Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 040256
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
955 PM EST TUE MAR 3 2015

.SYNOPSIS...HIGH PRESSURE AND ASSOCIATED COLD AIR DAMMING WILL
REMAIN UNTIL A WARM FRONT RETREATS NORTH ACROSS CENTRAL NC ON
WEDNESDAY. MEANWHILE...A STRONG COLD FRONT WILL APPROACH FROM THE
NORTHWEST...THEN MOVE THROUGH THE AREA LATE WED NIGHT THROUGH EARLY
THU.

&&

.NEAR TERM /TONIGHT/...
AS OF 955 PM TUESDAY...

THE COOL AND STABLE COLD AIR DAMMING AIRMASS IS FIRMLY WEDGED IN
ACROSS THE REGION...REACHING AS FAR SOUTH CENTRAL GEORGIA...WITH
HIGH PRESSURE CENTERED OVER SOUTHEASTERN NC. IN THE ABSENCE OF AN
EROSION MECHANISM AND WITH STRONG SOUTHWESTERLY FLOW ABOVE THE COLD
DOME MAINTAINING THE STRONG STABILITY...THE AIRMASS IS LIKELY TO
REMAIN UNCHANGED OVERNIGHT.  12Z MODELS WERE ALL TOO WARM AT
00Z...SOME BY AS MUCH AS 10 DEGREES OR MORE...AND MANY 18Z RUNS WERE
ARE STILL TO WARM.  THE NAM...AND SUBSEQUENTLY OUR LOCAL WRF-
ARW...HAVE THE BEST HANDLE ON TEMPS...SO WILL LEAN HEAVILY ON THOSE.
 EXPECT THE WARM FRONT TO BEGIN TO MIX ITS WAY INLAND AFTER
MIDNIGHT...THOUGH IT MAY NOT REACH THE I-95 CORRIDOR UNTIL AROUND
12Z AS TEMPS HOLD IN THE MID 30S TO AROUND 40.  MEANWHILE...THE
SETUP IS GOOD FOR DENSE FOG AFTER MIDNIGHT ONCE A FINAL SURGE OF
DEEPER ISENTROPIC LIFT AND ASSOCIATED BATCH OF LIGHT RAIN DEPARTS
THE NORTHERN COASTAL PLAIN. HOWEVER...A LIGHT SOUTHWEST WIND MAY
CONTINUE OVERNIGHT GIVEN THAT THE HIGH IS CENTERED TO OUR
SOUTHEAST...SO ITS UNCERTAIN HOW QUICKLY THE CURRENT LOW CEILINGS
WILL SETTLE TO THE SURFACE. WILL HOLD OFF ON A DENSE FOG ADVISORY
FOR NOW...BUT EXPECT THAT ONE WILL BE NEEDED AFTER MIDNIGHT AND MAY
CONTINUE WELL INTO THE DAY ON WEDNESDAY.

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
AS OF 300 PM TUESDAY...

WEDNESDAY:

INSOLATION FROM THE HIGHER SOLAR SUN ANGLE AND BL MIXING VIA STRONG
40-45KT H8 SOUTHWEST FLOW WILL SCOUR OUT ANY LINGERING SHALLOW WEDGE
AIRMASS WITH CENTRAL NC FIRMLY IN THE WARM SECTOR...SOUTH OF THE
COLD FRONT SETTLING INTO THE TN VALLEY. GUIDANCE
OVERCAST LOW CLOUDS WILL BECOME SCT/BKN BY AFTERNOON...WITH BREEZY
SOUTHWESTERLY WINDS DEVELOPING AS THE BL WARMS AND DEEPENS.
SUSTAINED WINDS OF 15 TO 20KTS WITH GUSTS AS HIGH AS 30-35KTS ARE
EXPECTED AS TEMPERATURES RISE INTO THE UPPER 60S NW TO MID 70S
ACROSS THE SOUTH. ONCE THE WEDGE MIXES OUT...FORCING LOOKS LARGELY
ABSENT UNTIL THE ARRIVAL OF THE BACK-DOOR COLD FRONT INTO THE AREA
BETWEEN 06 TO 12Z WITH VERY LITTLE DESTABILIZATION INDICATED...SO
EXPECT MOSTLY DRY CONDITIONS WEDNESDAY AFTERNOON.

