Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KRAH 141456
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1055 AM EDT MON APR 14 2014

.SYNOPSIS...SOUTHERLY FLOW WILL ADVECT AN INCREASINGLY MOIST AND
UNSTABLE AIRMASS INTO THE REGION TODAY AND TONIGHT AS A POTENT UPPER
LEVEL TROUGH AND ASSOCIATED COLD FRONT TRACK EAST INTO THE TENNESSEE
VALLEY. THE COLD FRONT WILL PROGRESS EAST THROUGH THE CAROLINAS
TUESDAY AFTERNOON AND EVENING.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1055 AM MONDAY...

THE 12Z KGSO SOUNDING WAS CAPPED TO DEEP CONVECTION WITH A GOOD CAP
BETWEEN 850MB AND 700MB...AND CONSIDERABLE MOISTURE ABOVE 500MB. THE
LATEST SPC MESOANALYSIS SHOWED A RELATIVE MINIMUM OF PRECIPITABLE
WATER VALUES OVER MUCH OF CENTRAL NORTH CAROLINA ALTHOUGH WITH A
NARROW RIBBON OF INCREASING VALUES...JUST BELOW AN INCH...EXTENDING
FROM SOUTH CAROLINA INTO THE SOUTHWEST PIEDMONT. HIGH PRESSURE
EXTENDING OVER CENTRAL NORTH CAROLINA FROM THE EAST WAS PROVIDING A
MOIST...SOUTHERLY FLOW OFF OF THE ATLANTIC INTO THE AREA...WITH
SURFACE DEW POINTS IN THE MID 50S TO AROUND 60.

TO OUR WEST...THE SURFACE LOW WILL INCREASE IN STRENGTH DUE TO THE
OFFSET UPPER LEVEL TROUGH TO THE WEST. DIVERGENCE ALOFT IS
DECREASING THE SURFACE PRESSURE AHEAD OF THE FRONT BRINGING IN
CYCLONIC VORTICITY ADVECTION IN A SHORT WAVE AHEAD OF THE FRONT.
SURFACE WINDS ARE SOUTHERLY AND HAVE INCREASED THE DEWPOINTS AS
MOIST AND WARM AIR IS ADVECTED INTO THE AREA AHEAD OF THE COLD
FRONT. WARM ADVECTION ALONG WITH CYCLONIC VORTICITY ADVECTION WILL
BRING AN INCREASE IN LIFT AND CLOUD COVER OVER THE AREA AND AN
INCREASED CHANCE FOR PRECIPITATION AND CONVECTION. A FEW SHOWERS ARE
POPPING UP TO OUR WEST AND ARE EXPECTED TO INCREASE IN NUMBER AND
EVENTUALLY PRODUCE CONVECTIVE STORMS AS THE COLD FRONT MOVES
EASTWARD.

THE 12Z UPPER-AIR ANALYSIS SHOWED SOME DIFFLUENCE TO OUR WEST AND
THIS IS FORECAST TO CONTINUE THIS AFTERNOON INTO TONIGHT AS A SERIES
OF MID-LEVEL WAVES MOVE THROUGH CENTRAL NORTH CAROLINA. THE LATEST
RAP SHOWS THE MID-LEVEL CAP WEAKENING WITH TIME THROUGH EARLY
AFTERNOON...AND SLIGHT 700MB COOLING ON THE 12Z UPPER-AIR ANALYSIS
WOULD SUGGEST THIS...ALTHOUGH THE RAP ALSO FORECASTS A MODEST
INCREASE IN THOSE MID-LEVEL TEMPERATURES LATE IN THE DAY. WITH THE
MOISTURE IN PLACE...MODEST INSTABILITY WITH SURFACE-BASED CAPE
AROUND 400J/KG AND MLCAPE IN THHIGHS TODAY WERE LOWERED ABOUT A
DEGREE IN THE TRIAD DUE TO EXPECTED CLOUD COVER...AND RAISED ABOUT A
DEGREE TOWARD INTERSTATE 95 DUE TO THINNER CLOUDS FOR A LONGER
PERIOD OF TIME THERE. E LOWEST KM AROUND 200J/KG...AND SOME LIFT
WITH THE MID-LEVEL SHORTWAVES...AS THE CAP ERODES ANTICIPATE
ISOLATED TO SCATTERED SHOWERS DEVELOPING...WITH AN ISOLATED
THUNDERSTORM POSSIBLE. AS THE MID-LEVEL TEMPERATURES WARM SLIGHTLY
LATER...THIS COULD FOR A TIME INHIBIT MORE DEEP CONVECTION...AND
THIS SCENARIO IS NOTED BY MORE THAN ONE WRF MODEL AS WELL AS IMPLIED
BY RAP QPF.

