FXUS61 KRLX 012149
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
450 PM EST TUE DEC 1 2009
.SYNOPSIS...
VIGOROUS LOW SYSTEM PASSES WEDNESDAY NIGHT...FOLLOWED BY COLDER
WEATHER THURSDAY AND FRIDAY. A WEEKEND SYSTEM MAY BRUSH THE AREA
WITH LIGHT SNOW...THEN HIGH PRESSURE IS BACK SUNDAY AND MONDAY.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
SFC HIGH PRESSURE CENTERED OVER THE CAROLINAS SHIFTS EAST
TONIGHT...AS VIGOROUS WAVE WORKS N ALONG THE APPALACHIAN MOUNTAIN
CHAIN BY WEDNESDAY. OVERUNNING MOISTURE IN THE FORM OF MID TO HIGH
LEVEL CLOUDS WILL SPREAD NORTH TONIGHT WITH GRADUAL MOISTENING OF
THE ATMOSPHERIC COLUMN.
DIFFERENCES WERE STILL APPARENT BETWEEN THE 12Z RUNS OF THE GFS AND
NAM. GFS WAS A LITTLE FASTER WITH TRANSITION LOW DEVELOPMENT AND
NORTHWARD MOVEMENT THAN THE NAM. FOR TIMING THE ONSET OF PRECIP FROM
NORTH TO SOUTH...SPLIT THE DIFFERENCE BETWEEN THE NAM GFS
SOLUTION...WHICH COINCIDES WITH SREF AND PREVIOUS FCST TIMING.
BOTH MODELS PAINT DECENT LLJ OVER WV AS LOW DEEPENS WEDNESDAY...WITH
VALUES REACHING AS HIGH AS 75 KTS. ISSUING WND ADVSY FOR EASTERN
MOUNTAINS FOR MID MORNING WEDNESDAY...THROUGH WEDNESDAY EVENING. FOR
TEMPS...NOTED THAT THERE WAS NOT A LARGE AMOUNT OF SPREAD BETWEEN
GUIDANCE VALUES...WHICH TRANSLATED INTO GENERAL FOLLOWING THE METBC
GRIDS WITH A FEW MINOR ADJUSTMENTS.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
GFS TRACKS LOW NE ACROSS FCST AREA WED NT WHILE ECMWF AND NAM
FARTHER W...UP THROUGH OHIO. EASIEST MODEL ADJUSTMENT OR MODEL
CHOICE TO MAKE IN METEOROLOGY IS WESTWARD TRACK OF LOW CENTERS
TRACKING N TO NE THROUGH THIS CWA. THUS ROLLED WITH NAM TRACK WHICH
IS ALSO A BIT SLOWER...AND THE COMBINATION SLOWS THE ARRIVAL OF
COLDER AIR FROM THE W AS THE SYSTEM PASSES.
RAIN WEDNESDAY NIGHT SHOULD TAPER GENERALLY FROM SW TO NE AS SFC LOW
AND POTENT UPPER LEVEL TROUGH MOVE THROUGH. USED SREF POPS AS A
STARTING POINT. WHILE CANNOT RULE OUT THUNDER IN WARM SECTOR JUST
AHEAD OF COLD FRONT WITH GOOD LLJ...OPTED TO LEAVE OUT OF FCST FOR
NOW. PERUSAL OF VARIOUS MODEL QPF OUTPUT SUGGESTS NO THREAT FOR
EXCESSIVE RAINFALL...THIS AIDED BY SE FLOW RAIN SHADOW PRIOR TO THIS
PERIOD.
WIND ADV QUITS LATE IN THE EVENING AS LOW PRESSURE CENTER IS BROAD
ENOUGH TO TAKE OUT GRADIENT AHEAD OF IT EVEN AS IT TRACKS THROUGH
OHIO.
UPSLOPE EVENT THU AND CONTINUES THU NT AND THEN GRADUALLY TAPERS OFF
FRI. WIND DIRECTION...A LITTLE S OF W...AND MARGINAL ICE CRYSTAL IN
CLOUD POTENTIAL SPELL ONLY MINOR ACCUMULATIONS OVER THE HIGHER
TERRAIN AS ARCTIC AIR MASS MODIFIES INITS TREK ACROSS THE DEEP S
BEFORE ARRIVING HERE.
