-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 031243
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
743 AM EST TUE MAR 3 2015

.SYNOPSIS...HIGH PRESSURE OVER THE REGION WILL SHIFT OFFSHORE THIS
AFTERNOON AS A LOW PRESSURE SYSTEM TRACKS NORTHEAST FROM THE CENTRAL
PLAINS INTO THE GREAT LAKES. A WARM FRONT WILL LIFT NORTHWARD
THROUGH THE REGION LATE TONIGHT AND EARLY WEDNESDAY. THE NEXT COLD
FRONT WILL APPROACH FROM THE NORTHWEST WEDNESDAY NIGHT...TRACKING
THROUGH THE CAROLINAS ON THURSDAY.

&&

.NEAR TERM /TODAY AND TONIGHT/...
AS OF 400 AM TUESDAY...

TODAY: THE 12Z GSO RAOB WILL LOOK LESS LIKE THE 00Z TUE RAOB AND
MORE LIKE THE 12Z MON RAOB. A COLD AIR DAMMING WEDGE IS RE-
DEVELOPING ACROSS THE AREA THIS MORNING AS PROGRESSIVE HIGH PRESSURE
SHIFTS OFFSHORE AND LOW-LEVEL WARM ADVECTION QUICKLY STRENGTHENS
ATOP A RECENTLY REPLENISHED COOL/DRY SFC AIRMASS. THOUGH MODEST/
PERSISTENT WARM ADVECTION WILL BE PRESENT THROUGHOUT THE DAY...
LITTLE IF ANY UPPER LEVEL FORCING WILL BE PRESENT WITH RIDGING ALOFT
ALONG THE SOUTHEAST COAST. AS A RESULT...PRECIP CHANCES AND COVERAGE
ARE VERY MUCH IN DOUBT...THOUGH AMOUNTS SHOULD BE LIGHT REGARDLESS.
EXPECT PERIODS OF LIGHT RAIN/DRIZZLE TO DEVELOP OVER THE SW PIEDMONT
AND SPREAD NORTHEASTWARD TO THE TRIANGLE BY THIS AFTERNOON...AND NE
COASTAL PLAIN BY SUNSET. MARGINAL AMOUNTS OF ELEVATED INSTABILITY
MAY ALLOW PRECIP TO BECOME MORE CONVECTIVE (ELEVATED) AND
MODERATE/HEAVIER AT TIMES...AS EVIDENCED BY 08-09Z REGIONAL RADAR
IMAGERY OVER THE SW PIEDMONT...THOUGH THE BREVITY AND ISOLATED
NATURE OF SUCH ACTIVITY WOULD STILL SUGGEST LIGHT AMOUNTS. HIGH
TEMPERATURES FOR THE CALENDAR DAY HAVE LIKELY ALREADY OCCURRED IN
MOST LOCATIONS. EXPECT TEMPS TO FALL IN ASSOC/W EVAP COOLING THIS
MORNING...WITH AFTERNOON TEMPS RANGING FROM THE LOWER/MID 30S
(NORTH/NE) TO UPPER 30S/LOWER 40S (SOUTH/SW).

TONIGHT: LOW CONFIDENCE WITH TEMPERATURES OVERNIGHT. LOW TEMPS FOR
WED MORNING (CALENDAR DAY) WILL LIKELY OCCUR AT MIDNIGHT TONIGHT IN
MOST AREAS. A WARM FRONT LIFTING NORTHWARD INTO CENTRAL NC WILL
RESULT IN RISING TEMPS FROM SOUTH-NORTH AFTER MIDNIGHT...THOUGH THE
PROGRESS OF THE FRONT AND EXTENT OF CAD EROSION IS DIFFICULT TO
GAUGE...ESP WITH AN ATYPICAL REGIME CHARACTERIZED BY A LARGELY
UNAMPLIFIED SYNOPTIC PATTERN AND LACK OF A WELL DEFINED UPSTREAM
CYCLONE /WARM SECTOR/ AND MORE CHARACTERISTIC OF DEVELOPING RETURN
FLOW IN THE WAKE OF A DEPARTING SFC HIGH...AND IN ADVANCE OF AN
INCREASINGLY STALLED/WSW-ENE ORIENTED COLD FRONT (WELL SEPARATED
FROM THE PARENT LOW) APPROACHING THE WESTERN SLOPES OF THE
APPALACHIANS. ONE WOULD TYPICALLY BE SKEPTICAL OF SIGNIFICANT CAD
EROSION DURING THE OVERNIGHT HOURS IN SUCH A SCENARIO...THOUGH WEDGE
EROSION IS A FUNCTION OF MANY FACTORS...PARTICULARLY THE STRENGTH
AND CHARACTERISTIC OF THE CAD WEDGE. IF THE CAD WEDGE IS
SUFFICIENTLY SHALLOW...MODEL GUIDANCE MAY WELL BE REASONABLE IN
SHOWING SIGNIFICANT WARMING OVERNIGHT ACROSS MOST OF THE AREA
TONIGHT...THOUGH IF A STRONGER/DEEPER WEDGE IS PRESENT THEN SFC
TEMPS MAY REMAIN STEADY AND GRADUALLY/MARGINALLY INCREASE BY
SUNRISE...PARTICULARLY NORTH OF HWY 64. WITH LITTLE TO GO ON ONE WAY
OR THE OTHER...PLAN ON SPLITTING THE DIFFERENCE. REGARDLESS...SUCH A
REGIME CERTAINLY FAVORS AN ENHANCED POTENTIAL FOR THE
DEVELOPMENT OF DENSE FOG OVERNIGHT.

