Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 181824
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
224 PM EDT THU SEP 18 2014

.SYNOPSIS...HIGH PRESSURE CENTERED NORTHEAST OF THE GREAT LAKES WILL
EXTEND DOWN THROUGH VIRGINIA AND THE CAROLINAS THROUGH THE
WEEKEND... AS IT SLIDES EAST. A COLD FRONT WILL APPROACH FROM THE
NORTHWEST LATE SUNDAY... THEN MOVE SOUTHEAST THROUGH THE REGION
MONDAY.

&&

.NEAR TERM /THROUGH FRIDAY NIGHT/...
AS OF 220 PM THURSDAY...

THROUGH TONIGHT: QUIET AND DRY NIGHT FOR MOST. SURFACE MAP SHOWS A
WEAK MSLP PATTERN OVER NC WITH A WEAK INVERTED TROUGH OVER THE WRN
PIEDMONT... HELPING TO FOCUS MOISTURE IN THE LOWEST 5-6 THOUSAND FT
IN THIS AREA AND FOSTERING DEVELOPMENT OF VERY ISOLATED SHALLOW
SHOWERS. THESE SHOULD PERSIST INTO THE EVENING HOURS... GIVEN THIS
WEAK LOW LEVEL MASS CONVERGENCE IN CONJUNCTION WITH WEAK TERRAIN
UPGLIDE... BUT WITH A CAPPING INVERSION EVIDENT AT 775-750 MB AND
WARM/DRY/STABLE AIR ABOVE... EXPECT DEVELOPMENT TO BE STUNTED BOTH
VERTICALLY AND IN COVERAGE... AS PW REMAINS BELOW NORMAL. THE LATEST
SEVERAL HRRR RUNS SUPPORT THIS AS WELL. WILL KEEP AN ISOLATED SHOWER
CHANCE IN THE WRN AND EXTREME SW CWA THROUGH THE EVENING.
OTHERWISE... FORECAST SOUNDINGS SHOW THE LOW LEVEL MOISTURE
GRADUALLY DISPERSING WITH TIME... STILL GREATER OVER THE WRN CWA
THAN IN THE EAST... SO EXPECT MOSTLY CLEAR SKIES EAST AND PARTLY
CLOUDY WEST. SLOWLY LOWERING SURFACE DEWPOINTS SHOULD LOWER THE RISK
OF FOG... EXCEPT PERHAP IN THE WRN CWA NEAR THE SURFACE TROUGH.
BASED ON LAST NIGHT`S LOWS AND STATISTICAL GUIDANCE... EXPECT LOWS
OF 58-63.

FOR FRI/FRI NIGHT: RAIN CHANCES WILL REMAIN LOW. THE MID LEVEL
TROUGH AXIS IS EXPECTED TO BE SHIFTING TO OUR SE WITH RISING HEIGHTS
ALOFT. LOW LEVEL MOISTURE TRANSPORT PERSISTS BUT IS CONFINED TO THE
FAR SRN AND SE CWA... WHERE PW VALUES WILL HOVER NEAR 1.4-1.5". THE
ONSHORE-DIRECTED LOW LEVEL STEERING FLOW COULD DRAW SHALLOW SEA
BREEZE SHOWERS INLAND OVER THE FAR SE CWA. ISOLATED UPSLOPE-
SUPPORTED SHOWERS REMAIN POSSIBLE IN THE FAR WRN CWA AS WELL. IN
GENERAL HOWEVER... THE TRADITIONAL MODELS REMAIN TOO WET... SHOWING
PRECIP COVERING THE MAJORITY OF THE CWA... WHICH APPEARS UNLIKELY
GIVEN THE LACK OF FORCING AND INSTABILITY WITH LIMITED MOISTURE.
WILL KEEP ISOLATED POPS ALONG THE WRN/SRN AND SE EDGES OF THE CWA
FRI AFTERNOON INTO THE EVENING. THICKNESSES ARE EXPECTED TO DIP
SLIGHTLY... INDICATING HIGHS OF 76-81. LOWS 56-61 WITH PARTLY CLOUDY
SKIES WEST AND MOSTLY CLEAR EAST. -GIH

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
AS OF 224 PM THURSDAY...

SATURDAY AND SATURDAY NIGHT: HEIGHTS ALOFT WILL CONTINUE TO RISE
OVER THE CAROLINAS ON SATURDAY...AS AN EXTENSION OF THE MID LEVEL
RIDGE CENTERED OVER THE CENTRAL US RIDGE NOSES NORTHEASTWARD INTO
THE AREA...SANDWICHED BETWEEN THE AMPLIFYING NORTHERN STREAM DIVING
SEWD OUT OF SOUTHERN CANADA AND THE REMNANT LOW ALONG THE SOUTHEAST
COAST. AT THE SURFACE...DRY AIR SURFACE RIDGE AXIS WILL WEDGE
SOUTHWESTWARD DOWN THE MID ATLANTIC STATES AND THROUGH THE CAROLINAS
AND GEORGIA. RESULTANT LOW PWATS AND A STABLE AIR COLUMN WILL SECURE
DRY CONDITIONS. HIGHS IN THE UPPER 70S TO LOWER 80S. LOWS SATURDAY
NIGHT UPPER 50S TO LOWER 60S.