WEDNESDAY NIGHT: A STRONG COLD FRONT WILL DROP SOUTH INTO THE AREA
IN BACK-DOOR FASHION DURING THE PREDAWN HOURS. AS A WAVE DEVELOPS
ALONG THE FRONT...ANA-FRONTAL PRECIP WILL SPREAD SOUTH INTO THE
AREA. THERE IS STILL SOME MINOR TIMING ISSUES WITH THE TIMING OF THE
FRONT AND PRECIP INTO THE NORTHERN AREAS...WITH THE NAM BEING A BIT
SLOWER THAN THE GFS AND EC...BUT EXPECT CATEGORICAL POPS BY DAYBREAK
FROM HIGHWAY 64 NORTH...MAKING FOR A MESSY MORNING COMMUTE FOR THE
TRIAD AND TRIANGLE. EXPECT QUITE A SHARP NORTH-SOUTH CONTRAST IN
TEMPERATURES...RANGING FROM LOWER 40S TO LOWER 60S.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
AS OF 300 PM TUESDAY...

THURSDAY AND THURSDAY NIGHT: BY 12Z ON THURSDAY...PRECIPIATION
ASSOCIATED WITH THE APPROACHING COLD FRONT WILL HAVE WORKED INTO
NORTHERN SECTIONS OF THE CWA. AT THIS TIME ALL MODELS ARE HINTING AT
THE FORMATION OF A SMALL MESO-LOW FORMING OVER UPSTATE SOUTH
CAROLINA. THIS COULD ACT TO TEMPORARILY INCREASE PRECIPITATION OVER
CENTRAL NC DURING THE DAYTIME HOURS AS FLOW BECOMES MORE
SOUTHEASTERLY AND LOW LEVEL CONVERGENCE INCREASES. THIS FEATURE WILL
QUICKLY ADVECT AWAY BY THURSDAY NIGHT. THE MAIN COLD FRONT HOWEVER
WILL LINGER OVER THE AREA WITH A SOUTHWEST TO NORTHEAST ORIENTATION
AS THE UPPER LEVEL TROUGH REALLY LAGS BACK OVER THE CENTRAL PLAINS
ON THURSDAY AND THE REAL DRIVING FORCE PUSHING IT THROUGH WILL BE A
SURFACE HIGH BACK ACROSS THE TENNESSEE VALLEY. THE EXTREMELY WARM
TEMPERATURES FROM WEDNESDAY WILL QUICKLY COME CRASHING BACK TO
REALITY AS TEMPERATURES DROP THROUGH THE DAY IN THE NORTH AND ONLY
RISE BRIEFLY IN THE SOUTH BEFORE THE FRONT PASSES AND TEMPERATURES
EVENTUALLY DROP BACK BELOW FREEZING THURSDAY NIGHT.

THE COLD AIRMASS WILL BE CHASING THE PRECIPITATION AND AT LEAST IN
SECTION NORTH OF HIGHWAY 64 THERE IS A GOOD CHANCE FOR A WINTRY MIX
OF PRECIPITATION AT THE END OF THE EVENT THURSDAY NIGHT. PRIMARY
TIMING WOULD BE BETWEEN 00Z AND 06Z WITH SLEET THE MOST LIKELY
FROZEN PRECIPITATION TYPE. NORTHEASTERN COUNTIES MAY ALSO SEE A
BRIEF PERIOD OF FREEZING RAIN AT THE INITIAL TRANSITION AROUND 00Z
BUT THEN ALSO CHANGING OVER TO SLEET. FORECAST SOUNDINGS SUPPORT
THIS WITH A VERY WARM NOSE INITIALLY AS TEMPERATURES AT THE SURFACE
DROP BELOW FREEZING AT THE SURFACE. THIS WARM NOSE WILL ERODE RATHER
QUICKLY AND JUST BELOW THAT AN EQUALLY STRONG COLD NOSE
DEVELOPS...SUGGESTING THAT ANY REMAINING PRECIPITATION WILL REFREEZE
PRIOR TO HITTING THE SURFACE. THE GOOD NEWS IS THAT MOST SREF
MEMBERS POINTING TO THE VAST MAJORITY OF PRECIPITATION ENDING PRIOR
TO THE CHANGEOVER TO FREEZING P-TYPES. AS A RESULT NO ICE
ACCUMULATION AND VERY LITTLE SLEET ACCUMULATION IS
EXPECTED...ESPECIALLY WHEN FACTORING IN VERY WARM GROUND
TEMPERATURES FROM WEDNESDAY. MOST PRECIPITATION SHOULD WORK ITS WAY
OUT OF THE AREA AROUND OR JUST AFTER 6Z.

