179
FXUS62 KRAH 210827
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
427 AM EDT TUE JUL 21 2026
WHAT HAS CHANGED
* A HEAT ADVISORY HAS BEEN ISSUED FOR THIS AFTERNOON FOR CUMBERLAND,
HOKE, SAMPSON, SCOTLAND, AND WAYNE CO., FOR THE RISK OF 2-3 HOURS
OF HEAT INDEX VALUES TO AROUND 105 F.
KEY MESSAGES
AS OF 425 AM TUESDAY...
1) A HEAT ADVISORY HAS BEEN ISSUED FOR THIS AFTERNOON FOR
CUMBERLAND, HOKE, SAMPSON, SCOTLAND, AND WAYNE CO., FOR THE RISK OF
2-3 HOURS OF HEAT INDEX VALUES TO AROUND 105 F.
2) AFTER A SCATTERING OF AFTERNOON SEA BREEZE AND POSSIBLY PIEDMONT
TROUGH CONVECTION TODAY, SHOWERS/STORMS WILL INCREASE IN COVERAGE
ACROSS THE NRN PIEDMONT LATER TONIGHT INTO WED, THEN SETTLE, WITH AN
ASSOCIATED OUTFLOW-REINFORCED FRONTAL ZONE, SEWD AND ACROSS MOST ALL
OF CNTL NC THROUGH WED NIGHT.
3) A COLD FRONT WILL MOVE ACROSS NC ON THURSDAY AND THEN STALL
ACROSS THE CAROLINAS INTO THE WEEKEND PRODUCING A PERIOD OF
UNSETTLED WEATHER WITH COOLER THAN AVERAGE TEMPERATURES. THERE IS
SIGNIFICANT UNCERTAINTY IN THE PLACEMENT OF THE FRONT WHICH WILL
GREATLY DETERMINE FORECAST DETAILS INCLUDING THE POTENTIAL FOR
SIGNIFICANT RAINFALL.
DISCUSSION
AS OF 425 AM TUESDAY...
KEY MESSAGE 1... A HEAT ADVISORY HAS BEEN ISSUED FOR THIS AFTERNOON
FOR CUMBERLAND, HOKE, SAMPSON, SCOTLAND, AND WAYNE CO., FOR THE RISK
OF 2-3 HOURS OF HEAT INDEX VALUES TO AROUND 105 F.
NEAR PERSISTENCE HEAT AND HUMIDITY, WHICH YIELDED HEAT INDEX VALUES
OF 100-107 F OVER PARTS OF THE SANDHILLS AND COASTAL PLAIN ON
MONDAY, WILL PROBABLY DO THE SAME THIS AFTERNOON. SEA BREEZE
CONVECTION AND OUTFLOW IN THE SRN AND CNTL COASTAL PLAIN WILL HAVE
THE POTENTIAL TO SHORTEN THE DURATION OF ADVISORY CRITERIA HEAT, OR
PREVENT IT ALTOGETHER.
KEY MESSAGE 2... AFTER A SCATTERING OF AFTERNOON SEA BREEZE AND
POSSIBLY PIEDMONT TROUGH CONVECTION TODAY, SHOWERS/STORMS WILL
INCREASE IN COVERAGE ACROSS THE NRN PIEDMONT LATER TONIGHT INTO WED,
THEN SETTLE, WITH AN ASSOCIATED OUTFLOW-REINFORCED FRONTAL ZONE,
SEWD AND ACROSS MOST ALL OF CNTL NC THROUGH WED NIGHT.
A SERIES OF VIGOROUS SHORTWAVE PERTURBATIONS WILL AMPLIFY AN
ANOMALOUSLY DEEP SYNOPTIC TROUGH, WITH STANDARDIZED 500 MB HEIGHT
ANOMALIES FORECAST TO REACH 2-3 SIGMA, ACROSS THE GREAT LAKES AND
MIDDLE ATLANTIC THROUGH MID-WEEK. IN A TIGHT HEIGHT GRADIENT AT ITS
BASE, THE MID-LATITUDE WESTERLIES WILL DIP TO ATYPICALLY LOW
LATITUDES FOR THIS TIME OF YEAR, WITH 500-700 MB WINDS OF 30-50 KTS
LIKELY FROM THE VIRGINIAS TO NRN NC FROM LATE THIS AFTERNOON THROUGH
WED, ATOP A BROAD REGION OF LWR-LEVEL WARM AIR ADVECTION AND
CONTRIBUTION TO QG FORCING FOR ASCENT.
AT THE SURFACE, AN OUTFLOW-REINFORCED FRONT WILL PROGRESS ACROSS THE
LWR OH VALLEY AND VIRGINIAS THROUGH EARLY TONIGHT, THEN SETTLE
ACROSS SRN VA AND POSSIBLY INTO THE NRN PIEDMONT AND NRN COASTAL
PLAIN OF NC LATE TONIGHT-EARLY WED. IT WILL BE PRECEDED BY A PRE-
FRONTAL, APPALACHIAN-LEE TROUGH OVER THE SRN MIDDLE ATLANTIC
PIEDMONT TODAY. THE FRONT WILL THEN WAVER OVER CNTL NC WED-WED
NIGHT, MODULATED BY TRAINING CONVECTION/OUTFLOW AND DIFFERENTIAL
DIABATIC HEATING, AND PROBABLY SETTLE INTO SC AND SERN NC BY EARLY
THU.
