Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 130540
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1240 AM EST SAT FEB 13 2016

.SYNOPSIS...ARCTIC HIGH PRESSURE WILL BUILD INTO CENTRAL NC TODAY
AND SUNDAY. AN AREA OF LOW PRESSURE WILL APPROACH FROM THE WEST ON
MONDAY AND CROSS THE REGION MONDAY NIGHT AND TUESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 940 PM FRIDAY...

STARTING TO FINALLY SEE BETTER WEST TO EAST CLEARING OF MOISTURE
AROUND 6000-7000 FT AS A JET ON THE BACK SIDE OF THE UPPER TROUGH
APPROACHES AND NORTHWEST FLOW STRENGTHENS. LOW-LEVEL MOISTURE IS
STILL MORE PREVALENT ON THE COASTAL PLAIN WHERE SOME SUB-1000 FT
STRATUS IS LINGERING.  A PERIOD OF PATCHY FOG MAY DEVELOP IN THE
SOUTHERN COASTAL PLAIN AS THE HIGHER LEVEL CLOUDS CLEARING (HINTED AT
BY SREF PROBS AND KFAY/KGSB RAP SOUNDINGS)...BUT IT WOULD LIKELY BE
BRIEF...PRIOR TO 06Z...WITH A NORTHWEST WIND AND COLD ADVECTION
FORECAST TO SLOWLY STRENGTHEN AFTER MIDNIGHT. OTHERWISE...WHILE WE
MAY SEE A SOME PATCHES OF STRATOCU DRIFT ACROSS THE AREA GIVEN ALL
THE MOISTURE BANKED UPSTREAM OF THE MOUNTAINS...CLEARING SKIES AND
COLD ADVECTION WILL PUSH LOWS INTO THE LOWER 20S NORTH AND WEST TO
UPPER 20S SOUTH AND EAST.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
AS OF 300 PM FRIDAY...

AS EAST COAST TROUGH TRIES TO PULL OFF THE COAST...VERY STRONG COLD
AIR ADVECTION WILL ENSUE BEHIND THE EXITING COASTAL SYSTEM. WITH
VERY STRONG PRESSURE GRADIENT ACROSS THE AREA...COLD TEMPERATURES
AND STRONG WINDS WILL BE THE FORECAST PROBLEM OF THE DAY. EXPECT
WINDS TO REMAIN SUSTAINED OUT OF THE NORTH OR NORTHWEST AT 10-15 KTS
WITH GUSTS OF 25-30 KTS FOR MUCH OF THE DAYLIGHT HOURS. AFTER SUNSET
GUSTS WILL SUBSIDE. HIGH TEMPERATURES ONLY IN THE LOW TO MID 30S AND
WITH WIND CHILL VALUES IN THE UPPER 10S TO LOW 20S FOR MUCH OF THE
DAY. AS AN ASIDE...WITH THE COLD BUT ALSO DRY AIRMASS IN PLACE...MIN
RH VALUES WILL DIP DOWN INTO THE LOW 20S. COMBINE THESE VALUES WITH
THE HIGHER WINDS AND THERE WILL BE A SMALL INCREASE IN FIRE DANGER
SATURDAY IN OUR SOUTHERN COUNTIES THAT MAY SQUEAK INTO THE LOWER
40S.

SATURDAY NIGHT WILL SEE THE GUSTS SLACK OFF BUT SUSTAINED WINDS TO
REMAIN UP IN THE 5 TO 10 KT RANGE KEEP THINGS MIXED A LITTLE.
COMBINE THIS WITH VERY COLD EXPECTED LOW TEMPERATURES IN THE LOW TO
MID TEENS...WIND CHILL VALUES SATURDAY NIGHT WILL RESIDE IN THE 5-10
DEGREE RANGE. PREPARATIONS SHOULD BE MADE NOW TO PROTECT ANYTHING
SUSCEPTIBLE TO THE COLD WIND CHILLS...ESPECIALLY PETS. SOME CLOUDS
WILL BEGIN TO APPROACH THE AREA LATE SATURDAY NIGHT INTO SUNDAY
MORNING FROM THE WEST IN ADVANCE OF THE NEXT STORM SYSTEM.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
AS OF 315 PM FRIDAY...

...STORM SYSTEM LIKELY TO BRING WINTRY WEATHER THREAT SUN NIGHT/MON
FOLLOWED BY HEAVY RAIN THREAT AND A FEW STORMS MON NIGHT/TUE...

