-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 022043
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
343 PM EST MON MAR 2 2015

.SYNOPSIS...HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE NORTH
TONIGHT AND WILL SHIFT OFFSHORE DURING THE DAY TUESDAY AS A LOW
PRESSURE SYSTEM TRACKS NORTHEAST FROM THE CENTRAL PLAINS INTO THE
GREAT LAKES.

&&

.NEAR TERM /TONIGHT THROUGH TUESDAY NIGHT/...
AS OF 330 PM MONDAY...

IN THE WAKE OF THE COLD FRONT PASSAGE EARLIER TODAY...A STRONG BUT
TRANSIENT +1030MB SURFACE HIGH WILL BUILD EAST ACROSS THE AREA
TONIGHT...AND THEN MOVE OFFSHORE DURING THE DAY ON TUESDAY. IN A
BROAD REGION OF WAA WELL DOWNSTREAM OF AN AREA OF LOW PRESSURE
MOVING EASTWARD FROM THE ROCKIES INTO THE UPPER MS VALLEY AND GREAT
LAKES REGION...STRENGTHENING SOUTHERLY ISENTROPIC LIFT ATOP THE
SURFACE WEDGE OF COLD HIGH PRESSURE WILL RESULT IN THE DEVELOPMENT
OF IN-SITU DAMMING ACROSS THE AREA ON TUESDAY.

LITTLE IF ANY UPPER LEVEL FORCING ANTICIPATED ACROSS THE AREA. IN
FACT...500MB HEIGHTS ACTUALLY RISE THROUGHOUT THE DAY ON TUESDAY. AS
SUCH...PRECIPITATION WILL BE VERY LIGHT ACROSS THE AREA...SO LIGHT
THAT THE BIG 4 IN WEATHER MODELS(GFS,NAM,EC,CANADIAN)....GENERATE
ONLY A FEW HUNDREDTHS ACROSS THE CWA THROUGH 00Z WEDNESDAY. PATCHY
RAIN AND/OR DRIZZLE LOOKS TO DEVELOP ACROSS THE WESTERN PIEDMONT
BETWEEN 06-12Z...IN A ZONE OF SELY UPSLOPE COMPONENT EAST OF THE
MOUNTAINS...WITH PATCHY RAIN/DRIZZLE THEN POSSIBLE ACROSS THE
REMAINDER OF THE FORECAST AREA INTO THE AFTERNOON AND INTO THE
EVENING WITHIN THE BROAD WAA REGIME.

CONCERNING P-TYPE....GIVEN TRANSIENT NATURE OF HIGH...COLD AIR IS
VERY SHALLOW AND LESS LIKELY TO SUPPORT ANY SUBSTANTIAL FROZEN OF
FREEZING PRECIP. PRECIP IS EXPECTED TO FALL AS MOSTLY A COLD/CHILLY
RAIN. HOWEVER THE EXCEPTION MAY BE ACROSS THE NORTHERN
PIEDMONT/NORTHERN COASTAL PLAIN...NEAR THE NC/VA BORDER WHERE WE
WILL SEE DECENT RADIATIONAL COOLING ACROSS THE AREA THIS
EVENING...WHICH COULD ALLOW LOWS TONIGHT TO FALL INTO THE UPPER
20S/NEAR 30. IF PRECIP CAN MAKE IT INTO THE NORTHERN PIEDMONT/NE
COASTAL PLAIN TUESDAY MORNING BEFORE THE MARCH SUN WARMS
TEMPERATURES BACK ABOVE FREEZING... WE COULD SEE A BRIEF PERIOD OF
LIGHT FREEZING RAIN/DRIZZLE BEFORE CHANGING OVER TO RAIN. DO NOT
EXPECT IMPACTS...THUS NO ADVISORY WILL BE ISSUED. HOWEVER EVENING
AND MIDNIGHT SHIFTS WILL MONITOR TRENDS AND ADJUST AS NEEDED. LOWS
TONIGHT RANGING FROM NEAR 30 NE TO UPPER 30S SOUTHWEST. EXPECT NEAR
STEADY TEMPERATURES ON TUESDAY...IN THE LOWER/MID 30S NORTH TO UPPER
30S/NEAR 40 SOUTH.

A WARM FRONT IS EXPECTED TO LIFT NORTHWARD TOWARD CENTRAL NC TUE
NIGHT...WITH TEMPERATURES RISING OVERNIGHT ACROSS MUCH OF THE
AREA...ALTHOUGH THEY COULD REMAIN NEAR STEADY IN THE N/NW PIEDMONT.
LIGHT RAIN/DRIZZLE COULD TAPER AS THE WARM FRONT LIFTS WITH
EXPANDING FOG CONDITIONS POSSIBLE.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
AS OF 300 PM MONDAY...

