FXUS61 KRNK 221740
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1240 PM EST TUE DEC 22 2009
.SYNOPSIS...
A SURFACE RIDGE OF HIGH PRESSURE EXTENDING FROM THE UPPER GREAT
LAKES SOUTHEAST INTO THE MID ATLANTIC REGION WILL REMAIN NEARLY
STATIONARY THROUGH THURSDAY. LOW PRESSURE WILL THEN MOVE EAST INTO
THE MID ATLANTIC STATES THURSDAY NIGHT...BRINGING ANOTHER ROUND OF
WINTRY PRECIPITATION THAT SHOULD CHANGE TO RAIN ON CHRISTMAS DAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HIGH CLOUDS WERE SPREADING INTO THE AREA AS A SHORT WAVE MOVES
INTO INDIANA. LITTLE CHANGE IS EXPECTED FOR THE REST OF THE DAY.
HAVE MADE MINOR ADJUSTMENTS TO HIGH TEMPERATURES FOR THIS
AFTERNOON BASED ON THE 16Z OBSERVATIONS AND LATEST LAV GUIDANCE.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
FOLLOWING PASSAGE OF THIS WAVE TONIGHT...SKIES ACROSS THE NORTHEAST
WILL GRADUALLY CLEAR...SUPPORTING THE POSSIBILITY OF A GOOD
RADIATIVE EVENT. HOWEVER...CLOUDS SHOULD LINGER OVER THE
MOUNTAINS...AND MAY EVEN BEGIN TO DEVELOP ALONG THE FOOTHILLS OF
SOUTHWESTERN VIRGINIA INTO NORTHWESTERN NORTH CAROLINA AS SURFACE
WINDS BECOME UPSLOPE FROM THE EAST OR SOUTHEAST. AS A RESULT...
COLDEST TEMPERATURES OF UPPER TEENS TO LOWER 20S TONIGHT WILL LIKELY
BE NORTH AND EAST OF LYNCHBURG...WITH TEMPERATURES HOLDING TO MID OR
UPPER 20S FURTHER SOUTHWEST AND WEST UNDER CLOUD CANOPY.
WEDNESDAY WE WILL CONTINUE WITH A DRY FORECAST AS HIGH PRESSURE
BUILDS INTO THE REGION. WILL FAVOR TEMPERATURES BELOW GUIDANCE AS
EXPECT THERE TO STILL BE A GOOD COVERAGE OF SNOW ACROSS THE
AREA...ESPECIALLY OVER THE MOUNTAINS.
FORECAST CHALLENGE CONTINUES TO BE TIMING OF THE CHRISTMAS EVE AND
CHRISTMAS DAY FORECAST. GUIDANCE CONTINUES TO TREND SLOWER WITH THE
ONSET OF PRECIPITATION. THIS WILL ALSO MEAN A BETTER OPPORTUNITY FOR
TEMPERATURES TO BE MILDER A THE ONSET. FOR THE LATEST FORECAST
HAVE REMOVED PRECIPITATION ALMOST COMPLETELY DURING THE DAY ON
THURSDAY...SAVE A SLIGHT CHANCE IN THE FAR SOUTHWEST. HAVE ALSO
GONE A LITTLE MILDER WITH THE DAYTIME HIGH.
THURSDAY NIGHT...STILL EXPECTING A DECENT WARM NOSE TO YIELD
PRECIPITATION OF EITHER RAIN OR FREEZING RAIN...AND PERHAPS A
LITTLE SLEET. HAVE CONTINUED WITH LIKELY TO CATEGORICAL POPS IN
THE WEST...BUT NOW WITH TIMING AFTER MIDNIGHT AND CONTINUING INTO
CHRISTMAS DAY. AS CHRISTMAS DAY PROGRESSES...MILDER AIR ENTERING
THE REGION WILL MEAN A TRANSITION TO ALL RAIN BY THE AFTERNOON.
MAY HAVE TO WATCH FOR THE POTENTIAL OF SOME LOCALIZED FLOODING AS
WELL DURING PERIOD AS THE RAINS MELT THE REMAINING SNOW COVER IN
THE MOUNTAINS. PLUS...THE GROUND ITSELF IS GOING TO BE SOGGY FROM
WHAT SNOW HAS MELTED PRIOR TO THE RAIN.
