FXUS62 KRAH 280739
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
239 AM EST SAT NOV 28 2009
.SYNOPSIS...
HIGH PRESSURE WILL BUILD TOWARD THE CAROLINAS FROM THE SOUTHWEST
TODAY AND MOVE OFFSHORE TO THE SOUTH ON SUNDAY. A COLD FRONT WILL
APPROACH THE CAROLINAS FROM THE WEST SUNDAY NIGHT...MOVING THROUGH
THE AREA MONDAY AFTERNOON AND EVENING.
&&
.NEAR TERM /THROUGH SUNDAY/...
AS OF 235 AM SATURDAY...
SFC ANALYSIS THIS MORNING SHOWED AN IMPRESSIVELY DEEP 970 MB LOW
CENTERED OVER THE GULF OF MAINE. A TROUGH AXIS EXTENDED
SOUTHWESTWARD INTO THE MID-ATLANTIC AND CAROLINAS. 1021 MB HIGH
PRESSURE WAS CENTERED OVER THE DEEP SOUTH GULF COAST. ALOFT...00Z
RAOB ANALYSIS SHOWED A DEEP UPPER LOW OVER THE GULF OF MAINE...WITH
A TROUGH AXIS EXTENDING SOUTHWARD BETWEEN CAPE HATTERAS AND BERMUDA.
AN UPPER RIDGE WAS CENTERED OVER THE MID-SECTION OF THE COUNTRY. A
SOUTHERN STREAM WAVE WAS LOCATED OVER NORTH-CENTRAL TX.
TODAY:
THE CAROLINAS/MID-ATLANTIC ARE CURRENTLY LOCATED IN A ZONE OF STRONG
SYNOPTIC SUBSIDENCE UPSTREAM OF THE OFFSHORE TROUGH AND DOWNSTREAM
OF THE MIDWEST RIDGE. FCST SOUNDINGS FOR TODAY INDICATE AS
MUCH...SHOWING A PRONOUNCED MID-LEVEL SUBSIDENCE INVERSION IN
PLACE...WITH PWAT VALUES AROUND 0.30". AS A RESULT...CLEAR SKIES ARE
EXPECTED...AND THE PRIMARY FORECAST PROBLEM WILL BE MAX/MIN
TEMPERATURES. 1000-850 MB THICKNESSES ARE PROGGED TO BE ~1315-1320M
AT 12Z...INCREASING TO 1340-1350M BY 21-00Z THIS EVENING. BOTH MOS
GUIDANCE AND THICKNESSES ARGUE FOR HIGHS IN THE MID/UPPER 50S TO
~60F...COOLEST NE AND WARMEST SW.
TONIGHT:
THE SOUTHERN STREAM WAVE CURRENTLY OVER TX IS PROGGED TO MOVE EAST
THROUGH THE DEEP SOUTH INTO THE SOUTHEAST STATES BY 12Z SUN.
ALTHOUGH LIMITED MOISTURE AND MARGINAL FORCING ASSOC/W THIS WAVE
WILL PRECLUDE THE POSSIBILITY OF ANY PRECIPITATION...AN INCREASE IN
UPPER LEVEL CLOUD COVER IS LIKELY...PRIMARILY AFTER MIDNIGHT. IT
IS DIFFICULT TO ASCERTAIN JUST HOW MUCH UPPER LEVEL CLOUD COVER
THERE WILL BE...NOT TO MENTION THE OPACITY. AT THIS TIME PREFER TO
SHOW PARTLY CLOUDY SKIES IN THE SOUTH/WEST PORTIONS OF THE AREA BY
SUNRISE SUN...WITH MOSTLY CLEAR TO PARTLY CLOUDY SKIES ELSEWHERE.
MIN TEMPS TONIGHT WILL BE COMPLICATED PRIMARILY BY HOW MUCH UPPER
LEVEL CLOUD COVER IS AROUND. MOS GUIDANCE IS IN PRETTY GOOD
AGREEMENT WITH LOWS IN THE MID/UPPER 30S...AND GIVEN THAT TEMPS
SHOULD DROP PRECIPITOUSLY AFTER SUNSET WITH CLEAR SKIES AND CALM
WINDS...PREFER TO REMAIN ON THE LOW SIDE OR JUST BELOW MOS GUIDANCE
WITH LOWS IN THE MID 30S IN MOST LOCATIONS...ALTHOUGH LOWER 30S WILL
BE POSSIBLE IN THE TYPICAL COLD AREAS...ESPECIALLY IF UPPER LEVEL
CLOUD COVER IS MINIMAL OR ABSENT.