MOISTENING OF THE UPPER LEVELS WILL INCREASE CLOUD DEPTH AND ALLOW
FOR LIFTING OVER A DEEPER LAYER. THIS WILL INCREASE THE CHANCE FOR
SOME DEEP MOIST CONVECTION AND SHOWERS OVER THE AREA...
HOWEVER...THE STRONGEST LIFTING WILL STAY TO THE WEST WITH THE COLD
FRONT. CONVECTION SHOULD BECOME MORE NUMEROUS IN COVERAGE OVER
CENTRAL NORTH CAROLINA THIS EVENING INTO TONIGHT DUE TO ONGOING
MOISTENING...STRENGTHENING HEIGHT FALLS...AND PERIODIC DPVA IN SW
FLOW ALOFT...ESPECIALLY IN WESTERN PORTIONS OF THE STATE.
HOWEVER...SEVERAL LARGE MESOSCALE CONVECTIVE SYSTEMS ARE EXPECTED TO
DEVELOP UPSTREAM IN THE DEEP SOUTH IN THIS PERIOD...ONE THIS
AFTERNOON AND PERHAPS ANOTHER LATE TONIGHT...AND HOW THESE FEATURES
EVOLVE/INTERACT WITH THE LARGER SCALE PATTERN WILL MOST CERTAINLY
AFFECT PRECIP CHANCES DOWNSTREAM IN CENTRAL NC...LENDING A FAIR
AMOUNT OF UNCERTAINTY TO THE PRECISE COVERAGE/AMOUNT OF CONVECTION
TONIGHT.

THE INCREASED CLOUD COVER WILL RESULT IN A SLIGHT DECREASE...ROUGHLY
A DEGREE...FOR HIGH TEMPERATURES FOR THE WESTERN PART OF CENTRAL
NORTH CAROLINA. HIGHS WERE RAISED ABOUT A DEGREE TOWARD INTERSTATE
95 WHERE THERE WILL BE MORE PERIODS OF THINNER CLOUDS AND MORE
SUNLIGHT HITTING THE GROUND. A VERY MOIST AND BREEZY SOUTHERLY FLOW
THROUGHOUT THE WARM SECTOR IN THE CAROLINAS WILL MAINTAIN TEMPS IN
THE MID 60S OVERNIGHT.

THOUGH QUITE CONDITIONAL/UNCERTAIN...IF DEEP CONVECTION DEVELOPS AND
PROGRESSES INTO CENTRAL NC THIS EVENING AND TONIGHT...AN ISOLATED
SEVERE STORM WOULD BE POSSIBLE GIVEN INCREASINGLY IMPRESSIVE
LOW/DEEP-LAYER SHEAR.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
AS OF 330 AM MONDAY...

TUE/TUE NIGHT: EXPECT CHANCES FOR CONVECTION NEAR 100% ON TUESDAY AS
A POTENT UPPER LEVEL TROUGH AND ATTENDANT COLD FRONT PROGRESS
THROUGH THE CAROLINAS IN THE PRESENCE OF A MOIST AND UNSTABLE
AIRMASS VIA PERSISTENT SOUTHERLY LOW-LEVEL FLOW OFF THE ATLANTIC. AT
THIS TIME...FROPA IS EXPECTED TO OCCUR BETWEEN 18-21Z IN THE NW
PIEDMONT AND BY 00-03Z IN THE COASTAL PLAIN...WITH STRONG COLD
ADVECTION THEREAFTER. EXPECT HIGHS RANGING FROM THE MID/UPPER 60S IN
THE NW PIEDMONT WHERE CLOUD COVER/CONVECTION WILL PREVENT MUCH OF A
RISE IN TEMPS PRIOR TO FROPA...TO THE MID/UPPER 70S POTENTIALLY IN
THE COASTAL PLAIN WHERE FROPA WILL BE LATER. STRONG LOW/DEEP LAYER
SHEAR...FAVORABLE DIURNAL TIMING...AND MARGINAL TO MODERATE
DESTABILIZATION (500-1000 J/KG MLCAPE) CERTAINLY INDICATE A
POTENTIAL FOR SEVERE THUNDERSTORMS...THOUGH THE PRECISE NATURE OF
THE THREAT IS STILL DIFFICULT TO ASCERTAIN GIVEN A POTENTIAL FOR
UPSTREAM CONVECTION /MCS ACTIVITY/ LATE TONIGHT AND TUE MORNING.
DAMAGING WINDS AND ISOLD TORNADOES WILL BE THE PRIMARY THREAT(S)...
THE LATTER OF WHICH COULD BE FURTHER ENHANCED BY BACKED SFC WINDS
/LARGE CLOCKWISE CURVED HODOGRAPHS/ POSSIBLE ON THE EASTERN
PERIPHERY OF ANY SFC WAVES WHICH COULD DEVELOP ALONG THE FRONT IN
CENTRAL/EASTERN NC...PARTICULARLY ALONG AND EAST OF I-95 WHERE
DIURNAL TIMING AND DESTABILIZATION WILL BE MOST FAVORABLE. STRONG
COLD ADVECTION WILL RESULT IN A STARK CONTRAST IN TEMPERATURES IN
COMPARISON TO THE PREVIOUS FEW DAYS...WITH LOWS RANGING FROM THE
LOWER TO UPPER 30S...POTENTIALLY NEAR FREEZING ALONG/WEST OF HWY 1.
A FREEZE WATCH MAY BE NEEDED FOR PORTIONS OF THE AREA TUE NIGHT/WED
MORNING. SINCE LOWS WILL PRIMARILY DEPEND UPON COLD ADVECTION...
SUFFICIENT UNCERTAINTY EXISTS TO PRECLUDE ANY FROST/FREEZE PRODUCT
ISSUANCE AT THIS TIME. -VINCENT

