-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 030813
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
310 AM EST MON MAR 3 2014

.SYNOPSIS...
AN ARCTIC COLD FRONT WILL MARCH SOUTH ACROSS CENTRAL NC
TODAY.  ARCTIC AIR WILL OVERSPREAD THE REGION BEHIND THE FRONT AND
LINGER THROUGH EARLY WEDNESDAY.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
AS OF 900 PM SUNDAY...

...WINTRY STORM WARNING IN EFFECT FOR THE NORTHERN PIEDMONT
AND NORTHERN COASTAL PLAIN FROM 10 AM MONDAY MORNING UNTIL MIDNIGHT
MONDAY NIGHT...

...WINTRY STORM ADVISORY IN EFFECT FOR THE REMAINDER OF THE
PIEDMONT COUNTIES AND CENTRAL COASTAL PLAIN FROM NOON MONDAY UNTIL
MIDNIGHT MONDAY NIGHT...

TONIGHT...PERSISTENT SLY WIND IN CONJUNCTION WITH
INCREASING/THICKENING CLOUD DECK RESULTING IN CONTINUED MILD
TEMPERATURES THIS EVENING WITH MOST AREAS STILL IN THE LOWER 60S.

HOWEVER MAJOR CHANGES ARE ON THE WAY AS LEADING EDGE OF ARCTIC FRONT
CURRENTLY OVER CENTRAL VIRGINIA...WILL SURGE SOUTH-
SOUTHEASTWARD...ARRIVING FIRST INTO THE NORTHERN COASTAL
PLAIN/PIEDMONT BETWEEN 10 TO 13Z. LOWS RANGING FROM UPPER 30
NORTHEAST TO LOWER 50S SE. AS FAR AS PRECIP CHANCES...AVAILABLE
MOISTURE AND FORCING ALONG FRONT COUPLED WITH LIFT ALOFT ATTRIBUTED
TO 50-70M HEIGHT FALLS AND RIGHT ENTRANCE OF 180KT JET SHOULD RESULT
IN A MARKED INCREASE IN PRECIP CHANCES ACROSS OUR FAR NORTHWESTERN
ZONES RIGHT AROUND DAYBREAK...ALL LIQUID THROUGH 14Z.

MONDAY... CHALLENGING FORECAST DUE TO TIMING/DEGREE OF LOW LEVEL
COLD AIR ADVECTION AND AMOUNT OF PRECIPITATION.

S/WE LIFTING E-NE OUT OF THE SOUTHERN PLAINS THIS AFTERNOON WILL
ENTER THE TN VALLEY MONDAY MORNING THEN SCOOT EAST INTO THE
CAROLINAS BY 00Z TUESDAY. THIS FEATURE WILL AID TO ENHANCE SLY
CONVERGENCE AND MOISTURE TRANSPORT ALONG/INTO THE SFC BOUNDARY.
ADDITIONAL LIFT SUPPLIED BY A TANDEM OF UPPER LEVELS CROSSING THE
REGION. PRECIPITATION APPEARS TO BE A GOOD BET ACROSS THE NORTHERN
PIEDMONT-NORTHERN COASTAL PLAIN MONDAY MORNING...AND ACROSS THE
SOUTHERN COUNTIES MONDAY AFTERNOON-EARLY EVENING.

PER THERMAL PROFILES/PARTIAL THICKNESSES...PRECIP SHOULD BE ALL
LIQUID THROUGH MID-LATE MORNING. GFS BUFKIT SOUNDINGS AND PARTIAL
THICKNESSES/NOMOGRAM SUGGEST PRECIP TRANSITIONING TO PREDOMINATELY
SLEET MIXED WITH RAIN/FREEZING RAIN. THIS TRANSITION ZONES WILL SAG
SOUTHWARD THROUGH THE AFTERNOON...OCCURRING IN THE RDU AND TRIAD
REGION AROUND MID DAY OR NO LATER THAN EARLY AFTERNOON...AND INTO
THE SOUTHERN COASTAL PLAIN AND SANDHILLS BY LATE AFTERNOON. THE FAR
NORTHERN PIEDMONT AND NORTHERN COASTAL PLAIN WILL REMAIN IN THE
SLEET OR SLEET/FREEZING RAIN MIX THE LONGEST. BASED ON PRECIP
AMOUNTS BETWEEN A QUARTER AND A HALF INCH AND A WATER EQUIVALENT
RATIO OF 3:1....COULD SEE UPWARDS OF A HALF OR A LITTLE MORE OF
SLEET ACROSS THE FAR NORTH-NORTHEAST ALONG WITH A POSSIBLE DUSTING
(HALF LESS OR LESS) OF SNOW. HALF INCH OF SLEET MEETS WINTER STORM
CRITERIA SO WILL UPGRADE WATCH TO WARNING AND INCLUDE HALIFAX IN THE
WARNING. FARTHER SOUTH INCLUDING THE TRIAD AND TRIANGLE...EXPECT
MOSTLY SLEET WITH A LITTLE SNOW MIXED IN THE BEGINNING (AND FREEZING
RAIN NEAR THE END). BELIEVE ENOUGH WINTRY PRECIP WILL OCCUR TO
WARRANT AN ADVISORY AS ROADS...ESPECIALLY UNTREATED BRIDGES AND
OVERPASSES...WILL LIKELY BECOME SLICK AND HAZARDOUS. FINALLY...WHILE
SOME SLEET EXPECTED IN THE SOUTH...SLEET WILL BE PREDOMINATELY MIXED
WITH RAIN WHICH SHOULD CUT DOWN ON AMOUNTS. THUS WILL NOT ISSUE AN
ADVISORY FOR THIS REGION AT THIS TIME.

