FXUS61 KRNK 160357
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1057 PM EST TUE DEC 15 2009
.SYNOPSIS...
HIGH PRESSURE WILL BE OVER THE AREA FOR WEDNESDAY THROUGH FRIDAY.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
AXIS OF UPPER JET AND HIGHER RELATIVE HUMIDITY ABOVE 500 MB WILL
BE MOVING SOUTHEAST OF THE FORECAST AREA BY 10Z. HAVE SLOWED DOWN
THE CLEARING BY A FEW HOURS TO ACCOUNT FOR THIS TIMING. ONLY
MINOR CHANGES TO MINIMUM TEMPERATURES FOR TONIGHT.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
MOS TEMPS LOOK PRETTY GOOD. USED A DRY LAPSE SPREAD FOR WEDNESDAY
(ELEVATION DEPENDENT) PER MORE SUN AND A WELL MIXED ATMOSPHERE.
AN AREA OF HIGH PRESSURE BUILDS IN OVER THE AREA WEDNESDAY NIGHT.
THIS SHOULD ALLOW TEMPERATURES TO FALL OFF NICELY INTO THE UPPER
TEENS TO NEAR 20 ACROSS THE WESTERN HIGH TERRAIN...AND INTO THE
MID TO UPPER 20S IN THE PIEDMONT. DRY WEATHER WILL CONTINUE ON
THURSDAY WITH JUST SOME MID AND HIGH CLOUDS DIMMING THE
SUNLIGHT...HIGHS WILL BE A FEW DEGREES BELOW NORMAL AS 850MB
TEMPERATURES REMAIN IN THE 0 TO -3C RANGE.
BY THURSDAY NIGHT WINDS TURN SOUTHERLY LEADING TO SOME SLIGHT WARM
AIR ADVECTION. THIS SHOULD KEEP TEMPERATURES A LITTLE WARMER IN THE
HIGHER ELEVATIONS...WITH MOST OTHER LOCATIONS SEEING TEMPERATURES
SIMILAR TO WEDNESDAY NIGHT. OUR NEXT SYSTEM BEGINS TO APPROACH FROM
THE SOUTHWEST ON FRIDAY. AT THIS TIME KEPT MOST OF FRIDAY DRY...BUT
LOWERED HIGH TEMPERATURES SEVERAL DEGREES WITH MORE MID AND HIGH
LEVEL CLOUDS EXPECTED. THE GFS AND ECMWF HAVE TRENDED FASTER AND
BRING PRECIP INTO THE SOUTHERN THIRD OF THE CWA BY 0Z SATURDAY...SO
WILL HAVE TO MONITOR FUTURE MODEL TRENDS FOR PRECIP TIMING.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
DEEPENING NORTHERN STREAM 5H POLAR VORTEX WILL CONTINUING SINKING
SOUTH THRU THE MIDWEST FRIDAY NIGHT AS SOUTHERN STREAM LOW
PRESSURE SHIFTS NE TO OFF THE SE COAST BY SAT MORNING. SOME OF THE
NEWER MODEL GUIDANCE SHOWING A BIT MORE INTERACTION BETWEEN THE
TWO NOW VIA A MORE VIGOROUS/SHARPENING UPPER TROF DURING THE
WEEKEND. LATEST GFS REMAINS THE WETTEST IN THE WEST SHOWING LESS
LINKAGE BETWEEN THE SYSTEMS WHILE ALSO GIVING MORE EMPHASIS TO THE
UPPER COLD POOL OVER THE WEST THRU SAT WHICH MAY BE OVERDONE.
HOWEVER IT HAS THE COASTAL LOW COMPLEX FARTHER OFFSHORE WHILE THE
12Z ECMWF CLOSER TO THE COAST WITH A MUCH FASTER BUT MORE PHASED
DEEPER SYSTEM SIMILAR TO THE LATEST HPC PROGS ON SUNDAY. 12Z
CANADIAN/NAM BLEND NEVER CAPTURE THE COASTAL MOISTURE AND KEEP
THINGS DRY WITH ALL DEEP RH TO THE SE. SINCE THINGS QUITE IFFY AND
CONFIDENCE IN ANY SOLUTION LOW...WILL ONLY INTRO A LOW POP SW
LATER FRIDAY NIGHT AND GO WITH CHANCE POPS MAINLY WEST SAT MAINLY
WITH THE UPPER SYSTEM. BETTER COVERAGE MAY COME INTO PLAY SAT
NIGHT PENDING TIMING OF LATER RUNS AND DEGREE OF PHASING WITH THE
COASTAL...SO BASICALLY BLANKETED WITH LOW CHANCES SAT
NIGHT...EXITING THE EAST SUNDAY...WHILE LINGERING IN UPSLOPE AREAS
INTO SUNDAY EVENING UNDER THE COLD ADVECTION. PTYPE LOOKS TO BE
MAINLY LIGHT SNOW EXCEPT ACROSS THE FAR SOUTH/SE SAT WHEN THE
BOUNDARY LAYER MAY BE WARMER...OTRW RUNNING WITH SNOW/RAIN WITHOUT
MIX SINCE STILL A WAYS OUT. WENT CLOSER TO A MORE BLENDED ENSEMBLE
APPROACH ON TEMPS GIVEN SUCH RANGES IN MODEL VALUES WHICH PRODUCES
HIGHS MAINLY 30S SAT AND LOWS IN THE 20S
DRIER AIR WORKS IN MONDAY BEHIND THE SYSTEM WITH WEAK BUT CHILLY
HIGH PRESSURE SETTLING IN FROM THE WEST. NEXT SHOT OF MOISTURE LOOKS
TO BE MORE UPSLOPE VARIETY BY TUESDAY AS NW FLOW ALOFT LIKELY
STREAKS IN SOME SNOW SHOWERS INTO THE NW AHEAD OF THE NEXT IMPULSE
ROTATING ROUND THE 5H TROF. TEMPS REMAIN COLD WITH REINFORCING
PIECES OF COLD ADVECTION KEEPING HIGHS MAINLY 30S WEST TO LOW/MID
40S EAST SUNDAY-TUES...WITH TEENS MOUNTAINS TO 20S EAST FOR LOWS.
&&
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
MVFR CLOUDS ALONG AND WEST OF THE BLUE RIDGE WILL SLOWLY LIFT
THROUGH 12Z. WINDS WILL CONTINUE TO DIMINISH AS HIGH PRESSURE
BUILDS INTO THE AREA.
HIGH PRESSURE WILL INFLUENCE THE AREAS WEATHER THROUGH THE END OF
THE WEEK. THE GROUND REMAINS SATURATED AND WITH GOOD RADIATIONAL
COOLING EACH NIGHT...SO MOUNTAIN VALLEY FOG IS POSSIBLE EACH
MORNING AROUND SUNRISE. A SIGNIFICANT STORM SYSTEM COULD AFFECT
THE EAST COAST THIS WEEKEND.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...PM
NEAR TERM...AMS
SHORT TERM...PM/NONE
LONG TERM...JH
AVIATION...AMS/RCS
