FXUS62 KRAH 271132
AFDRAH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
632 AM EST FRI NOV 27 2009
.SYNOPSIS...
BLUSTERY...CHILLY CONDITIONS WILL OCCUR TODAY BEHIND STRONG LOW
PRESSURE MOVING TOWARD NEW ENGLAND...AND AHEAD OF HIGH PRESSURE
BUILDING EAST TOWARD THE CAROLINAS. A COLD FRONT SWEEPS ACROSS THE
REGION MONDAY. HIGH PRESSURE MOVES BACK INTO THE AREA BRIEFLY
TUESDAY...WITH ANOTHER LOW PRESSURE SYSTEM AFFECTING THE REGION FOR
THE MIDDLE OF NEXT WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
AS OF 258 AM FRIDAY...
SHOWERS WERE BECOMING MORE SCATTERED OVER THE NORTHERN COASTAL
PLAIN EARLY THIS MORNING AS THE STRONG MID-LEVEL TROUGH MOVED EAST
AND DRIER AIR AND SUBSIDENCE PUSHED ACROSS CENTRAL NORTH CAROLINA.
EXPECT THESE SHOWERS TO BE BASICALLY OFF TO THE EAST AND NORTHEAST
BY 4 AM OR SO AND DO NOT PLAN TO INCLUDE THEM IN THE SCHEDULED
FORECAST. AS LOW PRESSURE CONTINUES TO STRENGTHEN AND MOVE NORTH
TOWARD NEW ENGLAND...THE GRADIENT BETWEEN THE LOW AND HIGH
PRESSURE BUILDING EAST WILL RESULT IN BREEZY CONDITIONS FOR
CENTRAL NORTH CAROLINA. THE STRONGEST WINDS SHOULD BE IN THE
NORTHEAST...CLOSER TO THE SURFACE LOW AND WHERE BUFR SOUNDINGS
SUPPORT THE HIGHEST WINDS WITH MIXING...TO 30-35KT AT 925MB AT
00Z. WHILE MUCH OF CENTRAL NORTH CAROLINA SHOULD BE CLOUD-FREE
AROUND SUNRISE...LINGERING 850MB MOISTURE...AND FORECAST 850MB
CONVERGENCE IN THE NORTH ALONG WITH REMAINING 700MB LIFT...SHOULD
COMBINE TO PROVIDE FOR AREAS OF STRATOCU ESPECIALLY ALONG AND
NORTH OF U.S. 64 FOR THE LATE MORNING INTO THE MID AFTERNOON
BEFORE DIMINISHING LATE. THE NAM IS DRIER THAN THE GFS IN THIS
REGARD...BUT AMOUNT OF 850MB MOISTURE AROUND THE TROUGH ON UPPER-
AIR DATA AT 00Z SUGGESTS THE GFS MAY BE MORE ACCURATE IN ITS
PORTRAYAL OF GOOD 850MB MOISTURE ON PLAN VIEW AND BUFR SOUNDINGS
ESPECIALLY OVER NORTHERN ZONES FROM ABOUT 15Z THROUGH 21Z. MOS
TEMPERATURES FROM THE MAV AND MET ARE ESSENTIALLY IDENTICAL AT ALL
SITES AND CORRESPOND CLOSELY TO 1000-850MB THICKNESSES PLUS A
DEGREE OR TWO FOR DOWNSLOPE...RESULTING IN COOL HIGHS IN THE LOWER
TO MID 50S.
TONIGHT...SUBSIDENCE WILL BE THE RULE AS HIGH PRESSURE CONTINUES
TO BUILD IN AND HEIGHTS CONTINUE TO RISE ALOFT. THE GRADIENT
STARTS TO LOOSEN...BUT THERE SHOULD BE A MEASURABLE WIND FOR MUCH
OF THE NIGHT...ESPECIALLY NORTHEAST. ASIDE FROM POSSIBLY A FEW...
THIN CIRRUS IN THE FAST NORTHWEST FLOW ALOFT...MAINLY NORTHEAST
CLOSER TO THE JET WHICH WILL BE LIFTING NORTHEAST...CLOUD-FREE
CONDITIONS SHOULD PREVAIL. OVERNIGHT LOWS WILL BE NEAR OR JUST
BELOW FREEZING IN MOST LOCATIONS...WITH SOME UPPER 20S POSSIBLE IN
RURAL LOCATIONS IN THE WESTERN PIEDMONT AS WINDS BECOME LIGHTER
OVERNIGHT AND DEW POINTS FALL INTO THE 20S.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 258 AM FRIDAY...
SATURDAY THROUGH SUNDAY NIGHT: A 1026 MB SURFACE HIGH OVER SOUTHERN
TX THIS MORNING WILL GRADUALLY WEAKEN AS IT BUILDS EASTWARD ACROSS
THE SOUTHEAST US AND INTO THE WESTERN ATLANTIC THROUGH THE WEEKEND.
