Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 242346
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
746 PM EDT FRI APR 24 2015

.SYNOPSIS...A SERIES OF UPPER DISTURBANCES WILL CAUSE UNSETTLED
WEATHER ACROSS CENTRAL NC THROUGH THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 310 PM FRIDAY...

MID-UPPER LEVEL S/W RIDGE WILL DRIFT ACROSS THE FORECAST AREA
TONIGHT. THIS WEATHER FEATURE WILL INITIALLY CAUSE MOSTLY CLEAR
SKIES OVERHEAD. THE ATTENDANT DRY AIR MASS (SFC DEWPOINTS THIS
AFTERNOON DOWN INTO THE 20S) WILL ALLOW THE ATMOSPHERE TO COOL
EFFICIENTLY AFTER SUNSET. WHILE NOT AS COOL AS LAST NIGHT...LATE
EVENING TEMPS SHOULD BE IN THE 40S TO NEAR 50. MOST PLACES WILL
LIKELY ACHIEVE THEIR MIN TEMPS SHORTLY AFTER MIDNIGHT. DURING THE
OVERNIGHT HOURS...INCREASING MID-HIGH LEVEL CLOUDS ASSOCIATED WITH
AN AREA OF LOW PRESSURE CROSSING THE LOWER MS VALLEY WILL INCREASE
WEST-TO EAST ACROSS CENTRAL NC. THIS INCREASING/THICKENING CLOUD
COVER SHOULD CAUSE TEMPS TO HOLD STEADY OR POSSIBLY SLOWLY RISE
DURING THE PRE-DAWN OURS. CANNOT RULE OUT THE POSSIBILITY OF A
SHOWER OR TWO SKIRTING ALONG OUR WESTERN PERIPHERY BEFORE 7 AM.
ELSEWHERE NO RAIN SHOULD OCCUR. MIN TEMPS NEAR 40 FAR NE TO THE MID-
UPPER 40S WEST.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
AS OF 310 PM FRIDAY...

INCREASING LOW LEVEL WARM AIR ADVECTION ASSOCIATED WITH AN UPPER
LEVEL DISTURBANCE MOVING EAST ACROSS THE DEEP SOUTH INTO THE SE U.S.
WILL CAUSE AREAS OF RAIN TO INCREASE IN COVERAGE AND INTENSITY
SATURDAY ACROSS CENTRAL NC. EXPECT THE BULK OF THE RAIN TO OCCUR
WEST OF THE HIGHWAY 1 CORRIDOR THROUGH MID DAY...THEN OVERSPREAD THE
REMAINDER OF THE REGION IN THE AFTERNOON.  THE RAIN FALLING THROUGH
THE DRY SUB CLOUD LAYER MAY CAUSE AN IN-SITU OR WEAK HYBRID DAMMING
EVENT TO OCCUR...MAINLY LIMITED TO THE NORTHWEST PIEDMONT. THE
TIMING OF THE RAIN WILL HAVE AN IMPACT ON HIGH TEMPS FOR THE DAY.
EXPECTING THE RAIN NOT TO ARRIVE IN THE RDU AREA UNTIL CLOSE TO MID
DAY WHICH SHOULD ALLOW FOR SOME TEMP RECOVERY. IN THE TRIAD...EXPECT
THE RAIN TO START BETWEEN 8 AM AND 12 PM. DUE TO THE RAIN ARRIVING
SHORTLY AFTER DAYBREAK...TEMPS IN THE TRIAD MAY STRUGGLE TO WARM
MUCH ABOVE THE LOWER 50S.

