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296
FXUS62 KRAH 202021
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
320 PM EST THU NOV 20 2014

.SYNOPSIS...A DRY COLD FRONT WILL MOVE THROUGH THE AREA THIS EVENING
BEFORE HIGH PRESSURE RETURNS FOR THE END OF THE WEEK. A LOW PRESSURE
SYSTEM WILL APPROACH THE AREA ON SUNDAY...CAUSING MORE UNSETTLED
CONDITIONS.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 215 PM THURSDAY...

THE UPPER LEVEL LOW THAT HAS BEEN SITTING OVER EASTERN CANADA IS
EXPECTED TO MOVE OFF TO THE ENE THROUGH TONIGHT...WITH THE TROUGH
AND ASSOCIATED COLD FRONT PUSHING THROUGH THE REGION. THE FRONTAL
PASSAGE WILL BE DRY...WITH JUST SOME SCATTERED LOW TO MID CLOUDS
AHEAD OF IT...AND BRING WITH IT A REINFORCING SHOT OF COLD AIR AS
SURFACE HIGH PRESSURE BUILDS IN FROM THE WEST. EXPECT THE WINDS TO
SHIFT NORTHWESTERLY BEHIND THE FRONT THEN MORE NORTHERLY OVERNIGHT.
SUSTAINED WINDS AROUND 10 KTS...WITH GUSTS TO 15-20 KTS THIS
AFTERNOON SHOULD ABATE AFTER SUNSET. OVERNIGHT LOWS WILL GENERALLY
RANGE FROM THE MID 20S NW TO LOW 30S SOUTH...BUT THIS IS DEPENDENT
ON THE TIMING AND SOUTHWARD PROGRESS OF THE FRONT OVERNIGHT.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 225 PM THURSDAY...

HIGH PRESSURE OVER THE OHIO VALLEY WILL RIDGE INTO THE AREA ON
FRIDAY...MOVING SOUTHWARD AND SETTLING OVER NC FRIDAY NIGHT. EXPECT
SKIES TO REMAIN CLEAR AND THE WINDS TO RELAX SOME AS WELL AS THE
HIGH RIDGES IN. THE REINFORCING SHOT OF COLD AIR WILL YIELD HIGHS
ABOUT 10 DEGREES OR SO COOLER THAN THURSDAY...MID 40S NORTH TO LOW
50S SOUTH. THIS IS SUPPORTED BY A DECREASE IN THICKNESSES...WITH THE
LOWEST VALUES ACROSS THE NORTHEAST WHERE HIGHS WILL BE LOWEST. WINDS
WILL BE GENERALLY NORTH AND NORTHEASTERLY DURING THE DAY...VEERING
OVERNIGHT AS THE HIGH BUILDS IN. WITH THE CLEAR SKIES AND CALM WINDS
YIELDING GOOD RADIATIONAL COOLING CONDITIONS...EXPECT LOWS FRIDAY
NIGHT GENERALLY IN THE MID 20S. -KC

AS OF 315 AM THURSDAY...
SATURDAY AND SATURDAY NIGHT: SOUTHERN STREAM TROUGH OVER THE
SOUTHWEST US WILL ADVANCE EASTWARD THROUGH THE SOUTHERN PLAINS ON
SATURDAY AND THEN INTO THE LOWER/CENTRAL MS VALLEY SATURDAY NIGHT.
STRONG 1035MB SURFACE HIGH CENTERED OVER NC TO START THE DAY WILL
QUICKLY SHIFT OFFSHORE WITH AN EAST-WEST DRY AIR RIDGE LINGERING
UNDERNEATH WEAK/MINOR HEIGHT RISES ALOFT. MODEL ARE IN GOOD
AGREEMENT THAT PRECIP WILL BE DELAYED UNTIL AFTER DAYBREAK
SUNDAY...THOUGH STRENGTHENING S/SE LOW-LEVEL ATLANTIC MARITIME FEED
SATURDAY EVENING/NIGHT WILL RESULT IN RAPID MOISTURE RECOVERY AND
WIDESPREAD LOW CLOUDS/STRATUS.  DRY ADIABATIC MIXING TO 950-970MB
WILL SUPPORT HIGHS OF 50 TO 55. NOT NEARLY AS COLD SATURDAY NIGHT
COMPARED TO FRIDAY NIGHT/SATURDAY MORNING OWING TO THICKENING CLOUD
COVER AND RETURN FLOW. LOWS IN THE LOWER 30S TO UPPER 30S.  -CBL

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
AS OF 320 PM THURSDAY...

