Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 211906
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
307 PM EDT TUE OCT 21 2014

.SYNOPSIS....A COLD FRONT WILL CROSS CENTRAL NC LATE THIS AFTERNOON
AND THIS EVENING. AN UPPER LEVEL LOW WILL SETTLE SOUTHEAST ACROSS
THE MIDDLE ATLANTIC REGION TONIGHT...AND LINGER OVER THE REGION
THROUGH WEDNESDAY NIGHT.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 305 PM TUESDAY...

REMAINDER OF THE AFTERNOON-EARLY EVENING...A COLD FRONT WILL CROSS
THE TRIAD REGION BY 22Z...THE EASTERN PIEDMONT AND SANDHILLS BY
00Z...AND EXIT THE COASTAL PLAIN BY 02Z. PER MESO-ANALYSIS
PLOTS...AIR MASS STILL RELATIVELY DRY AND STABLE. HOWEVER LATEST RAP
AND HRR MODEL GUIDANCE SUGGESTING ENOUGH MOISTURE AND CONVERGENCE
ALONG AND BEHIND THE FRONT TO TRIGGER A FEW SHOWERS ACROSS THE FAR
NE PIEDMONT AND THE NORTHERN COASTAL PLAIN. SOME OF THESE WRF MODELS
ARE NAM BASED WHICH IS WETTER MORE AGGRESSIVE WITH SHOWER
DEVELOPMENT. THUS...BELIEVE A 1:3 CHANCE OF A SHOWER IN THE VICINITY
OF ROANOKE RAPIDS IS A WORST CASE SCENARIO.

MARGINALLY BLUSTERY CONDITIONS EXPECTED BEHIND THE FRONT WITH A N0NW
WIND GUSTING UP TO 20KTS WELL INTO THE NIGHT.

OTHERWISE NEAR TERM MODEL GUIDANCE IN GOOD AGREEMENT IN THE
DEVELOPMENT/MOVEMENT OF AN UPPER LEVEL LOW ACROSS THE NORTHERN MID
ATLANTIC LATE TONIGHT-EARLY WED. THE CIRCULATION AROUND THIS
DEVELOPING SYSTEM SHOULD MAINTAIN VARYING CLOUDINESS NEAR THE
VIRGINIA BORDER UNTIL LATE TONIGHT WITH PARTIAL CLEARING TOWARD
MORNING. 850MB THERMAL TROUGH POSITIONED TO OUR NW TONIGHT WITH
BETTER LOW LEVEL CAA EXPECTED TO COMMENCE BY DAYBREAK. MOS GUIDANCE
IN GENERAL AGREEMENT RANGING IN THE MID 40S OVER THE WEST TO THE
UPPER 40S/AROUND 50 EAST.

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
AS OF 307 PM TUESDAY...

WEDNESDAY... AN UPPER LEVEL FLOW OVER THE NORTHERN MID ATLANTIC WILL
MAINTAIN A STRONG CYCLONIC FLOW OVER CENTRAL NC. PERTURBATIONS
WITHIN THIS FLOW IN CONJUNCTION WITH AVAILABLE MOISTURE WILL CAUSE
PERIODS OF CLOUDINESS...MAINLY ACROSS THE NE HALF THROUGH EARLY
WEDNESDAY EVENING. STEEP MID LEVEL LAPSE RATES (7-7.5 DEG C/KM)
COUPLED WITH AFTERNOON HEATING MAY TRIGGER AN ISOLATED SHOWER OR
TWO...MAINLY IN VICINITY OF ROANOKE RAPIDS/WARRENTON AND TARBORO.
FARTHER SOUTH AND EAST...AIR MASS APPEARS TOO DRY TO SUPPORT
ANYTHING MORE THAN A FEW CLOUDS.

N-NW WINDS WILL REMAIN A LITTLE BLUSTERY WITH GUSTS AROUND 25 MPH
POSSIBLE.

