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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 151506
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1055 AM EDT SAT JUN 15 2013

.SYNOPSIS...
-- Changed Discussion --
HIGH PRESSURE WILL BUILD OVER THE REGION THROUGH TONIGHT... THEN
MOVE OFF THE SOUTHEAST COAST SUNDAY. SOUTHERLY FLOW BEHIND THIS HIGH
WILL BRING INCREASING MOISTURE INTO THE AREA... AHEAD OF A COLD
FRONT THAT WILL MOVE IN FROM THE WEST ON TUESDAY.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 1055 AM SATURDAY...

FORECAST IS IN GOOD SHAPE. LATEST SURFACE ANALYSIS SHOWS THE HIGH
PRESSURE AREA CENTERED JUST TO OUR NORTHWEST... SPREADING TO THE
ESE. LOOKING ALOFT... THE DEW POINT DEPRESSION ON THE 850 MB
ANALYSIS REMAINS UNDER 8 DEGREES C AROUND THE REGION... TOPPED OFF
BY DRY AND WARM AIR AT 700 MB WITH MORE WARMING ADVECTING IN FROM
THE WEST. STILL EXPECT WE`LL SEE SCATTERED FLAT CUMULUS FORMING
BENEATH THE SUBSIDENCE INVERSION ALOFT WITH FURTHER HEATING THIS
AFTERNOON. HIGH LEVEL MOISTURE NOTED UPSTREAM OVER THE OHIO VALLEY
(BLOWN OFF FROM MCS ACTIVITY) IS POISED TO EXPAND SOUTHEAST INTO NC
THROUGH THE DAY BASED ON UPPER LEVEL FLOW ON THE BACK SIDE OF THE
DEPARTING FULL-LATITUDE LONGWAVE TROUGH SITUATED JUST OFF THE EAST
COAST... SO WE SHOULD SEE INCREASING HIGH THIN CLOUDS AS THE DAY
WEARS ON. TEMPS ARE RUNNING A FEW DEGREES ABOVE YESTERDAY`S PACE...
AND DESPITE SLIGHTLY BELOW NORMAL THICKNESSES THIS MORNING...
THICKNESSES ARE EXPECTED TO RISE AROUND 20 METERS TODAY. BASED ON
THIS AND THE FACT THAT TEMPS ARE ALREADY IN THE UPPER 70S TO AROUND
80 IN SPOTS... HAVE NUDGED UP HIGHS TO 84-89. -GIH

NAM AND GFS BUFR SOUNDINGS SHOW A RELATIVELY DRY AND CAPPED AIR MASS
PERSISTS OVERNIGHT. AS THE SURFACE HIGH QUICKLY MOVES SOUTHEAST...THE
NAM AND GFS BOTH INCREASE WINDS JUST OFF OF THE SURFACE APPRECIABLY
COMPARED TO CURRENT CONDITIONS. THIS SHOULD RESULT IN MORE MIXING
OVERNIGHT AND A MORE NOTICEABLE SOUTH OR SOUTHWEST BREEZE CERTAINLY
COMPARED TO THE CALM CONDITIONS OF EARLY THIS MORNING...ALTHOUGH NOT
SURE ABOUT THE WINDS BEING QUITE AS HIGH AS THE 10KT THE MOS
GUIDANCE SUGGESTS LATE TONIGHT. STILL...WITH A SOUTHWEST FLOW AND A
LITTLE MORE MIXING...EXPECT WARMER OVERNIGHT LOWS...60 TO 65
DEGREES. -DJF
-- End Changed Discussion --

&&

.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
AS OF 640 AM SATURDAY...