LOW LEVEL THICKNESSES REBOUND TO 1350 METERS +/- 5 FROM SOUTHWEST TO
NORTHEAST BY 00Z SUNDAY... BUT THIS WARMING WILL NOT BE FULLY
REALIZED BEFORE A LATE NOVEMBER SUNSET. HIGHS IN THE MIDDLE 50S TO
AROUND 60 EXPECTED UNDER A SUNNY SKY... WARMEST SOUTH.
THE SOUTHERN STREAM TROUGH OVER NORTHWESTERN MEXICO... AND
ATTENDING MID AND HIGH CLOUD SHIELD AS FAR NORTHEAST AS TX AND THE
WESTERN GOM THIS MORNING... ARE STILL EXPECTED TO SPREAD EAST
NORTHEASTWARD ACROSS NC SATURDAY NIGHT AND SUNDAY. THE COMBINATION
OF INCREASING HIGH CLOUDS AND A RISK OF AN OCCASIONAL LIGHT SW
STIRRING TO THE NORTH OF SURFACE RIDGE SHOULD HOLD LOW TEMPERATURES
IN THE LOWER TO MIDDLE 30S SATURDAY NIGHT... WHICH IS STILL A BIT
BELOW CONSENSUS MOS (WHICH IS LIKELY ARTIFICIALLY WARM OWING TO
THE PRESENCE OF A WARM SUBSIDENCE INVERSION BETWEEN H85-9).
TEMPERATURES WITH PARTLY CLOUDY SKIES SUNDAY AND SUNDAY NIGHT IN
THE MIDDLE TO UPPER 60S AND UPPER 30S TO LOWER 40S...RESPECTIVELY...
GIVEN DEVELOPING RETURN FLOW AROUND THE DEPARTING RIDGE.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 315 AM THURSDAY...
NO SIGNIFICANT CHANGES IN FORECAST RATIONALE FROM PREVIOUS 24 HOURS.
DESPITE INDICATIONS OF A TYPICALLY POORLY RESOLVED SPLIT FLOW
PATTERN ALOFT... THE MEDIUM RANGE NWP MODELS REMAIN IN REMARKABLY
GOOD AGREEMENT WRT THE EVOLUTION OF A POSITIVELY-TILTED TROUGH ALOFT
FROM THE GREAT LAKES TO THE BAJA EARLY NEXT WEEK. THE SOUTHERN
PORTION OF THE TROUGH IS PROGGED TO CUTOFF INVOF CA FRIDAY AND
MIGRATE SLOWLY EASTWARD ACROSS THE SOUTH CENTRAL US THROUGH THE
MIDDLE OF NEXT WEEK... WHILE A FAST NORTHERN STREAM REMAINS
PROGRESSIVE OVER THE NORTHERN TIER OF THE CONUS. THIS SCENARIO WOULD
LEAD TO A PAIR OF PRECIPITATION EVENTS FOR CENTRAL NC EARLY TO MID
NEXT WEEK... THE FIRST OF WHICH WOULD BE RELATIVELY LIGHT OWING TO A
DOMINANT NORTHERN STREAM TROUGH THAT WOULD ONLY GRAZE NC... WITH THE
RISK OF A MORE SIGNIFICANT STORM SYSTEM IN ASSOCIATION WITH THE
SLOW-MOVING SOUTHERN CLOSED LOW.
MONDAY THROUGH MONDAY NIGHT: WARM CONVEYOR BELT CLOUDS AND
PRECIPITATION AHEAD OF THE NORTHERN STREAM TROUGH SHOULD EASE INTO
CENTRAL NC LATE MONDAY INTO MONDAY NIGHT... BUT GULF MOISTURE RETURN
SHOULD BE RELATIVELY LIMITED OWING TO THE POSITIVE TILT AND QUICK
PASSAGE OF THE FAST NORTHERN STREAM TROUGH. ANOTHER MILD DAY IN THE
60S EXPECTED WITH INCREASING CLOUDS FROM THE WEST. MOST LOCATIONS
EAST OF HWY 1 SHOULD REMAIN DRY DURING THE DAYLIGHT HOURS. THE
BETTER CHANCE OF SHOWERS WILL OCCUR AREA WIDE OVERNIGHT... AS THE
WCB SWEEPS EASTWARD. INSTABILITY IS NIL... SO NO THUNDER IS
ANTICIPATED. RAINFALL AMOUNTS SHOULD BE LIGHT GIVEN THE BRIEF AND
WEAK GULF TAP... WITH PERHAPS A TENTH OF AN INCH OR TWO TOTAL.