LATE IN THE AFTERNOON...THE PASSAGE OF THE 850MB WARM FRONT ACROSS
OUR SOUTHERN COUNTIES MAY ERODE THE STABLE LAYER ENOUGH TO ALLOW FOR
THE DEVELOPMENT OF A FEW THUNDERSTORMS. WITH BETTER INSTABILITY
LYING TO OUR SOUTH...LOW LEVEL FLOW WILL BE ADVECTING THIS SLIGHTLY
UNSTABLE AIR MASS INTO OUR SOUTHERN COUNTIES INTO THE EVENING HOURS.
SHEAR WILL BE SUFFICIENT TO SUPPORT ORGANIZED CONVECTION AND LATEST
CAM DEPICTIONS SUGGEST A FEW STORMS CROSSING THE SC BORDER SATURDAY
EVENING. WHILE CANNOT RULE OUT THE POTENTIAL FOR A SEVERE STORM
NEAR THE SC BORDER SATURDAY NIGHT...CONFIDENCE NOT HIGH ENOUGH AT
THIS TIME TO MENTION IN FORECAST OR THE HWO.

THE CONTINUED NEWD PROGRESSION OF THE 850 MB WARM FRONT
SHOULD PUSH THE RAIN OUT OF THE NE PIEDMONT/NORTHERN COASTAL PLAIN
SATURDAY EVENING...WITH SCATTERED SHOWER HIGHLY PROBABLE IN ITS
WAKE. WITH THE WARM AIR ALOFT ABOVE THE RELATIVELY COOL SFC
LAYER...WILL LIKELY SEE AREAS OF FOG AND/OR LOW CLOUDS OVER THE
PIEDMONT AND NORTHERN COASTAL PLAIN SATURDAY NIGHT.

MAX TEMPS SATURDAY LOW-MID 50S NW TO THE MID 60S SOUTH. MIN TEMPS
SATURDAY NIGHT UPPER 40S/NEAR 50 NORTH AND THE MID-UPPER 50S SOUTH.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
AS OF 300 PM FRIDAY...

SUNDAY: EXPECT WARM MOIST WEST-SOUTHWESTERLY FLOW TO START THE
PERIOD...WITH THE RETREATING WARM FRONT INVOF THE NC/VA BORDER. AN
UPPER LEVEL SHORTWAVE WILL TRAVERSE THE REGION DURING THE DAY
SUNDAY. AT THE SURFACE...A WEST-EAST ORIENTED LOW OVER THE CAROLINAS
WILL SLOWLY BE PUSHED SOUTH AND EAST AS A COLD FRONT SLIDES THROUGH
THE REGION. EXPECT SOME RAIN TO MOVE THROUGH CENTRAL NC FROM NORTH
TO SOUTH AHEAD OF THE FRONT...ENDING LATE SUNDAY EVENING...ALTHOUGH
THE EXACT TIMING REMAINS UNCERTAIN. THE 12Z GFS SOLUTION IS CLOSE TO
THE 00Z ECMWF SOLUTION WITH RESPECT TO TIMING OF THE FRONT...THE 12Z
CANADIAN LAGS 6-12 HOURS BEHIND. WILL CONTINUE TO LEAN MORE TOWARD
THE ECMWF...WITH THE FRONT MAKING ITS WAY THROUGH THE AREA BY SUNDAY
NIGHT. HIGHS WILL DEPEND ON THE TIMING OF THE FRONT AND IF AND HOW
MUCH SKIES CLEAR ACROSS THE SOUTH DURING THE DAY. FOR NOW...EXPECT A
WIDE RANGE OF HIGHS...MID 50S NORTH TO POTENTIALLY LOW 70S SOUTH.

SUNDAY NIGHT THROUGH TUESDAY NIGHT: AS PREVIOUSLY STATED...THE RAIN
SHOULD BE OUT OF THE REGION BY SUNDAY NIGHT...AND EXPECT THE WEATHER
TO REMAIN DRY THROUGH TUESDAY NIGHT UNDER NW FLOW AND SUBSIDENCE
ALOFT. AT THE SURFACE...COLD BUT WEAKENING HIGH PRESSURE WILL
GRADUALLY BUILD INTO THE AREA THROUGH THE PERIOD. HIGHS WILL
GENERALLY BE IN THE MID 60S TO LOW 70S...LOWS IN THE LOW TO MID 40S.