IN A SOUTHWEST FLOW...MOISTURE GRADUALLY INCREASES SUNDAY INTO
SUNDAY NIGHT...WITH BOTH THE NAM AND GFS SUGGESTING THAT
PRECIPITABLE WATER VALUES INCREASE FROM AROUND AN INCH TO OVER 1.5
INCHES BY 00Z MONDAY. SUBSIDENCE PERSISTS THROUGH THE DAY SUNDAY
AHEAD OF A WEAK SURFACE FRONT THAT APPEARS TO BE MOVING NORTH FROM
THE GULF TOWARD CENTRAL NORTH CAROLINA LATE IN THE DAY. THIS FRONT
MAY SOMEHOW MERGE WITH A WEAK SURFACE TROUGH THAT THE NAM AND THE
GFS MOVE INTO CENTRAL NORTH CAROLINA FROM THE NORTH BY SUNDAY
EVENING...AND THERE IS ALSO AN 850MB TROUGH FORECAST TO MOVE INTO
THE AREA AS THE RIDGE ALOFT FLATTENS WITH WEAK MID-LEVEL SHORTWAVES
MOVING TOWARD THE MID-ATLANTIC AND CENTRAL NORTH CAROLINA. AS
COOLING ALOFT TAKES PLACE LATE SUNDAY AND ESPECIALLY SUNDAY NIGHT...
UNDER WEAK UVV...THERE MAY BE JUST ENOUGH MOISTURE AND LIFT TO
SUPPORT AN ISOLATED SHOWER OR THUNDERSTORM EITHER DEVELOPING OVER
THE AREA...OR MORE LIKELY A COMBINATION OF ISOLATED DEVELOPMENT AND
ISOLATED REMNANTS OF DEEP CONVECTION TO THE NORTH BEING ABLE TO
SUSTAIN THEMSELVES MOVING INTO THE AREA. IT IS INTERESTING HOW THE
00Z MAV MOS POPS WERE JUST BELOW SLIGHT CHANCE SUNDAY NIGHT WHILE
THE GFS ITSELF PRODUCED FAIRLY WIDESPREAD...ALBEIT LIGHT...QPF OVER
THE ENTIRE AREA...AND THE NAM IS JUST THE CONVERSE...DRY WITH ITS
QPF YET SOLIDLY WITH SLIGHT CHANCE-TO-CHANCE POPS FOR CENTRAL NORTH
CAROLINA. THE LATEST...06Z...GFS SHOWED ITS MOS GUIDANCE POPS
INCREASING WHILE STILL SHOWING VERY LIGHT QPF...ALTHOUGH THE ECMWF
WAS BASICALLY DRY EXCEPT FOR THE FAR NORTH LATE SUNDAY NIGHT. FOR
THIS FORECAST...INTRODUCED A SLIGHT CHANCE OF A SHOWER OR
THUNDERSTORM SUNDAY NIGHT MAINLY NORTH OF A LINE FROM KAFP TO
KGSB...WITH BELOW SLIGHT CHANCE POPS SOUTH OF THAT LINE WHERE THE
MID-LEVEL CAP REMAINS LONGER. THE CONSENSUS OF THE LATEST WRF MODELS
OBSERVED SUGGEST CHANCE POPS OVERNIGHT SUNDAY NIGHT ALONG JUST SOUTH
OF THE VIRGINIA BORDER...AND MOSTLY DRY SOUTH.

SHOULD BE A LITTLE MORE CIRRUS SUNDAY...THOUGH MOSTLY THIN FOR A
LARGE PART OF THE DAY...AND 1000-850MB THICKNESSES SUPPORT HIGHS
GENERALLY A BLEND OF MAV AND MET MOS GUIDANCE...85 TO 90. THE
SURFACE GRADIENT TIGHTENS BEHIND HIGH PRESSURE AND AHEAD OF THE
SURFACE TROUGH SUCH THAT SOUTHWEST WINDS SHOULD SHOW A GUSTY
CHARACTER TO AROUND 20 TO POSSIBLY 25 MPH AT TIMES SUNDAY. SOME
CONTINUED BREEZE PLUS MORE CLOUDS SUNDAY NIGHT...MOSTLY CLOUDY OR
BECOMING MOSTLY CLOUDY AT LEAST WITH SOME MID- AND HIGH-LEVEL CLOUDS
MOVING IN FROM THE NORTHWEST...WILL RESULT IN AGAIN WARMER OVERNIGHT
LOWS...MOSTLY UPPER 60S.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 640 AM SATURDAY...

