-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 240724
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
324 AM EDT THU JUL 24 2014

.SYNOPSIS...A COLD FRONT WILL PUSH SOUTHEASTWARD THROUGH THE REGION
LATE TODAY THROUGH TONIGHT. THIS FRONT WILL STALL OUT NEAR THE SOUTH
CAROLINA BORDER ON FRIDAY... AS WEAK HIGH PRESSURE BUILDS IN FROM
THE NORTH. THIS FRONT WILL THEN WEAKEN AND HEAD BACK NORTH OF THE
AREA OVER THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 320 AM THURSDAY...

IT`S LOOKING LIKE THE BROAD BROKEN BAND OF PREFRONTAL SHOWERS AND
STORMS WILL MOVE INTO AND THROUGH THE CWA FAIRLY EARLY TODAY...
DURING THE MORNING THROUGH MID AFTERNOON... WHICH WILL GREATLY CUT
DOWN ON OUR SEVERE THREAT OVER ALL BUT THE SE AND EXTREME ERN CWA.
THE LATEST SURFACE MAP SHOWS THE INCOMING SURFACE FRONT STRETCHING
ACROSS THE OH VALLEY... WITH A PREFRONTAL TROUGH EXTENDING THROUGH
CENTRAL VA AND THE NC FOOTHILLS. WE`RE ALREADY STARTING TO SEE A FEW
SHOWERS FORMING ESE OF THIS CONVECTION OVER THE EAST SLOPES... AND
THE HRRR SHOWS THIS MORE EASTERLY ACTIVITY EXPANDING AND BECOMING
THE DOMINANT PREFRONTAL CONVECTION THIS MORNING AS IT HEADS INTO THE
TRIAD REGION... EVENTUALLY SHIFTING EAST THROUGH THE PIEDMONT
THROUGH THE NOON HOUR. THE LARGER SCALE MODELS SUGGEST THIS AS
WELL... DEPICTING PRETTY GOOD COVERAGE OF PRECIP OVER NEARLY THE
ENTIRE CWA BY 18Z. GIVEN THIS TREND IN BOTH RADAR IMAGERY AND MODEL
OUTPUT... WILL FOLLOW THIS PATH AND BRING IN HIGH CHANCE TO LIKELY
POPS EARLIER THIS MORNING OVER THE WRN/NRN CWA... HIGHEST ACROSS THE
NRN HALF OF THE FORECAST AREA FROM LATE MORNING INTO EARLY
AFTERNOON. THE FOCUS OF THE GREATEST CONVECTION COVERAGE SHOULD THEN
SHIFT TO THE COASTAL PLAIN AND SANDHILLS FROM MID AFTERNOON TO EARLY
EVENING AS THE PREFRONTAL TROUGH PUSHES SOUTHEASTWARD THROUGH THE
CWA. BUT ADDITIONAL SCATTERED SHOWERS/STORMS ARE EXPECTED JUST AHEAD
OF AND WITH THE COLD FRONT ITSELF... WHICH IS EXPECTED TO REACH THE
SPINE OF THE APPALACHIANS BY 00Z THIS EVENING... PROPELLED BY
RELATIVELY COOL HIGH PRESSURE CENTERED NEAR CHICAGO. THE SOUTHEAST
MOVEMENT OF THIS FRONT IS APT TO BE SLOWED BY THREE FACTORS: THE
EXTRA EFFORT IT WILL TAKE THE DENSER HIGH PRESSURE AREA TO GET OVER
THE MOUNTAINS... A STEERING FLOW THAT WILL BE NEARLY PARALLEL TO THE
SURFACE FRONT... AND EXPECTATIONS OF SURFACE LOW PRESSURE
ENHANCEMENT OVER THE SOUTHERN FOOTHILLS TONIGHT. GIVEN THE POTENTIAL
FOR A DELAY IN THE ARRIVAL OF THE DRIER AND MORE STABLE COLUMN FROM
NW TO SE UNTIL THE OVERNIGHT HOURS... WILL HOLD CHANCE POPS THROUGH
THE MID-LATE EVENING AREAWIDE BEFORE TRENDING THEM DOWN AND OUT NW
TO SE LATE TONIGHT.

