FXUS61 KRNK 062342
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
642 PM EST SUN DEC 6 2009
.SYNOPSIS...
HIGH PRESSURE WILL HEAD EAST OFF THE ATLANTIC COAST AS A WEAK
DISTURBANCE MOVES THROUGH THE OHIO VALLEY MONDAY NIGHT INTO
TUESDAY. A STRONG AREA OF LOW PRESSURE WILL MOVE THROUGH THE GREAT
LAKES REGION ON WEDNESDAY...BRINGING A COMPLEX SERIES OF FRONTS
THROUGH OUR REGION. HIGH PRESSURE WILL RETURN NEXT WEEKEND.
&&
.NEAR TERM /THROUGH MONDAY/...
AT THE SURFACE..HIGH PRESSURE IS NEARLY CENTERED OVER THE REGION.
ALOFT...THE AREA IS IN ZONAL TO BARELY SOUTHWEST FLOW IN ADVANCE OF
A DEVELOPING SYSTEM IN THE CENTRAL MISSISSIPPI VALLEY. THE AXIS OF A
NEGATIVELY TITLED RIDGE IS JUST NORTH OF THE REGION. THE RESULT IS
DRY CONDITIONS IN THE LOW LEVELS...WITH INCREASING DEBRIS CIRRUS
CLOUDS BEING ADVECTED INTO THE AREA ON THE SOUTHWEST FLOW ALOFT. AS
TONIGHT PROGRESSES...THE CENTER OF THE SURFACE HIGH WILL SLOWLY
DRIFT TO THE EAST WHILE THE CENTRAL U.S. SYSTEM DIGS A LITTLE DEEPER
AND SOUTHWEST FLOW ALOFT INCREASES AND DESCENDS TO NEAR THE SURFACE.
THE RESULT WILL BE A TREND TOWARDS GREATER COVERAGE...AND THICKER
CLOUD COVER BY MONDAY...ALONG WITH A TREND TOWARDS MILDER
TEMPERATURES. VERY LATE IN THE DAY MONDAY...PARTS OF THE SE WV
MOUNTAINS MAY START TO SEE SOME ISOLATED SHOWERS IN ASSOCIATION WITH
A WAVE MOVING THROUGH THE OHIO VALLEY...AND INCREASING MOISTURE
RETURN.
TEMPERATURES TONIGHT WILL BE TRICKY...ESPECIALLY IN THE WEST. SNOW
COVER IS STILL IN PLACE WHICH TYPICALLY WOULD SUGGEST GOING COLDER
THAN GUIDANCE. HOWEVER...CLOUDS WILL BE INCREASING...AND A SOUTHWEST
FLOW WILL BE DEVELOPING...ESPECIALLY AT ELEVATIONS...BOTH OF THESE
FACTORS SUGGESTION MILDER THAN GUIDANCE. SINCE THE MODELS SEEMS ON
TRACK WITH THE CLOUD COVER...BUILT INTO ITS MOS OUTPUT MOST LIKELY
WOULD BE A TREND TOWARD THE WARMER SIDE AS WELL...BUT MISSING THE
SNOW COVER COMPONENT. GIVEN THIS...WILL FAVOR LOWS TONIGHT A LITTLE
BE LOW AND MOSGUIDE AND ADJMET BLEND IN THE WEST...EXCEPT AT OR
ABOVE 3000 FEET WHERE I WILL BE AT OR LITTLE ABOVE GUIDANCE. IN THE
EAST...I WILL USE NUMBERS IN THE BALLPARK OF THE MOSGUIDE AND ADJMET
BLEND. WHILE WE FOR FRIDAY...I WILL LEAN TOWARD THE MILD SIDE OF
GUIDANCE.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
A WEAK SHORTWAVE PUSHES THROUGH MONDAY NIGHT. THE LATEST RUN OF THE
NAM IS MUCH SLOWER BRINGING THIS FEATURE THROUGH THE AREA THAN THE
GFS. MOISTURE WILL BE LIMITED BUT WITH A WEST NORTHWEST FLOW...THERE
COULD STILL BE SOME LIGHT RAIN ALONG THE USUAL WESTERN UPSLOPE AREAS
OF SOUTHEAST WEST VIRGINIA. THEREFORE...MAINTAINED THE SLIGHT CHANCE
GOING IN THE WEST FOR A SHORT PERIOD OF TIME BEFORE THE FLOW BEGINS
VEERING TOWARD THE NORTHEAST ALONG THE EASTERN PERIPHERY OF THE
HIGH.
LOW TEMPERATURES WILL BE A FEW DEGREES WARMER MONDAY NIGHT WITH WARM
AIR ADVECTING IN FROM A LIGHT SOUTHWESTERLY FLOW.
A STRONGER LOW PRESSURE SYSTEM APPROACHES THE FORECAST AREA TUESDAY
AND MODELS HAVE IT PROGGED TO PUSH THROUGH TUESDAY NIGHT.