WEDNESDAY AND THURSDAY: THERE IS QUITE A BIT OF DIVERGENCE BETWEEN
THE MODELS DURING THIS PART OF THE FORECAST...THUS THERE IS NOT A
LOT OF CONFIDENCE WITH RESPECT TO TIMING AND INTENSITY OF VARIOUS
FEATURES. GENERALLY SPEAKING THOUGH...EXPECT A SURFACE LOW TO
DEVELOP OVER THE GULF COAST ON WEDNESDAY AND SLOWLY MOVE EAST-
NORTHEAST TOWARD THE CAROLINAS THROUGH THURSDAY. ALOFT...THOUGH
THERE IS UNCERTAINTY ON WHETHER IT WILL BE CUTOFF OR OPEN...EXPECT
AN UPPER LEVEL LOW TO DEVELOP OVER OK/TX ON TUESDAY AND MOVE EAST
TOWARD THE CAROLINAS TUESDAY NIGHT/EARLY WEDNESDAY. THE ECMWF SEEMS
TO BE MORE INTENSE/AMPLIFIED AND QUICKER MOVING INTO THE AREA THAN
THE GFS AT THIS TIME. REGARDLESS...EXPECT INCREASING RAINFALL
CHANCES BEGINNING LATE TUESDAY NIGHT/WEDNESDAY MORNING THROUGH
THURSDAY AND POSSIBLY THURSDAY NIGHT. WITH THE LOW LEVEL FLOW
DEPENDENT ON THE POSITION OF THE LOW...AND THE TEMPERATURES
DEPENDENT ON THE LOW LEVEL FLOW...THERE IS A HIGH DEGREE OF
UNCERTAINTY IN THE TEMPERATURES FOR WEDNESDAY AND THURSDAY AND THERE
COULD QUITE POSSIBLY BE A LARGE RANGE OF TEMPERATURES FROM NW TO SE
ACROSS THE AREA. HIGHS IN THE MID 60S TO NEAR 70 DEGREES AND LOWS
UPPER 40S TO LOW 50S.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
AS OF 745 PM FRIDAY...

AVIATION: VFR CONDITIONS ACROSS THE CWA WITH CALMING WINDS AND
SCATTERED TO BROKEN HIGH CEILINGS WILL CONTINUE THROUGH MOST OF THE
NIGHT AND THEN CEILINGS WILL MOVE IN FROM THE WEST REMAINING VFR AT
FIRST BUT THEN LOWERING TO MVFR RIGHT AFTER DAYBREAK IN THE TRIAD TO
MID MORNING ACROSS THE CENTRAL AND LATE MORNING/EARLY AFTERNOON AT
KRWI. CEILINGS WILL STEADILY LOWER THROUGH THE DAY EVENTUALLY
OBTAINING AT LEAST IFR AND MAYBE LIFR IN THE WEST BY THE END OF THE
TAF PERIOD. VISIBILITIES ARE ALSO EXPECTED TO DROP ON SATURDAY
AFTERNOON/EVENING BUT MOST LIKELY ONLY TO MVFR LEVELS. RAIN IS
EXPECTED TO BEGIN SATURDAY MORNING IN THE WEST AND LATE
MORNING/EARLY AFTERNOON IN THE EAST...COULD BE MODERATE TO HEAVY AT
TIMES WHICH MAY CAUSE BRIEF DROPS IN VISIBILITIES TO IFR. RAIN IS
EXPECTED TO CONTINUE THROUGH THE END OF THE TAF PERIOD.

24 HOUR TAF PERIOD:

LONG TERM: ADVERSE CONDITIONS ASSOCIATED WITH THE LOW PRESSURE
SYSTEM WILL CONTINUE THROUGH SUNDAY NIGHT BEFORE RETURNING TO VFR ON
MONDAY. CONDITIONS SHOULD REMAIN VFR UNTIL WEDNESDAY WHEN THE NEXT
SYSTEM APPROACHES FROM THE SOUTHWEST.

&&


.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SYNOPSIS...RAH
NEAR TERM...WSS
SHORT TERM...WSS
LONG TERM...KCP
AVIATION...ELLIS



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