-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 271145
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
645 AM EST TUE JAN 27 2015

.SYNOPSIS...STRONG LOW PRESSURE OFF NEW ENGLAND THIS MORNING WILL
LIFT NORTHEAST AWAY FROM OUR AREA TODAY. HIGH PRESSURE WILL BUILD IN
FROM THE NORTHWEST THIS AFTERNOON THROUGH EARLY THURSDAY. ANOTHER
CLIPPER LOW PRESSURE SYSTEM WILL SWING BY JUST TO OUR NORTH LATE
THURSDAY THROUGH THURSDAY NIGHT... THEN HIGH PRESSURE WILL AGAIN
BUILD INTO OUR AREA FROM THE NORTHWEST ON FRIDAY.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
AS OF 240 AM TUESDAY...

TODAY AND TONIGHT: FRONTAL SYSTEM IS CURRENTLY MOVING THROUGH THE
AREA AS LOW PRESSURE CONTINUES TO DEEPEN ACROSS THE DELMARVA. THE
CWA IS CURRENTLY SPLIT BETWEEN DRIER AIR TO THE WEST OF ROUTE 1 AND
MORE MOISTURE TO THE EAST. A BAND OF PRECIPITATION HAS SET UP ALONG
WHAT APPEARS TO BE THE FRONTAL BOUNDARY AND HAS BROUGHT SOME
SCATTERED REPORTS OF A RAIN/SNOW MIX FROM PERSON COUNTY DOWN THROUGH
WAKE COUNTY WITH MOSTLY RAIN OR DRIZZLE SOUTH OF THERE. THIS BAND
WILL MOVE GRADUALLY EASTWARD THROUGH THE EARLY MORNING HOURS TOWARDS
TEH I-95 CORRIDOR AND THE EASTERN TIER OF COUNTIES. SCATTERED
REPORTS OF LIGHT SNOW OR RAIN WILL CONTINUE THROUGH THE MORNING
BEFORE MOST LOCALES DRY OUT. THE THREAT FOR SNOW SHOULD END AFTER
12Z AS RAP FORECAST SOUNDINGS INDICATE SIGNIFICANT DRYING IN THE
SNOW GROWTH ZONE. NO ACCUMULATION IS EXPECTED OR ANY IMPACTS FROM
THE SNOW ASIDE FROM A POTENTIAL DUSTING ON ELEVATED SURFACES AT BEST
AS SOIL TEMPERATURES ARE STILL NEAR 40 DEGREES.

THIS SETUP HAS ALSO CAUSED A SPLIT IN CLOUD COVER WITH AREAS UNDER
AND EAST OF THE PRECIPITATION BAND EXPERIENCING MAINLY MVFR CEILINGS
WITH VFR CONDITIONS BACK TO THE WEST. A FEW WIND GUSTS STILL OUT
THERE UP TO 20 KTS OR SO OUT OF THE NORTHWEST. GUSTS MAY DIE OFF
TOWARDS SUNRISE BUT WILL PICK UP AGAIN LATER THIS AFTERNOON.
TEMPERATURES THIS AFTERNOON IN THE LOW TO MID 40S NE TO SW AS CLOUDS
LINGER LONGER AND COLD AIR ADVECTION IS MORE PRONOUNCED IN THE
NORTHEAST. EXPECT DRYING TO CONTINUE INTO TONIGHT WITH CLEARING
SKIES BUT WINDS REMAINING 5-10 KTS SO NOT EXACTLY GREAT FOR
RADIATIONAL COOLING BUT TEMPS WILL STILL MANAGE TO DROP INTO THE
MIDDLE 20S WITH THE CHANGE IN AIRMASS.

WEDNESDAY AND WEDNESDAY NIGHT: A DRY DAY EXPECTED FOR WEDNESDAY AS
CENTRAL NC IS SANDWICHED BETWEEN THE EXITING BLIZZARD TO THE
NORTHEAST AND INCOMING HIGH PRESSURE TO THE NORTHWEST. SURFACE
PRESSURE GRADIENT WILL RELAX A LITTLE BUT STILL A GOOD COLD AIR
ADVECTION REGIME BOTH AT THE SURFACE AND ALOFT ON THE BACK SIDE OF
THE UPPER LEVEL TROUGH. THIS WILL KEEP TEMPS DOWN IN THE LOW TO MID
40S...ABOUT 10 DEGREES BELOW NORMAL FOR THIS TIME OF YEAR. WINDS 5-
10 KTS OUT OF THE NORTH VEERING TO NORTHEASTERLY LATER IN THE DAY.
CLOUDS WILL GRADUALLY INCREASE IN THE NORTHWEST ON WEDNESDAY NIGHT
AS THE NEXT LOW PRESSURE SYSTEM MOVES INTO THE OHIO VALLEY. THIS
WILL HELP TO KEEP LOW TEMPERATURES UP IN THE TRIAD. GENERALLY MID
20S BUT POSSIBLY SOME LOWER 20S IN OUR EASTERN NORMALLY COLD ZONES.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
AS OF 200 AM TUESDAY...