LOWS WED NT DEPEND UPON TIMING OF THE ARRIVAL OF COLD AIR...STILL
FAST ENOUGH TO GO WITH THE LOWER MAV NUMBERS THOUGH STILL LEARY OF
THE HIGHER NAM PANNING OUT. AS IT IS...FCST IS HIGHER THAN PREV.
TEMPERATURES DO NOT MOVE MUCH THU THOUGH DIFFERENCES IN THE GUIDANCE
DO NOT REALLY REFLECT A PATTERN. TEMPERATURES THU NT AND FRI WERE
ALSO RAISED A BIT TO REFLECT THE NEWER GUIDANCE...SO A WARMER FCST
OVERALL WITH THE MODIFIED AIR MASS MOVING IN.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
GFS WAS TEASING US WITH ITS 06Z RUN THIS MORNING...BRINGING A
SOUTHERN STREAM SHORTWAVE OVER REGION WITH PLENTY OF GULF MOISTURE
ON FRIDAY NIGHT AND SATURDAY...A SETUP THAT COULD HAVE BROUGHT
SEVERAL INCHES OF SYNOPTIC SNOW TO MUCH OF THE REGION.
HOWEVER...THE 12Z RUNS OF THE GFS/ECMWF/GEM DIG THE SHORTWAVE
FURTHER SOUTH INTO THE TENNESSEE VALLEY BEFORE TURNING IT NORTHEAST.
AT BEST...IT LOOKS LIKE WE MAY BE GRAZED BY THE NORTHWESTERN FRINGE
OF SYNOPTIC SNOW SHIELD...AND WOULD NOT BE SURPRISED IF TRENDS
CONTINUE AND SYSTEM MISSES US ALTOGETHER. HAVE CHANCE POPS EAST OF
THE OHIO RIVER ONLY FOR THIS SYSTEM FOR NOW...AND DO NOT THINK
SYSTEM IS WORTHY OF AN HWO MENTION.
HAVE A SHORT PERIOD OF UPSLOPE ACTIVITY IN THE NORTHERN MOUNTAINS
SATURDAY NIGHT BEHIND SYSTEM...WHILE THE LOWLANDS DRY OUT. PATTERN
THEN TRANSITIONS TO A ZONAL PATTERN ALOFT WITH HIGH PRESSURE IN
PLACE AT THE SURFACE FOR SUNDAY AND MONDAY. THE RESULT WILL BE DRY
WEATHER...OCCASIONAL BOUTS OF MID/HI CLOUDS IN FAST FLOW ALOFT...AND
TEMPERATURES MODERATING BACK TO SEASONAL LEVELS. USED HPC NUMBERS
FOR TEMPERATURES WITH SOME TWEAKING. A WEAK DISTURBANCE IN THE FLOW
MAY PRODUCE PRECIPITATION FOR TUESDAY...SO HAVE SLIGHT CHANCE POPS
IN THE GRIDS FOR THAT.
&&
.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
VFR CONDITIONS AND LIGHT WINDS FOR REMAINDER OF DAY UNDER SURFACE
HIGH PRESSURE. MID AND HIGH LEVEL CLOUDS ADVECT IN TONIGHT.
INCREASING PRESSURE GRADIENTS...ESPECIALLY OVER THE EASTERN
MOUNTAINS LEAD TO SHORT PERIOD OF LLWS AT KBKW AND KEKN BEFORE BL
MIXING OCCURS WED MORN. SE WINDS CONT TO INCREASE THROUGH THE DAY
WEDNESDAY...WITH LOWERING AND THICKENING CLOUDS AS STRONG STORM
SYSTEM APPROACHES FROM THE SW.
AFTER 18Z WEDNESDAY...
IFR POSSIBLE IN RAIN WEDNESDAY AFTERNOON AND NIGHT.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...WIND ADVISORY FROM 10 AM TO 10 PM EST WEDNESDAY FOR WVZ033>038-
046-047.
OH...NONE.
KY...NONE.
VA...WIND ADVISORY FROM 10 AM TO 10 PM EST WEDNESDAY FOR VAZ003-004.
&&
$$
SYNOPSIS...KMC/TRM/CL
NEAR TERM...KMC
SHORT TERM...TRM
LONG TERM...CL
AVIATION...KMC