MONDAY THROUGH TUESDAY NIGHT: WITHIN A BROAD TROUGH ALOFT EAST OF
THE ROCKIES...A LOW AMPLITUDE SOUTHERN STREAM SHORTWAVE TROUGH WILL
MOVE EASTWARD FROM THE CENTRAL PLAINS TO TN VALLEY MON...FOLLOWED
QUICKLY BY A MORE SUBSTANTIAL NORTHERN STREAM ONE FROM THE UPPER
MIDWEST TO THE CENTRAL APPALACHIANS MON NIGHT. THE FORMER FEATURE IS
OVER-AMPLIFIED BY GRID SCALE FEEDBACK ON (AT LEAST) THE PAST COUPLE
OF RUNS OF THE DETERMINISTIC GFS...AND INCLUDES A WRAPPED-UP
SUB-1000 MB LOW TRACKING THROUGH THE MIDDLE ATLANTIC REGION BY
TUE-TUE NIGHT. SUCH A SOLUTION HAS LITTLE TO NO SUPPORT FROM ANY
OTHER NWP GUIDANCE...WHICH RENDERS THE GFS MODEL MOSTLY UNUSABLE
BEYOND THE SHORT TERM.

IN THE LOW LEVELS...INSTEAD OF THE STRONG MID-ATLANTIC SURFACE LOW
DEPICTED BY THE GFS...A LEE TROUGH WILL DEVELOP OVER THE WESTERN
CAROLINAS MON...WHILE A WEAKENING SURFACE FRONT STALLS TO OUR NW. A
STRONGER COLD FRONT ATTENDING THE AFOREMENTIONED NORTHERN STREAM S/W
TROUGH IS THEN FORECAST TO OVERTAKE THE WEAKENING LEAD ONE AS THE
MERGED BOUNDARY THEN SETTLES INTO CENTRAL NC TUE AND TUE NIGHT. WITH
PRECIPITABLE WATER VALUES STEADILY INCREASING TO AT OR SLIGHTLY
ABOVE 1.75 INCHES...THE HEIGHT FALLS IN ADVANCE OF THE SHORTWAVE
TROUGHS ALOFT AND LOW LEVEL CONVERGENCE PROVIDED BY THE LEE TROUGH
WILL SUPPORT AN INCREASING CHANCE OF SHOWERS AND STORMS MON...WITH
HIGHEST CHANCES AROUND 50 PERCENT INVOF THE LEE TROUGH OVER THE
WESTERN PIEDMONT. GENERALLY WEAK MID LEVEL FLOW/BULK SHEAR...ON THE
ORDER OF ABOUT 15-25 KTS FROM SOUTH TO NORTH ACROSS THE CWA SUGGESTS
MULTI-CELL STORM ORGANIZATION...WITH ASSOCIATED STRONG WIND GUSTS.
CONVECTION WILL THEN LIKELY DIMINISH IN COVERAGE AND INTENSITY OVER
NC MON NIGHT...BEFORE BECOMING NUMEROUS TO WIDESPREAD AS THE SURFACE
COLD FRONT SETTLES INTO OUR AREA ON TUE. WSW MEAN FLOW ALIGNED
PARALLEL TO THE UNDERLYING SURFACE FRONT SUGGESTS HEAVY RAIN/
LOCALIZED FLOODING IN TRAINING STORMS ALONG THE BOUNDARY SHOULD
PROVIDE THE GREATEST IMPACT.

TEMPERATURES IN THE MIDDLE TO UPPER 80S MON...THE WARMEST DAY OF THE
WEEK...WILL TREND 3-5 DEGREES COOLER IN MOSTLY CLOUDY AND STORMY
CONDITIONS TUE. LOWS IN THE MID-UPPER 60S.