A SHALLOW BACKDOOR COLD FRONT AND LEADING EDGE OF CANADIAN HIGH
PRESSURE WILL SLIP SOUTH THROUGH THE AREA FRIDAY NIGHT.   THE CORE
OF THE HIGH WILL SETTLE OVER THE AREA EARLY SATURDAY AND THEN SHIFT
EAST OFFSHORE DURING THE DAY. A STRONG MID-LEVEL INVERSION SUGGEST
AND VERY WEAK MIXING SUGGEST TEMPS WONT GET ANYWHERE NEAR THEIR
THICKNESS-CORRELATED VALUES...WITH GUIDANCE MOSTLY IN THE UPPER 40S
NORTHEAST TO MID 50S SOUTHWEST.  HIGH CLOUDS WILL BEGIN TO POUR IN
SATURDAY EVENING AS A SYSTEM BEGINS TO LIFT OUT OF THE SOUTHERN
PLAINS...WITH LOW LEVEL MOISTURE QUICKLY RETURNING AROUND THE
OFFSHORE HIGH.  SOUTHEASTERLY LOW-LEVEL FLOW AND ISENTROPIC LIFT
SHOULD BE FOCUSED ACROSS SC AND INTO THE SOUTHWESTERN NC SATURDAY
NIGHT...LEAVING NC DRY THROUGH SUNRISE SUNDAY.  LOWS WILL BE
MILDER...LIKELY ABOVE GUIDANCE IN THE MID TO UPPER 30S.

SUNDAY AND SUNDAY NIGHT... SOUTH TO SOUTHEASTERLY FLOW REALLY RAMPS
UP SUNDAY BETWEEN THE HIGH AND A LOW PRESSURE SYSTEM LIFTING FROM
TEXAS TO THE GREAT LAKES.  BASED ON THE ORIENTATION OF THE SURFACE
HIGH...STRONG COLD AIR DAMMING IS NOT VERY LIKELY...THOUGH PRECIP
OVER THE WESTERN PIEDMONT EARLY SUNDAY WILL LIKELY STABILIZE THAT
AREA AND LEAD TO A IN-SITU WEDGE AIRMASS.  WE SHOULD THEN SEE RAIN
SPREAD ACROSS THE AREA TO THE NORTHEAST SUNDAY AFTERNOON...WITH THE
HEAVIEST PRECIP SUNDAY EVENING INTO SUNDAY NIGHT AS A 50-60KT
SOUTHERLY LLJ BRINGS AND A SFC/850MB WARM FRONT AND STRONG WARM
ADVECTION ACROSS THE AREA.  PW WILL WILL BE OVER 1.75 INCHES...2 SD
ABOVE NORMAL...WITH A DEEP WARM RAIN LAYER...SO THE POTENTIAL FOR
SOME LOCALLY HEAVY RAINFALL MAY EXIST ACROSS EASTERN AREAS.  MODELS
ALSO SHOW CONVECTION MOVING FROM THE GULF COAST TOWARD COASTAL
CAROLINA...WHICH LEADS TO SOME UNCERTAINTY IN THE QPF
FORECAST...WITH MODELS CURRENTLY SHOWING AROUND AN INCH AREAWIDE.

