Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 010845
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
345 AM EST SUN MAR 1 2015

.SYNOPSIS...
WHILE COLD HIGH PRESSURE WILL EXTEND ACROSS THE AREA
TODAY...INCREASING MOISTURE WILL HELP PROVIDE FOR UNSETTLED WEATHER.
A COLD FRONT WILL MOVE THROUGH THE AREA MONDAY...FOLLOWED BY HIGH
PRESSURE FOR TUESDAY...BEFORE ANOTHER COLD FRONT MOVES INTO THE
REGION LATE WEDNESDAY.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 345 AM SUNDAY...

TODAY...RIDGE EXTENDING FROM PARENT ARCTIC HIGH OVER THE NORTHERN
MID ATLANTIC MAINTAIN A SUPPLY OF COLD DRY AIR INTO CENTRAL NC THIS
MORNING. RETURN SLY FLOW ON THE BACKSIDE OF THE RETREATING 925-850MB
HIGH OFF THE SE U.S. COAST ADVECTING OVER THE COLD STABLE AIR MASS
AT THE SURFACE. THIS HAS RESULTED IN PATCHES OF LIGHT PRECIP TO BEAK
OUT OVER OUR FAR SOUTHERN COUNTIES SHORTLY AFTER MIDNIGHT ...AND
BEGINNING TO SPREAD ACROSS THE WESTERN PIEDMONT AT 08Z. WITH SFC
DEWPOINTS SPREAD OF 12-16 DEGREES ACROSS THE PIEDMONT AND NORTHERN
COASTAL PLAIN...EVAPORATIVE COOLING SHOULD DROP SFC TEMPS TO BELOW
FREEZING FOR SEVERAL HOURS ONCE THE PRECIPITATION SETS IN. OVER THE
FAR SOUTH-SE...THIS TIME BELOW FREEZING SHOULD BE NO MORE THAN A
COUPLE OF HOURS (IF THAT).

APPEARS BEST THREAT FOR ICE ACCRUAL OF A TENTH OF AN INCH OR A
LITTLE MORE WILL BE ACROSS THE FAR NORTHERN PIEDMONT/VA BORDER
COUNTIES...AND INTO THE NORTHERN SECTIONS OF FORSYTH...GUILFORD AND
ALAMANCE COUNTIES. ELSEWHERE...EXPECT ENOUGH ICE ACCRUAL ON EXPOSED
SURFACE OBJECTS AS WELL AS BRIDGES AND OVERPASSES TO FORM A THIN
GLAZE...ENOUGH TO MAKE TRAVEL HAZARDOUS IN SPOTS ACROSS THE PIEDMONT
THIS MORNING.

FAIRLY SUBSTANTIAL WARM NOSE ALOFT (APPROACHING 8 DEGREES C IN THE
NW PIEDMONT BY LATE MORNING) MAY BE ENOUGH TO OVERCOME THE SUB
FREEZING CONDITIONS AT THE SURFACE. THUS WHILE SFC TEMPS IN THE
NORTHERN PIEDMONT MAY BE 31-32 DEGREES BY MID DAY...ADDITIONAL ICE
ACCRUAL WILL BE SEVERELY LIMITED. PLAN TO MAINTAIN ADVISORY ACROSS
THE FAR NORTH-NW UNTIL 4 PM BUT WILL ASSESS TEMP RESPONSE LATER THIS
MORNING WITH A POSSIBILITY OF ENDING THE ADVISORY A FEW HOURS
EARLIER. ELSEWHERE CURRENT ADVISORY END TIMES APPEAR ON TARGET.

MAX TEMPS THIS AFTERNOON DEPENDENT UPON ON HOW EXTENSIVE THE PRECIP
BECOMES AND WHEN IT TAPERS OFF. COUNTING ON PRECIP LINGERING THROUGH
A GOOD PART OF THE AFTERNOON ACROSS THE EAST SO HAVE LOWERED TEMPS
THERE A FEW DEGREES FROM PREVIOUS FORECAST. CONVERSELY...HAVE
ADJUSTED MAX TEMPS UP A DEGREE OR TWO ACROSS THE WEST-SW WHERE
PRECIP MAY TAPER OFF BY EARLY-MID AFTERNOON.


&&

.SHORT TERM /TONIGHT AND MONDAY/...
AS OF 345 AM SUNDAY...

TONIGHT...EXTENSIVE LOW CLOUDS AND AREAS OF FOG EXPECTED WHILE A SLY
SFC WIND WILL BEGIN TO STIR AS A COLD FRONT APPROACHES FROM THE WEST-
NW. THESE CONDITIONS SHOULD CAUSE TEMPS TO HOLD STEADY OVERNIGHT.
MIN TEMPS IN THE MID-UPPER 30S.

