Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 021146
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
745 AM EDT THU OCT 02 2014

.SYNOPSIS...WEAK HIGH PRESSURE WILL EXTEND OVER THE AREA TODAY. A
COLD FRONT WILL APPROACH FROM THE WEST FRIDAY... AND CROSS THE AREA
FRIDAY NIGHT. COOL HIGH PRESSURE WILL BUILD IN FROM THE WEST OVER
THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 240 AM THURSDAY...

WEAK HIGH PRESSURE RIDGING HOLDS OVER NC THIS MORNING. FOG THUS FAR
HAS BEEN A BIT LIGHTER AND MORE PATCHY THAN THIS TIME YESTERDAY...
PERHAPS DUE IN PART TO AREAS OF SCT-BKN MID CLOUDS DRIFTING OVER THE
AREA... ASSOCIATED WITH A WEAK MID LEVEL PERTURBATION PASSING ESE
THROUGH THE REGION JUST EAST OF THE INCOMING MID LEVEL SHORTWAVE
RIDGE. ADDITIONAL MID CLOUDS OVER NE NC AND TO THE NE ARE ASSOCIATED
WITH THE MID LEVEL LOW JUST OFF NEW ENGLAND. WE MAY SEE A FEW
SPRINKLES OVER NE PORTIONS OF THE FORECAST AREA EARLY THIS
MORNING... BUT THE MOISTURE APPEARS TOO SHALLOW FOR ANY APPRECIABLE
PRECIP. THE VERY LIGHT WIND FIELD IN THE LOW LEVELS SHOULD ONCE
AGAIN MAKE FOR A SLOW DISSOLUTION OF THIS MORNING`S FOG... HOWEVER
IF IT REMAINS MORE LIGHT AND PATCHY THROUGH DAYBREAK (IN CONTRAST TO
THE HRRR WHICH DEPICTS WIDESPREAD LOW CIGS/VSBYS THROUGH SUNRISE)...
WE WOULD THEN SEE SOME SUNSHINE EARLIER THAN YESTERDAY.
REGARDLESS... FORECAST SOUNDINGS SHOW SUFFICIENT LOW LEVEL MOISTURE
BENEATH THE SUBSIDENCE INVERSION ALOFT (JUST ABOVE 700 MB) FOR
PARTLY CLOUDY SKIES FOR MUCH OF THE DAY. MANY OF THE CONVECTION
ALLOWING MODELS AS WELL AS THE NAM/GFS AND SREF PROBABILITIES
SUGGEST THAT A FEW SHALLOW SHOWERS WILL POP UP THIS AFTERNOON...
PROMPTED BY HEATING WHICH SHOULD YIELD PERHAPS A FEW HUNDRED J/KG OF
CAPE... ALMOST ALL BELOW 700 MB. THESE SHOWERS SHOULD BE ORIENTED
ALONG THE DIFFUSE WARM FRONTAL ZONE MOVING NE THROUGH THE AREA LATE
TODAY THROUGH TONIGHT. WILL BRING IN ISOLATED SHOWERS FROM MID-LATE
AFTERNOON STRETCHING THROUGH THE EVENING AND EARLY OVERNIGHT HOURS.
AS DEWPOINTS CREEP UPWARD A BIT OVERNIGHT IN THE WAKE OF THE WARM
FRONTAL ZONE... EXPECT YET ANOTHER ROUND OF LIGHT FOG... BUT THIS
FOG SHOULD STAY LIGHT GIVEN EXPECTATIONS OF STRATOCUMULUS TO CURB
NOCTURNAL COOLING. HIGHS FROM 78 NE TO 84 SW... WITH THICKNESSES
RUNNING NEARLY 10 M ABOVE NORMAL. MILD LOWS TONIGHT OF 60-64. -GIH

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
AS OF 310 AM THURSDAY...