SUNDAY: CONTINUED CHILLY WITH THE ARCTIC HIGH PRESSURE EXTENDING
FROM THE ERN GREAT LAKES DOWN THROUGH NC. WILL HAVE INCREASING
CLOUDS AHEAD OF THE APPROACHING STORM... AS OUR MID LEVEL FLOW
SHIFTS FROM FAST NORTHWESTERLY TO WEST-SOUTHWEST... A FUNCTION OF
PACIFIC NORTHWEST ENERGY DIVING INTO AN INITIALLY FLAT/BROAD CENTRAL
CONUS TROUGH CAUSING ITS AMPLIFICATION. STATISTICAL GUIDANCE STILL
SUPPORTS HIGHS FROM 29 NE TO 35 SW. -GIH

SUN NIGHT THROUGH TUE:

OVERVIEW: CONFIDENCE IS BEGINNING TO INCREASE REGARDING THE
TIMING... MOST PROBABLE PRECIP TYPE PATTERN... AND PRIMARY WEATHER
THREATS FOR THE INCOMING SYSTEM. LATEST GUIDANCE SHOWS A BIT QUICKER
ONSET... WITH PRECIP ARRIVING IN THE NRN/WRN CWA SUN NIGHT... AS
WELL AS A SLIGHTLY EARLIER DEPARTURE ON TUE. LONGWAVE TROUGHING WILL
CONTINUE TO AMPLIFY ALONG THE MISS VALLEY AS NRN STREAM ENERGY DROPS
INTO ITS BASE OVER THE GULF STATES... CULMINATING IN A NARROW DEEP
SHORTWAVE TROUGH TAKING ON A POSITIVE TILT AS IT SWINGS ENE INTO THE
CAROLINAS. AT THE SURFACE... THE POLAR HIGH SITUATED OVER THE
NORTHEAST AND MIDATLANTIC STATES SUN NIGHT CONTINUES TO PUSH
STEADILY NORTHEAST AND OFFSHORE THROUGH MON... WHILE A COASTAL FRONT
FORMS ALONG THE CAROLINA COAST EXTENDING BACK TO DEVELOPING LOW
PRESSURE OVER THE CENTRAL GULF STATES. THIS LOW THEN TRACKS EAST
THEN NE THROUGH WRN NC MON NIGHT/TUE MORNING BEFORE MOVING QUICKLY
INTO THE NORTHEAST STATES... WITH A TRAILING FRONT SWEEPING THROUGH
CENTRAL/ERN NC BY EARLY TUE AFTERNOON.

PRECIPITATION CHANCES: THE INITIAL PROCESSES TO FORCE ASCENT SUNDAY
NIGHT INTO EARLY MONDAY INCLUDING DPVA AND MOIST ISENTROPIC UPGLIDE
ARE RATHER WEAK AND FOCUSED PRIMARILY ON WRN AND NRN PORTIONS OF
CENTRAL NC. WILL TREND POPS UP TO LIKELY NW AND RETAIN HIGH CHANCES
ACROSS THE SOUTH AND EAST SUN NIGHT INTO MON MORNING... WITH QPF
FAIRLY LIGHT... UNDER A QUARTER INCH MAINLY IN THE NW. BUT THIS
CHANGES QUICKLY WITH THE ADDITION OF STRONG UPPER DIVERGENCE (DUE TO
IDEALLY JUXTAPOSED POLAR AND SUBTROPICAL JETS) AND VIGOROUS LOW
LEVEL MOISTURE TRANSPORT EAST OF THE LOW. WILL RAMP UP POPS FURTHER
TO CATEGORICAL WEST/LIKELY EAST LATE MON... THEN TO CATEGORICAL
EVERYWHERE MON NIGHT THROUGH TUE MORNING... ENDING SW TO NE TUE
AFTERNOON.

PTYPES: USING THE TOP-DOWN METHODOLOGY WITH CONSIDERATION OF THE
INITIALLY VERY COLD/DENSE NATURE OF THE SURFACE AIR MASS... THE
INITIAL COLD AIR ALOFT GIVING WAY TO A WARM NOSE... AND THE STRONG
LOW LEVEL WARM ADVECTION APT TO DISLODGE THIS SURFACE AIR MASS
GRADUALLY FROM SE TO NW MON EVENING... EXPECT THIS TO START AS
MOSTLY LIGHT SNOW WITH PERHAPS PATCHY LIGHT SLEET SUN NIGHT ACROSS
THE NRN AND WRN CWA... FOLLOWED BY A SLOW STEADY TRANSITION FROM SSE
TO NNW TO FREEZING RAIN/SLEET THEN TO ALL RAIN... WITH THE FAR NW
COUNTIES INCLUDING THE TRIAD THE LAST TO SEE AN END TO THE WINTRY
PRECIP MON EVENING. TENTATIVE ACCUMULATIONS ARE UP TO ONE TO TWO
HUNDREDTHS OF AN INCH OF ICING (TRACE AMOUNTS) FOR MUCH OF THE
CWA... AND SNOW TOTALS OF 1-3" NW QUARTER WITH AN INCH OR LESS
ELSEWHERE... ALL OF WHICH SHOULD BE QUICKLY SWEPT AWAY BY MODERATE
TO POTENTIALLY HEAVY RAINFALL LATE MON NIGHT INTO TUE MORNING.

