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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 120721
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
321 AM EDT WED MAR 12 2014

.SYNOPSIS...A DEEPENING AREA OF LOW PRESSURE OVER THE OHIO VALLEY
WILL TRACK EAST-NORTHEASTWARD THROUGH THE MIDDLE ATLANTIC STATES
TODAY...WITH ATTENDANT TRAILING COLD FRONT CROSSING CENTRAL NC THIS
EVENING.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
AS OF 300 AM WEDNESDAY...

...A WIND ADVISORY HAS BEEN ISSUED FOR THE NORTHERN HALF OF THE
FORECAST AREA FOR LATE THIS AFTERNOON THROUGH MIDNIGHT ...

NORTHERN-STREAM WAVE DIVING SEWD OUT OF MANITOBA WILL MERGE WITH
THE CENTRAL PLAINS SYSTEM ACROSS THE MIDDLE MS VALLEY LATER THIS
MORNING. THE MERGER OF THESE TWO SYSTEMS WILL RESULT IN THE
DEVELOPMENT OF A DEEP EASTERN US TROUGH TONIGHT AND THURSDAY... AND
MORE IMPORTANTLY AN INTENSIFYING SURFACE CYCLONE THAT WILL TRACK
FROM THE OHIO VALLEY ENE ACROSS THE MID-ATLANTIC REGION TODAY...WITH
TRAILING SURFACE COLD FRONT MOVING EAST THROUGH THE AREA LATE THIS
AFTERNOON/EVENING. MEANWHILE...AHEAD OF THIS SYSTEM...A QUICK MOVING-
DEAMPLIFYING SOUTHERN STREAM WAVE OVER THE NORTHERN GULF WILL MOVE
OFF THE SOUTHEAST COAST THIS MORNING.

ENHANCED SOUTHERLY WARM MOIST ADVECTION BETWEEN THE AFOREMENTIONED
AMPLIFYING NORTHERN STREAM TROUGH AND THE DE-AMPLIFYING SOUTHERN
STREAM WAVE WILL SUPPORT SCATTERED LIGHT RAIN SHOWERS THIS MORNING.
IN THE WAKE OF THE MORNING SHOWERS/LOW CLOUDS AND IN ADVANCE OF THE
APPROACHING COLD FRONT...PARTIAL INSOLATION...AIDED BY THE EXTRA
HOUR OF DAYLIGHT AND INCREASING SUN ANGLE WILL ALLOW AFTERNOON
TEMPERATURES TO WARM UP INTO THE LOWER TO MID 70S. AS THE BOUNDARY
LAYER DEEPENS IN RESPONSE TO DAYTIME HEATING...PRESSURE GRADIENT
WILL ALSO BE TIGHTENING AS THE DEEPENING SURFACE CYCLONE CROSSES THE
CENTRAL APPALACHIANS AND MOVES INTO THE VIRGINIAS. BUFR FORECAST
SOUNDINGS INDICATE MIXED LAYER WINDS OF 30-40 KTS...SUPPORTIVE OF
SUSTAINED SW WINDS OF 20 TO 25 MPH...WITH GUSTS OF 30 TO 35
MPH...ALL AHEAD OF THE ACTUAL COLD FRONTAL PASSAGE AND THE ATTENDANT
SKINNY LINE OF SHOWERS WITH SOME EMBEDDED THUNDER THROUGH THE AREA
BETWEEN 21Z TO 03Z.

THEN...IN THE WAKE OF THE FRONT...STRONG POST-FRONTAL NORTHWESTERLY
WINDS OWING TO IMPRESSIVE PRESSURE RISES OF 8-10 MB/3HR...WILL MOVE
THROUGH THE AREA BETWEEN 00Z TO 06Z...STRONGEST ACROSS THE NORTHERN
PIEDMONT. SOUNDINGS SUGGEST 40 TO 45KTS WITHIN THE MIXED
LAYER...ENHANCED BY STEEPENING LAPSE RATES/COOLING ALOFT
ACCOMPANYING THE NORTHERN STREAM SHORTWAVE...BUT PERHAPS ALSO
HINDERED BY LOSS OF DAYTIME AND PERHAPS A SHALLOW NEAR SFC BASED
INVERSIONS THAT STILL SOMEHOW SEEM TO SET-UP AND LESSEN WINDS
NOCTURNALLY.

WHILE ITS DIFFICULT TO TELL WHETHER THE STRONGEST WINDS WILL OCCUR
PRE-FRONTAL...FRONTAL...OR POST-FRONTAL...THE SYNOPTIC PATTERN
FAVORS STRONGEST WINDS ACROSS THE NORTHERN HALF OF THE FORECAST
AREA...IN PROXIMITY TO THE DEEPENING LOW. AND THUS WILL ISSUE A WIND
ADVISORY FOR 3 PM TO MIDNIGHT FOR ALL AREAS ALONG AND NORTH OF
HIGHWAY 64.

