FXUS62 KRAH 272033
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
331 PM EST FRI NOV 27 2009
.SYNOPSIS...
HIGH PRESSURE WILL BUILD EAST TOWARDS THE CAROLINAS THROUGH THE
WEEKEND. A COLD FRONT WILL SWEEP ACROSS THE REGION ON MONDAY. HIGH
PRESSURE WILL MOVE BACK INTO THE AREA BRIEFLY ON TUESDAY...BEFORE
ANOTHER LOW PRESSURE SYSTEM AFFECTS THE REGION BY THE MIDDLE OF NEXT
WEEK.
&&
.NEAR TERM /THROUGH SATURDAY NIGHT/...
AS OF 215 PM FRIDAY...
TONIGHT: RESIDUAL MOISTURE NEAR 850M (WHICH IS EVIDENT FROM 12Z
UPPER AIR ANALYSIS) CONTINUES TO MOVE OVER THE REGION FROM THE
NORTHWEST...RESULTING IN STRATOCU ACROSS THE NORTHEASTERN PORTIONS
OF THE CWA THIS AFTERNOON. FORECAST SOUNDINGS ARE INDICATING LOW
LEVEL DRYING BY 00Z AS HIGH PRESSURE AND SUBSIDENCE BECOMES MORE
ENTRENCHED ACROSS THE REGION. THIS WILL RESULT IN CLEAR SKIES
AREAWIDE BY EARLY EVENING. MAINLY CLEAR SKIES AND DRY AIR WILL ALLOW
TEMPS TO COOL SIGNIFICANTLY TONIGHT...HOWEVER IDEAL RADIATIONAL
COOLING CONDITIONS WILL NOT OCCUR TONIGHT (WINDS WILL GENERALLY
REMAIN BETWEEN 4-8 KNOTS). NEVERTHELESS OVERNIGHT LOWS WILL BE NEAR
OR JUST BELOW FREEZING IN MOST LOCATIONS...WITH SOME UPPER 20S
POSSIBLE IN RURAL LOCATIONS IN THE WESTERN PIEDMONT WHERE WINDS ARE
FORECAST TO BE THE LIGHTEST.
SATURDAY THROUGH SATURDAY NIGHT: A VERY PLEASANT WEEKEND IS IN STORE
FOR CENTRAL NORTH CAROLINA AS A 1020 MB SURFACE HIGH WILL BE
ANCHORED ACROSS THE SOUTHEAST US THROUGH AT LEAST SATURDAY NIGHT.
LOW LEVEL THICKNESSES ARE PROGGED TO REBOUND TO NEAR 1345 METERS ON
SATURDAY AND WITH PLENTY OF SUNSHINE...TEMPS ARE EXPECTED TO CLIMB
TO NEAR 60 DEGREES. BY SATURDAY NIGHT...MID/HIGH CLOUDS ASSOCIATED
WITH AN UPPER LEVEL LOW CURRENTLY NEAR THE BIG BEND REGION OF TEXAS
SHOULD START TO EDGE INTO THE REGION FROM THE SOUTHWEST. THESE
CLOUDS ARE EXPECTED TO HOLD OVERNIGHT LOWS IN THE LOW TO MID 30S.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 230 PM FRIDAY...
SUNDAY AND SUNDAY NIGHT...FLAT RIDGING ALOFT AND WITH SOUTHERLY
RETURN FLOW WILL RESULT IN DRY AND MILD CONDITIONS ACROSS CENTRAL
NC ON SUNDAY. UPPER SHORTWAVE VORT CURRENTLY OVER THE BIG BEND
OF TEXAS WILL CAST A BAND OF MID AND HIGH CLOUDS ACROSS THE AREA AS
IT SLIDES JUST SOUTH OF THE AREA. DEPENDING ON THE OPAQUENESS OF
THESE CLOUDS...THEY COULD HAMPER THE MILD AFTERNOON HIGHS. HIGHS
65 TO 70. OVERNIGHT LOWS SUNDAY NIGHT WILL BE IMPACTED BY A
SEPARATE AREA OF MID AND HIGH CLOUDS ADVANCING EAST IN THE BROAD
ZONE OF WAA AHEAD OF THE APPROACHING NORTHERN STREAM TROUGH.
CONTINUED DRY...BUT UNDER A THICKENING CLOUD COVER. WILL ERR ON THE
WARM SIDE OF GUIDANCE. LOWS IN THE MID TO UPPER 40S.
MONDAY AND MONDAY NIGHT...MODEL GUIDANCE IS FAIRLY CLUSTERED
WITH THE TIMING OF THE NORTHERN STREAM TROUGH AND ATTENDANT
SURFACE FRONT...PUSHING THE SYSTEM EAST OF THE AREA BY 06Z TUESDAY.
WITH MODELS TRENDING TOWARD A NEUTRAL-TILTED TROUGH...MOISTURE
ADVECTION AND SW FLOW APPEAR ALONG AND AHEAD OF THE WAVE IS LESS
RESTRICTIVE THAN PREVIOUS RUNS. IMPRESSIVE JET ENTRANCE DIVERGENCE
SPREADS OVER THE AREA AS 140 TO 150KT UPPER JET STREAK TRAVERSES
THE MID-ATLANTIC REGION. AS SUCH...AM CONFIDENT ENOUGH TO INTRODUCE
LIKELY POPS FOR MONDAY EVENING/MONDAY NIGHT. INSTABILITY CONTINUES
TO LOOK DISMAL...SO WILL KEEP JUST RAIN SHOWERS. WITH QUICKER
TIMING...HAVE NUDGED TEMPS DOWN A TAD FROM PREVIOUS FORECAST.