RAINFALL TOTALS AND STORM POTENTIAL: AT THIS TIME STORM TOTAL LIQUID
QPF IS EXPECTED TO BE 1-2" WITH LOCALLY HIGHER AMOUNTS POSSIBLE...
GIVEN THE HIGH WATER CONTENT AND STRONG LIFT MON NIGHT/TUE MORNING.
BASED ON THE ANTECEDENT CONDITIONS AND SEVERAL RIVERS AND CREEKS
RUNNING HIGH... A FLOOD WATCH MAY BE NEEDED FOR SOME PORTION OF THE
AREA. ALSO... WHILE LAPSE RATES ARE UNLIKELY TO BE VERY
IMPRESSIVE... THE STRONG AND FOCUSED LIFT POSSIBLE WITH THIS SYSTEM
AND WARMING LOW LEVELS ESPECIALLY IN THE SANDHILLS AND COASTAL PLAIN
MAY SUPPORT A FEW LIGHTNING STRIKES ON TUE.

TEMPS: EXPECT LOWS SUN NIGHT OF 22-26. TEMPS SHOULD SLOWLY RISE MON
THROUGH MON NIGHT... REACHING THE LOW 30S NW TO LOW 40S SE LATE
MON... RISING TO THE MID 30S NW TO MID 40S SE MON NIGHT... AND
PEAKING AT 48-56 TUE PRIOR TO FRONTAL PASSAGE.

WED THROUGH FRI: WE MAY SEE A PERTURBATION SWING THROUGH THE
LONGWAVE ERN TROUGH BASE ACROSS VA ON WED... BUT MODELS VARY ON THE
STRENGTH AND LATITUDE OF ANY SUCH WAVE... AND REGARDLESS THE
MOISTURE WILL BE LIMITED YIELDING NO IMPACTS ON CENTRAL NC OTHER
THAN SOME CLOUDS ACROSS THE NORTH. OTHERWISE... THIS PERIOD WILL
FEATURE A TRANSITION AWAY FROM WRN RIDGE/ERN TROUGH OVER THE
CONUS... AS FLAT RIDGING BUILDS OVER THE GULF/SOUTHEAST STATES FROM
THE WEST... WITH A NET RESULT OF DRY WEATHER AND NEAR TO SLIGHTLY
ABOVE NORMAL TEMPS FOR CENTRAL NC. -GIH

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
AS OF 1240 AM SATURDAY

A LAYER OF SCATTERED-BROKEN STRATOCU WILL LINGER ACROSS THE NORTHERN
COUNTIES THROUGH 10Z...THEN GRADUALLY DIMINISH. THE LEADING EDGE OF
AN ARCTIC AIRMASS WILL OVERSPREAD CENTRAL NC THROUGH 11Z. SFC WINDS
WILL GUSTS BETWEEN 20-25KTS WITH THE PASSAGE OF THE BOUNDARY.

AFTER 11Z...EXPECT VFR CONDITIONS WITH FEW-SCATTERED STRATOCU. SFC
WINDS WILL BE BRISK WITH GUSTS 22-27KTS HIGHLY PROBABLE FROM THE NW.
THESE BRISK WINDS WILL SLOWLY SUBSIDE LATER TONIGHT.

VFR CONDITIONS TO CONTINUE INTO SUNDAY THOUGH MID-HIGH LEVEL CLOUDS
WILL BE INCREASING DURING THE DAY AS AN AREA OF LOW PRESSURE APPROACHES
FROM THE WEST. MOISTURE AHEAD OF THIS SYSTEM WILL LEAD TO SUB VFR
CEILINGS ALONG WITH PATCHES OF PRECIPITATION LATE SUNDAY NIGHT INTO
MONDAY MORNING. AT ONSET...THIS PRECIPITATION MAY OCCUR AS A WINTRY
MIX. THE SUB VFR CONDITIONS MAY LINGER INTO EARLY TUESDAY WITH
IMPROVING CONDITIONS LATE TUESDAY INTO WEDNESDAY.


&&

.CLIMATE...

HERE ARE THE RECORD LOWS AND RECORD LOW MAXIMUM TEMPERATURES FOR SAT
FEB 13TH AND SUN FEB 14TH AT GSO... RDU... AND FAY:


       REC    YR     REC    YR
       LOW         LOW MAX
----------------------------------------------
GSO:
02/13   11   1955     31   1986
02/14    6   1905     22   1914

RDU:
02/13    4   1899     10   1899
02/14   -2   1899     27   1916

FAY:
02/13   14   1973     32   1955
02/14   12   1968     33   1916

&&

.RAH WATCHES/WARNINGS/ADVISORIES...

NONE

&&

$$

SYNOPSIS...WSS
NEAR TERM...SMITH
SHORT TERM...ELLIS
LONG TERM...HARTFIELD
AVIATION...WSS
CLIMATE...RAH


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