THE FORECAST PROBLEM FOR THIS PART OF THE FORECAST CONTINUES TO BE
THE UNCERTAINTY IN TEMPERATURES DUE TO THE POTENTIALLY LINGERING
WEDGE AND THE TIMING AND EXTENT TO WHICH THE WARM FRONT RETREATS
NORTHWARD. GIVEN THAT THE MODELS HAVE A TENDENCY TO ERODE THE WEDGE
TOO QUICKLY...ESPECIALLY IF THERE IS PRECIPITATION FALLING INTO
IT...CURRENTLY FORECAST THE WEDGE STICKING AROUND INTO WEDNESDAY
AFTERNOON IN THE FAR NW PIEDMONT...WITH A LARGE SPREAD IN TEMPS FROM
NW TO SE ACROSS THE AREA. CONFIDENCE REMAINS SOMEWHAT LOW WITH
RESPECT TO TEMPS...AS ANY CHANGES TO THE TIMING AND POSITION OF THE
WEDGE/WARM FRONT AS THEY ERODE/RETREAT NORTHWARD WILL HIGHLY IMPACT
TEMPERATURES. THEY WILL HOWEVER INCREASE GRADUALLY THROUGH AROUND
MIDNIGHT THURSDAY BEFORE THE COLD FRONT BEGINS MOVING INTO THE NW.
KEEPING IN MIND THE POTENTIAL MARGIN FOR ERRORS...FORECAST HIGH
TEMPS IN THE MID 60S NW TO MID 70S SE ON WEDNESDAY. A NORMAL DIURNAL
TEMPERATURE CURVE SHOULD RETURN WEDNESDAY NIGHT...ALTHOUGH THE
TEMPERATURE GRADIENT WILL BE QUITE LARGE AND WILL DEPEND ON THE
TIMING AND POSITION OF THE COLD FRONT...EXPECT LOWS IN THE UPPER 30S
NORTH TO LOW 50S SOUTH WEDNESDAY NIGHT AND HIGHS IN THE LOW 40S
NORTH TO MID 50S SOUTH ON THURSDAY AND DECREASING BEHIND THE FRONT.

PRECIPITATION: THERE WILL BE A SLIGHT CHANCE OF PRECIP...MAINLY
ACROSS THE WESTERN PORTIONS OF THE AREA WEDNESDAY...EVEN THOUGH THE
MAIN PRE-FRONTAL CONVECTIVE RAINFALL REMAINS LARGELY ALONG OR WEST
OF THE APPALACHIANS UNTIL WEDNESDAY AFT/EVE. SOUTHWESTERLY WINDS
WILL BE QUITE STRONG ON WEDNESDAY AFT/EVE AS THE GRADIENT TIGHTENS
AHEAD OF THE FRONT. LATE WEDNESDAY AFTERNOON IS STARTING TO SHAPE UP
AS A HIGH SHEAR/LOW CAPE EVENT. FORECAST SOUNDINGS INDICATE 200-300
JOULES OF CAPE AND 0-3 KM SHEAR VALUES AROUND 35 KTS...MAINLY ALONG
AND EAST OF I-95 AT THIS TIME. WITH SURFACE TEMPS EXPECTED IN THE
MID 70S AND DEWPOINTS AROUND 60 DEGREES...THUNDERSTORMS WILL BE
POSSIBLE WEDNESDAY AFTERNOON...THUS WILL INTRODUCE A SLIGHT CHANCE
ACROSS THE EAST WITH THIS AFTERNOON`S FORECAST. THE LATEST 12Z ECMWF
AND GFS MODEL RUNS ARE IN BETTER AGREEMENT WITH THE TIMING OF THE
FROPA AND THE ASSOCIATED RAINFALL AS IT MOVES THROUGH THE AREA. THE
LATEST RUNS SUGGEST THAT RAIN WILL BE LIKELY WEDNESDAY NIGHT...
PROGRESSING NW TO SE THROUGH CENTRAL NC THROUGH MIDNIGHT FRIDAY.
THIS REMAINS CASE OF THE COLD AIR CHASING THE PRECIP...BUT FOR NOW
STILL EXPECT ALL PRECIP TO FALL AS RAIN...HOWEVER THERE IS A SMALL
CHANCE THAT A FEW SNOWFLAKES COULD MIX IN ON THE TAIL END OF THE
EVENT.


