FXUS61 KRNK 151550
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1050 AM EST TUE DEC 15 2009
.SYNOPSIS...
A COLD FRONT WILL CROSS THE AREA TODAY...FOLLOWED BY HIGH
PRESSURE FOR WEDNESDAY THROUGH FRIDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
AT 15 UTC...SFC COLD WAS ALONG THE BLUE RIDGE...MOVING EAST.
FRONT SHOULD CLEAR THE FCST AREA BY THIS EVENING. COLDER AIR WILL
OOZE INTO THE AREA. TEMPS IMMEDIATELY BEHIND THE FRONT ARE NOT
THAT COLD...FRONT ACTING MORE AS A WIND SHIFT...BUT COLDER
READINGS WILL BE ON THE WAY AS CAA STRENGTHENS PER INCREASE IN
NORTHWESTERLY FLOW TONIGHT.
ANY PCPN THIS AFTERNOON AND TONIGHT WILL BE MAINLY CONFINED TO THE
WINDWARD SLOPES. THE RADAR OUT OF RLX INDICATES SOME LIGHT RETURNS
ENTERING THE MTNS WEST OF THE GREENBRIER VALLEY...BUT ACTIVITY
SHOULD DRY UP AS IT CROSSES THE PLATEAU AND ENCOUNTERS THE
DOWNSLOPE FLOW. AS THE FRONT SHIFTS EAST INTO THE PIEDMONT THIS
AFTN...WINDS WILL SWING TO THE NW WHILE THE UPPER TROUGH DIGS INTO
THE OHIO VALLEY. STRONG SHORTWAVE SLIDES SOUTHEAST INTO HE CENTRAL
APPS BY THIS EVENING AND SHOULD KEEP AN ENHANCED UPSLOPE COMPONENT
AND SOME DYNAMICS TO BRING A LITTLE BETTER SHOT OF RAIN CHANGING
TO SNOW SHOWERS AS COLDER AIR INFILTRATES THE MTNS...ALBEIT CHANCE
POPS OVER THE WRN UPSLOPES FROM SE WV INTO THE MTN EMPIRE. THE
SHORTWAVE AND 8H THERMAL TROUGH TAKE A NEWD TRACK AWAY FROM THE
SRN APPS...SO DO NOT FORESEE MUCH IN THE WAY OF POPS IN THE NC
MTNS THIS TIME AROUND. LEANING TOWARD LIFTING THE SHORTWAVE NE
AWAY FROM THE AREA AFTER MIDNIGHT SHOULD END PRECIP ACROSS THE SE
WV UPSLOPE AREAS WITH A FEW FLURRIES LINGERING. SNOW AMOUNTS
SHOULD BE A FEW TENTHS OF AN INCH IN WRN GREENBRIER...BUT NOT MUCH
MORE THAN THAT.
TEMPS TODAY WILL BE VARYING WIDELY AS THINK THE PIEDMONT WILL SHOOT
UP INTO THE UPPER 50S TO AROUND 60 PER DOWNSLOPE FLOW ARRIVING
BEHIND THE FRONT WITH COLD AIR LAGGING BEHIND TIL 00Z. MAIN CULPRIT
INTO CAUSING TEMPS TO EVEN WARM MORE...WILL BE CLOUD COVER. THIS
PATTERN SUGGEST POTENTIAL FOR LINGERING CS SHIELD/OR STANDING WAVE
AS CROSS SECTIONS KEEP A HIGH LEVEL DECK INTO THE AFTERNOON OUT
EAST...PLUS SUN ANGLE IS GETTING CLOSE TO ITS LOWEST POINT.
IN THE WEST...HIGHS HAVE ALREADY BEEN REACHED AND WITH THE
WIND PICKING UP BEHIND THE FRONT AND COLD AIR OOZING INTO THE MTNS
THIS AFTERNOON SHOULD SEE FALLING TEMPS IN THE MTNS THIS AFTERNOON.