LOW LEVEL CAA MORE PRONOUNCED WITH THERMAL TROUGH OVER THE REGION.
AFTERNOON TEMPS WILL STRUGGLE TO REACH THE LOWER 60S IN THE NW WITH
MID-UPPER 60S COMMON ELSEWHERE.

WEDNESDAY NIGHT...UPPER LEVEL LOW BEGINS TO PULL OUT WEDNESDAY
NIGHT. MID LEVEL SUBSIDENCE IN ITS WAKE WILL RID ARE AREA OF ANY
LINGERING SHOWERS AND CLOUDINESS. LOW LEVEL MIXING WILL
PERSIST...AIDING TO MAINTAIN OVERNIGHT TEMPS. OF SFC WINDS WERE TO
DECOUPLE (MAINLY WESTERN-SOUTHERN PIEDMONT)...COULD SEE MIN TEMPS AS
LOW AS THE MID 30S AT A FEW SPOTS. FOR NOW WILL BOTTOM OUT TEMPS IN
THE UPPER 30S IN THE WESTERN-SOUTHERN PIEDMONT WITH IN TEMPS IN THE
LOW-MID 40S ELSEWHERE.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
AS OF 3 PM TUESDAY...

THURSDAY THROUGH FRIDAY NIGHT: WEAK SHORTWAVE RIDING WILL BRIEFLY
APPROACH/BUILD OVER THE AREA ON THURSDAY INTO THURSDAY NIGHT AS THE
DEEP MID LEVEL LOW SLOWLY CONTINUES TO LIFT OFF TO THE NORTHEAST.
THIS WILL YIELD MOSTLY SUNNY/SUNNY SKIES-CLEAR/MOSTLY CLEAR SKIES.
HOWEVER... WITH THE DEPARTING SYSTEM... WE MAY SEE SUSTAINED
NORTHWESTERLY WINDS IN THE 10 TO 15 MPH RANGE... WITH SOME GUSTS OF
AROUND 20 MPH OR SO DURING THE DAYLIGHT HOURS OF THURSDAY. AFTERNOON
LOW LEVEL THICKNES VALUES AREA EXPECTED TO BE IN THE 1350S TO 1360S.
THUS... GIVEN FULL SUN IS EXPECTED ALONG WITH SOMEWHAT OF A
DOWNSLOPE FLOW WILL GO WITH HIGH TEMPS RANGING FROM THE MID TO UPPER
60S. LOWS THURSDAY NIGHT WITH CLEAR/MOSTLY CLEAR SKIES AND A
WEAKENING WIND ARE EXPECTED TO BE IN THE LOWER TO MID 40S... WITH A
FEW UPPER 30S NOT OUT OF THE QUESTION IN THE USUAL RURAL COLD SPOTS.

ONE LAST S/W DISTURBANCE IS FORECAST TO TRACK SOUTHEASTWARD FROM THE
NORTHERN PLAINS/UPPER MIDWEST ON THURSDAY AND MOVE ACROSS CENTRAL NC
ON FRIDAY INTO FRIDAY NIGHT. THE ECMWF CONTINUES TO BE MUCH STRONGER
WITH THIS FEATURE THAN THE GFS AND NAM. HOWEVER... WITH SUCH A DRY
AIRMASS IN PLACE PRECEDING THE FEATURE AND LACK OF ANY REAL MOISTURE
RETURN IN ADVANCE OF IT MODELS DO NOT SHOW ANY PRECIP BEING
GENERATED ACROSS CENTRAL NC AS IT ACROSS THE AREA. THUS... WILL JUST
SHOW AN INCREASE IN CLOUD COVER ON FRIDAY. HOW STRONG THE SYSTEM
ENDS UP BEING WILL HAVE AN AFFECT ON HIGH TEMPS THOUGH (WITH CLOUD
COVER BEING THE VARIABLE IN QUESTION). FOR NOW WILL JUST SHOW PARTLY
SUNNY SKIES ON FRIDAY... WITH HIGH TEMPS IN THE UPPER 60S TO NEAR 70
SOUTH. LOWS FRIDAY NIGHT WITH CLEARING SKIES ARE EXPECTED TO BE IN
THE 40S.