LATEST MODEL OUTPUT ARE IN PRETTY CLOSE AGREEMENT ON THE TIMING OF
POTENT MID LEVEL LOW ACROSS THE LOWER GREAT LAKES... ITS ATTENDING
LARGE SCALE TROUGH PUSHING THROUGH EASTERN NOAM... AND THE
ASSOCIATED SURFACE COLD FRONT. WE GET FULLY INTO THE WARM SECTOR
DURING FRI MORNING... AND THE FRONT ITSELF SHOULD GET INTO WRN NC BY
MID EVENING... AND THEN SWEEP EASTWARD OVERNIGHT... REACHING THE
COASTAL PLAIN BY DAYBREAK. MOISTURE SPREADS IN FROM THE WEST AHEAD
OF THE FRONT... WITH PW VALUES CLIMBING QUICKLY FROM AROUND 1 INCH
TO AT OR ABOVE 1.5 INCHES DURING THE AFTERNOON HOURS. THE KINEMATICS
WITH THIS SYSTEM ARE DECENT... WITH A 35-40 KT SWRLY LOW LEVEL JET
ALIGNED JUST AHEAD OF THE SURFACE FRONT AND DEEP LAYER BULK SHEAR
INCREASING TO 30 (EAST) TO 50 (EAST) KTS FRI NIGHT. BUT THE
PROJECTED MUCAPE VALUES ARE MINOR... PEAKING AT JUST 250-500 J/KG...
MADE WORSE BY THE LOSS OF HEATING WITH AN EVENING/NIGHT PASSAGE.
DYNAMICS ARE BETTER BUT SIMILARLY MUTED... GIVEN THAT THE LEAD
SHORTWAVE TRACKING ENE OVER NC IS RATHER WEAK... AND THE BULK OF THE
HEIGHT FALLS ARE HELD TO OUR NW OVER THE MIDWEST AND OH VALLEY
CLOSER TO THE MID LEVEL VORTEX. BUT GIVEN THE STRONG WIND FIELD AND
UPPER DIVERGENCE MAX SHIFTING EAST THROUGH THE AREA... STILL EXPECT
GOOD SHOWER/ISOLATED STORM COVERAGE. WILL BRING IN LOW CHANCE POPS
WEST BY MID AFTERNOON... SPREADING EASTWARD WITH HIGH POPS TOPPING
OUT AT 60-80% IN THE EVENING/OVERNIGHT... BEFORE STARTING TO PUSH
OUT OF THE CWA TOWARD MORNING. OVERALL QPF LOOKS MEAGER WITH THIS
EVENT... LIKELY TOTALLING A QUARTER INCH OR LESS. THE LOW POTENTIAL
INSTABILITY WILL GREATLY CUT THE SEVERE THREAT... ALTHOUGH A FEW
BOWING SEGMENTS MAY BRING DOWN SOME OF THE 30-40 KTS OF WIND FROM
ALOFT... EVEN WITH JUST SHOWERS. HIGHS NEAR 80 NW (WHERE CLOUDS
SHOULD BE FIRST TO SPREAD IN DURING THE AFTERNOON) TO 85 SE. LOWS 57
NW TO 66 SE. -GIH

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 230 AM THURSDAY...