SOME THINGS TO CONSIDER: WARM AFTERNOON HAS HEATED THE TOP SOIL. IF
PRECIP INTENSITY LIGHTER THAN EXPECTED...THEN MOST OF SLEET WILL
MELT SHORTLY AFTER IMPACT. ALSO...IF COLD AIR ADVECTION NOT AS
STRONG AS ADVERTISED...THIS WILL LEAD TO A LONGER PERIOD OF
RAIN/SLEET MIXED WHICH WILL RESULT IN LOWER SLEET TOTALS.
FINALLY...MID LEVELS OF TEH ATMOSPHERE DRY OUT IN TEH AFTERNOON.
THIS SHOULD LEAD TO LIGHT PRECIP AMOUNTS ESPECIALLY BEYOND 20-21Z
WITH HARDLY ANY MOISTURE IN THE FAVORED ICE NUCLEATION ZONE. IF TEH
COLD NOSE IS NOT AS STRONG AS PROJECTED...THEN COULD A 2-4 HOURS
PERIOD OF FREEZING RAIN/DRIZZLE VERSUS SLEET WITH ICE ACCRUAL AROUND
A TENTH OF AN INCH

MAX TEMPS MONDAY WILL OCCUR AT DAYBREAK-MID MORNING ACROSS THE NORTH
AND AROUND NOON-EARLY AFTERNOON IN THE SOUTH. HIGHS RANGING FROM
AROUND 40 TO LOWER 60S SOUTH. UPSTREAM TEMP TRENDS SUPPORT MODEL
GUIDANCE WHICH SUPPORTING TEMPS PLUMMETING 15 TO 20 DEGREES IN THE
FIRST 1-2 HOURS AFTER FRONTAL PASSAGE. WIND CHILLS MONDAY AFTERNOON
ACROSS THE NORTH WILL BE IN THE TEENS TO LOWER 20S.

LATE MONDAY-MONDAY NIGHT...PRECIP WILL QUICKLY DIMINISH SW-NE AS
SYSTEM PULLS AWAY FROM THE REGION...EXPECT MAINLY PATCHY AND LIGHT
FREEZING DRIZZLE/SLEET TO OCCUR ALONG AND EAST OF I-95 AFTER SUNSET
WITH SKIES CLEARING WEST-EAST BY LATE EVENING. FRIGID TEMPS IN THE
TEENS WILL FREEZE ANY MOISTURE ON THE ROADS. BASED ON WHAT FALLS
MONDAY AFTERNOON...WILL LIKELY NEED TO ISSUE ANOTHER ADVISORY FOR
ICY PATCHES LATE MONDAY NIGHT INTO TUESDAY MORNING FOR THE ENTIRE
CWA.

&&

.SHORT TERM /TUESDAY AND WEDNESDAY NIGHT/...
AS OF 122 PM SUNDAY...

A SLIGHT CHANCE OF SOME LIGHT FREEZING RAIN IN THE SE ZONES LATE
TUESDAY NIGHT INTO WEDNESDAY MORNING (LOW CONFIDENCE IN
PRECIPITATION OCCURRING).