THU/THU NIGHT: THE GREAT LAKES SHORTWAVE TROUGH WILL TRACK ESE THEN
EASTWARD ACROSS THE NORTHEAST/MIDATLANTIC STATES... TRACKING THROUGH
THE BASE OF THE POLAR LOW OVER HUDSON BAY... WHILE ITS CORRESPONDING
SURFACE LOW CROSSES THE OH VALLEY AND MIDATLANTIC COAST. AFTER A
CHILLY MORNING WITH THE SURFACE RIDGE OVERHEAD... INCREASING
SOUTHERLY LOW LEVEL FLOW AS THE HIGH SHIFTS SSE WILL ALLOW FOR A
MODEST RECOVERY IN THICKNESSES... BUT STILL BELOW NORMAL... AND THE
TEMP RISE WILL BE HINDERED BY THICKENING AND LOWERING CLOUDS WITH
APPROACHING WEAK MID LEVEL DPVA AND LOW LEVEL FRONTAL ZONE. BUT
MODELS STILL SHOW PW VALUES JUST BARELY REACHING ABOVE NORMAL... AND
GFS/NAM BUFR FORECAST SOUNDINGS SHOW A DRY SUBCLOUD LAYER BELOW 850
MB THROUGH THU. MODEL QPF IS ALSO SCANT WITH THE GFS/NAM/SREF MEAN
STAYING DRY OVER CENTRAL NC THROUGH THU NIGHT. AFTER 00Z THE COLUMN
STARTS TO DRY OUT ALOFT BEHIND THE 700 MB TROUGH... AND JUST AHEAD
OF THE SURFACE FRONT WHICH IS EXPECTED TO SWEEP EAST THROUGH CENTRAL
NC AFTER MIDNIGHT. WILL TRIM BACK EXISTING SLIGHT CHANCE POPS A
BIT... FOCUSING THEM LATE THU AFTERNOON UNTIL SHORTLY AFTER
MIDNIGHT... HOWEVER AM RELUCTANT TO REMOVE THEM ENTIRELY AS THE
ECMWF CONTINUES TO GENERATE LIGHT PRECIP LATE THU AFTERNOON AND THU
EVENING. EXPECT HIGHS THU IN THE MID 40S TO AROUND 50. LOWS THU
NIGHT 32-38.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
AS OF 200 AM TUESDAY...

FRI-SAT: THE MID LEVEL TROUGH AXIS WILL BE SWINGING TO OUR EAST FRI
MORNING WITH THE SURFACE COLD FRONT PUSHING OFF THE NC COAST. NW LOW
LEVEL FLOW WILL BRING IN COOLER AIR AS HIGH PRESSURE INITIALLY
CENTERED OVER NRN MINN DRIFTS SOUTHEAST... BUILDING INTO AND OVER
THE MIDATLANTIC THROUGH VA/ERN NC THROUGH SAT. SHOULD SEE MOSTLY
CLEAR SKIES FRI/FRI NIGHT... FOLLOWED BY INCREASING HIGH THIN CLOUDS
SAT AS WE START TO SEE INITIAL ENERGY EJECTING FROM THE DESERT SW
LOW TRACK EASTWARD WITHIN CONFLUENT NW MID LEVEL FLOW. WITH FALLING
THICKNESSES FRI... EXPECT BELOW-NORMAL HIGHS IN THE MID 40S TO LOWER
50S. LOWS FRI NIGHT IN THE MID 20S... THEN WITH SUCH A CHILLY START
AND THE CANADIAN-SOURCE AIR MASS BUILDING IN YIELDING THICKNESSES AT
LEAST 30 M BELOW NORMAL... HIGHS SAT SHOULD ONLY BE IN THE 40-45
RANGE.

