569
FXUS62 KRAH 180533
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1233 AM EST MON NOV 18 2024
SYNOPSIS
OFFSHORE HIGH PRESSURE WILL EXTEND ACROSS THE SOUTH ATLANTIC STATES
AHEAD OF A STRONG COLD FRONT THAT WILL MOVE THROUGH THE REGION
WEDNESDAY NIGHT.
NEAR TERM /TONIGHT/
AS OF 955 PM SUNDAY...
A SUB-TROPICAL HIGH AT THE SURFACE AND ALOFT WILL CONTINUE TO EXTEND
ACROSS THE SOUTHEAST TONIGHT. ASSOCIATED CALM, TO OCCASIONAL, LIGHT,
SWLY STIRRING WITH THE CENTER OF THE SURFACE HIGH OFF THE SC COAST,
WILL FAVOR STRONG RADIATIONAL COOLING AMID PASSING CIRRUS. WITH
ANOTHER DAY OF MODIFICATION OF THE ASSOCIATED AIRMASS, OVERNIGHT-MON
MORNING TEMPERATURES WILL BE LESS CHILLY/FROSTY THAN SUN MORNING --
BY 4-8 F ON AVERAGE-- AND MOSTLY IN THE UPR 30S TO MID 40S. LOW-
LEVEL MOISTURE HAS LIKELY NOT INCREASED OR DEEPENED SUFFICIENTLY, AS
INDICATED BY NEARLY STEADY, OBSERVED MEAN MIXING RATIOS AT GSO AND
MHX FOR THE PAST COUPLE OF DAYS, TO ALLOW FOR ANYTHING MORE THAN
PATCHY MIST/FOG DEVELOPMENT AT THE USUAL AWOS SITES AND RWI.
SHORT TERM /MONDAY AND MONDAY NIGHT/
AS OF 135 PM SUNDAY...
ALOFT, THE SUB-TROPICAL RIDGE WILL BUILD TO THE WEST MON, THEN SHIFT
EWD INTO THE AREA MON NIGHT. AT THE SURFACE, HIGH PRESSURE WILL SIT
JUST OFF THE SOUTHEAST US COAST THROUGH MON NIGHT, WITH GENERALLY
WEAK HIGH PRESSURE OVER CENTRAL NC IN THE WAKE OF A WEAK TROUGH
EXITING TO THE EAST EARLY MON. WINDS SHOULD INITIALLY BE WLY TO NWLY
AT 3-5 KTS DURING THE DAY, THEN BECOME MORE WSWLY/SWLY BEFORE GOING
CALM OVERNIGHT. THE WEATHER SHOULD REMAIN DRY THROUGH MON NIGHT. AS
FOR TEMPERATURES, HIGHS SHOULD RANGE FROM UPPER 60S TO LOW 70S. AS
FOR LOWS SUN NIGHT, LOW-LEVEL THICKNESSES ARE AGAIN FORECAST TO BE
IN THE 1360-1375 METER RANGE BY 12Z TUE, WITH CLOUD COVER INCREASING
FROM THE WNW AFTER MIDNIGHT. GIVE THE GENERALLY CALM WINDS EXPECTED,
LOWS MAY BE SIMILAR TO PERHAPS A CATEGORY HIGHER THAN TONIGHT,
MAINLY IN THE MID 40S.
LONG TERM /TUESDAY THROUGH SUNDAY/
AS OF 318 PM SUNDAY...
FLOW ALOFT WILL TURN INCREASINGLY MORE SWLY TUESDAY AS A STRONG
UPPER TROUGH LIFTS THROUGH THE TN VALLEY. THE TROUGH AND AN
ASSOCIATED UPPER LOW WILL THEN PUSH EAST ACROSS THE EASTERN SEABOARD
WEDNESDAY THROUGH FRIDAY. BEHIND THIS FEATURE, STRONG NWLY FLOW
ALOFT RETURNS THROUGH THE WEEKEND.
THERE CONTINUES TO BE BETTER AGREEMENT AMONGST MODELS WRT TO
PRECIPITATION CHANCES AND QPF MIDDLE OF THIS UPCOMING WEEK. ON
TUESDAY, LIGHT RAIN WILL BE POSSIBLE STARTING IN THE AFTERNOON AND
CONTINUING INTO THE OVERNIGHT PERIOD VIA INCREASING ISENTROPIC LIFT
AND MOISTURE DEPTH (PWAT WILL SURGE TO ~250 % OF NORMAL THROUGH
TUESDAY NIGHT). SPC HAS INTRODUCED A VERY SMALL AREA OF THE TRIAD IN
A DAY 3 MARGINAL FOR SEVERE STORMS (VALID 12Z TUESDAY THROUGH 12Z
WEDNESDAY). AS OF NOW, NOT OVERLY CONCERNED FOR THIS AREA, AS ANY
INSTABILITY SHOULD LARGELY BE SHUNTED TO OUR SOUTH OVER THE GULF
STATES/GA.