AS OF 245 AM MONDAY...RISING HEIGHTS ALOFT/DNVA AND ASSOCIATED
STRONG SUBSIDENCE WILL RESULT IN FURTHER DEEP LAYER DRYING
WED...FOLLOWED BY GENERALLY NEUTRAL VERTICAL MOTION BUT WITH STILL A
RESIDUALLY DRY AND STRONGLY CAPPED REGIME OVER OUR REGION. SURFACE
HIGH PRESSURE WILL CONSEQUENTLY BECOME UNSEASONABLY STRONG - INTO
THE 1040-1045 MB RANGE AS IT BUILDS FROM THE OH VALLEY TO NEW
ENGLAND. UNSEASONABLY COOL NORTHEASTERLY FLOW...WITH TEMPERATURES 10
TO 20 DEGREES BELOW AVERAGE...WILL RESULT OVER CENTRAL NC. INITIALLY
CLEAR SKIES WED WILL BECOME PARTLY CLOUDY...TO PERHAPS MOSTLY SO IN
THE COASTAL PLAIN...BY THU AFTERNOON...AS MOISTURE FLAT
STRATOCUMULUS IS ADVECTED INLAND BENEATH THE CAP.

PROJECTED LOW LEVEL THICKNESS VALUES IN THE 1300-1310 METER RANGE AT
12Z THU AND CLEAR SKIES WOULD SUPPORT SUB-FREEZING TEMPERATURES THU
MORNING...BUT CONFIDENCE IS LOW REGARDING THE DEGREE OF CALM GIVEN A
PROJECTED 4-6 MB RISE IN MSL PRESSURE WITH THE STRENGTHENING HIGH
WED NIGHT. WILL ADJUST LOWS TO REFLECT MOSTLY LOWER TO MIDDLE
30S...COOLEST WEST...BUT THESE MAY NEED FURTHER DOWNWARD ADJUSTMENT
(OR AT LEAST OPEN THE RANGE) TO INCLUDE SOME UPPER 20S (AROUND
RECORD LOWS) IF IT INDEED APPEARS ANY PERIOD OF APPRECIABLE CALM
WILL BE ATTAINED. SIMILARLY COOL IN THE MIDDLE 50S WED...WHICH MAY
THREATEN THE RECORD LOW MAX OF 56 DEGREES AT KFAY FOR THE DATE. SEE
CLIMATE SECTION BELOW. SLOW MODERATION TO AROUND 60 AND 40 DEGREES
FOR HIGHS AND LOWS...RESPECTIVELY...THU AND THU NIGHT. -MWS

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
AS OF 300 AM MONDAY...

THOUGH MODEL SOLUTION SPREAD REMAINS ABOVE AVERAGE DURING THE LONG
TERM...THE EMERGING SIGNAL FROM THE MAJORITY OF BOTH THE ENSEMBLE
AND  SOLUTIONS OS FOR A DOMINANT NORTHERN STREAM ACROSS THE NORTHERN
THIRD OF THE US...ONE THAT WILL INCLUDE AT LEAST ONE PRIMARY
SHORTWAVE TROUGH AND ACCOMPANYING SURFACE CYCLONE FORECAST TO CROSS
THE UPPER MIDWEST AND LOWER GREAT LAKES FRI-SAT - A STORM TRACK THAT
WOULD RESULT IN A MOSTLY DRY COLD FRONTAL PASSAGE SAT-SAT NIGHT AS
DEPICTED BY AT LEAST THE LAST SEVERAL RUNS OF THE GFS. ON THE OTHER
HAND...THE LAST COUPLE OF RUNS OF THE OPERATIONAL ECMWF...WHICH HAVE
MINIMAL SUPPORT FROM THE EC ENSEMBLE MEAN...SUGGEST MORE IN THE WAY
OF SOUTHERN STREAM TROUGHING/INTERACTION THAT WOULD RESULT IN SOME
DEGREE OF COASTAL CYCLOGENESIS AND A WETTER PATTERN FOR AT LEAST THE
EASTERN HALF OF NC DURING THE SAME TIME FRAME. IN EITHER
SCENARIO...THE BEST CHANCES OF RAIN WOULD BE LATE FRI NIGHT-SAT
EVENING...SO MENTIONABLE POP WILL BE CONFINED TO THAT TIME UNTIL A
CLEARER PICTURE EMERGES.