REGARDING THE RISK OF STRONG/SEVERE STORMS... AS NOTED ABOVE... THIS
RISK LOOK GREATLY LIMITED ACROSS THE NRN AND FAR WRN CWA DUE TO
CLOUD COVER AND EARLY PRECIP ARRIVAL. CHANCES ARE BETTER IN THE
SOUTHEAST AND EXTREME EAST... WHERE THE NAM DEPICTS MLCAPE NEAR 1500
J/KG LATE MORNING INTO EARLY AFTERNOON. WE`VE GOT IMPROVED DEEP
LAYER SHEAR TO 25-35 KTS AS WELL. BUT THE ENTIRE TIMING OF THIS
SYSTEM (WELL BEFORE MAX HEATING) AND EARLY CLOUD COVER SHOULD KEEP
INSTABILITY DOWN. BUT THE NRN/WRN CWA IS NOT OUT OF THE WOODS AS WE
MAY ACTUALLY HAVE A BIT MORE CONCERN LATE THIS AFTERNOON THROUGH
EARLY EVENING AHEAD OF THE FRONT... IF WE CAN GET PARTIAL CLEARING
BEHIND THIS MORNING ACTIVITY. THE GFS SHOWS INITIALLY SMALL MUCAPE
IN THE MORNING IN THE NW CWA REBOUNDING ABOVE 1000 J/KG LATE
TODAY... NOT A HUGE NUMBER OF COURSE BUT ENOUGH TO RETAIN AT LEAST
SOME CONCERN FOR A STRONG WIND-PRODUCING STORM OR TWO AREAWIDE.

TEMPS SHOULD INITIALLY BE HELD DOWN BY CLOUDS AND PATCHY PRECIP THIS
MORNING... BUT ANY THIN SPOTS IN THE CLOUDS BETWEEN THIS PREFRONTAL
CONVECTION AND SHOWERS/STORMS IMMEDIATELY AHEAD OF THE FRONT WILL
PUSH TEMPS UP QUICKLY. SO STILL EXPECT HIGHS FROM 86 TO 92. LOWS
TONIGHT 66-72... STILL MUGGY ACROSS THE SE. -GIH

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
-- Changed Discussion --
AS OF 320 AM THURSDAY...

FRI-FRI NIGHT TO BE UPDATED...

SAT AND SAT NIGHT: THE REMNANT FRONT FROM EARLY IN THE PERIOD WILL
BECOME INCREASINGLY DIFFUSE AS IT RETREATS NORTH ACROSS THE MIDDLE
ATLANTIC STATES ON SAT...WITH A PRIMARY IMPACT FOR CENTRAL NC BEING
THE DEVELOPMENT OF A WARMING SOUTHERLY FLOW - HIGH TEMPERATURES
GENERALLY BETWEEN 89 AND 93 DEGREES. ALOFT...MODEL GUIDANCE IS IN
GOOD AGREEMENT REGARDING THE PROGRESSION OF A MID LEVEL TROUGH FROM
THE APPALACHIAN SPINE SAT MORNING TO THE COAST BY EVENING...BUT
ASSOCIATED FORECAST VERTICAL MOTION WITH THIS FEATURE IS WEAK...AND
NAM FORECAST BUFR SOUNDINGS ARE AN UNSTABLE AND UNCAPPED OUTLIER
RELATIVE TO THE GFS AND SREF ENSEMBLE MEAN. THE NAM QPF MAXIMUM FROM
SE VA THROUGH CENTRAL NC IS ALSO AN OUTLIER RELATIVE TO OTHER
GUIDANCE...WHICH OTHERWISE CONFINES ANY SHOWERS/STORMS TO THE SEA
BREEZE. WILL CONSEQUENTLY MAINTAIN JUST A SLIGHT CHANCE POP OVER THE
SOUTHERN AND CENTRAL COASTAL PLAIN...WHERE WEAK LIFT AHEAD OF THE
AFOREMENTIONED TROUGH ALOFT WILL BE DIURNALLY MAXIMIZED AND
COINCIDENT WITH LOW LEVEL FORCING INVOF THE SEA-BREEZE/SUBSEQUENT
OUTFLOW DURING THE MID-LATE AFTERNOON.

SHORTWAVE RIDGING WILL BRIEFLY FOLLOW FOR SAT NIGHT...WITH DRY
CONDITIONS AND LOWS MAINLY IN THE LOWER 70S.
-- End Changed Discussion --

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
AS OF 235 PM WEDNESDAY...

THE NEXT UPPER TROUGH APPROACHES FROM THE NORTHWEST ON SUNDAY WITH A
COLD FRONT DROPPING ACROSS THE OH VALLEY. A LEE TROUGH AHEAD OF THE
FRONT ACROSS THE PIEDMONT OF VA AND THE CAROLINAS IS EXPECTED TO
BECOME CONVECTIVELY ACTIVE DURING THE AFTERNOON AND EVENING WITH
SCATTERED CONVECTION. THE SOUTHERLY FLOW AHEAD OF THE UPPER
TROUGH... COMBINED WITH DEEP MIXING WILL RESULT IN HIGHS IN THE
LOWER 90S. THE UPPER TROUGH AXIS AND COLD FRONT WILL CROSS CENTRAL
NC ON MONDAY WITH GOOD CONVECTIVE COVERAGE ANTICIPATED. WILL
INCREASE POPS INTO THE HIGH CHANCE RANGE. WITH THE APPROACHING
TROUGH...THE LOW AND MID LEVEL FLOW INCREASES WITH BULK SHEAR VALUES
OF 30-40 KTS EXPECTED SUGGESTING SOME HIGH-BASED STORM ORGANIZATION
IS POSSIBLE.  SLIGHTLY COOLER TEMPERATURES ARE EXPECTED ON MONDAY
WITH THE CLOUD COVER AND PRECIPITATION...HIGHS SHOULD RANGE IN THE
86 TO 91 RANGE WITH LOWS MONDAY MORNING IN THE 69 TO 74 RANGE.

