FXUS61 KRNK 282311
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
611 PM EST SAT NOV 28 2009

.SYNOPSIS...
HIGH PRESSURE OVER THE GULF COAST REGION WILL MOVE EAST TONIGHT
AND SUNDAY. A COLD FRONT WILL MOVE THROUGH THE APPALACHIANS
MONDAY. WEDNESDAY AND THURSDAY...A LARGE LOW PRESSURE SYSTEM WILL
MOVE FROM THE LOWER MISSISSIPPI VALLEY ACROSS THE MID ATLANTIC
STATES.

&&

.NEAR TERM /THROUGH SUNDAY/...
HIGH PRESSURE WILL BUILD EAST ACROSS OUR AREA TONIGHT. THE 
MID-ATLANTIC REGION REMAINS IN A ZONE OF STRONG SYNOPTIC SUBSIDENCE 
UPSTREAM OF THE OFFSHORE TROUGH AND DOWNSTREAM OF THE MIDWEST RIDGE. 
DECOUPLING OF THE WINDS EXCEPT FOR THE RIDGES TONIGHT AND GOOD 
RADIATIONAL COOLING WILL BE BALANCED BY WEAK WARM ADV AND INCREASES 
IN DEW PTS. PLAYED LOW TEMPERATURES CLOSE TO THE COOLER ADJMAV. 

HIGH PRESSURE WILL CONTINUE TO MOVE EAST OVER THE MID ATLANTIC REGION
SUNDAY. WITH WESTERLY FLOW RAISED HIGH TEMPERATURES A FEW DEGREES
NEAR ADJMET WITH READINGS GENERALLY FROM THE MID 50S TO THE MID 60S.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
HIGH PRESSURE PASSES TO THE SOUTH OF THE FORECAST AREA. THIS WILL 
RESULT IN LOW LEVEL WINDS OUT OF THE SOUTHWEST THEN WEST. 850MB 
TEMPERATURES REMAIN AROUND +8 THROUGH SUNDAY NIGHT. THERE WILL BE 
ENOUGH MIXING AND CLOUD COVER SUNDAY NIGHT TO KEEP LOW TEMPERATURES 
CLOSER TO MET GUIDANCE...MAINLY IN THE 40S. 

OVERALL THE TIMING OF THE NEXT FRONT IN THE MODELS IS SLIGHTLY 
SLOWER...WITH SOME DIFFERENCES REMAINING BETWEEN THE FASTER 
GFS/ECMWF AND SLOWER NAM. ALL MODELS BRING THE FRONT THROUGH THE 
FORECAST AREA ON MONDAY. EXPECT ANY MEASURABLE RAINFALL TO REACH THE 
WESTERN COUNTIES AFTER 09Z MONDAY...THEN SPREAD EAST TO THE BLUE 
RIDGE DURING THE MORNING. 

PRECIPITABLE WATER VALUES CLIMB CLOSE TO AN INCH AHEAD OF THE FRONT 
BUT WITH WESTERLY LOW LEVEL WINDS AHEAD OF THE BOUNDARY...CHANCE OF 
PRECIPITATION EAST OF THE BLUE RIDGE WILL NOT BE AS GOOD AS IN THE 
MOUNTAINS. INCREASED PROBABILITY OF RAIN IN THE WEST ON MONDAY 
MORNING AND HELD AROUND 50 PERCENT IN THE EAST DURING THE AFTERNOON. 
09Z SREFS FROM SPC AND NCEP BOTH HAD LESS THAN A 10 PERCENT CHANCE 
OF 0.10 INCH OF RAINFALL EAST OF THE BLUE RIDGE ON MONDAY SO KEEP 
QUANTITATIVE FORECAST PRECIPITATION VERY LIGHT. 