&&

.AVIATION /12Z MONDAY THROUGH SATURDAY/...
AS OF 600 AM MONDAY...

24-HR TAF PERIOD: LOW-LEVEL MOISTENING /WARM ADVECTION/ IS EXPECTED
TO RESULT IN THE RAPID DEVELOPMENT OF MVFR OR IFR CEILINGS BY 12-15Z
ACROSS MUCH OF CENTRAL NC. SHALLOW CONVECTION (SHRA) WITH TOPS
AROUND 10 KFT WILL BE POSSIBLE THROUGH EARLY AFTERNOON IN ASSOC/W AN
ONSHORE FLOW IN THE LOWER-LEVELS...WITH ISOLD TO SCT SHOWERS AND
THUNDERSTORMS POSSIBLE BY LATE THIS AFTERNOON AND EVENING IN ADVANCE
OF A COLD FRONT PROGRESSING EAST INTO THE TN VALLEY. THERE SHOULD BE
SOME MARGINAL IMPROVEMENT TO CEILINGS IN ASSOC/W DIURNAL HEATING...
HOWEVER...DUE TO CONTINUED LOW-LEVEL MOISTENING CEILINGS MAY REMAIN
IN THE MVFR CATEGORY...AT OR BELOW 2000 FT AGL. EXPECT CEILINGS TO
DETERIORATE TO IFR/LIFR TONIGHT ALONG WITH AN INCREASING LIKELIHOOD
OF SHOWER ACTIVITY IN ADVANCE OF THE APPROACHING COLD FRONT.
SOUTHERLY WINDS AT 7-12 KT EARLY THIS MORNING WILL INCREASE TO 10-15
KT WITH GUSTS UP TO 22-25 KT DURING THE DAY...LIKELY REMAINING
BREEZY AND GUSTING UP TO 20 KT OVERNIGHT AS THE MSLP GRADIENT
TIGHTENS FROM THE WEST.

LOOKING AHEAD: ADVERSE AVIATION CONDITIONS ASSOCIATED WITH
WIDESPREAD SHOWERS AND THUNDERSTORMS ARE EXPECTED ON TUESDAY AS THE
AFOREMENTIONED COLD FRONT PROGRESSES EAST ACROSS THE CAROLINAS.
ISOLD SEVERE THUNDERSTORMS WILL BE POSSIBLE...ESPECIALLY AT THE
RDU/FAY/RWI TERMINALS. SOUTHERLY OR SSW WINDS AT 15 KT WITH GUSTS UP
TO 25 KT CAN BE EXPECTED IN ADVANCE OF THE FRONT THROUGH 18Z
TUE...BECOMING NW/NNW AT 15 KT WITH GUSTS UP TO 25 KT BETWEEN
ROUGHLY 18-21Z TUE AFTERNOON (INT/GSO) TO 00-03Z WED (FAY/RWI).
IFR/LIFR CEILINGS MAY LINGER FOR A WHILE IN THE WAKE OF THE FRONTAL
PASSAGE...EVENTUALLY CLEARING FROM WEST-EAST AND BECOMING VFR AFTER
MIDNIGHT WED MORNING. VFR CONDITIONS WILL PREVAIL IN THE WAKE OF THE
FRONT WED-FRI. -VINCENT

&&

.CLIMATE...
THE FOLLOWING ARE THE RECORD LOW TEMPERATURES FOR WED AND THU MORNING...
AND THE RECORD LOW MAXIMUM TEMPERATURES FOR THU:

            WED 04/16                    THU 04/17
     LOW/YEAR   LOW MAX/YEAR             LOW/YEAR
FAY:  28/1943        56/1950             31/1953
GSO:  25/1943        48/1929             29/1953
RDU:  28/1950        46/1890             29/1962

&&

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

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...DJF/SR/VINCENT
SHORT TERM...VINCENT
LONG TERM...MWS
AVIATION...VINCENT
CLIMATE...MWS



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.