FXUS61 KRNK 290941
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
441 AM EST SUN NOV 29 2009
.SYNOPSIS...
HIGH PRESSURE WILL BE ON CONTROL TODAY...THEN GIVE WAY TO A COLD
FRONT APPROACHING FROM THE WEST EARLY MONDAY...WHICH WILL PASS
THROUGH THE APPALACHIANS AND INTO THE PIEDMONT BY EARLY AFTERNOON
MONDAY. WEDNESDAY AND THURSDAY...A LARGE LOW PRESSURE SYSTEM WILL
MOVE FROM THE LOWER MISSISSIPPI VALLEY ACROSS THE MID ATLANTIC
STATES.
&&
.NEAR TERM /THROUGH MONDAY/...
HIGH PRESSURE OVER THE SOUTHEAST COAST WILL BE IN CONTROL TODAY AS
THE SW GRADIENT SLOWLY PICKS UP AHEAD OF THE APPROACHING FRONT
CURRENTLY MOVING INTO THE MIDWEST STATES. WEAK SHORT WAVE IN WSW
FLOW BRINGING SOME CIRRUS ACROSS THE SOUTH...BUT MUCH OF THIS WILL
MOVE EAST DURING THE MORNING...RESULTING IN MAINLY SUNNY SKIES
TODAY. LEANED CLOSER TO WARMER MAV NUMBERS FOR HIGHS
TODAY...ESPECIALLY IN THE WEST WITH SW FLOW AND PLENTY OF SUN.
THE FRONT SO FAR HAS VERY LITTLE MSTR TO WORK WITH BUT THE
SYSTEM SHOULD BEGIN TO TAP SOME GULF MSTR BY TONIGHT AS IT MOVES
INTO OHIO VALLEY AND EAST OF THE MISSISSIPPI RIVER. MODELS ARE IN
GOOD AGREEMENT WITH TIMING OF FRONT TO REACH WRN SLOPES BETWEEN
09Z AND 12Z MONDAY...THEN QUICKLY PUSH EAST OF THE CWA BETWEEN 15Z
AND 18Z...JUMPING INTO A WEAK LEE TROUGH. THIS IS A LITTLE FASTER
THAN PREVIOUS RUNS. LOOKS LIKE MUCH OF THE PRECIP WILL BE RIGHT
WITH THE FRONT AND A LITTLE BEHIND IT...AND GIVEN FAST MOVEMENT
AND TAPPING GULF MSTR LATE IN THE GAME...NOT LOOKING AT QPF VALUES
OVER A QTR OF AN INCH IN THE WEST...WITH THE USUAL BREAK UP OF
SHWRS TO SOME DEGREE AS IT PASSES OVER BLUE RDG...AND THEN SOME
REDEVELOPMENT AGAIN TO THE EAST...AND MAYBE JUST ON OUR FAR
SOUTHEASTERN FRINGE. AS SUCH...WENT WITH CATEGORICAL POPS IN WEST
STARTING 12Z MONDAY...AND THIS MAY NOT BE SOON ENOUGH...TO LIKELY
UP TO ABOUT THE BLUE RIDGE...THEN DROPPING TO CHC ACROSS MOST OF
THE WEST WITH LOW LIKELY IN THE PIEDMONT AFTER 18Z...BUT EVEN THIS
QUICKLY DROPPING TO CHC BY 21Z. PROBABLY WILL NEED TO SPEED THIS
UP EVEN MORE. USED SREF PRECIP PROBABILITIES TO TIME MOST OF THESE
POPS...AND TO SHOW A SMALL GAP IN CENTRAL PART OF CWA WHERE NOT
EVEN WORTH GOING WITH LIKELY POPS AS SHWRS WITH FRONT BREAK UP A
LITTLE.
FOR MONDAY TEMPS...ALSO WENT CLOSER TO MAV GUIDANCE WITH COOLER
HIGHS IN THE WEST AND BOTH MAV AND MET SIMILAR IN THE EAST. TEMPS
MAY END UP WARMER THAN GUIDANCE IN THE EAST IF PRECIP MOVES OUT MORE
QUICKLY AND A PERIOD OF AFTERNOON SUN WITH DOWNSLOPE
WARMING...DESPITE THE COLD ADVECTION...TAKES PLACE.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
UPSLOPE SHWRS MAY CONTINUE IN FAR WRN SLOPES OF WEST VIRGINIA
THROUGH MONDAY EVENING...BUT FLOW TURNS FROM NW TO WESTERLY
PRETTY QUICKLY SO NOT IDEAL. DECIDED TO KEEP A SMALL STRIP OF
LIKELY ACROSS WRN GREENBRIER TO FLAT TOP...AS COLDER AIR MOVES IN
LATE IN DAY AND OVERNIGHT TO TURN RAIN SHOWERS INTO SNOW SHWRS.
