FXUS62 KRAH 290139
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
840 PM EST SAT NOV 28 2009

.SYNOPSIS...
HIGH PRESSURE OVER THE REGION MOVES OFFSHORE ON SUNDAY. A COLD FRONT 
APPROACHES THE AREA FROM THE WEST SUNDAY NIGHT...PASSING THROUGH THE 
REGION MONDAY AFTERNOON AND EVENING. A LOW PRESSURE SYSTEM MOVES 
FROM THE GULF TOWARD THE CAROLINAS ON WEDNESDAY.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
AS OF 840 PM SATURDAY...

LATEST SURFACE ANALYSIS SHOWED HIGH PRESSURE OVER CENTRAL NORTH 
CAROLINA...WITH A WEAK SURFACE TROUGH OVER THE NORTH CAROLINA 
FOOTHILLS. OF INTEREST TO CENTRAL NORTH CAROLINA WEATHER OVERNIGHT 
IS THE MID-LEVEL SHORTWAVE...VERY VISIBLE ON WATER VAPOR IMAGERY...
MOVING EAST ACROSS LOUISIANA INTO MISSISSIPPI AND PROVIDING ENOUGH 
DIFFLUENCE AND LIFT AHEAD OF IT TO PUSH MID- AND HIGH-LEVEL CLOUDS 
EAST AND NORTHEAST TOWARD THE AREA. BOTH THE 18Z RUNS OF THE NAM AND 
GFS BRING AMPLE HIGH CLOUDINESS INTO CENTRAL NORTH CAROLINA...
SPREADING IT SOUTHWEST-TO-NORTHEAST OVERNIGHT. LAST VISIBLE IMAGES 
AND LATEST INFRARED SATELLITE IMAGES APPEARED TO SHOW ENOUGH BREAKS 
IN THE CLOUDS TO AVERAGE PARTLY CLOUDY...THOUGH A PERIOD OR TWO OF 
MOSTLY CLOUDY CONDITIONS ARE LIKELY ESPECIALLY WEST. TEMPERATURES 
WERE FAIRLY VARIABLE OVER CENTRAL NORTH CAROLINA...FROM THE MID TO 
UPPER 30S IN A COUPLE OF LOCATIONS...TO WARM READINGS NEAR 50 IN THE 
TRIAD WHERE THERE REMAINED A LIGHT WIND. THE WINDOW FOR QUICKLY 
FALLING TEMPERATURES IS NARROWING AS THE CLOUDS MOVE IN AND OPTED TO 
RAISE MINS IN MOST PLACES MAINLY SOUTH OF A LINE FROM THE TRIAD...
THROUGH THE TRIANGLE...TO CLINTON. COOLEST LOWS SHOULD BE 
NORTHEAST...WHERE ANY CLOUDS WILL MOVE IN LATEST.

SUNDAY AND SUNDAY NIGHT...MID AND HIGH LEVEL CLOUD COVER ASSOCIATED 
WITH THE SOUTHERN STREAM WAVE PASSING JUST SOUTH OF THE AREA WILL 
RESULT IN PARTLY SUNNY SKIES FOR MUCH OF THE DAY. 18Z NAM AND GFS 
BUFR SOUNDINGS SUGGEST MOSTLY HIGH CLOUDS EARLY WITH A SMALL VOLUME 
OF MOISTURE DESCENDING INTO THE MID-LEVELS BY AFTERNOON. CENTRAL AND 
WEST...THERE MAY BE A SMALL WINDOW OF MOSTLY SUNNY SKIES IN SOME 
LOCATIONS IN THE AFTERNOON BEFORE THE NEXT BATCH OF MID AND HIGH 
LEVEL CLOUD COVER SPREADS INTO THE STATE FROM THE WEST TOWARD AND 
AFTER 00Z MONDAY. THIS WILL OCCUR DOWNSTREAM OF THE STRENGTHENING 
FRONTAL ZONE AND WESTERLY 140KT UPPER LEVEL JET EXTENDING ACROSS THE 
MID-MISSISSIPPI AND TENNESSEE VALLEY. HIGH TEMPS WILL BE COMPLICATED 
BY THE AMOUNT AND OPACITY OF UPPER LEVEL CLOUD COVER OVER THE AREA. 
THICKNESSES ARE PROGGED TO INCREASE TO AROUND 1360-1365M SUN...AND 
WITH FULL SUN...LOCAL RESEARCH WOULD SUGGEST HIGHS IN THE UPPER 60S. 
A MAV/MET MOS GUIDANCE BLEND YIELDS SIMILAR VALUES...WARMEST IN THE 
SOUTH. UNDER THE THICKENING CLOUD COVER AND A STEADY 5KT SOUTHWEST 
RETURN FLOW...LOWS SUNDAY NIGHT WILL BE A GOOD TEN DEGREES WARMER 
THAN THE PREVIOUS NIGHT...LOWS IN THE MID 40S.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... 
AS OF 145 PM...