&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 300 PM MONDAY...

FRIDAY THROUGH SATURDAY: HIGH PRESSURE WILL BUILD IN BEHIND THE
FRONT THURSDAY NIGHT...REMAINING OVER THE REGION INTO THE WEEKEND.
EXPECT A DRY FORECAST FRIDAY THROUGH SATURDAY...WITH HIGHS IN THE
UPPER 30S TO LOW 40S FRIDAY...INCREASING THROUGH THE WEEKEND AND
INTO THE UPPER 50S TO LOW 60S BY MONDAY. LOWS WILL SEE A SIMILAR
TREND...INCREASING FROM MAINLY LOW 20S LOW 20S THU AND FRI NIGHTS TO
THE LOW TO MID 30S BY SAT AND SUN NIGHTS. THERE IS SOME MODEL
DISAGREEMENT TOWARD THE END OF THE PERIOD WITH REGARD TO PRECIP
CHANCES...AS THE ECMWF BRINGS PRECIP IN FROM THE SOUTHWEST SUNDAY
NIGHT AND THE GFS IS COMPLETELY DRY. WILL FORECAST A SLIGHT CHANCE
FOR RAIN SUN NIGHT/MONDAY...ALTHOUGH CONFIDENCE IS LOW AT THIS TIME.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
AS OF 115 PM MONDAY...

24-HR TAF PERIOD:

A STRONG BUT TRANSIENT +1030MB SURFACE HIGH WILL BUILD EAST ACROSS
THE AREA THIS AFTERNOON AND TONIGHT IN THE WAKE OF THE COLD FRONT
PASSAGE EARLIER TODAY. DRY AIR ADVECTION ALONG AND BEHIND THE FRONT
HAS RESULTED IN VFR CONDITIONS ACROSS THE AREA. WILL SEE NWLY WIND
GUSTS INTO THE UPPER TEENS IMMEDIATELY BEHIND THE FRONT...BECOMING
LIGHT THIS EVENING FROM THE EAST-NORTHEAST.

AVIATION CONDITIONS WILL QUICKLY DETERIORATE TONIGHT...ESPECIALLY
ACROSS THE WESTERN PIEDMONT(KINT AND KGSO)WITH MVFR/IFR CEILINGS
RETURNING BETWEEN MIDNIGHT AND SUNRISE TUE MORNING AS THE SFC HIGH
MOVES QUICKLY OFFSHORE...ALLOWING LOW-LEVEL SOUTHERLY RETURN FLOW TO
DEVELOP WITH PATCHY LIGHT RAIN/DZ. ITS POSSIBLE THAT AREAS ALONG AND
NEAR THE NC/VA BORDER MAY SEE A BRIEF PERIOD OF FREEZING
RAIN/DRIZZLE TUESDAY MORNING...BEFORE CHANGING OVER TO A COLD RAIN
THEREAFTER AS TEMPERATURES WARM INTO THE LOWER/MID 30S.

CONFIDENCE IS MUCH LOWER AT KRDU...KRWI...KFAY...WHERE THERE IS A
LARGE SPREAD IN THE MODEL GUIDANCE. SOME MODEL GUIDANCE SUGGESTS
SOME THAT THE EAST-NORTHEASTERLY FLOW COULD SPREAD STRATUS INTO THE
AREA  BETWEEN 00-06Z. OTHER MODELS INDICATE THAT CEILINGS WILL
REMAIN IN THE LOW END VFR RANGE OVERNIGHT(4-5KT)....EVENTUALLY
BECOMING SUB-VFR NEAR THE END OF THE TAF PERIOD IN ASSOCIATION WITH
COLD AIR DAMMING AS THE WARM MOIST ADVECTION SPREADS EASTWARD
AS THE HIGH SHIFTS OFFSHORE.

LOOKING AHEAD: ADVERSE AVIATION CONDITIONS (IFR TO MVFR /LIFR
CEILINGS AND RAIN) ASSOC/W A PRONOUNCED COLD AIR DAMMING WEDGE WILL
PREVAIL TUESDAY AFTERNOON ... WITH SOME IMPROVEMENT IN CEILINGS
POSSIBLE AT SOUTHERN TERMINALS LATE TUE NIGHT AS A WARM FRONT LIFTS
NORTHWARD THROUGH THE CAROLINAS. ADVERSE AVIATION CONDITIONS ARE
LIKELY TO PREVAIL THE REMAINDER OF THE WEEK. -VINCENT

&&

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

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...CBL/VINCENT
SHORT TERM...KC
LONG TERM...KC
AVIATION...CBL/VINCENT