SEVERE WEATHER POTENTIAL WILL BE LIMITED BY 1) MOIST ADIABATIC
PROFILES AND THE LACK OF INSTABILITY...AND 2) THE MAIN DYNAMIC
FORCING LIFTING WELL WEST OF THE MOUNTAINS.  HOWEVER...BASED ON THE
INTENSITY OF THE LLJ/WARM ADVECTION...WOULDNT BE SURPRISED IF THE
MODELS ARE UNDERDOING INSTABILITY A BIT...ESPECIALLY ELEVATED WITH
CRUX OF THE WARM ADVECTION ACROSS THE SOUTHEAST SUNDAY
EVENING/NIGHT.  FORECAST SOUNDINGS SHOW LITTLE POTENTIAL FOR ANY
(NEAR)SURFACE BASED INSTABILITY...AND IF THERE IS A POTENTIAL FOR
SEVERE WEATHER IT SHOULD BE CONFINED TO THE FAR SOUTHEAST. WILL
LEAVE THUNDER OUT FOR NOW GIVEN THE UNCERTAINTY IN INSTABILITY.

TEMPS WILL LIKELY HOLD STEADY IN THE LOW-MID 50S IN THE WEDGE
AIRMASS TO LOWER 60S IN THE EAST SUNDAY EVENING...RISING WELL INTO
THE 60S SUNDAY NIGHT AS THE WARM FRONT MOVES THROUGH AND THEN INTO
THE UPPER 60S/LOWER 70S ON MONDAY.

MONDAY THROUGH THURSDAY... THE DEEP MOIST AXIS WILL SHIFT EAST TO
THE COAST ON MONDAY...WITH SOUTHWESTERLY FLOW ALOFT.  THERE IS A BIT
OF UNCERTAINTY REGARDING ADDITIONAL ENERGY WITHIN THE BASE OF THE
LONGWAVE TROUGH AND HOW THAT WILL EVOLVE.  THE GFS SHOWS ANOTHER
WAVE MOVING UP THE APPALACHIANS ON TUESDAY AND SPITS OUT A LITTLE
QPF...WHILE THE ECMWF MAINTAINS AN ELONGATED...POSITIVELY TILED
TROUGH THAT FINALLY EJECTS EAST ON WEDNESDAY.  WILL SHOW A SLOW
DOWNWARD TREND IN POPS FROM WEST TO EAST ON TUESDAY AND WEDNESDAY AS
TEMPS HEAD BACK BELOW NORMAL LATE NEXT WEEK.

&&

.AVIATION /18Z THURSDAY THROUGH MONDAY/...
AS OF 1244 PM THURSDAY...

24-HOUR TAF PERIOD: VERY HIGH CONFIDENCE OF VFR CONDITIONS THROUGH
THE TAF PERIOD. CLEAR SKIES MAY GIVE WAY TO SOME MID LEVEL CLOUDS
THIS AFT/EVE...MAINLY ACROSS THE NORTH...AS A DRY COLD FRONT MOVES
INTO THE AREA. EXPECT CLEAR SKIES OVERNIGHT. SOUTHWEST WINDS WILL
CONTINUE TO GUST IN THE 15-20 KT RANGE THIS AFTERNOON...WITH GUSTS
ABATING AFTER SUNSET. AS THE COLD FRONT MOVES INTO AND THROUGH THE
AREA...WINDS WILL VEER FROM SOUTHWESTERLY TO NORTHERLY THROUGH THE
OVERNIGHT HOURS.

LOOKING AHEAD: THE NEXT THREAT TO AVIATION CONDITIONS WILL BE WITH
A LOW PRESSURE SYSTEM APPROACHING AND MOVING THROUGH THE AREA SUNDAY
INTO MONDAY...YIELDING INCREASING CLOUD COVER AND PRECIPITATION
CHANCES. CONDITIONS COULD REMAIN BELOW VFR UNTIL THE COLD FRONTAL
PASSAGE...EITHER MONDAY NIGHT OR EARLY TUESDAY. WINDS WILL LIKELY
BECOME GUSTY AS THE FRONT APPROACHES AND MOVES THROUGH THE REGION.

&&

.CLIMATE...

RECORD LOW:   GSO  RDUFAY

SAT 11/22 - 13 IN 1914    21 IN 2008    20 IN 2000

&&

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

&&

$$

SYNOPSIS...ELLIS
NEAR TERM...KC
SHORT TERM...KC
LONG TERM...BLS
AVIATION...KC
CLIMATE...RAH




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