THE COLD FRONT WILL CONTINUE TO PROGRESS THROUGH CENTRAL NC EARLY
SATURDAY...WITH THE PRE-FRONTAL CONVECTION ENDING FROM WEST TO EAST
AHEAD OF IT...EXITING THE AREA BY NOON SATURDAY. ONCE THE RAIN ENDS
SATURDAY...EXPECT DRY WEATHER THROUGH THE WEEKEND AND INTO EARLY
NEXT WEEK. THERE IS STILL SOME UNCERTAINTY IN THE RAINFALL CHANCES
FOR TUESDAY AND WEDNESDAY AS ANOTHER DISTURBANCE TRAVERSES THE UPPER
LEVEL TROUGH AND APPROACHES THE CAROLINAS. FOR NOW WILL KEEP THE
FORECAST DRY. AT THE SURFACE...COOL HIGH PRESSURE WILL BUILD INTO
THE REGION BEHIND THE FRONT...MOVING NE OVER NC THROUGH THE WEEKEND
AND OUT OVER THE ATLANTIC EARLY NEXT WEEK. EXPECT A RELATIVELY COOL
AND COMFORTABLE TEMPERATURE FORECAST FOR THE WEEKEND...WITH HIGHS IN
THE MID 60S TO LOW 70S SATURDAY AND MID 60S EVERYWHERE SUNDAY.
SATURDAY NIGHT WILL BE THE COLDEST NIGHT OF THE SEASON SO FAR...LOW
40S NW TO UPPER 40S SE. SUNDAY NIGHT WILL ALSO BE CHILLY...MID 40S
ACROSS THE AREA. TEMPERATURES WILL REBOUND SOME EARLY NEXT WEEK...
HIGHS MAINLY IN THE LOW 70S MONDAY INCREASING TO MID TO UPPER 70S BY
WEDNESDAY. LOWS 50-55 DEGREES MONDAY NIGHT...INCREASING INTO THE 55-
60 DEGREE RANGE BY WEDNESDAY NIGHT.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
AS OF 745 AM THURSDAY...

YET ANOTHER ROUND OF WIDESPREAD FOG WITH AREAS OF DENSE FOG AND
STRATUS ACROSS CENTRAL NC THIS MORNING. CONDITIONS AT CENTRAL NC TAF
SITES HAVE VARIED AMONG MVFR AND IFR/LIFR OVER THE LAST FEW HOURS...
WITH THE WORST CONDITIONS AT RWI. THESE ADVERSE AVIATION CONDITIONS
ARE EXPECTED TO SLOWLY IMPROVE TO MVFR AT ALL SITES BETWEEN 13Z AND
15Z... AND TO VFR BY 17Z. RAIN CHANCES REMAIN VERY LOW AT CENTRAL NC
TAF SITES... ALTHOUGH PASSAGE OF A WEAK UPPER LEVEL DISTURBANCE THIS
MORNING COULD BRING AN ISOLATED SPRINKLE OR TWO TO RDU/RWI. AND
ADDITIONAL ISOLATED VERY LIGHT (VFR) SHOWERS ARE POSSIBLE LATE THIS
AFTERNOON INTO TONIGHT ASSOCIATED WITH A WEAK WARM FRONT MOVING
NORTHEASTWARD THROUGH THE AREA. WINDS WILL BE LARGELY CALM THROUGH
MID MORNING... THEN REMAIN LIGHT/VARIABLE THIS AFTERNOON AND EVENING
BUT PREDOMINANTLY FROM THE SE. PATCHY MVFR-IFR FOG MAY FORM ONCE
AGAIN LATE IN THE TAF VALID PERIOD (AFTER 06Z FRI)... AND THIS
SHOULD HOLD THROUGH DAYBREAK FRI MORNING.

LOOKING BEYOND 12Z EARLY FRI MORNING... EXPECT IMPROVEMENT OF VSBYS
TO VFR DURING MID-LATE FRI MORNING. A STRONG FRONTAL SYSTEM WILL
BRING INCREASING SURFACE WINDS FROM THE SW AND A GOOD CHANCE OF SUB-
VFR CONDITIONS IN WIDESPREAD SHOWERS AND A FEW STORMS FRI EVENING
THROUGH FRI NIGHT... EXITING THE EASTERN TAFS EARLY SAT MORNING. VFR
CONDITIONS SHOULD THEN RESUME SAT AFTERNOON... LASTING THROUGH
MONDAY... AS HIGH PRESSURE BUILDS IN FROM THE WEST. -GIH

&&

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

&&

$$
SYNOPSIS...HARTFIELD
NEAR TERM...HARTFIELD
SHORT TERM...HARTFIELD
LONG TERM...KC
AVIATION...HARTFIELD


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