LOWS TONIGHT RANGING FROM THE MID-UPPER 20 NW TO LOWER-MID 30S SE.
-- End Changed Discussion --

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 300 AM WEDNESDAY...

AFTER SEVERAL DAYS OF SPRING-LIKE TEMPS...DEEP UPPER TROUGHING OVER
THE EAST COAST ON THURSDAY WILL LEAD TO AN ABRUPT CHANGE BACK TO
WINTER-LIKE TEMPS...AS HIGHS WILL ONLY BE IN THE 40S...A GOOD 15-20
DEGREES BELOW NORMAL. IN ADDITION...A STRONG GRADIENT BETWEEN THE
DEPARTING SURFACE LOW AND THE HIGH BUILDING IN WILL RESULT IN BREEZY
CONDITIONS...MAKING IT FEEL EVEN COLDER. THESE BREEZY WINDS...IN
ADDITION TO DEWPOINTS IN THE SINGLE DIGITS RESULTING IN RELATIVE
HUMIDITY VALUES IN THE TEENS...MAY CAUSE SOME FIRE WEATHER CONCERNS.
CONTINUED COORDINATION WILL TAKE PLACE WITH THE FOREST SERVICE LATER
THIS MORNING REGARDING THE NEED FOR ANY STATEMENTS. WINDS WILL RELAX
THURSDAY NIGHT AS HIGH PRESSURE MOVES OVERHEAD AND WITH CLEAR
SKIES...OVERNIGHT LOWS WILL FALL INTO THE MID 20S.

THESE WELL BELOW NORMAL TEMPS WILL BE SHORT LIVED THOUGH AS WEAK
SHORTWAVE RIDGING BUILDS EAST OVER THE AREA AND THE SURFACE HIGH
SLIPS OFFSHORE (SETTING UP RETURN FLOW) ON FRIDAY. ALL OF THIS WILL
RESULT IN TEMPS MODERATING INTO THE MID/UPPER 50S...WITH OVERNIGHT
LOWS IN THE UPPER 30S TO LOWER 40S.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 300 AM WEDNESDAY...

A NORTHERN STREAM SHORT WAVE TROUGH WILL MOVE ACROSS THE GREAT LAKES
AND INTO THE NEW ENGLAND AREA SATURDAY INTO SUNDAY...PROPELLING A
COLD FRONT THROUGH OUR AREA LATE SATURDAY NIGHT INTO EARLY SUNDAY
MORNING. HOWEVER...THERE CONTINUES TO BE DISAGREEMENT AMONG THE
MODELS ON OUR PRECIP CHANCES. THE GFS CONTINUES TO BE THE WETTER
MODEL AS IT SHOWS SOME SOUTHERN STREAM ENERGY ALSO TRANSLATING EAST
DURING THIS TIME FRAME. THE ECMWF STILL IS VIRTUALLY DRY AS THE
SOUTHERN STREAM ENERGY DOES NOT KICK EAST AS FAST. WILL MAINTAIN THE
CURRENT FORECAST THINKING UNTIL MODELS COME INTO BETTER AGREEMENT.
THEREFORE...WILL HOLD PRECIP CHANCES DOWN...WITH ONLY AN INCREASE IN
CLOUD COVER. CONTINUED LOW LEVEL SOUTHERLY FLOW WILL RESULT IN MORE
AIR MASS MODIFICATION...WITH HIGHS EXPECTED TO RISE INTO THE MID 60S
ON SATURDAY. BRIEF NORTHERLY WINDS BEHIND THE FRONT EARLY ON SUNDAY
SHOULD RESULT IN SLIGHTLY LOWER TEMPS...GENERALLY MORE IN THE WAY OF
UPPER 50S TO LOWER 60S.