BY WEDNESDAY, THE ANOMALOUSLY MOIST AIRMASS WILL LINGER WITH
INCREASING MID-LEVEL HEIGHT FALLS OVER OUR AREA VIA INFLUENCE FROM
THE AMPLIFYING CYCLONIC FLOW ALOFT. DEW POINTS ARE EXPECTED TO RISE
INTO THE LOWER TO MID 60S WEDNESDAY AFTERNOON, AND AS SUCH MODELS
ARE HINTING AT THE POSSIBILITY OF SOME INSTABILITY DEVELOPING (CAPE
VALUES ARE GENERALLY LESS THAN 500 J/KG AMONGST MODELS). GIVEN THAT
BULK-LAYER SHEAR WILL BE QUITE POTENT (35 TO 45 KTS), WE'LL HAVE TO
MONITOR FOR THE POTENTIAL FOR ISOLATED SEVERE STORMS. SPC DID NOTE
AT LEAST A NON-ZERO, CONDITIONAL, THREAT FOR A FEW STRONGER STORMS
WEDNESDAY WITH THEIR OVERNIGHT FORECAST. POPS SHOULD DROP OFF FROM
WEST TO EAST AS CONSIDERABLY DRY AIR CRASHES INTO OUR AREA BY
WEDNESDAY NIGHT. MEAN ENSEMBLE QPF AMONGST ENSEMBLES SUGGEST A FEW
TENTHS OF AN INCH TO A QUARTER OF AN INCH IS POSSIBLE THROUGH
WEDNESDAY NIGHT. HOWEVER, THE HIGHER PERCENTILES SUGGEST UPWARDS OF
A HALF TO THREE QUARTERS OF AN INCH MAYBE POSSIBLE. THIS DOESN'T
SEEM OUT OF THE REALM OF POSSIBILITY, ESPECIALLY IF INSTABILITY CAN
ACTUALLY BE REALIZED WEDNESDAY.
PERSISTENT NWLY FLOW WITH STRONG CAA IS EXPECTED BEHIND THE EXITING
UPPER TROUGH (AS THE UPPER LOW MOVES OVERHEAD THURSDAY NIGHT INTO
SATURDAY). AS SUCH, A DRASTIC TEMPERATURE CHANGE IS EXPECTED FROM
HIGHS IN THE UPPER 60S/LOWER 70S TUESDAY/WEDNESDAY TO HIGHS
STRUGGLING TO REACH THE LOWER TO MID 50S THURSDAY THROUGH SUNDAY.
THE RAW NBM IS ALSO ALREADY SUGGESTING THE POTENTIAL FOR SOME QUITE
COLD NIGHTS PARTICULARLY THIS UPCOMING WEEKEND. WE COULD SEE
OVERNIGHT LOWS DIP NEAR FREEZING FOR A GOOD PORTION OF OUR AREA.
DRY CONDITIONS ARE GENERALLY EXPECTED FROM THURSDAY THROUGH SUNDAY.
HOWEVER, SOME LINGERING MOISTURE, COMBINED WITH STEEP MID-LEVEL
LAPSE RATES, MAY PROMOTE SPRINKLES (AND PERHAPS ISOLATED GRAUPEL
REPORTS) THURSDAY AND FRIDAY.
AVIATION /06Z MONDAY THROUGH FRIDAY/
AS OF 1233 AM MONDAY...
GENERALLY VFR CONDITIONS UNDER HIGH PRESSURE WILL CONTINUE THROUGH
06Z/TUESDAY. THERE IS A CHANCE OF A PERIOD OF IFR FOG AT RWI, WITH
ONLY A FEW HOURS OF MVFR VSBYS POSSIBLE ELSEWHERE. ANY FOG THAT
DEVELOPS SHOULD MIX OUT BY MID MORNING, WITH ONLY HIGH CLOUDS IN
PLACE THROUGH THE END OF THE TAF PERIOD.
OUTLOOK: A STRONG COLD FRONT MOVING THROUGH THE REGION WILL BRING A
CHANCE OF SHOWERS AND ASSOCIATED SUB-VFR RESTRICTIONS TO THE AREA
LATE TUESDAY INTO WEDNESDAY. VFR CONDITIONS ARE EXPECTED TO RETURN
LATE WEDNESDAY AFTERNOON. A DEEPENING AREA OF LOW PRESSURE INVOF THE
GREAT LAKES WILL YIELD FREQUENT GUSTS OF 20 TO 30 KTS THURSDAY AND
AGAIN ON FRIDAY.
RAH WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...KC
LONG TERM...LUCHETTI
AVIATION...BADGETT
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