AFTERNOON SHOWERS/STORMS TODAY WILL LIKELY CONCENTRATE IN THE SRN
AND CNTL COASTAL PLAIN AND POSSIBLY THE NW PIEDMONT, ALONG THE SEA
BREEZE AND PIEDMONT TROUGH, RESPECTIVELY. WHILE THE MOST INTENSE
CELLS WILL BE CAPABLE OF PRODUCING DAMAGING DOWNBURST WINDS, THE
AFOREMENTIONED STRENGTHENING MID-LEVEL WINDS ACROSS NRN NC WILL
CONDITIONALLY FAVOR MULTI-CELL CLUSTERING ALONG COMMON COLD POOLS
AND A SOMEWHAT GREATER RISK OF DAMAGING WIND GUSTS, WHERE A SLIGHT
RISK FOR SEVERE STORMS, LEVEL 2 OF 5, REMAINS.
TRAINING AND BACKBUILDING CONVECTION, WITH AN INCREASING RISK OF
EXCESSIVE RAIN AND FLASH FLOODING, WILL THEN BECOME FAVORED ALONG
THE OUTFLOW-REINFORCED FRONTAL ZONE OVER SRN VA AND NRN NC LATE
TONIGHT-EARLY WED, BEFORE SETTLING SWD ACROSS MOST OF ALL CNTL NC
LATER WED-WED NIGHT. A CATEGORICAL UPGRADE FROM SLIGHT RISK TO
MODERATE FOR EXCESSIVE RAIN MAY BECOME NECESSARY (LEVEL 2 TO 3) AS
UNCERTAINTIES FROM MESOSCALE AND CONVECTIVE INFLUENCES TO THE
PLACEMENT AND EVOLUTION OF THE BOUNDARY BECOME CLEARER; AND A FLASH
FLOOD WATCH MAY BE NEEDED BY LATER THIS AFTERNOON OR OVERNIGHT.
WHILE A FEW STRONG TO SEVERE DOWNBURSTS WILL ALSO BE POSSIBLE, THE
FLASH FLOOD RISK WILL HAVE BECOME RELATIVELY GREATER BY WED.
KEY MESSAGE 3... A COLD FRONT WILL MOVE ACROSS NC ON THURSDAY AND
THEN STALL ACROSS THE CAROLINAS INTO THE WEEKEND PRODUCING A PERIOD
OF UNSETTLED WEATHER WITH COOLER THAN AVERAGE TEMPERATURES. THERE IS
SIGNIFICANT UNCERTAINTY IN THE PLACEMENT OF THE FRONT WHICH WILL
GREATLY DETERMINE FORECAST DETAILS INCLUDING THE POTENTIAL FOR
SIGNIFICANT RAINFALL.
A MID AND UPPER-LEVEL TROUGH WILL PERSIST ACROSS THE GREAT LAKES AND
NORTHEAST THROUGH THE THURSDAY THROUGH MONDAY PERIOD. A COLD FRONT
WILL MOVE SOUTH ACROSS NC ON THURSDAY AND LIKELY STALL ACROSS ALONG
THE CAROLINA COAST AND EXTEND WESTWARD SOMEWHERE IN THE CAROLINAS ON
FRIDAY THROUGH MONDAY. THE FRONT WILL MARK THE LEADING EDGE OF A
COOLER AND MORE STABLE AIRMASS AND THE FRONTAL ZONE WILL BE THE
FOCUS FOR SHOWERS AND THUNDERSTORMS THROUGH MUCH OF THE PERIOD.
WHILE THE OPERATIONAL GFS AND EC MOVE THE FRONT INTO NC ON THURSDAY
NIGHT AND THEN WAVER IT NEAR THE NC/SC BORDER OR EVEN ACROSS EASTERN
NC ON FRIDAY THROUGH THE WEEKEND THE VARIOUS GEFS AND ENS ENSEMBLE
MEMBERS PROVIDE A WIDE RANGE OF SOLUTIONS INCLUDING PUSHING THE
FRONT FURTHER SOUTH THROUGH SC INTO GA WHILE OTHERS LIFT THE FRONT
ACROSS NC INTO VA. CLIMATOLOGY WOULD SUGGEST A SIGNIFICANT SOUTHWARD
PUSH WOULD BE UNUSUAL AND A NORTHWARD RETREAT WOULD BE MORE COMMON.
IN ADDITION SUB-SYNOPTIC FACTORS INCLUDING THE DEVELOPMENT OF
CONVECTION NEAR THE FRONT COULD IMPACT THE EVOLUTION AND PLACEMENT
OF THE FRONT.