MONDAY AND MONDAY NIGHT...
MODELS IN AGREEMENT IN PLACING AN 850 MILLIBAR TROUGH FROM
MEMPHIS NORTHEAST INTO THE MID ATLANTIC STATES AT SUNRISE MONDAY.
THIS WILL BE THE DRIVING FORCE FOR PRECIPITATION... WITH A
RELATIVELY WEAK 35 TO 40 KNOT 850 MILLIBAR JET MOVING THROUGH
NORTH CAROLINA AHEAD OF THE TROUGH. FLOW IS RELATIVELY UNIFORM
WITH NO SIGNIFICANT ISENTROPIC LIFT... AND THIS WILL LIMIT
RAINFALL AMOUNTS. INDICATIONS ARE HEAVIEST RAINFALL WILL BE NEAR
AND EAST OF HIGHWAY ONE...PERHAPS TO ONE QUARTER INCH... AS THE
LOW LEVEL JET SLIGHTLY ENHANCES LIFT DURING THE AFTERNOON.
THICKENING CLOUDS AND PRECIPITATION WILL HINDER AFTERNOON HEATING.
WITH THE CURRENT TIMING OF RAIN... AND EARLY AFTERNOON THICKNESSES
EXPECTED TO EXCEED 1350 METERS... HIGH TEMPERATURES NEAR 60
NORTHWEST TO UPPER 60S SOUTHEAST.

THE GFS MODEL HAS BEEN MOST AGGRESSIVE WITH LIFTING THE TROUGH OUT 
INTO THE ATLANTIC AND THE 12Z RUN CONTINUES TO BE AN OUTLIER. WILL 
CONTINUE RAIN CHANCES IN THE EAST INTO THE EARLY MORNING HOURS OF
TUESDAY. MODELS USUALLY TOO AGGRESSIVE WITH BRINGING COLD AIR OVER
THE MOUNTAINS... AND LOCATIONS IN THE NORTH COULD HAVE AT LEAST A
LITTLE MOISTURE ON THE GROUND TO HOLD TEMPERATURES UP. LOW
TEMPERATURES IN THE MID TO UPPER 30S NORTH... WITH 40 TO 45
DEGREES IN THE SOUTH.

TUESDAY AND TUESDAY NIGHT...
THE EXITING LOW LEVEL TROUGH IS QUICKLY REPLACED BY SURFACE HIGH
PRESSURE... WHICH QUICKLY CROSSES THE CAROLINAS TUESDAY AND IS
OFFSHORE TUESDAY NIGHT. SOME CIRRUS EXPECTED TO TOP THE UPPER
LEVEL RIDGE OVER THE SOUTHEAST BUT OVERALL IT SHOULD BE SUNNY
TUESDAY. LOW LEVEL THICKNESSES EXPECTED TO BE NEAR CLIMATOLOGY AND
HIGH TEMPERATURES WILL FOLLOW SUIT... AT 54 TO 59 DEGREES.
SIMILARLY... LOW TEMPERATURES SHOULD NOT BE FAR FROM CLIMATOLOGY...
AT MID 30S.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/... 
AS OF 145 PM...