MONDAY...SFC COLD FRONT SHOULD CROSS THE AREA IN THE MORNING.
APPEARS MOISTURE DEPTH FAIRLY LIMITED TO GENERATE ANY PRECIP ACROSS
THE NW BUT MAY BE ENOUGH ACROSS THE FAR SOUTH-SE TO DEVELOP A FEW
PATCHES OF LIGHT RAIN. NWLY FLOW BEHIND THE FRONT WILL AID TO ADVECT
A DRIER AIR MASS IN THE REGION. THIS WILL SLOWLY ERODE CLOUD
COVERAGE FROM THE NW DURING THE AFTERNOON. SHOULD SEE TEMPS REBOUND
INTO THE LOW AND MID 50S WITH PARTIAL SUNSHINE OVER MOST OF THE
PIEDMONT BY AFTERNOON (LESS SO ACROSS THE FAR SOUTH-SE). FAVORED
COOLER NAM MOS GUIDANCE VERSUS THE WARMER MOS GUIDANCE.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
AS OF 320 PM SUNDAY...

MONDAY NIGHT AND TUESDAY: SURFACE HIGH PRESSURE LOCATED JUST TO THE
NORTH OF CENTRAL NC AND AND MID LEVEL RIDGING EXTENDING INTO THE
AREA FROM THE SOUTH WILL BOTH QUICKLY SHIFT EASTWARD ON MONDAY NIGHT
INTO TUESDAY. HOWEVER... THE LINGERING COLD DRY SURFACE AIR
DEPOSITED BY THE SURFACE HIGH WILL AGAIN SET THE STAGE FOR AN INSITU
CAD EVENT ON TUESDAY INTO TUESDAY NIGHT... POSSIBLY LINGERING INTO
WEDNESDAY MORNING ACROSS THE FAR NORTHWEST PIEDMONT. WARM MOIST AIR
WILL INCREASING IN SOUTHERLY TO SOUTHWESTERLY FLOW ALOFT. GIVEN THIS
AND THE LINGERING COLD SURFACE AIRMASS... WE SHOULD SEE SOME
ISENTROPICALLY DRIVEN PRECIP DEVELOP TUESDAY MORNING INTO THE
AFTERNOON. TUESDAY MORNING LOW TEMPS ARE EXPECTED TO BE AROUND 30
NORTH TO NEAR 40 SOUTH. MODELS CONTINUE TO BRING THE LIGHT PRECIP IN
AFTER SURFACE TEMPS AND DEWPOINTS INCREASE ENOUGH TO AVOID AND
NUISANCE FREEZING RAIN. HOWEVER... HIGH TEMPS WILL BE WELL BELOW
NORMAL AND GREATLY AFFECTED BY THE CAD AIRMASS. MAV STATISTICAL
GUIDANCE APPEARS TO BE WAY TOO WARM FOR TUESDAY... WITH THE RAW GFS
TEMPS CLOSER TO MET GUIDANCE VALUES. FOR NOW WILL LOWER TEMPS
FURTHER... AND THIS MAY NOT EVEN BE FAR ENOUGH. WILL WO WITH HIGH
TEMPS RANGING FROM THE UPPER 30S NORTH TO NEAR 50 IN THE FAR
SOUTHEAST.

TUESDAY NIGHT THROUGH THURSDAY NIGHT: ANOTHER STRONG ARCTIC COLD
FRONT WILL APPROACH THE REGION ON TUESDAY NIGHT... BEFORE SLOWLY
MOVING ACROSS THE AREA WEDNESDAY INTO THURSDAY MORNING. THE FRONT IS
EXPECTED TO BECOME PARALLE WITH THE MID LEVEL FLOW AS THE MID/UPPER
LEVEL TROUGH BECOMES MORE OF A FULL LATITUDE TROUGH... WHICH
APPEARS TO PHASE SOME THE THE SOUTHERN STREAM ENERGY WITH THE
NORTHERN STREAM... RESULTING IN A DEEP FETCH OF SOUTHWESTERLY MID
LEVEL FLOW... ALONG WITH SEVERAL SURFACE LOWS TRACKING ALONG THE
FRONT FROM TIME TO TIME. MOST OF THE SHOWERS WILL BE ALONG AND
BEHIND THE FRONT... MAINLY FROM WEDNESDAY MID-MORNING INTO THE
AFTERNOON UNTIL LATE THURSDAY (WITH A GOOD CHANCE OF PRECIP...
POSSIBLY SOME HEAVY AMOUNTS OF RAIN). IN ADDITION... MODELS HAVE
TRENDED FASTER WITH SURGING THE STRONG/DEEP COLD LOW LEVEL AIRMASS
INTO THE REGION. IF THIS WERE TO OCCUR... WE COULD POSSIBLE SEE SOME
WINTRY P-TYPES ON THURSDAY. HOWEVER... GIVEN WE ARE STILL TALKING
ABOUT DAY 5 IN THE FORECAST AND WE ARE NOW IN THE MONTH OF MARCH...
WILL WAIT TO ADD ANY NON-LIQUID P-TYPE TO THE FORECAST. DRY WEATHER
IS EXPECTED TO RETURN FOR AT LEAST FRIDAY. HOWEVER...  THE SYNOPTIC
PATTERN MAY REMAIN CONDUCIVE FOR WAVES OF LOW PRESSURE TO DEVELOP
AND TRACK ALONG THE FRONT... WHICH IS EXPECTED TO BE LOCATED OFF THE
CAROLINA COAST LATE WEEK INTO THE WEEKEND. THUS... WE COULD
CONCEIVABLY SEE SOME PRECIP IF ONE SUCH SYSTEM DEVELOPS NEXT WEEKEND.