HEADING INTO FRIDAY NIGHT...AS WE GET ON THE BACKSIDE OF THE
SYSTEM...WE WILL NEED TO WATCH FOR SOME UPSLOPE SNOW SHOWERS IN THE
MOUNTAINS. NOT MUCH WILL REMAIN OF A SATURATED PREFERRED CRYSTAL
GROW LAYER IN THE LOWER LEVELS...BUT FORECAST SOUNDINGS SHOW A
DECENT HIGH LEVEL CANOPY WHICH MAY LEAD TOWARD SOME SEEDER FEEDER
SNOWS.
&&
.LONG TERM /SATURDAY THROUGH MONDAY/...
5H TROF PIVOTING BY TO THE NORTH SHOULD ENHANCE UPSLOPE -SHSN A
BIT SAT INTO SAT NIGHT BUT GIVEN MORE OF A WESTERLY TRAJECTORY
ONLY CHANCE POPS WESTERN THIRD FOR NOW. MORE OF AN OVERALL ZONAL
FLOW WILL TAKE SHAPE LATER IN THE WEEKEND INTO EARLY NEXT WEEK
ALLOWING HIGH PRES TO BUILD IN FROM THE SW BY MONDAY. THUS OTHER
THAN SOME RESIDUAL UPSLOPE FLURRIES EXPECTING A DRY SCENARIO UNDER
MORE SUN FOR DAYS 6/7. TEMPS WILL REMAIN A BIT BELOW NORMAL SAT-
MON SPCLY AT NIGHT BUT NOT TERRIBLY COLD AS THE ARCTIC AIR
BASICALLY REMAINS LOCKED UP TO THE NORTH AT THIS POINT.
&&
.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
HIGH PRESSURE WILL BUILD SOUTHEAST INTO THE REGION TONIGHT INTO
WEDNESDAY FOLLOWING PASSAGE OF SHORT WAVE TROF. THIS SYSTEM WILL
INITIALLY SUPPORT VFR CONDITIONS AT ALL TERMINAL FORECAST POINTS.
HOWEVER...EXPECT SOME RETURN TO MVFR OR EVEN IFR RESTRICTIONS
TOWARD DAYBREAK WEDNESDAY DUE TO DEVELOPMENT OF PATCHY FOG AND
STRATUS GIVEN SNOW ON GROUND AND SOME INCREASE IN MOISTURE
ALOFT. BEST THREAT FOR FOG AND STRATUS WILL BE IN NORMALLY FAVORED
MOUNTAIN VALLEYS AND NEAR RIVERS AND LAKES...SUCH AS NEAR KLWB.
ANY EARLY MORNING FOG AND LOW CLOUD WILL DISSIPATE DURING THE
MORNING. LATEST GUIDANCE HAS CONDITIONS IMPROVING TO VFR AT BLF
AND LWB BY 14Z.
AS SURFACE RIDGE BUILDS FURTHER SOUTHEAST INTO AREA ON WEDNESDAY
NIGHT LOW LEVEL WINDS WILL BECOME SOUTHEAST. MVFR CEILINGS MAY
DEVELOP IN SOUTHWEST VIRGINIA AND NORTHWEST NORTH CAROLINA ON THE
EASTERN UPSLOPE SIDE OF THE BLUE RIDGE.
AN APPROACHING STORM SYSTEM WILL LIKELY BRING ANOTHER LENGTHY PERIOD
OF WIDESPREAD IFR TO LIFR WEATHER THURSDAY NIGHT THROUGH CHRISTMAS
DAY...WITH FREEZING RAIN AND/OR RAIN THE MOST PROBABLE
PRECIPITATION THREAT. ARRIVAL OF STRONG COLD WESTERLY WINDS ON THE
BACKSIDE OF THIS SYSTEM SHOULD ALLOW FOR RETURN TO VFR WEATHER
EAST OF THE BLUE RIDGE FRIDAY INTO SATURDAY...BUT WITH TYPICAL
MVFR TO LOCALIZED IFR RESTRICTIONS CONTINUING IN THE UPSLOPE AREAS
WEST OF THE BLUE RIDGE (KBLF/KLWB) DUE TO SCATTERED SNOW SHOWERS.
&&
.HYDROLOGY...
WILL BE MONITORING POTENTIAL OF LOCALIZED FLOODING FOR CHRISTMAS
DAY AS NEXT WEATHER SYSTEM AND ASSOCIATED RAINS COMBINE WITH
MELTING SNOW PACK TO PRODUCE NOTABLE RUNOFF.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...WERT
NEAR TERM...AMS
SHORT TERM...DS/WERT
LONG TERM...JH
AVIATION...AMS/WERT
HYDROLOGY...WERT