AS FOR THE WINDS...THE STRONGEST CAA AND LOW LVL JET ARRIVE IN THE
00Z-03Z TIME FRAME AS THE 00Z GFS DEPICTING 45-50 KNOTS WITH THIS
SHORTWAVE. NAM A LITTLE LESS AGGRESSIVE. KEPT WINDS GUSTING TO UNDER
ADVISORY LEVELS IN THE MTNS. WINDS WILL BECOME LIGHTER TOWARD 12Z
WED.
LOWS TONIGHT WILL STILL BE CLOSE TO THE MAV/MET MOS BLEND. ALTHOUGH
FAVORING A LITTLE WARMER IN THE MTNS AS WINDS STAY UP KEEPING THE
AIR MIXED...WITH THE SFC HIGH NOT MOVING INTO THE AREA TIL AFTER
12Z WED.
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
HIGH PRESSURE WILL PROVIDE A TRANQUIL PERIOD...HOWEVER THERE WILL
NOT BE ANY MAJOR COOLDOWN WITH ITS PRESENCE. JET STREAM NEVER
DROPS FAR ENOUGH SOUTH FOR OUR CWA TO EXPERIENCE THE SUB -10C H85
TEMPS THAT STAY ALONG THE GREAT LAKES. VERY DRY AIR THOUGH WILL
ARRIVE...AND CONTINUED LAST NIGHTS TREND OF UNDERCUTTING MOS
DEWPOINTS. THIS TIDBIT MAY ALSO ALLOW MAX T TO RUN A FEW DEGREES
WARMER THAN GUIDANCE. AS AN UPPER HIGH RETROGRADES OVER
GREENLAND...AN UPPER LOW WILL BE SEPARATED AND HEAD SOUTH THROUGH
JAMES BAY INTO LAKE SUPERIOR. BEFORE A TROUGH DEEPENS ALONG THE
EASTERN CONUS THIS WEEKEND...AND AN AREA OF LOW PRESSURE IS FORCED
OUT OF THE GULF OF MEXICO...HIGH CLOUDS WILL OVERSPREAD THE AREA
AND MAKE FRIDAYS MAX T A LITTLE TRICKY. A SOONER ARRIVAL OF THE
CIRRUS SHIELD MAY LEAD TO A COOLER SOLUTION. SOME LIGHT SNOW MAY
BE POSSIBLE ALONG THE EXTREME SW CWA LATE FRIDAY NIGHT...AS JET ENERGY
ROUNDS THE LAKE SUPERIOR UPPER LOW...BUT THIS SHOULD TO HOLD OFF
UNTIL SATURDAY PM.
&&
.LONG TERM /SATURDAY THROUGH MONDAY/...
THE UPPER LEVEL FLOW WILL SLOWLY AMPLIFY OVER THE WEEKEND.
DRY INITIALLY...WILL HAVE TO MONITOR CLOSELY FOR SURFACE LOW
PRESSURE DEVELOPMENT ALONG THE SOUTHEAST COAST. ON SATURDAY...
SURFACE RIDGE IS STILL HANGING ACROSS THE COUNTY WARNING AREA.
THIS WILL RESULT IN CONTINUING DRY WEATHER THROUGH THE EARLY PART
OF THE WEEKEND. AS THE SURFACE HIGH PUSHES NORTHEAST...UPPER LEVEL
TROUGHING WILL MOVE OVERHEAD BY LATE SATURDAY.
A SURFACE LOW IS EXPECTED TO DEVELOP OVER THE GULF OF MEXICO AND
SLIDE EAST ACROSS FLORIDA AND OVER THE ATLANTIC. BOTH THE GFS AND
ECMWF SHOW THIS LOW PRESSURE SYSTEM MOVING FAR EAST ACROSS THE
ATLANTIC WHILE A SECONDARY LOW DEVELOPS ON A WAVE ALONG THE
SOUTHEAST COAST. THIS LOW WILL DEEPEN AS IT RIDES NORTHEAST
WITH THE GFS INDICATING A STRONGER AND DEEPER LOW THAN THE ECMWF.
