000
FXUS61 KRNK 032002
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
302 PM EST WED DEC 3 2008
.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFF THE COAST TONIGHT MAKING WAY FOR A
COLD FRONT TO DROP DOWN THRU THE AREA THURSDAY. COLD HIGH PRESSURE
BUILDS BACK ACROSS THE AREA FRIDAY AND FRIDAY NIGHT...WITH A
CLIPPER SYSTEM MOVING THROUGH ON SATURDAY.
&&
.NEAR TERM /THROUGH THURSDAY/...
HIGH PRESSURE WILL MOVE OFF THE SOUTHEASTERN COAST TONIGHT. WITH A
SOUTHERLY FLOW AROUND THIS HIGH AND AHEAD OF A COLD FRONT IN THE
OHIO VALLEY...TEMPERATURES WILL BE MILD TONIGHT. CLOUDS MOVING OVER
THE TENNESSEE VALLEY WILL EDGE INTO THE WESTERN CWA THIS EVENING AND
EVENTUALLY INTO THE EAST AFTER MIDNIGHT. WESTERN RIDGES TEMPERATURES
WILL BE SLOW TO DROP THROUGH THE NIGHT. AREAS OUTSIDE OF THESE
RIDGES WILL SEE GOOD RADIATIONAL COOLING THIS EVENING WITH
TEMPERATURES DROPPING RATHER QUICKLY. AFTER MIDNIGHT...CLOUDS WILL BE
THICKENING AND TEMPERATURES WILL WARM FROM THIS POINT ON.
RAIN CHANCES ARE NOT LOOKING TO IMPRESSIVE TONIGHT...AS PREFRONTAL
SHOWERS ARE SLOWER WITH GULF WAVE BECOMING STRONGER. THE COLD FRONT
TO GET HELD UP IN THE TENNESSEE-OHIO VALLEY OVERNIGHT AS JET AXIS
REMAINS PARALLEL TO THE APPALACHIANS. ALSO...SLOWING DOWN THE FRONT
WILL BE A DEVELOPING GULF STATES DISTURBANCE. MODELS AGREE THAT
THROUGH THE DAY THURSDAY...THE GULF LOW BECOMES THE DOMINATE FEATURE
TAKING MOISTURE AND JET DYNAMICS TO THE SOUTH. CHANCES OF RAIN WILL
BEST BE ACROSS THE MOUNTAINS THURSDAY MORNING THEN INCREASES IN THE
EAST AS EJECTED SHORT WAVE FROM THE GULF LOW CROSSES OVER THE
CAROLINAS IN THE AFTERNOON. WITH DEEP MOIST SOUTHWESTERLY FLOW AND
THIS SHORT WAVE IN THE VICINITY...WILL INCREASE CHANCES OF LIGHT
RAIN IN THE EAST DURING THE AFTERNOON.
WITH PREFRONTAL RAIN MORE TOWARDS OR AFTER SUNRISE AND DEW POINTS
ARE COMING UP THIS AFTERNOON...THE CHANCES OF FREEZING RAIN IS
UNLIKELY. CAN NOT RULE OUT ISOLATED POCKETS OF FREEZING RAIN IN
DEEPER MOUNTAIN VALLEYS OF THE ALLEGHANY HIGHLANDS AND SOUTHERN
SHENANDOAH VALLEYS...IF RADIATIONAL COOLING IS MAXIMIZE THIS EVENING
COUPLED WITH EVAPORATE COOLING TOWARDS SUNRISE FROM VIRGA. GROUND
TEMPERATURES WERE ALLOWED TO WARM THIS AFTERNOON AND LOW LEVEL
THICKNESSES SHOULD BE WARM ENOUGH NOT TO ADDED IN GRIDS. THERE MAY
ALSO BE AN OUTSIDE SHOT OF A BRIEF PERIOD OF SLEET DURING THE ONSET
WITH EVAPORATIVE COOLING...THAT IS IF PRECIPITATION FALLS PRIOR TO
SUNRISE.
TEMPERATURES ON THURSDAY WILL BE ALLOWED TO WARM SOME WITH THE DELAY
OF PRECIPITATION...ESPECIALLY IN THE EAST. CLOUDS WILL BE THICK
ENOUGH AND EARLY ENOUGH TO KEEP TEMPERATURES ON THE COOL SIDE. WITH
850 MB TEMPERATURES +8C AHEAD OF THE FRONT...STILL COULD SEE ABOVE
NORMAL TEMPERATURES IN THE PIEDMONT.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
SOUTHERN STREAM ENERGY SHEARS OUT OVERNIGHT THURSDAY AS THE FRONT
MOVES THRU AND EAST TO THE COAST. SCTD SHOWERS MAY STILL ACCOMPANY
THE FRONT AS IT MOVES THRU THE PIEDMONT...BUT VERY LITTLE RAINFALL
IS EXPECTED WITH THE WEAKENING SYSTEM.