PTYPE: BASED ON THE LATEST OBSERVATIONAL DATA AND MOST RECENT MODEL
GUIDANCE...WETBULB TEMPERATURES SHOULD NOT BE SUPPORTIVE OF FZRA
THIS MORNING ACROSS VIRTUALLY THE ENTIRE AREA....EXPECT PERHAPS THE
NE COASTAL PLAIN WHERE PRECIP WOULD ARRIVE TOO LATE AND AT A
DIURNALLY UNFAVORABLE TIME...ESP FOR EARLY MARCH. -VINCENT

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
AS OF 400 AM TUESDAY...

IF THE WARM FRONT HAS NOT PROGRESSED THROUGH THE BULK OF CENTRAL NC
BY SUNRISE WED...IT SHOULD DO SO SHORTLY THEREAFTER AS THE
INCREASINGLY SHALLOW CAD WEDGE DISSIPATES VIA INCREASING
INSOLATION/MIXING AND STRENGTHENING SOUTHWEST FLOW. INITIALLY
OVERCAST SKIES WILL BECOME SCT/BKN BY AFTERNOON...WITH A BREEZY
SOUTHWEST WIND. THE GFS SUGGESTS DEEP/MORE VIGOROUS MIXING AND A
POTENTIAL FOR GUSTS AS HIGH AS 30-40 KT...THOUGH THE NAM INDICATES
LESS MIXING AND GUSTS NO HIGHER THAN 20-25 KT. GIVEN LITTLE IN THE
WAY OF DIURNAL DESTABILIZATION....UNIDIRECTIONAL SW FLOW ALOFT WITH
FEW (IF ANY) SHORTWAVE DISTURBANCES...AND UNIDIRECTIONAL SW LOW-
LEVEL FLOW...EXPECT LARGELY DRY CONDITIONS OVER CENTRAL NC DURING
THE DAY. AN AMPLIFYING TROUGH DIGGING SE INTO THE CENTRAL MS RIVER
VALLEY WED EVE/NIGHT WILL RESULT IN CYCLOGENESIS ALONG A SLOW MOVING
FRONTAL ZONE PROGRESSING INTO THE AREA WED NIGHT...THOUGH THE BULK
OF PRECIPITATION IS EXPECTED TO BE ANAFRONTAL...OCCURRING AFTER
SUNRISE. RAIN CHANCES WILL BE RELATIVELY HIGHEST NEAR THE VA BORDER
AND IN THE NW PIEDMONT /TRIAD/. -VINCENT

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
AS OF 400 AM TUESDAY...

THE LATEST MODELS ARE IN GOOD AGREEMENT IN BRING THE COLD FRONT
SOUTH THROUGH CENTRAL NORTH CAROLINA THURSDAY MORNING. A WAVE IS
EXPECTED TO FORM ALONG THE FRONT OVER UPSTATE SC... WHICH IN TURN
HELPS TO HOLD UP THE COLD FRONT FOR SEVERAL HOURS FROM REACHING THE
SOUTHERN ZONES. THE STRONGEST CAA SHOULD ALSO LAG THE FRONTAL
PASSAGE BY SEVERAL HOURS IT APPEARS. THIS SUPPORTS THE CONTINUATION
OF OUR CURRENT PREDOMINATELY RAIN FORECAST FOR THURSDAY WITH LIMITED
POTENTIAL FOR WINTERY MIX NEAR THE END OF THE EVENT BETWEEN 18Z AND
23Z OR SO THURSDAY AFTERNOON FOR THE NORTHERN PIEDMONT AND NORTHERN
COASTAL PLAIN.