VERY COLD AIR ASSOCIATED WITH THE STRONG (1030+ MB) SURFACE HIGH
PRESSURE TO OUR NORTH WILL BE IN PLACE TUESDAY MORNING... SLOWLY
MODIFYING WITH THE INCREASING MARCH SUN ANGLE DURING THE AFTERNOON.
WE WILL UNDERCUT GUIDANCE BY A CATEGORY OR TWO ACROSS THE NORTHERN
PIEDMONT ANTICIPATING SOME SLEET/ICE TO BE ON THE GROUND... AND THE
FACT THAT THE WINDS ARE FORECAST TO REMAIN NNE DURING THE DAY. THIS
WILL CONTINUE TO BRING CAA INTO THE REGION FROM VA. EXPECT MOSTLY
SUNNY SKIES BECOMING PARTLY CLOUDY IN THE AFTERNOON. PREFER THE GFS
(MAV) COLDER NUMBERS OVER THE WARMER NAM (MET) MOS GUIDANCE... GIVEN
THE NORTHERLY LOW LEVEL FLOW FROM THE EXPECTED ARCTIC AIR MASS TO
THE NORTH... AND THE LIKELIHOOD OF SNOW/ICE COVER FROM RDU NORTHWARD
WHERE THE LOW LEVEL FLOW IS COMING FROM. HIGHS 35-45 N TO S.

THE FORECAST BECOMES A BIT MORE PROBLEMATIC TUESDAY NIGHT... MAINLY
IN THE SOUTHEAST COASTAL PLAIN FROM FAYETTEVILLE TO GOLDSBORO. THIS
IS WHERE MODELS FORECAST A CHANCE OF LIGHT PRECIPITATION AS A WEAK
LOW PRESSURE IS FORECAST TO DEVELOP OUT ALONG THE ARCTIC BOUNDARY
OVER THE GULF STREAM. THERE IS LOW CONFIDENCE THAT LIGHT
PRECIPITATION WOULD REACH AS FAR WEST AND NORTH AS FAYETTEVILLE AND
GOLDSBORO GIVEN THAT THE DRY AIR RIDGE EXTENDING FROM PA/MD SOUTH
INTO NC/SC SHOULD REMAIN STRONGLY IN PLACE. HOWEVER... RECENT MODEL
TRENDS ARE INDICATING THAT THE CHANCE OF SOME LIGHT PRECIPITATION
MAY EXTEND AS FAR INLAND AS POSSIBLY FAYETTEVILLE AND GOLDSBORO
TUESDAY NIGHT AND EARLY WEDNESDAY. HOWEVER... THE P-TYPE IS ALSO LOW
CONFIDENCE GIVEN THAT THE GUIDANCE SURFACE WET BULB FORECASTS TAKE
THE TEMPERATURES SLIGHTLY ABOVE FREEZING IN THE AREAS IN
SOUTHEASTERN NORTH CAROLINA WHERE THE BEST CHANCE OF SOME LIGHT
PRECIPITATION SHOULD EXIST. FORECAST SOUNDINGS DO INDICATE A WARM
NOSE ALOFT AND 1000/850 AND 850/700 MB PARTIALS BY 12Z/WED IN THE
1310-1315M AND 1550-1555M RANGE SUGGEST JUST ENOUGH WARM AIR ALOFT
FOR LIQUID... WITH THE WET BULB 32 DEGREE LINE GENERALLY FORECAST TO
BE OVER THE NORTHERN SANDHILLS AND CENTRAL COASTAL PLAIN. BOTTOM
LINE... THERE IS A LOW CONFIDENCE FORECAST OF SOME VERY LIGHT
FREEZING RAIN MAINLY ALONG AND NORTH OF A LINE FROM FAYETTEVILLE TO
GOLDSBORO LATE TUESDAY NIGHT INTO EARLY WEDNESDAY MORNING. THEN
CLEARING SKIES AND BRIGHTER CONDITIONS WEDNESDAY WITH HIGHS
MODERATING BACK INTO THE MID 40S TO MID 50S.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
-- Changed Discussion --
AS OF 310 AM MONDAY...

RIDGING OVER THE WESTERN US BY MIDWEEK SHOULD SUPPORT A SHORTWAVE
DIGGING FROM THE CENTRAL PLAINS TO THE SOUTHEAST US ON WEDNESDAY AND
THURSDAY...WHICH PRODUCES A MILLER-A TYPE SURFACE LOW TRACK FROM THE
GULF COAST TO ALONG THE CAROLINA COAST THURSDAY NIGHT INTO FRIDAY.
MEANWHILE...A CANADIAN SURFACE HIGH IS EXPECTED TO EXTEND DOWN THE
EASTERN SEABOARD INTO THE CAROLINAS.  HOWEVER...MODELS PROJECT THE
CENTER OF THE HIGH TO BE FAR TO THE NORTH OVER EAST-CENTRAL QUEBEC
AND FAIRLY PROGRESSIVE. THUS...PARTIAL THICKNESSES...WHILE COOLING
IN THE MID-LEVELS AS THE SHORTWAVE CROSSES THE REGION...ARE FORECAST
TO REMAIN MOSTLY ABOVE 1300M IN THE 1000-850MB LAYER WITHOUT A
BETTER SUPPLY OF LOW-LEVEL COLD AIR.  RIGHT NOW IT APPEARS PRECIP
WILL BE PREDOMINATELY RAIN FOR MUCH OF CENTRAL NC...POSSIBLY
SWITCHING OVER TO A RAIN/SNOW MIX OR WET SNOW ACROSS THE NORTHWEST
PIEDMONT THURSDAY NIGHT.  THE ECMWF DEPICTS A STRONGER UPPER WAVE
AND IS WETTER THAN THE GFS...SO THERE IS STILL A LOT OF UNCERTAINTY
REGARDING THIS SYSTEM AND THE EVENTUAL TRACK OF THE SURFACE
LOW/EXTENT OF PRECIP.

