FXUS61 KRLX 040548
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
1249 AM EST FRI DEC 4 2009
.SYNOPSIS...
COLD AIR ADVECTION AND CLOUDS OVERNIGHT...WITH UPSLOPE CAUSING VERY
LIGHT PRECIPITATION IN WV MOUNTAINS. SURFACE RIDGE FRIDAY. SYSTEM
WILL BRUSH AREA SATURDAY...WITH LIGHT SNOW IN THE MOUNTAINS.
&&
.NEAR TERM /THROUGH TODAY/...
A LOT CALMER TONIGHT THAN 24 HOURS AGO. RETURNS GREATER THAN 16 DBZ
GETTING LESS ON RLX 88D. FIGURING THE SNOW SHOWERS OVER THE HIGHEST
ELEVATIONS OF OUR WV MOUNTAINS THIS EVENING MAY STILL END AS SOME
FREEZING DRIZZLE. SHOULD NOT BE WIDESPREAD. NO BIG CHANGES IN OUR
HOURLY WEATHER GRIDS..EXCEPT TO BASE THAT FREEZING DRIZZLE ON A NEW
SET OF HOURLY TEMPERATURES.
FIGURING ON SOME PARTIAL CLEARING IN OUR NE KY AND SE OHIO BEFORE
THIS LONG DECEMBER NIGHT IS OVER. SO...FURTHER E...INCREASED
MINIMUM TEMPERATURE WITH THE OVERCAST HOLDING..
WAS A BIT MORE OPTIMISTIC ON FRIDAY FOR COUNTIES NW OF CRW WITH A
BIT LESS CLOUDS. CLOUDS MAY HOLD TOWARD BKW.
&&
.SHORT TERM /TONIGHT THROUGH SUNDAY/...
MAIN ATTRACTION DURING THIS PERIOD IS AN H500 SHORT WAVE ROTATING
ACROSS ON SATURDAY...WITH AN OFFSHORE ASSOCIATED SURFACE LOW. ECMWF
WAS RECOMMENDED AS THE BEST MIDDLE-OF-THE-ROAD SOLUTION BETWEEN THE
DEEPER NAM AND THE WEAKER GFS. ALL MODELS KEEP THE SURFACE LOW
OFFSHORE AND STRENGTHEN IT AFTER IT LIFTS AWAY. TEMPERATURE
STRUCTURE CLEARLY SUPPORTS AN ALL-SNOW SYSTEM...SO THE ACCUMULATIONS
ARE THE BIG QUESTION.
BASE OF SHORTWAVE TROUGH/VORT MAX GENERALLY STAYS TO THE SOUTH AND
EAST OF THE CWA. WITH UPPER JET PASSING OVER CWA...MUCH OF THE
UPPER DIVERGENCE FROM RRQ FALLS OFF TO THE EAST. EXPECT THE EASTERN
COUNTIES TO GET BRUSHED BY THE DEFORMATION ZONE...WITH FIRST FLAKES
ARRIVING AFTER 06Z SATURDAY...AND OVERSPREADING EASTERN TWO-THIRDS
OF CWA BETWEEN 12Z AND 18Z. HAVE LIKELY POPS GENERALLY ALONG/EAST
OF I-79. MOISTURE IS ALSO A LIMITING FACTOR...WITH PW VALUES STAYING
AT OR BELOW A HALF INCH FOR THE MOST PART. WHILE THE CRYSTAL GROWTH
ZONE WILL BE SUFFICIENTLY MOIST...ABOVE-FREEZING TEMPS CLOSE TO THE
SURFACE WILL HELP LIMIT ACCUMULATION. USED HPC QPF AS A BASIS FOR
LIQUID...AND CAME UP WITH 1-3 INCHES OF ACCUMULATION IN THE
MOUNTAINS...AND GENERALLY AN INCH OR LESS TO THE WEST. MOST OF THIS
WILL FALL BETWEEN 12Z SATURDAY AND 00Z SUNDAY. WHILE THIS IS BELOW
ADVISORY CRITERIA...CANNOT RULE OUT A HEADLINE YET FOR AT LEAST A
FEW COUNTIES...AND WILL MENTION THIS POSSIBILITY IN HWO.
NOT MUCH UPSLOPE ON THE BACKSIDE...WITH MOISTURE DECREASING QUICKLY
AND UNFAVORABLE WIND TRAJECTORY. CLOUDS WILL CLEAR OUT SATURDAY
NIGHT...LEAVING HIGH PRESSURE IN CONTROL FOR SUNDAY. MAY SEE SOME
HIGH CLOUDS IN THE AFTERNOON FROM FAST FLOW ALOFT.
USED A BLEND OF PREVIOUS GRIDS AND BIAS-CORRECTED SREF FOR
TEMPERATURES. THIS WAS AT OR BELOW MET/MAV IN MOST CASES.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
MODELS IN FAIRLY DECENT AGREEMENT WITH THE GENERAL PATTERN THROUGH
THIS PERIOD. WILL FOLLOW A BLEND OF THE ECMWF AND ECMWF
ENSEMBLE...WHICH IS FAIRLY CLOSE TO THE GFS. THIS BRINGS A WEAK COLD
FRONT THROUGH ON MONDAY...WITH A MUCH STRONGER SYSTEM ON WEDNESDAY.
THE SYSTEM ON WEDNESDAY MOVES TO THE WEST OF THE REGION...SO EXPECT
RAIN IN ADVANCE OF THIS SYSTEM. THE AIR BEHIND THE COLD FRONT SEEMS
PLENTY COLD ENOUGH FOR SNOW SHOWERS WEDNESDAY NIGHT INTO THURSDAY.
&&
.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
WIDESPREAD STRATOCUMULUS CEILINGS AT 2 TO 3 KFT BKN TO OVC IN LOWER
ELEVATIONS EXCEPT ABOVE 3 KFT OHIO RIVER W...AND AROUND 1 KFT OVER
MOUNTAINS THROUGH 12Z. SPOTTY DRIZZLE...FREEZING DRIZZLE...LIGHT
SNOW OVER THE MOUNTAINOUS COUNTIES INCLUDING EKN TO BKW...VSBY COULD
BE 3 TO 5 MILES OVER HIGHEST TERRAIN THROUGH 12Z FRI.
AFTER 12Z FRI THROUGH 06Z SAT...CLOUDS BECOMING SCT W TO BKN E AND S
AROUND 4 KFT AND VSBY UNRESTRICTED.
AFTER 06Z SATURDAY...
IFR POSSIBLE IN LIGHT SNOW SATURDAY IN THE MOUNTAINOUS COUNTIES.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...CL/TRM/MDP/RPY
NEAR TERM...KTB
SHORT TERM...CL
LONG TERM...RPY
AVIATION...TRM