SAT NGT-MON: A LOT OF UNCERTAINTY IN THE DETAILS PERSISTS THIS
MORNING... HOWEVER IT`S LOOKING MORE LIKELY THAT WE`RE ENTERING INTO
A PERIOD OF MORE ACTIVE WEATHER DOMINATED BY SOUTHERN STREAM ENERGY
BUT WITH POTENTIAL INJECTIONS OF COOLER AIR FROM THE NORTHERN
STREAM. A NRN STREAM WAVE DROPPING SOUTHEAST FROM MT THROUGH THE
CENTRAL PLAINS WILL MERGE WITH SOUTHERN STREAM ENERGY EMANATING FROM
THE LOW OVER NRN MEX SAT NIGHT/SUN... BRINGING MID LEVEL DPVA INTO
NC SUN/SUN NIGHT. THE SHIFTING OF THE SURFACE HIGH ESE OFF THE COAST
WILL ALLOW A MOIST RETURN FLOW OFF THE GULF INTO THE GULF/MIDSOUTH
AND SOUTHEAST STATES... AS SURFACE LOW PRESSURE DEVELOPS ALONG THE
BAROCLINIC ZONE NEAR THE NW GULF COAST AND TRACKS NORTHEAST TOWARD
NC. THE GFS/ECMWF BRING PRECIP INTO WRN NC BY MIDDAY SUN... THEN
SPREAD IT EASTWARD THROUGH CENTRAL NC SUN NIGHT INTO EARLY MON
MORNING. BOTH THE GFS/ECMWF SHOW A MILLER TYPE-B CYCLOGENESIS
PATTERN BUT WITH VARIED LOW PLACEMENT... WITH THE ECMWF DEPICTING A
FURTHER-SOUTH TRIPLE POINT LOW TRACK VERSUS THE GFS. THE LATEST RUNS
SHOWS SUFFICIENTLY WARM LOW- AND MID-LEVEL THICKNESSES TO SUPPORT AN
ALL-RAIN EVENT... BUT GIVEN THIS PATTERN... WILL NEED TO WATCH MODEL
TRENDS CAREFULLY IN THE COMING DAYS. WITH OTHERWISE GOOD MODEL
AGREEMENT ON TIMING AND THE MID-LEVEL PATTERN... WILL BUMP UP
POPS... FOCUSING THE HIGHER CHANCES SUN AFTERNOON THROUGH SUN
NIGHT... TAPERING DOWN WEST-TO-EAST MON MORNING AS THE DAMPENING MID
LEVEL SHORTWAVE TROUGH SHIFTS EAST OVER THE MIDATLANTIC/ NORTHEAST
WITH SURFACE FRONTAL PASSAGE THROUGH NC. EXPECT IMPROVING WEATHER
LATE MON WITH ANOTHER CANADIAN HIGH CENTERED OVER THE MIDWEST
BUILDING INTO OUR AREA. EXPECT BELOW NORMAL TEMPS THROUGH SUN
NIGHT... WITH MORE UNCERTAINTY FOR HIGHS ON MON AS MUCH WILL DEPEND
ON WHETHER OR NOT WE GET INTO THE WARM SECTOR BEFORE FRONTAL
PASSAGE. WILL KEEP TEMPS BELOW NORMAL FOR NOW BUT IF MODEL WARMING
TRENDS HOLD... MAY NEED TO BUMP UP MON HIGHS QUITE A BIT IN LATER
FORECASTS. -GIH

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
AS OF 645 AM TUESDAY...

24 HOUR TAF PERIOD: LIGHT SNOW OVERSPREADING NORTHEASTERN AREAS OF
THE CWA THIS MORNING. SNOW IS CURRENTLY MOVING OUT OF THE KRWI AREA
AND IS NOW CONFINED NORTH AND EAST. ELSEWHERE PRECIPITATION HAS
LARGELY ENDED OUTSIDE OF A FEW SNOW FLURRIES. WINDS ARE LIGHT AND
VARIABLE AT THIS HOUR BUT WILL BE PICKING BACK UP TO 5-10 KTS OUT OF
THE NORTHWEST THIS MORNING AND THEN GUSTING TO 20 KTS THIS
AFTERNOON. SOME MVFR CEILINGS STILL IN PLACE IN AREAS WHERE LIGHT
SNOW IS STILL FALLING. ELSEWHERE VFR CEILINGS ARE PREVAILING AND
SKIES WILL CONTINUE TO CLEAR AS THE DAY PROGRESSES WITH THE
EXCEPTION OF THE NORTHEASTERN AREAS WHERE CLOUDS WILL LINGER.

LONG TERM: THE NEXT THREAT TO AVIATION CONDITIONS WILL BE THURSDAY
NIGHT INTO FRIDAY MORNING AS A FRONTAL SYSTEM CROSSES THE AREA AND
THEN ANOTHER SYSTEM SUNDAY INTO MONDAY.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...HARTFIELD
NEAR TERM...ELLIS
SHORT TERM...HARTFIELD
LONG TERM...HARTFIELD
AVIATION...ELLIS