WHERE
MULTIPLE CONVECTIVE ATTEMPTS WOULD BE MOST PROBABLE.
GREATEST CONFIDENCE IN LOCATION WHERE DAMAGING WINDS MAY CHANGE, BUT
CURRENT EXPECTATION IS ACROSS THE PIEDMONT, ESPECIALLY THE WESTERN
PIEDMONT, WHERE THE TRACK OF OUTFLOW SHIFTING ACROSS CENTRAL/EASTERN
KY IS MOST LIKELY, AND WHERE PRECEDING DEVELOPMENT IN THE HIGH
TERRAIN WITHIN THE LEE SURFACE TROUGH IS POSSIBLE. FROM THE
LONGITUDE OF THE TRIANGLE EASTWARD, A SIMILAR ENVIRONMENT IS
EXPECTED, BUT MAY BE VOID OF MUCH FORCING MECHANISMS TO SPARK
SCATTERED CONVECTION AND TAP INTO THE DAMAGING WIND POTENTIAL OVER
THE FORECAST AREA.
KEY MESSAGE 3... THE HEAT AND HUMIDITY WILL CONTINUE INTO LATE WEEK,
WITH DAILY AFTERNOON CHANCES FOR ISOLATED THUNDERSTORMS.
HOT AND HUMID CONDITIONS WILL PERSIST THROUGH LATE WEEK, ACCOMPANIED
BY DAILY CHANCES FOR ISOLATED AFTERNOON THUNDERSTORMS. HIGH
TEMPERATURES THURSDAY AND FRIDAY WILL RANGE FROM THE LOW 90S IN THE
NORTHWEST TO THE MID/UPPER 90S ELSEWHERE. HIGH DEW POINTS IN THE MID
70S WILL YIELD PEAK HEAT INDICES IN THE LOW TO MID 100S.
RELIEF ARRIVES OVER THE WEEKEND AS A FRONTAL BOUNDARY APPROACHES
THURSDAY AND PUSHES THROUGH LATE FRIDAY. EXPECT ISOLATED TO
SCATTERED SHOWERS AND STORMS IN THE AFTERNOON AND EVENING. HIGHS
WILL BE IN THE UPPER 80S TO LOW 90S, KEEPING HEAT INDICES
PREDOMINANTLY BELOW TRIPLE DIGITS. HOWEVER, SOUTHWEST FLOW QUICKLY
RETURNS EARLY NEXT WEEK, BRINGING ANOTHER ROUND OF TEMPERATURES IN
THE MID/UPPER 90S PAIRED WITH TRIPLE-DIGIT HEAT INDICES FOR MUCH OF
THE AREA.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
AS OF 200 PM TUESDAY...
A COMPLEX AND LOW PREDICTABILITY FORECAST IS EXPECTED TO EVOLVE OVER
THE NEXT 12 HOURS OVER CENTRAL NC. THE INTENSITY, TRACK, AND
LONGEVITY FOR A SERIES OF CONVECTIVE CLUSTERS AS THEY TRAVERSE THE
SOUTHERN/MIDDLE APPALACHIAN MOUNTAINS AND THEIR STATE AS THEY ENTER
CENTRAL NC IS THE BIGGEST FORECAST CHALLENGE AND WILL PRIMARILY
AFFECT AVIATION RESTRICTIONS DURING THAT TIME. WHERE CONVECTIVE
CLUSTERS TRACK, STRONG TO SEVERE AND ERRATIC WIND GUSTS (35-60 KTS),
HEAVY TO TORRENTIAL RAINFALL (<1-3 SM) AND LOW MVFR CIGS WILL BE
POSSIBLE, BUT PREDICTING THEIR LOCATION AND INTENSITY BEFORE THEY
DEVELOP IS HIGHLY UNCERTAIN.
BEST CHANCES MAY BE AROUND THE TRIAD TERMINALS WITH LESS CONFIDENCE
AT RDU, RWI AND ESPECIALLY FAY. PROB30S WITHIN THE 18Z TAFS HAVE
BEEN TRIMMED BASED ON PROBABILISTIC DATA FROM 12Z HREF/REFS AND
HOURLY NBM TEXT PRODUCTS. DEPENDENT ON HOW THIS FIRST WAVE OF
CONVECTION EVOLVES, AN ADDITIONAL SECOND ROUND OF CONVECTION MAY BE
POSSIBLE BETWEEN 03-07Z, BUT CONFIDENCE IS EVEN LOWER ON THIS WAVE.
OUTLOOK: PRIMARILY DIURNALLY MAXIMIZED SHOWERS/STORMS WILL BE
POSSIBLE THROUGH THURSDAY AND PERHAPS INTO FRI AHEAD OF A FRONTAL
PASSAGE AND NORTHEASTERLY POST-FRONTAL ONSHORE WINDS INTO SAT.
MORNING MIST/STRATUS WILL BE POSSIBLE EACH MORNING INTO SAT,
LOCALIZED WHERE THE HEAVIEST RAIN FALLS FROM THE AFTERNOON AND
EVENING CONVECTION.
RAH WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR NCZ078-088-089.
DISCUSSION...AS/CA
AVIATION...AS
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