WEDNESDAY THROUGH FRIDAY: GIVEN CONTINUED FRONT-PARALLEL FLOW ALOFT
IN THE BASE OF BROAD EASTERN CONUS TROUGH...THE SURFACE FRONT WILL
LIKELY LINGER OVER SOUTHERN NC WED...BEFORE DRIFTING SOUTHWARD AND
DIFFUSING BY THU. WILL ACCORDINGLY INDICATE ANOTHER DAY OF HIGH
CHANCE OF DIURNALLY-ENHANCED SHOWERS AND STORMS OVER THE SOUTHERN
TIER WED...TAPERING TO JUST A SLIGHT CHANCE ACROSS THE NORTH TO
ACCOUNT FOR UNCERTAINTY IN PLACEMENT OF THE FRONT. A DEVELOPING WEAK
SOUTHEASTERLY LOW LEVEL FLOW AND ASSOCIATED IMPROVING LOW LEVEL
MOISTURE...AND A LEE TROUGH...MAY SUPPORT A FEW SHOWERS OR STORMS
THU-FRI AFTERNOONS MAINLY ACROSS THE FAR SOUTHERN AND WESTERN TIERS
OF COUNTIES....WHEN AND WHERE A SLIGHT CHANCE POP WILL BE
MAINTAINED.  COOLER THAN AVERAGE OWING TO THE PRESENCE OF THE BROAD
EASTERN TROUGH...WITH HIGHS ABOUT A CATEGORY BELOW AVERAGE -
GENERALLY  LOWER 80S...TO PERHAPS MIDDLE 80S BY FRI.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
AS OF 640 AM SATURDAY...

VFR CONDITIONS OCCUR DURING THE 12Z VALID TAF PERIOD...OUTSIDE OF
ISOLATED MAINLY MVFR FOG EARLY THIS MORNING. EXPECT DIURNAL CU TO
DEVELOP ONCE AGAIN THIS AFTERNOON ACROSS CENTRAL NORTH CAROLINA...
POSSIBLY NOT AS MUCH AS OCCURRED FRIDAY AFTERNOON IN MOST PLACES BUT
STILL FEW-TO-SCATTERED DURING THE AFTERNOON. VARIABLE SURFACE WINDS
BECOME WEST-SOUTHWEST DURING THE MORNING...BUT WITH HIGH PRESSURE
OVERHEAD 10KT OR LESS...AND A FEW TYPICAL MIXING GUSTS IN THE LOWER
TEENS KNOTS DURING DAYLIGHT HOURS. SURFACE WINDS WILL BACK SOUTH AND
SOUTHWEST BY THE OVERNIGHT HOURS...BELOW 10KT AT THE SURFACE BUT
INCREASING TO SOUTHWEST 25KT BY 2000FT BASED ON THE LATEST GUIDANCE.

BEYOND THE 12Z VALID TAF PERIOD...THE AIR BECOMES INCREASINGLY MOIST
IN CENTRAL NORTH CAROLINA SUNDAY INTO MONDAY. AN ISOLATED SHOWER OR
THUNDERSTORM IS POSSIBLE SUNDAY NIGHT...WITH CHANCES FOR SHOWERS AND
THUNDERSTORMS...AND ASSOCIATED LOCAL SUB-VFR CONDITIONS...INCREASING
ALONG WITH THE MOISTURE MONDAY INTO TUESDAY. THERE IS SOME
PROBABILITY OF LOW CLOUDS LATE MONDAY NIGHT INTO TUESDAY MORNING
BASED ON THE MODEL SOUNDINGS OF THE GFS. CHANCES FOR SHOWERS AND
THUNDERSTORMS CURRENTLY SEEM TO DIMINISH WEDNESDAY RELATIVE TO
MONDAY AND TUESDAY...WITH THE BETTER POTENTIAL FOR ISOLATED SHOWERS
AND STORMS TOWARD KFAY COMPARED TO OTHER CENTRAL NORTH CAROLINA TAF
SITES.

&&

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

&&

$$

SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD/DJF
SHORT TERM...DJF
LONG TERM...MWS
AVIATION...DJF