THE LARGE AMPLITUDE UPPER LEVEL TROUGH SLOWLY MOVES EAST ON TUESDAY
WITH THE COLD FRONT PROGGED TO MOVE INTO THE COASTAL PLAIN MONDAY
NIGHT AND SLOWLY PUSH TOWARD THE COAST ON TUESDAY. COOL HIGH
PRESSURE BUILDS INTO THE REGION WITH ANY PRECIPITATION ON TUESDAY
LIKELY CONFINED TO THE COASTAL PLAIN AND POINTS EAST. MAINLY DRY
CONDITIONS ARE EXPECTED ON WEDNESDAY BUT IT IS WORTH NOTING THAT THE
GFS/ECMWF BOTH INDICATE THE STALLED FRONT NEAR THE COAST MAY TRY TO
WORK WEST. FOR NOW WILL INCLUDE A DRY FORECAST. THE MUCH COOLER AIR
MASS WITH LOW LEVEL THICKNESS VALUES FALLING INTO THE 1375-1390M
RANGE FOR TUESDAY AND WEDNESDAY MORNINGS. THIS WOULD SUPPORT LOWS IN
THE 60S AND PERHAPS UPPER 50S IN THE TRIAD OR NEAR THE VA BORDER ON
WEDNESDAY MORNING WITH HIGHS OF 79-86. -BLAES
-- End Changed Discussion --

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
AS OF 130 AM THURSDAY...

VFR CONDITIONS ARE LIKELY TO DOMINATE THROUGH DAYBREAK AT ALL TAF
SITES. A LIGHT BUT STEADY SURFACE BREEZE FROM THE SW WILL KEEP THE
LOW LEVELS STIRRED AND INHIBIT MOST FOG DEVELOPMENT... BUT A SHORT
PREDAWN PERIOD (UNDER 2 HRS) OF MVFR FOG IS NOT OUT OF THE QUESTION.
CURRENTLY ANY CLOUD COVER OVER CENTRAL NC IS LIMITED TO HIGH CLOUDS
BASED ABOVE 10 000 FT AGL MAINLY IN THE NW... AND WHILE CIGS WILL BE
DROPPING AHEAD OF THE COLD FRONT APPROACHING FROM THE NW... THEY
SHOULD STAY VFR THROUGH 13Z. SCATTERED TO NUMEROUS SHOWERS AND
STORMS ARE EXPECTED NEAR INT/GSO STARTING AROUND 13Z OR 14Z... AND
THESE COULD GENERATE MVFR CIGS/VSBYS AND ENHANCED WIND GUSTS. THESE
SHOWERS/STORMS ARE THEN EXPECTED TO AFFECT RDU AND RWI STARTING
AROUND 14Z OR 15Z... AND FAY STARTING AT 17Z OR 18Z. TOUGH CALL ON
WHEN THE STORM THREAT WILL EXIT TAF SITES... BUT VFR CONDITIONS
SHOULD RETURN SOON AFTER 22Z AT GSO... 00Z AT RDU/RWI... AND
PROBABLY NOT UNTIL AFTER 04Z AT FAY.

LOOKING BEYOND 06Z EARLY FRI MORNING... SURFACE WINDS WILL REMAIN
FAIRLY LIGHT LATE TONIGHT BUT SHIFT AROUND QUICKLY FROM WSW TO NNE
AS THE FRONT PUSHES SOUTHEAST THROUGH NC. THE FRONT WILL LIKELY SLOW
DOWN ENOUGH OVER SE NC TO KEEP A CHANCE OF SUB-VFR SHOWERS/STORMS AT
FAY THROUGH FRI AFTERNOON... BUT OTHERWISE VFR CONDITIONS ARE
EXPECTED FRI-SAT AS HIGH PRESSURE NOSES IN FROM THE NORTH. THIS
FRONT WILL SHIFT BACK NORTH AND DISSIPATE OVER THE WEEKEND WITH A
SURFACE TROUGH REFORMING OVER CENTRAL NC. AN UPPER LEVEL DISTURBANCE
AND ACCOMPANYING COLD FRONT WILL MOVE IN FROM THE NORTHWEST ON
SUNDAY... POTENTIALLY BRINGING ANOTHER ROUND OF SHOWERS/STORMS LATE
SUNDAY INTO MONDAY. -GIH

&&

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

&&

$$

SYNOPSIS..HARTFIELD
NEAR TERM...HARTFIELD
SHORT TERM...MWS
LONG TERM...BLAES
AVIATION...HARTFIELD