BEHIND THIS SYSTEM...HIGH PRESSURE IS FORECAST TO SETTLE OVER THE
SOUTHEAST STATE ON SATURDAY...WITH THE POTENTIAL FOR ANOTHER
SHORTWAVE IN THE NORTHERN STREAM TO IMPACT THE REGION BY SUNDAY.
HOWEVER... THE FORECAST IS COMPLICATED BY MODELS SHOWING FOW
SEPARATION AND A CUTOFF LOW OVER THE SOUTHERN PLAINS.  CONFIDENCE IN
AVAILABLE MOISTURE IN THIS PATTERN TO INTRODUCE POPS INTO THE
FORECAST AT THIS TIME.  INSTEAD...WILL KEEP IT DRY WITH TEMPS
WITHIN A FEW DEGREE SO OF NORMAL THROUGH THE WEEKEND.
-- End Changed Discussion --

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AS OF 110 AM MONDAY...

VFR CONDITIONS OVERNIGHT WILL QUICKLY DETERIORATE TO IFR/LOW END
MVFR AS AN ARCTIC FRONT SLIDES SOUTH ACROSS THE AREA BETWEEN 12Z-16Z
ACROSS THE NORTH AND 16Z-21Z ACROSS THE SOUTH. FRONTAL PASSAGE WILL
BE NOTED BY A SHARP SHIFT IN THE WINDS FROM SW TO N-NE AND
INCREASING TO 15KTS SUSTAINED AND GUSTS 24-28KTS. MAY SEE A BRIEF
ONE-TWO HOUR WINDOW OF LOW LEVEL WIND SHEAR IN THE LOWEST 3-4K FT
IMMEDIATELY BEHIND THE FRONT AS N-NE SFC WINDS BACK TO SW AT 25-
30KTS BETWEEN 3-4K FT.

RAIN WILL OCCUR IMMEDIATELY ALONG AND BEHIND THE FRONT. ONCE THE
COLDER NEAR SURFACE AIR BECOMES ESTABLISHED...RAIN WILL TRANSITION
TO SLEET MIXED AT TIMES WITH FREEZING RAIN/DRIZZLE. EXPECT THE SLEET
TO LAST THE LONGEST AT KRWI AND KRDU WITH LIGHTER AMOUNTS IN THE
TRIAD REGION. FARTHER SOUTH AT KFAY...MAY SEE MORE FRZA THAN SLEET
BUT AMOUNTS WILL BE LIGHT HERE AS WELL. EXPECT TRANSITION FROM
LIQUID TO WINTRY PRECIP TO OCCUR ACROSS THE NORTHERN TERMINALS
(TRIAD, KRDU, KRWI) BETWEEN 16Z-18Z...AND IN THE KFAY VICINITY 19-
21Z.

PRECIP WILL TAPER OFF EARLY THIS EVENING WITH CLEARING SKIES WEST-TO-
EAST OCCURRING DURING THE EVENING HOURS. EXPECT MOST TAF SITES TO BE
VFR BY 06Z.

BEYOND TUESDAY MORNING...A SERIES OF UPPER LEVEL DISTURBANCES WILL
MOVE THROUGH THE AREA THIS WEEK...BRINGING SUB-VFR CONDITIONS TO
MOST OF CENTRAL NC. THE HIGHEST LIKELIHOOD OF SUB-VFR CONDITIONS
APPEAR TO BE LATE TUESDAY INTO WEDNESDAY...AND LATE THURSDAY INTO
FRIDAY.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM NOON MONDAY TO MIDNIGHT EST MONDAY
NIGHT FOR NCZ021>028-038>043-078.
WINTER STORM WARNING FROM 10 AM MONDAY TO MIDNIGHT EST MONDAY NIGHT
FOR NCZ007>011.

&&

$$
SYNOPSIS...WSS
NEAR TERM...CBL/WSS
SHORT TERM...BADGETT
LONG TERM...SMITH
AVIATION...WSS