FRIDAY THROUGH SUNDAY NIGHT: THE WEEKEND WILL FEATURE DRIER WEATHER
WITH THE FRONTAL ZONE LOOMING JUST TO OUR SOUTH. A TRANSITORY
SURFACE HIGH WILL CONTROL THE WEATHER PATTERN INITIALLY FOSTERING
COLD TEMPERATURES ON THE EASTERN SIDE OF THE HIGH AND THEN
MODERATING NICELY THROUGH THE WEEKEND. INITIALLY HIGHS IN THE UPPER
30S/LOW 40S ON FRIDAY RISING TO MID TO UPPER 50S BY THE END OF THE
WEEKEND. LOWS SLIGHTLY BELOW FREEZING FRIDAY TO SLIGHTLY ABOVE ON
SUNDAY NIGHT.

MONDAY THROUGH TUESDAY: SOLUTIONS DIVERGE EARLY NEXT WEEK IN REGARDS
TO THE STRENGTH OF THE UPPER LEVEL TROUGH AND A LOW PRESSURE SYSTEM
COMING OUT OF THE GULF OF MEXICO THAT COULD AFFECT OUR AREA EARLY
NEXT WEEK. TEMPERATURES LOOK WARM ENOUGH THAT ANY PRECIPITATION
SHOULD BE LIQUID. HIGHS IN THE UPPER 50S TO LOW 60S. LOWS IN THE MID
TO UPPER 30S.

&&

.AVIATION /00Z TUESDAY THROUGH SUNDAY/...
AS OF 750 PM TUESDAY...

ALREADY LIFR CONDITIONS WITH RESPECT TO CEILINGS WILL WORSEN AS
CEILINGS LOWER FURTHER...AND VISIBILITIES LIKEWISE TREND DOWN. IN
FACT...AREAS OF DENSE FOG ARE LIKELY TO DEVELOP OVERNIGHT OR EARLY
WED...AS WARM AND MOIST AIR IS FORCED ATOP A COLD...SATURATED...AND
VERY STABLE LAYER OF AIR NEAR THE SURFACE. CONDITIONS WILL
TRANSITION UP BRIEFLY THROUGH IFR-MVFR RANGE...BEFORE LIKELY
SCATTERING OUT TO VFR ALTOGETHER...AS THE WARM FRONT AT THE SURFACE
FINALLY MAKES INROADS ACROSS CENTRAL NC DURING THE MIDDAY-EARLY
AFTERNOON HOURS AT EASTERN TAF SITES...TO MID-LATE AFTERNOON (IF AT
ALL) AT KINT/KGSO...BEFORE A COLD FRONT AND ASSOCIATED TRAILING AREA
OF RAIN AND SUB-VFR CONDITIONS ARRIVE FROM THE NORTHWEST WED
NIGHT...AND PERSISTS THROUGH THU. A BRIEF MIX OF SLEET AND/OR
FREEZING RAIN WILL BE POSSIBLE BEFORE PRECIPITATION ENDS LATE THU OR
THU EVENING AT KRWI AND KRDU.

OUTLOOK: VFR

&&

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

&&

$$

SYNOPSIS...RAH
NEAR TERM...CBL/BLS
SHORT TERM...CBL
LONG TERM...ELLIS
AVIATION...RAH


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