WEDNESDAY MORNING AN UPPER LEVEL CUT OFF LOW IS FORECAST TO BE OVER 
EASTERN TEXAS. AN ASSOCIATED SURFACE LOW IN THE NORTH GULF OF MEXICO 
WILL LIFT NORTHEAST TOWARD THE CAROLINAS DURING THE DAY WEDNESDAY. 
AT THIS TIME THE ATTEMPT OF THE GFS TO DEVELOP A MILLER B SURFACE 
LOW DEVELOPMENT... BUT OVER THE EASTERN PIEDMONT IS REJECTED... AND 
SOMETHING CLOSER TO THE ECMWF SOLUTION WITH A LOW WEST OF THE 
MOUNTAINS WILL BE FOLLOWED. WITH CENTRAL NORTH CAROLINA IN THE WARM 
SECTOR... THIS COULD BE A SIGNIFICANT RAIN EVENT... WITH AMOUNTS IN 
EXCESS OF ONE INCH. HOWEVER THERE IS STILL TOO MUCH UNCERTAINTY THIS 
FAR OUT IN TIME TO HAVE MUCH CONFIDENCE. 

THE REMAINDER OF THE PERIOD WILL BE DOMINATED BY A BROAD TROUGH OVER 
THE EASTERN HALF OF THE UNITED STATES. SURFACE HIGH PRESSURE TO THE 
WEST WILL KEEP SKIES MOSTLY CLEAR WHILE NORTHEAST FLOW AND DRY 
NIGHTS WILL KEEP TEMPERATURES BELOW NORMAL. AFTERNOON HIGH 
TEMPERATURES IN THE MID 50S BEFORE FALLING TO 49 TO 55 FRIDAY... AND 
NEAR 50 SATURDAY. OVERNIGHT LOWS MID 40S TO NEAR 50 WEDNESDAY NIGHT 
THEN MID 30S THURSDAY AND FRIDAY NIGHTS. 

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
AS OF 610 PM SATURDAY...

VFR CONDITIONS WILL CONTINUE THROUGH THE 00Z VALID TAF PERIOD. 
INCREASING MID- AND HIGH-LEVEL CLOUDS WILL TAKE PLACE FROM THE 
SOUTHWEST...ENOUGH FOR BROKEN CI AND AC FROM 06Z ONWARD IN MOST 
LOCATIONS. LIGHT...MAINLY SOUTHWEST WINDS OVERNIGHT INCREASE TO 
SUSTAINED 5 TO 10KT SUNDAY...AND WITH MIXING A LIGHT GUST IN THE 
LOWER TEENS IS LIKELY A TIME OR THREE DURING THE DAY.

NAM AND GFS MODELS INCREASE 925MB WINDS TO AROUND 35KT OVER MOST OF 
CENTRAL NORTH CAROLINA SUNDAY NIGHT...BY 06Z MONDAY. THIS COULD LEAD 
TO LLWS ESPECIALLY ON THE NAM MODEL WHICH HAS A LOWER INVERSION...
ABOUT 1000-1500FT...COMPARED TO THE GFS. TOP-DOWN MOISTENING THEN 
BEGINS MORE IN EARNEST ON MONDAY IN ADVANCE OF A COLD FRONTAL 
PASSAGE MONDAY EVENING. A 6-12 HOUR PERIOD OF MVFR/IFR CONDITIONS 
ASSOCIATED WITH SHOWER ACTIVITY IS LIKELY...WITH THE BEST CHANCE OF 
ADVERSE AVIATION CONDITIONS BETWEEN 18Z MONDAY AND 06Z TUESDAY. VFR 
CONDITIONS WILL RETURN ON TUESDAY AS HIGH PRESSURE BUILDS IN BRIEFLY 
BEHIND THE FRONT. A STRONG STORM SYSTEM IS EXPECTED TO DEVELOP ALONG 
THE DEEP SOUTH GULF COAST TUESDAY NIGHT...MOVING INTO THE CAROLINAS 
WEDNESDAY. WIDESPREAD IFR TO LIFR AVIATION CONDITIONS ARE LIKELY 
WEDNESDAY AFTERNOON THROUGH THURSDAY MORNING...ALONG WITH STRONG 
WINDS ALOFT...AS THE LOW MOVES ACROSS THE CAROLINAS.

&&

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

&&

$$

SYNOPSIS...DJF
NEAR TERM...DJF/BL
AVIATION...DJF/BL