P-TYPE NOMOGRAMS SUPPORT SOME MIX WITH OR CHANGE TO FREEZING RAIN
THEN EVEN A BRIEF PERIOD OF LIGHT SNOW/SLEET AT THE VERY VERY END OF
THE EVENT...ACROSS THE FAR NORTHERN PIEDMONT DURING THE MID TO LATE
AFTERNOON. FORECAST WET BULB TEMPERATURES DEPENDING ON THE MODEL OF
CHOICE WITH SOME MODEL VARIABILITY ALSO TARGET THE NORTHERN ZONES
FOR THIS POTENTIAL CHANGEOVER (ESPECIALLY NORTH OF A LINE EXTENDING
FROM DAVIDSON TO RANDOLPH TO WAKE TO WARREN COUNTIES. PRECIPITATION
SHOULD END QUICKLY BETWEEN 21Z-00Z...LIMITING THE WINDOW OF
OPPORTUNITY FOR ICE TO BECOME A SIGNIFICANT WEATHER HAZARD. TO THE
SOUTH...ALL RAIN IS EXPECTED WITH THE SLOWER TO COOL TEMPERATURES
THERE.

ALL IN ALL...A SIGNIFICANT WINTER WEATHER EVENT IS NOT EXPECTED AT
THIS TIME WITH THE PREDOMINATE P-TYPE EXPECTED TO BE RAIN. THE
CHANGEOVER WOULD OCCUR DURING THE AFTERNOON IN THE NORTH (IF AT
ALL)... AND THE WARM GROUND TEMPERATURES AND TIME OF DAY WOULD LIMIT
THE POTENTIAL TO MOSTLY ELEVATED SURFACES.

THURSDAY NIGHT...BREEZY AND COLDER CONDITIONS COULD LEAD TO A QUICK
FREEZE OF RESIDUAL WATER LEFT BEHIND WHICH MAY BECOME A WEATHER
HAZARD. OTHERWISE...SIMPLY CLEARING AND COLD WITH LOWS IN THE 20-25
RANGE.

FRIDAY IS EXPECTED TO BE MOSTLY SUNNY AND COLD WITH THE HEART OF THE
ARCTIC COLD EXPECTED OVER THE OHIO VALLEY AND NORTHERN MID ATLANTIC
STATES. WE WILL STILL BE A GOOD 20 DEGREES BELOW NORMAL WITH HIGHS
EXPECTED IN THE UPPER 30S TO LOWER 40S.

MODERATION WILL OCCUR IN THE TEMPERATURES OVER THE WEEKEND AS THE
HIGH SLIPS SOUTH AND A WESTERLY FLOW DEVELOPS. HIGHS SHOULD RAPIDLY
WARM INTO THE MID 40S TO LOWER 50S SATURDAY AND MID 50S TO LOWER 60S
SUNDAY. A DRIER PATTERN IS ALSO ANTICIPATED THROUGH THE WEEKEND.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
AS OF 730 AM TUESDAY...

24-HR TAF PERIOD: DETERIORATING CONDITIONS EXPECTED THROUGH THE TAF
PERIOD...ESPECIALLY THIS EVENING INTO TONIGHT WHEN 1/4SM +FG VV001
IS EXPECTED AT MOST OR ALL TERMINALS. CEILINGS WILL LOWER TO MVFR
THIS MORNING AND LOW MVFR/IFR THIS AFTERNOON AS POCKETS OF LIGHT
RAIN AND DRIZZLE DEVELOP SW-NE ACROSS THE REGION IN ASSOC/W
PERSISTENT WARM ADVECTION. CEILINGS WILL LOWER TO IFR/LIFR AFTER
SUNSET...QUICKLY FOLLOWED BY VISBYS FALLING TO LIFR/VLIFR WITH
WIDESPREAD DENSE FOG AS A WARM FRONT PROGRESSES NORTHWARD INTO THE
COLD AIR DAMMING WEDGE IN PLACE OVER CENTRAL NC AFTER ~03Z. AVIATION
CONDITIONS WILL REMAIN POOR THROUGH THE REMAINDER OF THE TAF PERIOD
(12Z WED).

LOOKING AHEAD: CEILINGS WILL IMPROVE WED MORNING AS A WARM FRONT
PROGRESSES THROUGH THE REGION AND A BREEZY SW FLOW DEVELOPS...THOUGH
MVFR CEILINGS MAY PERSIST THROUGH THE DAY. SOUTHWEST WINDS MAY
BECOME SUSTAINED AT 20-25 KT WITH GUSTS AS HIGH AS 30-35 KT WED
AFTERNOON...DEPENDING ON CLOUD COVER/MIXING. ADVERSE AVIATION
CONDITIONS ARE EXPECTED TO PREVAIL THU/THU NIGHT IN ASSOC/W A COLD
FRONTAL PASSAGE EARLY THU AND SUBSEQUENT CAD WEDGE DEVELOPMENT THU
AFTERNOON/EVENING. A PERIOD OF VFR CONDITIONS IS EXPECTED ON
FRIDAY...THOUGH ADVERSE CONDITIONS APPEAR LIKELY ONCE AGAIN OVER THE
WEEKEND. -VINCENT
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...VINCENT
SHORT TERM...VINCENT
LONG TERM...BADGETT
AVIATION...VINCENT