CONFIDENCE DECREASES EVEN FURTHER FOR VERY END OF THE WEEKEND AND
INTO EARLY NEXT WEEK...BUT THE GENERAL CONSENSUS IS THAT ANOTHER
NORTHERN STREAM TROUGH WILL DIG INTO THE SOUTHEAST...WITH YET
ANOTHER COASTAL LOW IMPACTING THE REGION AS SOUTHERN STREAM ENERGY
MOVES EAST. GIVEN THE HANDLING OF THE SOUTHERN STREAM ENERGY EARLIER
IN THE WEEKEND (SEE ABOVE PARAGRAPH)...IT IS NOT SURPRISING THAT
THERE CONTINUES TO BE LARGE MODEL SPREAD. THE GFS IS NOT AS DEEP
WITH THE NORTHERN STREAM TROUGH AND IS STILL INDICATING MUCH LESS
PRECIP FOR CENTRAL NC SUNDAY INTO MONDAY. THE ECMWF SHOWS THE
SOUTHERN STREAM ENERGY FINALLY KICKING EAST AND INDICATES A DEEPER
TROUGH DIGGING ACROSS THE SOUTHEAST. THE RESULTANT SURFACE LOW
TRACKS ACROSS THE SOUTHEAST AND EVENTUALLY OFF THE CAROLINA COAST
LATE SUNDAY INTO MONDAY. WILL LEAN MORE TOWARDS THE ECMWF AS IT HAS
BEEN THE MORE CONSISTENT MODEL (PER WPC) AND THEREFORE WILL SHOW
INCREASING PRECIP CHANCES SUNDAY...WITH HIGHEST POPS CENTERED ON THE
SUNDAY NIGHT/MONDAY TIME FRAME. THERE IS STILL A LOT TO BE IRONED
OUT...GIVEN THIS IS DAYS 5/6...BUT IF THE ECMWF VERIFIES...IT COULD
BE ANOTHER GOOD RAIN EVENT FOR CENTRAL NC. IN ADDITION...THERE WOULD
BE A POSSIBILITY OF SOME WINTRY PRECIP (MOST LIKELY A CHANGEOVER TO
SNOW AT THE TAIL END)...BUT GIVEN THE TIME OF YEAR AND THE NOT SO
FAVORABLE POSITION/STRENGTH OF THE HIGH...WILL MAINTAIN AN ALL
LIQUID FORECAST FOR NOW. TEMPS WILL BE NEAR NORMAL FOR MOST OF THE
WEEKEND BEFORE FALLING BACK TO BELOW NORMAL EARLY NEXT WEEK.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
AS OF 140 AM WEDNESDAY...

24-HR TAF PERIOD:

A QUICK MOVING SOUTHERN STREAM WAVE WILL TRAVERSE THE GULF COAST
OVERNIGHT AND WILL MOVE OFF THE SOUTHEAST COAST THIS MORNING.
MEANWHILE ACROSS THE CENTRAL US... AN INTENSIFYING LOW PRESSURE
SYSTEM WILL TRACK FROM THE OH VALLEY ENE INTO THE MID-ATLANTIC
REGION TODAY. MOISTURE WILL RAPIDLY SPREAD NEWD INTO THE AREA THIS
MORNING IN ASSOC/W STRENGTHENING 35-40KT LLJ...WITH SCATTERED
SHOWERS AND LIFR/IFR CEILINGS OVERSPREADING THE BETWEEN 09-15Z WED
AT MOST TERMINALS(EXCEPT PERHAPS KRWI). THERE MAY ALSO BE A BRIEF
PERIOD OF LOW LEVEL WIND SHEAR DURING THE PRE-DAWN HOURS HOUR AT THE
INT/GSO TERMINALS...BEFORE THE BOUNDARY/MIXED LAYER DEEPENS AND
CAUSES THE STRONG WINDS ALOFT TO MIX DOWN TO THE SURFACE...RESULTING
IN STRONG AND GUSTY SOUTHWESTERLY SURFACE WINDS BY EARLY WED
AFTERNOON.

EARLIER DAY MVFR CEILINGS WILL LIKELY LIFT AND SCATTER TO VFR...
BEFORE A STRONG COLD FRONT SWEEPS EASTWARD ACROSS CENTRAL NC BETWEEN
21Z-03Z. A BROKEN LINE OF SHOWERS...AND ISOLATED LOW-TOPPED
THUNDERSTORMS WITH WIND GUSTS IN EXCESS OF 40KTS...WILL LIKELY
ACCOMPANY THE COLD FRONT...FOLLOWED BY 35-40KTS OF POST-FRONTAL
NORTHWESTERLY WINDS....WHICH COULD RESULT IN CROSSWIND IMPACTS FOR
TERMINALS.

LOOKING AHEAD: EXPECT PREDOMINATELY VFR CONDITIONS THROUGH SATURDAY.
THE NEXT STORM COULD IMPACT THE AREA AS EARLY AS SUNDAY AND INTO
EARLY NEXT WEEK.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
WIND ADVISORY FROM 3 PM THIS AFTERNOON TO MIDNIGHT EDT TONIGHT
FOR NCZ007>011-021>028-038>041-043.
-- End Changed Discussion --

&&

$$

SYNOPSIS...MWS
NEAR TERM...CBL
SHORT TERM...KRD
LONG TERM...KRD
AVIATION...CBL