SOUTHEASTERLY FLOW AHEAD OF THIS SYSTEM WILL INCREASE MOISTURE AND
WILL RESULT IN SKIES BECOMING MOSTLY CLOUDY THROUGH TUESDAY
AFTERNOON.
A WEDGE OF COOLER 850MB TEMPERATURES WILL ENTER THE ALLEGHANY
HIGHLANDS AND SOUTHEAST WEST VIRGINIA...WHICH WILL ALLOW MIN
TEMPERATURE READINGS TO BE NEAR FREEZING ESPECIALLY IN THE HIGHER
ELEVATIONS. BUFKIT SOUNDINGS ARE NOW MUCH WARMER BUT STILL CONTAIN
THE WARM NOSE AROUND 800MB WHICH IS LOWER THAN THE PREVIOUS RUNS.
MAIN PRECIP TYPE WILL BE ALL RAIN ASIDE FROM THOSE LOCALIZED AREAS
WHICH WILL RECEIVE FREEZING RAIN.
THE LOW WELL PULL AWAY FROM THE FORECAST AREA LATE WEDNESDAY
AFTERNOON. RIDGING AT THE SURFACE AND ALOFT STARTS BUILDING INTO THE
AREA FROM THE WEST WEDNESDAY NIGHT.
TEMPERATURES FOR WEDNESDAY WILL RUN A FEW DEGREES BELOW SEASONAL
NORMS.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
THE UPPER PATTERN NEXT WEEK WILL BE DOMINATED BY AN OMEGA BLOCK OVER
ALASKA...AND A VERY STRONG POLAR VORTEX SPINNING THROUGH EXTREME NW
CANADA. TYPICALLY THIS SETUP DOES NOT MERIT COLD AIR DELIVERY INTO
THE MIDDLE ATLANTIC. HOWEVER...A PIECE OF THIS GYRE WILL BREAK OFF
AND FORM A RATHER STRONG UPPER LOW SOUTH OF HUDSON BAY. DESPITE THE
LACK OF ANY HIGH LATITUDE BLOCKING ACROSS GREENLAND...THIS SECOND
UPPER LOW WILL BE ENOUGH TO ALLOW COLDER AIR TO SPILL INTO THE CWA
LATE NEXT WEEK AND INTO NEXT WEEKEND. STILL POSSIBLE THAT PERHAPS
H85 PROGGED TEMPS WARM SOMEWHAT...AND THIS WILL BE IMPORTANT
CONSIDERING AN AREA OF LOW PRESSURE MOVING ALONG THE SOUTHEAST COAST
PER THE 0Z ECMWF AND THE 12Z GFS NEXT SATURDAY. THIS SYSTEM WILL BE
THE BEST OPPORTUNITY FOR PRECIP THROUGH THE LONG TERM FORECAST.
EXPECTING MAX TEMPS AROUND 40S ELEVATIONS AND MID UPPER 40S
PIEDMONT/SOUTHSIDE.
&&
.AVIATION /23Z SUNDAY THROUGH FRIDAY/...
THERE IS THE POTENTIAL FOR SOME PATCHY FOG TO DEVELOP NEAR OR
SOUTH OF KBLF EITHER LATE TONIGHT OR EARLY MONDAY AS SW WINDS
START TO INCREASE AND ALLOW FOR AN INC IN LLVL MOISTURE. AT THIS TIME
CONFIDENCE IS NOT HIGH ENOUGH TO INCLUDE ANY REDUCED VSBYS AT
KBLF.
PATCHY MVFR CONDITIONS POSSIBLE MONDAY NIGHT INTO TUESDAY IN THE
MOUNTAINS WITH A PASSING COLD FRONT.
WINTRY MIX OF PRECIPITATION POSSIBLE OVER WESTERN AND NORTHERN
PARTS OF THE AREA TUESDAY NIGHT INTO WEDNESDAY AS AN EXPANSIVE
STORM SYSTEM MOVES THROUGH BOTH THE OHIO VALLEY AND CENTRAL AND
SOUTHERN APPALACHIANS. VERY STRONG WINDS WILL ALSO ACCOMPANY THIS
SYSTEM AND PRODUCE A MIX OF STRONG SURFACE GUSTS IN THE MOUNTAINS
WITH THE POTENTIAL FOR LOW LEVEL WIND SHEAR EAST OF THE BLUE RIDGE.
A TIGHT PRESSURE GRADIENT BEHIND THE SYSTEM WILL ALLOW GUSTY
CONDITIONS AND THE POTENTIAL FOR LOW LEVEL WIND SHEAR TO CONTINUE
INTO FRIDAY. THERE MAY EVEN BE SOME LINGERING UPSLOPE SE WV
SCATTERED SNOW SHOWERS.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...DS
NEAR TERM...DS
SHORT TERM...REB
LONG TERM...KM
AVIATION...DS/KM