SUNDAY:
THE SOUTHERN STREAM WAVE IS EXPECTED TO PASS BY JUST SOUTH OF THE
AREA SUNDAY MORNING...MOVING OFFSHORE SUN AFTERNOON. SOME UPPER
LEVEL CLOUD COVER WILL LIKELY BE ASSOC/W THIS FEATURE. BY MID/LATE
AFTERNOON...MORE UPPER LEVEL CLOUD COVER SHOULD BEGIN MOVING INTO
THE CAROLINAS DOWNSTREAM OF A STRENGTHENING FRONTAL ZONE AND
WESTERLY UPPER LEVEL JET ACROSS THE MID-MISSISSIPPI RIVER VALLEY.
EXPECT PARTLY CLOUDY SKIES BY SUNSET...WITH CEILINGS AOA 15 KFT.
HIGH TEMPS WILL BE COMPLICATED BY THE AMOUNT AND OPACITY OF UPPER
LEVEL CLOUD COVER OVER THE AREA. THICKNESSES ARE PROGGED AT ~1360M
12-21Z SUN...AND WITH FULL SUN...LOCAL RESEARCH WOULD SUGGEST HIGHS
IN THE UPPER 60S. A MAV/MET MOS GUIDANCE BLEND YIELDS SIMILAR
VALUES...IN THE MID/UPPER 60S. WILL FCST HIGHS RANGING FROM
66-69F...WARMEST IN THE SOUTH. -VINCENT
&&
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
AS OF 230 PM FRIDAY...
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 /06Z SATURDAY THROUGH WEDNESDAY/...
AS OF 145 AM SATURDAY...
24-HR TAF PERIOD:
VFR CONDITIONS WITH CLEAR SKIES ARE EXPECTED THROUGH THE 24 HOUR TAF
PERIOD AS HIGH PRESSURE BUILDS TOWARD THE CAROLINAS FROM THE
SOUTHWEST. SURFACE WINDS ARE EXPECTED TO BE NORTHWESTERLY AT 5-10 KT
AFTER SUNRISE...WEAKENING TO ~5 KT AND BACKING TO THE WEST DURING
THE MID/LATE AFTERNOON. A FEW SPORADIC GUSTS IN THE 10-15 KT RANGE
WILL BE POSSIBLE DURING THE MORNING HOURS.
SUNDAY THROUGH SUNDAY NIGHT:
ALTHOUGH MID/UPPER LEVEL CLOUD COVER WILL INCREASE IN THIS PERIOD
AHEAD OF THE NEXT FRONTAL SYSTEM...THE LOWER LEVELS WILL REMAIN VERY
DRY...AND VFR CONDITIONS WILL REMAIN IN PLACE ACROSS CENTRAL NC.
MONDAY AND MONDAY NIGHT:
A COLD FRONT WILL MOVE INTO THE CAROLINAS FROM THE WEST ON MON/MON
NIGHT...AND A 6-12 HOUR PERIOD OF MVFR/IFR CONDITIONS ASSOC/W SHOWER
ACTIVITY IS LIKELY...WITH THE BEST CHANCE OF ADVERSE AVIATION
CONDITIONS BETWEEN 18Z MON AND 06Z TUE.
TUESDAY THROUGH WEDNESDAY:
VFR CONDITIONS WILL RETURN TO THE AREA BEHIND THE FRONT ON TUE...
HOWEVER...A SIGNIFICANT STORM SYSTEM IS EXPECTED TO DEVELOP ALONG
THE DEEP SOUTH GULF COAST TUE NIGHT...MOVING INTO THE CAROLINAS AS
EARLY AS WED MORNING. WIDESPREAD ADVERSE AVIATION CONDITIONS APPEAR
LIKELY. -VINCENT
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...VINCENT
NEAR TERM...VINCENT
SHORT TERM...CBL
LONG TERM...CBL
AVIATION...VINCENT
