FXUS61 KRNK 152055
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
355 PM EST TUE DEC 15 2009
.SYNOPSIS...
HIGH PRESSURE WILL BE OVER THE AREA FOR WEDNESDAY THROUGH FRIDAY.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
1039 MB SURFACE HIGH CENTERED OVER THE CENTRAL CONUS WILL MOVE
EAST AND BECOME OUR DOMINANT WEATHER FEATURE THE NEXT SEVERAL
DAYS. DENSE CIRROSTRATUS WHICH IS OVER OUR AREA TODAY WILL GET
SUPPRESSED TO THE SOUTHEAST AS THE HIGH BUILDS INTO THE FORECAST
AREA. LOW CLOUDS WILL PERSIST IN THE MOUNTAINS TONIGHT WITH A FEW
FLURRIES...BUT THEN DISSIPATE AS WE TRANSITION INTO THE DAY
WEDNESDAY. THE OVERALL TREND WILL BE FOR COOLING WITH COLD AIR
ADVECTING INTO THE FORECAST AREA FROM THE NORTHWEST. WINDS WILL BE
A BIT GUSTY...ESP IN THE HIGHER ELEVATIONS...WITH GRADIENT FLOW
PERSISTING THROUGH WEDNESDAY AND UNTIL THE HIGH BECOMES CENTERED
OVERHEAD FOR THE END OF THE WEEK.
MOS TEMPS LOOK PRETTY GOOD. STAYED A FEW DEGREES WARMER THAN MOS
TONIGHT PER CLOUD COVER...THEN USED A DRY LAPSE SPREAD FOR
WEDENSDAY (ELEVATION DEPENDENT) PER MORE SUN AND A WELL MIXED
ATMOSPHERE.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
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 /21Z TUESDAY THROUGH SUNDAY/...
SURFACE FRONT HAS PUSHED THROUGH THE AREA WITH WINDS BECOMING
WESTERLY. THE DEW POINT FRONT STILL LAGGING BACK IN THE OHIO
VALLEY EARLY THIS AFTERNOON. AS THE DEW POINT FRONT TRACKS
EAST...LIGHT RAIN SHOWERS EXPECTED THIS AFTERNOON...CHANGING TO
SNOW SHOWERS ACROSS THE EXTREME WESTERN CWA THIS EVENING.
VISIBILITIES WILL REMAIN VFR WITH THE EXCEPTION OF RIDGES BEING
OBSCURED. CEILINGS WILL CONTINUE TO RUN MVFR ACROSS THE MOUNTAINS
THIS AFTERNOON AND IMPROVE TO VFR THIS EVENING. WESTERN SLOPES AND
HIGHER RIDGES MAY MAINTAIN CLOUDS UNTIL LATER THIS EVENING...THEN
BECOME VFR. WITH A WESTERLY WIND OVER THE AREA AT 17Z
TUESDAY...LOW CLOUDS EAST OF THE BLUE RIDGE STARTING TO SCOUR OUT
WHILE MID/HIGH DECK WILL REMAIN INTO EARLY THIS EVENING.
ONCE THE DEW POINT FRONT PASSES EAST OF THE AREA...MODERATE PRESSURE
RISES WITH A TIGHTENING PRESSURE GRADIENT WILL HAVE WINDS
INCREASING. PROJECTED NORTHWEST LOW LEVEL JET ALONG THE BLUE
EXPECTED TO REACH 50KT LATE THIS AFTERNOON AND INTO EARLY EVENING.
THIS WILL BRING NEAR ADVISORY GUSTS ALONG THE HIGHEST RIDGES. HIGH
PRESSURE EDGES CLOSER TO THE AREA ON WEDNESDAY WITH WINDS RELAXING
SOME...BUT STILL REMAINING BREEZY THROUGH THE DAY.
HIGH PRESSURE WILL INFLUENCE THE AREAS WEATHER THROUGH THE END OF
THE WEEK. GROUND REMAINS SATURATED AND WITH GOOD RADIATIONAL COOLING
EACH NIGHT...MOUNTAIN VALLEY FOG IS POSSIBLE EACH MORNING AROUND
SUNRISE. A SIGNIFICANT STORM SYSTEM COULD PLAGUE THE EAST COAST
NEXT WEEKEND.
&&
.HYDROLOGY...
FLOOD WARNING REMAINS ALONG THE ROANOKE RIVER AT RANDOLPH. THE
RIVER IS FALLING. IT CRESTED AT 23.85 FEET AROUND MIDNIGHT LAST
NIGHT. THE RIVER IS EXPECTED TO FALL BELOW THE 21 FOOT FLOOD STAGE
BEFORE MIDNIGHT TONIGHT.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...PM
NEAR TERM...PM
SHORT TERM...MC
LONG TERM...JH
AVIATION...RCS
HYDROLOGY...PM