UNIMPRESSIVE UPSLOPE SNOW POTENTIAL BEHIND THE FRONT THURSDAY NIGHT
WITH SFC RIDGE NOSING IN SHARPLY FROM THE WEST. ANTICYCLONIC LOWER
LEVEL TRAJECTORIES WILL BE BRINGING IN RELATIVELY DRY AIR DIRECTLY
BEHIND THE FRONT.
UPPER TROUGH SLOWLY SAGS SOUTHWARD FRIDAY WITH SFC HIGH SHIFTING
FROM THE CENTRAL PLAINS TO THE OHIO VALLEY. COLD AIR MAY LAG A BIT
WEST OF THE MTNS UNTIL SFC CENTER REACHES PA LATE FRIDAY NIGHT.
MODELS HAVE A CLIPPER SHORT WAVE MOVING RAPIDLY THROUGH THE TROUGH
INTO THE SRN APPLNS BY SAT EVENING. THIS HAS THE POTENTIAL TO SPREAD
LIGHT SNOW INTO THE MTNS BY SAT MORNING...AND EVEN FURTHER EAST SAT
AFTERNOON OR EVENING WITH SOME LIGHT ACCUMS POSSIBLE (1-3 INCHES)
EVEN IN THE LOWER ELEVATIONS. BEST LIFT WILL BE ACROSS OUR NORTHERN
COUNTIES DURING THE AFTN WHERE LOW LEVEL TEMPS SHUD BE SUFFICIENTLY
COLD TO PRODUCE AN ALL SNOW EVENT.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
SUNDAY INTO MONDAY...RESIDUAL UPSLOPE SNOW/RAIN SHOWERS IN THE SE
WV MOUNTAINS WILL COME TO AN END AS HIGH PRESSURE BUILDS INTO THE
REGION. LOOK FOR A TREND TOWARDS MILDER TEMPERATURES DURING THIS
TIME.
OUR WARMING TREND WILL CONTINUE INTO TUESDAY AS SOUTHERLY FLOW
INCREASES IN ADVANCE OF OUR NEXT WEATHER SYSTEM. WARM FRONT
ASSOCIATED RAIN/SNOW WILL BEGIN BY LATE MONDAY NIGHT...AND INCREASE
IN COVERAGE ACROSS THE REGION ON TUESDAY. TUESDAY NIGHT INTO
WEDNESDAY WILL BE FOLLOWING THE TIMING OF THE HPC GUIDANCE FOR THE
TIMING OF THE ASSOCIATED COLD FRONT. BEHIND THE FRONT...BY WEDNESDAY
AFTERNOON...STRENGTHENING NORTHWEST FLOW WILL BRING A RETURN OF
UPSLOPE RAIN/SNOW SHOWERS TO THE SE WV MOUNTAINS.
&&
.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
VFR CONDITIONS ARE EXPECTED TODAY AND THROUGH MOST OF THE NIGHT AT
ALL TAF SITES. WINDS WILL COME AROUND TO THE SOUTH TO SOUTHWEST THIS
AFTERNOON ONCE THE SURFACE HIGH PRESSURE SLIDES EAST. SUSTAINED
WINDS OF 10 KNOTS ARE EXPECTED...ALONG WITH A FEW GUSTS OF 15-20
KNOTS. WINDS WILL DIMINSH THIS EVENING...ESPECAILLY IN THE VALLEYS.
WITH A SOUTHWEST FLOW...BLF WINDS MAY MAINTAIN 8 OR MORE KNOTS WITH
GUSTS TO 20 KTS THROUGH THE NIGHT.
A STRONG COLD FRONT WILL MOVE INTO THE MTNS IN THURSDAY
MORNING...AND THEN THROUGH THE PIEDMONT IN THE AFTERNOON. THIS WILL
BRING POOR FLIGHT CONDITIONS TO BLF AND LWB TOWARD 12Z
THURSDAY...AND THEN LAST MOST OF THE DAY. FURTHER EAST...THERE IS A
LOWER CHANCE OF POOR FLIGHT CONDITIONS. MUCH COLDER AIR COMING IN
BEHIND THIS FRONT WILL RESULT IN UPSLOPE -SHSN FOR SOUTHEAST WEST
VIRGINIA THURSDAY NIGHT. VFR SHOULD RETURN FRIDAY INTO SATURDAY
MORNING...AS HIGH PRESSURE BUILDS IN FROM THE WEST AND MOST MOISTURE
LIFTS BACK TO THE NORTH. A CLIPPER LOW PRESSURE WILL BRING A CHANCE
OF LIGHT SNOW TO MOST OF THE AREA...BUT ESPECIALLY BLF AND LWB
SITES...SAT AFTERNOON AND EVENING. COLD NORTHWEST FLOW BEHIND THE
CLIPPER LATER SATURDAY NIGHT INTO SUNDAY WILL GENERATE UPSLOPE SNOW
SHOWERS AND PERIODS OF MVFR TO IFR FOR BLF AND LWB.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...JS
NEAR TERM...RCS
SHORT TERM...JS
LONG TERM...DS
AVIATION...KK/RCS