SUNDAY: AMPLIFYING/DIGGING NORTHERN STREAM TROUGH AND ASSOCIATED
POLAR WESTERLIES WILL PICK UP THE LINGERING AREA OF LOW PRESSURE
NEAR THE SOUTHEAST COAST AND KICK IT EAST-NORTHEASTWARD...LIFTING UP
THE NC COAST AND THEN OUT INTO THE ATLANTIC ON SUNDAY. LITTLE TO NO
SENSIBLE WEATHER IMPACTS ARE EXPECTED FROM THIS FEATURE...BUT A PRE-
FRONTAL TROUGH IS EXPECTED TO DEVELOP IN THE LEE OF THE MOUNTAINS
SUNDAY AFTERNOON...OWING TO THE APPROACH OF THE NORTHERN STREAM
TROUGH. WOULD NOT BE SURPRISED TO SEE AN ISOLATED SHOWER DEVELOP
INVOF OF THIS TROUGH...BUT WILL KEEP FORECAST DRY. SUNDAY LOOKS TO
BE THE WARMEST DAY IN THE NEXT FORESEEABLE FUTURE WITH LOW-LEVEL
THICKNESSES PROJECTED TO CLIMB 20 METERS ABOVE NORMAL...HIGHS IN THE
LOWER TO MID 80S.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 224 PM THURSDAY...

SUNDAY NIGHT THROUGH MONDAY: 40 TO 60 METER HEIGHT FALLS TRAVERSING
THE REGION IN ADVANCE OF THE AMPLIFYING NORTHER STREAM TROUGH
ADVANCING EASTWARD INTO THE EASTERN US WILL DRIVE A SURFACE COLD
FRONT INTO THE AREA LATE SUNDAY NIGHT/EARLY MONDAY MORNING . WRT THE
COLD FRONTAL PASSAGE ON MONDAY...THE GFS HAS TRENDED TOWARDS THE
FASTER SOLUTION OF THE EC...WHICH HAS THE FRONT SOUTH AND EAST OF
THE AREA BY 18Z MONDAY. GIVEN THE FASTER TIMING...SUFFICIENT
INSTABILITY WILL BE LACKING AND GIVEN LIMITED MOISTURE
AVAILABILITY...CONVECTIVE/RAIN CHANCES REMAIN UNIMPRESSIVE. WILL
LEAVE IN SLIGHT CHANCE POPS...BUT FROPA COULD END BEING A NON-
MEASURABLE/SPRINKLE EVENT FOR MUCH OF THE CWA. FASTER FROPA WILL
RESULT IN SLIGHTLY COOLER TEMPERATURES MONDAY AFTERNOON. HIGHS IN
THE UPPER 70S NW TO LOWER 80S SE.

TUESDAY THROUGH THURSDAY: LIKE CLOCKWORK...A STRONG +1030MB CANADIAN
SURFACE HIGH... ANCHORED UNDERNEATH THE UPPER CONFLUENCE ZONE IN THE
WAKE OF THE EXITING UPPER TROUGH/CLOSED LOW OVER SOUTHERN NEW
ENGLAND...WILL PROVIDE THE FIRST DAYS OF FALL(AUTUMNAL EQUINOX
BEGINS MONDAY SEPT 22 AT 10:29 PM EDT)WITH BONA FIDE FALL
CONDITIONS. DRY WITH TEMPERATURES 5-8 DEGREES BELOW NORMAL. HIGHS 70
TO 75. LOWS IN THE LOWER TO MID 50S...WITH SOME UPPER 40S POSSIBLE
WEDNESDAY NIGHT ACROSS THE NORTHERN PIEDMONT.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AS OF 145 PM THURSDAY...

VFR CONDITIONS ARE LIKELY TO HOLD THROUGH THE TAF FORECAST PERIOD.
EARLIER MVFR CIGS AT INT/GSO HAVE MIXED OUT TO SCATTERED... ALTHOUGH
THESE MAY STILL GO BROKEN BRIEFLY PRIOR TO 20Z. OTHERWISE... ANY
CLOUDS THROUGH TONIGHT AND FRI MORNING SHOULD BE BASED ABOVE 3 000
FT AGL... MORE LIKELY TO BE BROKEN AT INT/GSO WITH LESS COVERAGE AT
RDU/RWI/FAY. LIGHT AND VARIABLE WINDS MAINLY FROM THE NE WILL
CONTINUE TONIGHT AT SPEEDS MAINLY UNDER 6 KTS... THEN SHOULD
INCREASE TO 7-10 KTS FROM THE ENE AFTER 14Z FRI.

LOOKING BEYOND 18Z FRI... VFR CONDITIONS SHOULD DOMINATE THROUGH AT
LEAST SUNDAY... ALTHOUGH MVFR FOG IS POSSIBLE EARLY SAT MORNING AS
THE LIGHT ONSHORE LOW LEVEL FLOW PERSISTS. A PERIOD OF MVFR CIGS IS
POSSIBLE LATE SUN INTO SUN NIGHT AHEAD OF A COLD FRONT. VFR
CONDITIONS SHOULD THEN RETURN FOR MON/TUE WITH HIGH PRESSURE
BUILDING IN FROM THE NW. -GIH

&&

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

&&

$$

SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD
SHORT TERM...CBL
LONG TERM...CBL
AVIATION...HARTFIELD


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