HAVE COOLED DOWN THE LOWS ON MONDAY NIGHT BEHIND THE FRONT...BUT 
FORECAST IS STILL ABOVE GUIDANCE IN THE EAST. LOW LEVEL JET BEHIND 
THE FRONT MAY BE AS HIGH AS 40 KNOTS SO ALSO RAISED WIND 
SPEEDS/GUSTS AT HIGHER ELEVATIONS ON MONDAY NIGHT. EXPECT UPSLOPE 
CLOUDS AND PRECIPITATION MONDAY NIGHT BUT LIFT WILL DISSIPATE EARLY 
ON TUESDAY.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AN UPPER LEVEL LOW WILL SPAWN A GULF DISTURBANCE ON WEDNESDAY. THE 
UPPER LEVEL LOW WILL TRACK FROM TEXAS ON WEDNESDAY THEN INTO THE 
OHIO VALLEY WEDNESDAY NIGHT. BY THURSDAY...THIS UPPER LEVEL FEATURE 
WILL BE OCCLUDED OVER LAKE ERIE/SOUTHEASTERN CANADA. THE GULF 
DISTURBANCE WILL STAY CLOSE TO THE UPPER LEVEL LOW AND TRACK INTO 
THE TENNESSEE VALLEY...THROUGH THE OHIO VALLEY...AND INTO 
SOUTHEASTERN CANADA. OVER THE MID ATLANTIC...A WEAKENING SURFACE 
RIDGE WILL CONVERT INTO A COLD AIR WEDGE WEDNESDAY THROUGH THURSDAY 
MORNING AS RAIN SPREADS ACROSS THE REGION. THIS WEDGE WILL ERODE 
THURSDAY MORNING AS A COLD FRONT MOVES TO THE EAST COAST. A 
SECONDARY LOW MAY FORM OVER THE CAROLINAS WEDNESDAY AFTERNOON AND 
NIGHT TO HELP SPREAD RAIN ACROSS THE AREA AND ENHANCE THE WEDGE. 

AN OVERRUNNING COLD RAIN WILL SLOWLY ADVANCE NORTH DURING THE DAY 
WEDNESDAY. RAINFALL COULD BE HEAVY AT TIME WITH MOIST WARM AIR 
ADVECTING OVER THE REGION AND AN INCREASING SOUTHEASTERLY LOW LEVEL 
JET. RAINFALL AMOUNTS ON THE ORDER OF AN HALF OF AN INCH TO AN INCH 
POSSIBLE WEDNESDAY INTO THURSDAY MORNING. HIGHER AMOUNTS OF AN INCH 
OR TWO POSSIBLE ALONG EASTERN SLOPES OF THE BLUE RIDGE. RAINFALL 
AMOUNTS COULD BE DRASTICALLY REDUCED IF SOUTHEAST COASTAL CONVECTION 
IS MORE PRONOUNCED. EITHER WAY...WEDNESDAY INTO THURSDAY WILL BE 
DAMP AND COLD. WITH AN EARLY ARRIVAL OF RAIN ...TEMPERATURES LIKELY 
TO MAXIMIZE WEDNESDAY MORNING AND IN THE UPPER 40S TO LOWER 50S. 
LITTLE DIURNAL SWING WEDNESDAY NIGHT AS THE WEDGE WITH WARM AIR 
ALOFT KEEPING TEMPERATURES MILD NEAR 40F. DESPITE THE ABUNDANT 
AMOUNT OF RAIN EXPECTED...THE WIND MAY BE THE BIGGER PROBLEM. MODELS 
PROJECTING A SOUTHEASTERLY 60-70 KT LOW LEVEL JET WEDNESDAY NIGHT. 
MAJORITY OF THE WINDS SHOULD NOT MIX DOWN WHILE THE WEDGE IS IN 
PLACE. HOWEVER...THE WEDGE WILL BE WEAKER/SHALLOWER ACROSS THE 
EXTREME WESTERN CWA. WIND ADVISORIES/WARNING POSSIBLE ACROSS THE 
GRAYSON HIGHLANDS...RICHLANDS AND TAZEWELL AREA IF MODELS CONTINUE TO 
SHOW THIS LOW LEVEL JET FORMING.

&&

.AVIATION /23Z SATURDAY THROUGH THURSDAY/...
VFR CONDITIONS EXPECTED UNDER HIGH PRESSURE THROUGH THE NEXT 36
HRS. 

A COLD FRONT ARRIVES IN THE MONDAY TIME FRAME WHICH SHOULD
BRING SOME MVFR OR LOWER CIGS TO THE BLF/LWB AREA...MAYBE EVEN TO
ROANOKE BY LATE AFTERNOON MONDAY. ANY IFR CONDITIONS SHOULD BE
VERY BRIEF. ALSO A QUICK PERIOD OF SNOW SHOWERS CAN BE EXPECTED AT
BLF AND LWB BEHIND THE FRONT BY MONDAY NIGHT. ANOTHER STORM SYSTEM
WILL BRING ANOTHER GOOD CHANCE FOR RAIN BY MIDWEEK...AND LOOKS
LIKE A BETTER CHANCE FOR MORE WIDESPREAD IFR CONDITIONS WITH THIS
SYSTEM.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.

&&

$$
SYNOPSIS...AMS
NEAR TERM...KK
SHORT TERM...AMS
LONG TERM...RCS
AVIATION...KK/WP