SATURDAY THROUGH TUESDAY: QUITE WEATHER IS EXPECTED TO CONTINUE FOR
THE UPCOMING WEEKEND AND INTO NEXT WEEK. MID LEVEL RIDGING IS
FORECAST TO BUILD OVER THE AREA FROM THE CENTRAL U.S. BY EARLY NEXT
WEEK... YIELDING A WARMING TREND. EXPECT TEMPS WILL BE NEAR NORMAL
TEMPS TO START THE PERIOD... INCREASING TO HIGH TEMPS A CATEGORY OR
TWO ABOVE NORMAL BY EARLY NEXT WEEK. THIS YIELDS HIGH TEMPS THIS
WEEKEND AROUND 70/LOWER 70S... WITH TEMPS WARMING TO THE LOWER TO
MID 70S BY MONDAY AND TUESDAY... WITH POSSIBLY SOME UPPER 70S BY
TUESDAY. GIVEN THE PATTERN CHANCE TO RIDING ALOFT... SKIES ARE
EXPECTED TO GENERALLY BE MOSTLY SUNNY/MOSTLY CLEAR FOR THIS ENTIRE
PERIOD. THIS SHOULD YIELD A NICE DIURNAL TEMP RANGE... GIVEN THE DRY
CONDITIONS AND RATHER LIGHT WINDS EXPECT FROM SUNDAY ONWARD. LOWS
ARE EXPECTED TO BE IN THE 40S... TO AROUND 50 ACROSS OUR FAR
SOUTHEAST BY EARLY NEXT WEEK.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
AS OF 115 PM TUESDAY...

A COLD FRONT WILL CROSS CENTRAL NC LATE THIS AFTERNOON THROUGH EARLY
THIS EVENING. THE FRONTAL PASSAGE WILL BE NOTED BY THE SURFACE WINDS
VEERING FROM THE WEST-SW TO THE N-NW WITH SUSTAINED WINDS 8-12KTS
AND GUSTS AROUND 20KTS. A LOW END VFR CEILING 3500-5000FT MAY ALSO
ACCOMPANY THE FRONT BETWEEN 20Z-02Z...MAINLY ACROSS THE NORTHERN
COUNTIES IN VICINITY OF THE TRIAD TERMINALS AS WELL AS KRDU AND
KRWI. ENOUGH LIFT MAY OCCUR TO PRODUCE A SHOWER OR TWO BUT
CONFIDENCE THAT A SHOWER WILL OCCUR IN VICINITY OF A TERMINAL IS TOO
LOW TO MENTION IN THE AERODROME FORECAST AT THIS TIME. SKIES ARE
EXPECTED TO TEMPORARILY CLEAR AFTER 04Z.

FOR WEDNESDAY...BLUSTERY N-NW WINDS WILL PERSIST WITH GUSTS 18-23KTS
HIGHLY PROBABLE. THE CLOSE PROXIMITY OF AN UPPER LEVEL LOW OVER THE
NORTHERN MID ATLANTIC WILL CAUSE PERIODS OF CLOUDINESS WITH CEILINGS
3500-5000FT IN VICINITY OF KRDU AND KRWI. A SHOWER OR TWO MAY OCCUR
IN VICINITY OF KRWI...BUT MORE SO NEAR THE VIRGINIA BORDER.

A HIGH PROBABILITY OF VFR CONDITIONS WILL PERSIST THURSDAY THROUGH
SUNDAY. THE UPPER LEVEL LOW IS PROJECTED TO LIFT TO THE NE THURSDAY
AND THURSDAY NIGHT. THIS WILL ALLOW AN AREA OF HIGH PRESSURE TO
BUILD THEN SETTLE OVER CENTRAL NC THROUGH THE WEEKEND.

&&

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

&&

$$

SYNOPSIS...WSS
NEAR TERM...WSS
SHORT TERM...WSS
LONG TERM...BSD
AVIATION...WSS



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