NOTABLY COOLER AND DRIER AIR WILL SETUP BEHIND THE FRONT WITH MUCH
LOWER PRECIPITATION CHANCES. NEAR THE FRONTAL ZONE AND ESPECIALLY
SOUTH OF THE FRONT EXPECT MUCH MORE CLOUDINESS, MUGGY CONDITIONS AND
UNSETTLED WEATHER WITH MULTIPLE ROUNDS OF SHOWERS AND STORMS. ON
FRIDAY PW VALUES WILL POTENTIALLY RANGE FROM NEAR 1.1 INCHES ACROSS
SOUTHERN VA TO 2.4 INCHES ACROSS SOUTHEASTERN NC. SIMILARLY SURFACE
DEWPOINTS MAY RANGE FROM NEAR 60 IN NORTHWESTERN NC TO THE MID 70S
ACROSS SOUTHEASTERN NC. WPC QPF GUIDANCE FOR THURSDAY THROUGH MONDAY
HIGHLIGHTS A DRAMATIC RANGE IN PRECIPITATION WITH RAINFALL TOTALS OF
A HALF INCH OR SO IN TRIAD, 1.5 TO 2.0 INCHES IN THE TRIANGLE AND 2
TO 4 INCHES IN THE SANDHILLS. A SLIGHT SHIFT IN THE FRONTAL
PLACEMENT COULD DRAMATICALLY ALTER THE PRECIPITATION AMOUNTS.
AT THIS POINT, THE MOST LIKELY SCENARIO IS FOR THE FRONT TO MOVE
ACROSS NC ON THURSDAY WITH SHOWERS AND STORMS FAIRLY WIDESPREAD
ACROSS THE AREA. WHILE RAIN CHANCES CONTINUE ACROSS CENTRAL NC ON
FRIDAY, THE FOCUS FOR SHOWERS AND STORMS SHIFTS TO SOUTHERN AND
EASTERN AREAS. PRECIPITATION COVERAGE AND INTENSITY DECREASES LATE
IN THE WEEKEND AND ON MONDAY. EXPECT A FAIR AMOUNT OF CLOUDINESS
THROUGH THE PERIOD WITH IMPROVEMENT LATE IN THE PERIOD. HIGH
TEMPERATURES WILL RANGE BELOW NORMAL THROUGH THE PERIOD, MOST
SIGNIFICANTLY ON THURSDAY WITH MORNING LOWS NEAR AVERAGE THROUGH THE
PERIOD.
AVIATION /06Z TUESDAY THROUGH SATURDAY/
AS OF 230 AM TUESDAY...
ASIDE FROM A CHANCE OF DIURNAL CUMULUS CLOUD BASES THAT MAY DEVELOP
WITH SCT-BKN COVERAGE IN MVFR RANGE BETWEEN 14-17Z, PRIMARILY VFR
CONDITIONS ARE EXPECTED AMID STRENGTHENING, SSWLY LOW-LEVEL FLOW
THAT WILL FAVOR SURFACE GUSTS TO AROUND 20 KTS OR SO WITH DAYTIME
HEATING AND THE POSSIBILITY OF MARGINAL LOW-LEVEL WIND SHEAR TONIGHT-
WED MORNING. THE COVERAGE OF SHOWERS/STORMS SHOULD BE LESS TODAY
VERSUS MON, SINCE THE FRONTAL ZONE AND CONVERGENCE AXIS FROM MON HAS
WEAKENED AND SHIFTED NWD ACROSS THE MIDDLE ATLANTIC. THERE WILL,
HOWEVER, BE A CHANCE OF AT LEAST A FEW CELLS AT FAY FROM THE SEA
BREEZE AND SUBSEQUENT OUTFLOW THIS AFTERNOON AND ALSO AT INT/GSO
THIS AFTERNOON-EVENING FROM THE PIEDMONT TROUGH AND/OR OUTFLOW FROM
UPSTREAM CONVECTION ACROSS THE VIRGINIAS.
OUTLOOK: AN OUTFLOW-REINFORCED FRONTAL ZONE AND FOCUS FOR TRAINING
CONVECTION AND FLIGHT RESTRICTIONS WILL SETTLE VERY SLOWLY SWD INTO
THE NRN NC PIEDMONT LATE TONIGHT AND BECOME QUASI-STATIONARY OVER
CNTL NC THROUGH WED NIGHT. WHILE THE SURFACE FRONT WILL PROBABLY
SETTLE INTO SC AND SERN NC THU-FRI, "OVERRUNNING" LIFT ATOP THE
FRONTAL ZONE WILL FAVOR CONTINUED ABOVE AVERAGE CHANCES OF FLIGHT
RESTRICTIONS AND RAIN/STORMS THROUGH THE END OF THE WEEK, WITH
HIGHER CHANCES AT ERN SITES VERSUS WRN ONES.
RAH WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY FROM NOON TODAY TO 7 PM EDT THIS EVENING FOR NCZ078-
085-086-088-089.
DISCUSSION...MWS/BLAES
AVIATION...MWS
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