VERY MINOR ACCUMULATIONS...IF ANY...GIVEN VERY LITTLE MSTR AND
POOR TRAJECTORIES...AS WELL AS SHORT LIVED NW FLOW CONDITIONS. BY
06Z...ANY LINGERING SNOW SHWRS SHOULD BE FADING AWAY UP THERE AS
FLOW TURNS WESTERLY.
BEHIND THE FRONT I INCREASED WINDS ALONG RIDGES A BIT GIVEN A
SLIGHT UPWARD TREND IN MODEL GUIDANCE...BUT STILL WELL SHORT OF ADV
CRITERIA.
SURFACE HIGH PRESSURE WILL CROSS EAST OVER THE AREA TUESDAY INTO
TUESDAY NIGHT. AS SKIES CLEAR OUT TUESDAY AFTERNOON TEMPERATURES
WILL BE HOVERING NEAR SEASONAL NORMS GIVE OR TAKE A COUPLE DEGREES.
A LOW PRESSURE SYSTEM DEVELOPS OVER THE GULF OF MEXICO AND SLIDES
NORTHEAST BRINGING OUR NEXT CHANCE FOR PRECIP WEDNESDAY INTO
THURSDAY. MODELS ARE HAVING A HARD TIME AGREEING ON THE TIMING OF
THIS SYSTEM. ECMWF HAS BEEN CONSISTENTLY SLOWER THAN THE GFS IN ITS
LATEST RUNS. HAVE LEANED TOWARD THE ECMWF AND HAVE SLOWED THE FRONT
COMING INTO THE FORECAST AREA. AS A RESULT...HAVE LINGERED THE
PRECIP A LITTLE LONGER ACROSS THE FORECAST AREA. DECENT OVERRUNNING
PRECIP WILL SPREAD ACROSS THE COUNTY WARNING AREA WEDNESDAY
AFTERNOON BEGINNING IN THE SOUTHWEST AND PUSHING NORTH NORTHEAST.
RAIN COULD BE HEAVY AT TIMES WITH MOIST WARM AIR ADVECTING OVER THE
REGION AND AN INCREASING LOW LEVEL JET. RAINFALL AMOUNTS OF A 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.
MODELS PROG A LOW LEVEL JET INCREASING TO 40 TO 50 KNOTS EAST OF THE
BLUE RIDGE MOUNTAINS CONCENTRATED IN THE PIEDMONT AREAS OF VIRGINIA
AND NORTH CAROLINA. WILL HAVE TO MONITOR THE SITUATION TO SEE HOW
THE WINDS PLAY OUT TO SEE IF THEY WILL REACH ANY ADVISORY CRITERIA.
WEDNESDAY WILL BE DAMP AND COLD. MAX TEMPERATURE READINGS WILL BE IN
THE 40S IN THE MOUNTAINS TO LOWER 50S IN THE PIEDMONT AREAS
WEDNESDAY. EXPECTING THE COLD AIR TO ADVECT IN LATE WEDNSDAY NIGHT
BUT IF THE FRONT MOVES EVEN SLOWER...THEN THE COLDER AIR WILL NOT
GET INTO THE AREA UNTIL THURSDAY NIGHT OR POSSIBLY LATER.
&&
.LONG TERM /THURSDAY THROUGH SATURDAY/...
THURSDAY WILL CONTINUE TO BE DAMP AND COLD IN THE WESTERN ZONES
WITH HIGH TEMPERATURES IN THE LOWER 40S IN SOUTHEAST WEST VIRGINIA
TO UPPER 50S IN THE PIEDMONT. THIS IS DUE TO A NORTHWESTERLY FLOW IN
THE WAKE OF THE FRONT AND THE DOWNSLOPING COMPONENT WILL WARM UP
READINGS A COUPLE DEGREES IN THE EAST FOR THURSDAY.
THE FRONT WILL BE EXITING THE AREA TO THE NORTHEAST THURSDAY NIGHT
INTO FRIDAY WITH A LOW DEEPENING OFF THE COAST OF MAINE. UPSLOPE
FLOW AND WRAP AROUND MOISTURE WILL MAINTAIN POSSIBLE SNOW SHOWERS
ALONG THE USUAL WESTERN UPSLOPE REGION OF SOUTHEAST WEST VRIGNINA
AND THE MOUNTAIN EMPIRE THROUGH FRIDAY. THE POPS WILL THEN TAPER OFF
FRIDAY NIGHT AS HIGH PRESSURE BUILDS INTO THE AREA FROM THE
SOUTHWEST BY THE WEEKEND.
&&
.AVIATION /10Z SUNDAY THROUGH THURSDAY/...
VFR CONDITIONS EXPECTED UNDER HIGH PRESSURE THROUGH THE NEXT 24
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/SK
NEAR TERM...SK
SHORT TERM...SK/REB
LONG TERM...REB/RCS
AVIATION...KK/WP