THERE ARE STILL UNCERTAINTIES BEING IN THE EXTENDED WITH THE ECMWF
CONTINUING TO BE SLOWER THAN THE GFS.
COLD AIR ADVECTION FILTERS IN BY THE END OF THE WEEK AND GETS
STRONGER BY LATE WEEKEND. IF THE TREND KEEPS UP...THE TEMPERATURES
WILL DEFINITELY BE COLD ENOUGH FOR SNOW BUT THE QUESTION OF HOW MUCH
MOISTURE WILL BE IN PLACE STILL REMAINS A MYSTERY. THE LATEST RUN OF
THE ECMWF SHOWS MUCH LESS PRECIP THAN THE PREVIOUS RUN WHICH MATCHES
MORE WITH THE GFS. AT THIS TIME...ONLY HAVE SLIGHT CHANCE POPS GOING
FROM WEST TO EAST THROUGH SUNDAY NIGHT BEFORE TAPERING OFF IN THE
EAST. WITH THE NORTHWESTERLY FLOW...LINGERING SNOW SHOWERS WILL
IMPACT THE FAVORABLE UPSLOPE REGIONS OF THE FORECAST AREA.
TEMPERATURES WILL CONTINUE COOLING THROUGH THE WEEKEND WITH THE
MOUNTAINS LOWERING INTO THE UPPER 30S...WHILE THE PIEDMONT WILL DROP
INTO THE MID 40S BY SUNDAY. MIN TEMPS WILL FALL IN THE RANGE FROM
UPPER TO LOWER 20S ACROSS THE BOARD.
&&
.AVIATION /16Z TUESDAY THROUGH SATURDAY/...
AVIATION CONDITIONS THIS MORNING ARE HIGHLY VARIABLE ACROSS THE
AREA. THE PIEDMONT AND FOOTHILLS HAVE BEEN FLUCTUATING BETWEEN LOW
CIGS IN THE 1-6 HUNDRED FOOT RANGE...AND WITH SUB IFR VSBYS. THE
INVERSION LOCATED HERE WILL BREAK OUT BY MIDDAY WITH A COLD FRONT
WONDERING THROUGH PICKING THE WINDS UP OUT OF THE WEST. FOR
NOW...KEEPING LYH/DAN SOCKED IN WITH IFR/LIFR CONDITIONS UNTIL
ABOUT 18Z...WITH THE WINDS PICKING UP THEREAFTER BRINGING THEM TO
VFR.
ROANOKE WILL STAY VFR ALTHOUGH CANNOT RULE SOME MVFR CIGS IN
SMALLER TIME INCREMENTS UNDER 30 MINUTES THIS MORNING WITH COLD
FRONTAL PASSAGE. WINDS WILL PICK UP HERE AND GUST TO 25 TO 30 KNOT
ARUOND 00Z THIS EVENING.
FURTHER WEST...BLF AND LWB WILL STAY DOWN MOST OF THE PERIOD AS
UPSLOPE WEST TO NW FLOW KEEPS CIGS DOWN IN THE IFR TO MVFR RANGE
THRU THE DAY WITH CIGS LIFTING TO MVFR AND VFR THIS EVENING WITH A
SURGE OF WIND PUSHING IN. LEFT OUT PRECIP AT BLF/LWB BUT CANNOT
RULE OUT A LIGHT RAIN OR SNOW SHOWER.
PAST THIS PERIOD...LOOKING AT HIGH PRESSURE DOMINATING THRU
FRIDAY. SHOULD SEE VFR CONDITIONS...ALTHOUGH CANNOT RULE OUT LATE
NIGHT FOG IN LWB/LYH WITH MOIST GROUND.
&&
.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/WP
NEAR TERM...PM/WP
SHORT TERM...KM
LONG TERM...REB
AVIATION...AMS/WP
HYDROLOGY...PM