TUESDAY AND TUESDAY NIGHT: CLEARING SKIES AND SURFACE RIDGING
EXPECTED BEHIND THE NORTHERN STREAM TUESDAY AND TUESDAY NIGHT. AT
LEAST PARTIAL SUNSHINE TUESDAY SHOULD ALLOW TEMPERATURES TO CLIMB
INTO THE 55 TO 60 DEGREE RANGE... COOLER THAN PREVIOUSLY DAYS GIVEN
THE PRESENCE OF A COOLER AIR MASS BEHIND THE LOW LEVEL FRONTAL ZONE
ATTENDING THE UPPER TROUGH. CLOUDS SHOULD INCREASE AGAIN FROM THE
SOUTH AND SOUTHWEST LATE TUESDAY NIGHT... IN ADVANCE OF THE
DEVELOPING STORM SYSTEM WITH THE SOUTHERN CLOSED LOW.
WEDNESDAY THROUGH THURSDAY: THE LAGGING SOUTHERN CLOSED LOW SHOULD
THEN DEAMPLIFY NORTHEASTWARD THROUGH THE LOWER MS... TN... AND OH
VALLEYS THIS PERIOD... IN RESPONSE TO UPSTREAM KICKER ENERGY. STRONG
ISENTROPIC LIFT AND GULF AND ATLANTIC MOISTURE TRANSPORT ATOP A
RETREATING FRONTAL ZONE (THE TRAILING PORTION OF THE ONE THAT WILL
HAVE MOVED THROUGH NC MONDAY NIGHT) COULD PRODUCE A WIDESPREAD
SOAKING RAIN FOR CENTRAL NC WEDNESDAY INTO THURSDAY. IT SHOULD BE
NOTED THAT THIS SYSTEM IS REMINISCENT OF THE ONE THAT AFFECTED
CENTRAL NC 22-23 NOV... WHICH THE MODELS EJECTED NORTHEASTWARD TOO
QUICKLY AND INITIALLY TOOK THE SURFACE LOW WEST OF THE MOUNTAINS.
ACCORDINGLY FAVOR AN OCCLUDING SURFACE WAVE INTO THE TN VALLEY...
WITH ENSUING COASTAL CYCLOGENESIS ALONG THE RETREATING BAROCLINIC
ZONE INVOF EASTERN NC/VA. THIS WOULD SPELL ANOTHER WET COLD AIR
DAMMING EVENT FOR OUR REGION... THE WET TIMING OF WHICH MAY BE
DELAYED MORE TOWARD WEDNESDAY NIGHT INTO THURSDAY IF THE RECENT PAST
IS ANY INDICATION.
&&
.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
AS OF 630 AM FRIDAY...
CONDITIONS WERE VFR OVER CENTRAL NORTH CAROLINA AND VFR CONDITIONS
ARE EXPECTED FOR THE DURATION OF THE 12Z VALID TAF PERIOD. WIND
GUSTS WILL BE THE PRIMARY AVIATION CONCERN TODAY AS
WEST-TO-NORTHWEST WINDS GUST TO AROUND 25KT...STRONGEST TOWARD
KRWI...BY 17Z. WITH LINGERING 850MB MOISTURE AND MODEST 850MB
CONVERGENCE...GFS MODEL BUFR SOUNDINGS SHOW THE POTENTIAL FOR
PERIODS OF BROKEN SC AT TAF SITES NORTH OF KFAY. IF CLOUDS DEVELOP
AS EXPECTED...HEIGHTS COULD INITIALLY BE CLOSE TO MVFR. MODEL
SOUNDINGS SHOW THE LOW LEVELS DRYING BY 00Z.
THIS EVENING...BOTH THE NAM AND THE GFS SHOW WINDS JUST OFF OF THE
SURFACE INCREASING TO NEAR 30KT FROM THE NORTHWEST BY 2000FT. BASED
ON THE FORECAST SURFACE WIND...THIS APPEARS TO BE JUST BELOW LLWS
CRITERIA EXCEPT AT KRWI...WHERE 2000FT WINDS ARE FORECAST CLOSER TO
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...RETURNING THE
CHANCE OF SHOWERS BY MONDAY NIGHT.
&&
.CLIMATE...
WITH 0.12 INCH OF RAIN AT KGSO NOVEMBER 26...THE TOTAL FOR THE MONTH
THERE IS NOW 7.78 INCHES. AS A RESULT...THIS IS THE SECOND WETTEST
NOVEMBER ON RECORD AT KGSO...SURPASSING THE 7.72 INCHES RECORDED IN
1948. THE WETTEST NOVEMBER ON RECORD AT KGSO IS 8.26 INCHES...
WHICH OCCURRED IN 1985.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...DJF
NEAR TERM...DJF
SHORT TERM...MWS
LONG TERM...MWS
AVIATION...DJF
CLIMATE...DJF