HIGHS NEAR 60 NW TO MIDDLE AND UPPER 60S SE. ONCE AGAIN...DUE
TO THE FASTER TIMING OF THE FROPA...CAA WILL BEGIN TO SPILL
INTO THE AREA BEFORE DAYBREAK...PARTICULARLY ACROSS THE WESTERN
AND CENTRAL PIEDMONT. OVERNIGHT LOWS IN THE UPPER 30S NORTH
TO MID 40S SOUTHEAST.
&&
.LONG TERM/TUESDAY THROUGH FRIDAY/...
AS OF 330 PM FRIDAY...
TUESDAY AND TUESDAY NIGHT...SHOWERS SHOULD BE EXITING THE COAST
BY DAYBREAK TUESDAY...WITH CLEARING OVERSPREAD FROM WEST TO EAST
AS DRY AIR SURFACE RIDGE BUILDS OVER THE AREA. HIGHS 55 TO 60.
CLOUDS SHOULD INCREASE AGAIN FROM THE SOUTH AND SOUTHWEST LATE
TUESDAY NIGHT... IN ADVANCE OF THE SOUTHERN STREAM STORM SYSTEM.
WEDNESDAY THROUGH FRIDAY: THE LAGGING SOUTHERN CLOSED UPPER LOW
SHOULD THEN DEAMPLIFY NORTHEASTWARD THROUGH THE LOWER MS... TN...
AND OH VALLEYS THIS PERIOD. STRONG ISENTROPIC LIFT OF GULF AND
ATLANTIC MOISTURE TRANSPORT ATOP A NORTHWARD RETREATING FRONTAL ZONE
(THE TRAILING PORTION OF THE ONE THAT WILL HAVE MOVED THROUGH NC
MONDAY NIGHT)WILL OVERSPREAD THE AREA FROM THE SOUTH WEDNESDAY
AFTERNOON. THERE IS THEN CONSIDERABLE MODEL SPREAD WEDNESDAY NIGHT
AND INTO THURSDAY MORNING...WITH VARIED TRACK AND INTENSITY OF
UPPER LOW AND RESULTANT MSL SURFACE PATTERN(MILLER A VS. B).
THE CANADIAN IS A FAR WESTERN OUTLIER...WHILE THE GFS IS MUCH
WEAKER WITH THE DAMPENING WAVE. THE LATEST EC IS DEFINITELY
THE MOST OMINOUS SOLUTION DEPICTING AN OCCLUDED LOW OVER EASTERN TN
WITH SECONDARY SFC CYCLOGENESIS ALONG THE RETREATING
WEDGE FRONT ACROSS CENTRAL/EASTERN NC. EXPECT ANOTHER WET COLD AIR
DAMMING EVENT FOR OUR REGION ON WEDNESDAY/...WITH THE POTENTIAL FOR
SOME SIGNIFICANT/SEVERE WX WEDNESDAY NIGHT AND INTO THURSDAY MORNING.
THESE EVENT WILL CERTAINLY MERIT MONITORING OVER THE NEXT COUPLE OF
DAYS.
CONDITIONS SHOULD BEGIN TO IMPROVE WITH CLEARING SW TO NE
THURSDAY AFTERNOON AND EVENING AS LOW LIFTS NE AWAY FROM THE AREA.
A CHILLY HIGH WILL BUILD INTO THE AREA FRIDAY AND INTO THE WEEKEND
AND A LONG WAVE TROUGH LOOKS TO SET UP OVER THE EASTERN US.
&&
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
AS OF 1230 PM FRIDAY...
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD AS HIGH PRESSURE
AND SUBSIDENCE MOVE IN BEHIND THIS MORNINGS FRONTAL PASSAGE. WIND
GUSTS WILL CONTINUE TO BE THE PRIMARY AVIATION CONCERN TODAY AS WEST
NORTHWEST WINDS GUST TO AROUND 25KT...WITH THE STRONGEST GUSTS
TOWARD KRWI WHERE THE PRESSURE GRADIENT WILL BE THE TIGHTEST. BROKEN
TO SCATTERED CEILINGS ASSOCIATED WITH STRATOCUMULUS...WHICH ARE
RESULTING FROM RESIDUAL MOISTURE NEAR 850MB...WILL AFFECT THE REGION
THROUGH THIS AFTERNOON. MODEL SOUNDINGS SHOW THE LOW LEVELS DRYING
BY 00Z AND LEADING TO CLEAR SKIES.
OVERNIGHT...MODEL SOUNDINGS SHOW WINDS JUST OFF OF THE SURFACE
INCREASING TO NEAR 30KT FROM THE NORTHWEST BY 2000FT. BASED ON
FORECAST SURFACE WINDS...THIS IS GOING TO RESULT IN MARGINAL LLWS
CONDITIONS ACROSS CENTRAL NORTH CAROLINA. HOWEVER... HAVE ONLY
INCLUDED LLWS IN THE TAFS FOR KRDU AND KRWI WHERE 2000FT WINDS ARE
FORECAST TO BE CLOSER TO 35-40KT AT 03Z.
VFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE WEEKEND AS
HIGH PRESSURE SETTLES ACROSS THE SOUTHEAST STATES. A COLD FRONT WILL
APPROACH FROM THE NORTHWEST LATE MONDAY...BRINGING THE NEXT CHANCE
OF SHOWERS BY MONDAY NIGHT.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...KRR
NEAR TERM...KRR
SHORT TERM...CBL
LONG TERM...CBL
AVIATION...KRR