TEMPS DURING THE MEDIUM RANGE WILL INCLUDE SOME DECENT SWINGS...
WITH HIGHS TEMPS WEDNESDAY IN THE 60S AND 70S... THURSDAY 40S AND
50S (MAYBE COLDER)... WITH FRIDAY BACK IN THE 40S (WITH MAYBE SOME
30S EVEN). WE WILL SEE SOME MODERATING BY SATURDAY... GENERALLY BACK
INTO THE 50S... GIVEN WE REAMIN DRY. LOWS WILL FOLLOW A SIMILAR
PATTERN. AS MENTIONED ABOVE...  ALL PRECIP AS OF NOW APPEARS TO BE
IN THE FORM OF LIQUID FOR THE MEDIUM RANGE... OUTSIDE OF *MAYBE* A
BRIEF PERIOD AS THE PRECIP ENDS ON THURSDAY.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
AS OF 100 AM SUNDAY...

ADVERSE AVIATION CONDITIONS WILL OVERSPREAD CENTRAL NC FROM THE
SOUTH THROUGH 12Z WITH MVFR/IFR CEILINGS AND PATCHES OF LIGHT RAIN
OR LIGHT FREEZING RAIN.

BY 12Z...EXPECT WIDESPREAD LOW END MVFR/IFR CEILINGS ALONG WITH
AREAS OF LIGHT FREEZING RAIN OVER THE PIEDMONT AND SANDHILLS...AND
EITHER LIGHT RAIN OR FREEZING RAIN IN THE COASTAL PLAIN. BETWEEN 12Z-
15Z...THE LIGHT FREEZING RAIN IN THE SANDHILLS AND EASTERN PIEDMONT
SHOULD TRANSITION TO A COLD RAIN. IN ADDITION...A STRENGTHENING LOW
LEVEL JET JUST ABOVE THE SURFACE WILL RESULT IN LOW LEVEL WIND SHEAR
CONDITIONS...ESPECIALLY IN VICINITY OF KRDU...KFAY AND KRWI.

THE FREEZING RAIN IN THE NW PIEDMONT WILL GRADUALLY CHANGE TO A COLD
RAIN BY MID AFTERNOON. ELSEWHERE EXPECT AREAS OF LIGHT RAIN OR
DRIZZLE WITH IFR/LIFR CEILINGS. WHILE THE BULK OF THE RAIN WILL
TAPER OFF BY SUNSET...WIDESPREAD FOG AND DRIZZLE ALONG WITH IFR/LIFR
CEILINGS WILL PERSIST INTO TONIGHT.

MONDAY...A COLD FRONT WILL CROSS THE REGION. WEST-NW FLOW BEHIND THE
BOUNDARY WILL ADVECT A DRIER AIR MASS...LEADING TO A SCOURING OF THE
MURKY NEAR SURFACE AIR MASS. EXPECT IMPROVING AVIATION CONDITIONS
LATE MONDAY THROUGH MONDAY NIGHT. HIGH PRESSURE OVER THE AREA
TUESDAY WILL PROVIDE VFR CONDITIONS. ANOTHER COLD FRONT WILL
APPROACH WEDNESDAY AND CROSS THE REGION WEDNESDAY NIGHT AND
THURSDAY. THIS WEATHER SYSTEM WILL LIKELY CAUSE ANOTHER PERIOD OF
SUB VFR CONDITIONS ACROSS CENTRAL NC.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR NCZ042-077-
078-083>086-088-089.
WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR
NCZ008>011-024>028-040-041-043-073>076.
WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR
NCZ007-021>023-038-039.

&&

$$
SYNOPSIS...WSS
NEAR TERM...WSS
SHORT TERM...WSS
LONG TERM...BSD
AVIATION...WSS


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