FXUS61 KRLX 050542
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
1242 AM EST SAT DEC 5 2009
.SYNOPSIS...
SURFACE LOW HEADS UP COAST...WHILE UPPER LEVEL WAVE PASSES THROUGH
WITH SOME SNOW FOR MUCH OF AREA...ON SATURDAY. HIGH PRESSURE
SUNDAY...THEN WEAK COLD FRONT MONDAY. STRONGER SYSTEM MIDWEEK.
&&
.NEAR TERM /THROUGH TODAY/...
WAS A BIT FASTER ON THE SNOW REACHING THE GROUND DURING THE 3 AM
TO 6 AM PERIOD IN THE SOUTH. THE OHIO RIVER COUNTIES STILL SEEM TO
BE ORIENTED ALONG THE POP GRADIENT/WESTERN EDGE. WE HAVE 3 TO 4
INCHES IN OUR CENTRAL WV MOUNTAINS...WHICH IS CLOSE TO THE HIGHER
ADVISORY CRITERIA IN THESE MOUNTAINS. WILL DIGEST 00Z MODELS AND
WATCH RADAR TRENDS DURING THE NIGHT. IF THE TREND IS UP BY ONLY AN
INCH...WILL EXPAND THE ADVISORY HEADLINE. WENT A BIT COLDER IN
RURAL AREAS SATURDAY NIGHT WITH THE CLEARING.
&&
.SHORT TERM /TONIGHT THROUGH MONDAY/...
FIGURE THAT MOST OF THE ACCUMULATING SNOW WILL BE OVER BY 00Z
SUNDAY. MOISTURE DEPTH WANES QUICKLY IN THE EVENING...DROPPING
BELOW THE IDEAL DENDRITIC GROWTH ZONE. THERE MAY BE A BRIEF PERIOD
OF UPSLOPE SHSN ON THE BACKSIDE OF THE DEPARTING H500 TROUGH...BUT
WIND TRAJECTORY IS NOT IDEAL AND AGAIN A LACK OF MOISTURE WILL END
THESE BY MIDNIGHT. WILL ONLY HAVE A COUPLE TENTHS OF ADDITIONAL
ACCUMULATION AT MOST IN THE NORTHEAST CWA.
PATTERN THEN TRANSITIONS TO A QUASI-ZONAL FLOW PATTERN WITH WSW FLOW
ALOFT...WITH HIGH PRESSURE IN CONTROL AT THE SURFACE THROUGH SUNDAY
NIGHT. DRY AIRMASS OVERALL BUT EXPECTING MID/HI CLOUDS FROM TIME TO
TIME...WITH A SLOW INCREASE IN THESE WITH TIME. SLOW RISE IN H500
HEIGHTS/MODERATING H850 TEMPS POINT TO MORE SEASONABLE TEMPERATURES
AT THE SURFACE INTO MONDAY.
SOME DIFFERING SOLUTIONS WITH WEAK FRONTAL BOUNDARY EARLY NEXT
WEEK. NAM APPEARS TO BE THE SLOWEST OF THE VARIOUS
GUIDANCE...KEEPING THE BOUNDARY OFF TO THE WEST THROUGH 00Z
TUESDAY. MOST OTHER MODELS ARE FASTER...BUT TIMING WILL BE AN ISSUE
IN THIS FAST FLOW. AT ANY RATE...WITH MAIN SHORTWAVE REMAINING OFF
TO THE NORTH AND NO MOIST FLOW INTO THE FRONT...LOW POPS ARE
APPROPRIATE IN ANY CASE.
FORECAST TEMPERATURES DO NOT STRAY FAR FROM MOS. USED
BIAS-CORRECTED SREF AND/OR A MET/MAV BLEND FOR THE MOST PART.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
MODELS IN FAIRLY DECENT AGREEMENT WITH GENERAL PATTERN THROUGH THIS
PERIOD. WILL FOLLOW A BLEND OF THE ECMWF AND ECMWF ENSEMBLE.
TEMPERATURES ARE MARGINAL MONDAY NIGHT BEHIND A COLD FRONT FOR
UPSLOPE SNOW SHOWERS. WILL CONTINUE WITH JUST A VERY SMALL POP. A
STRONG SYSTEM THEN MOVES UP WEST OF THE REGION TUESDAY NIGHT AND
WEDNESDAY...PROVIDING A DECENT SHOT OF RAIN. BEHIND THE
SYSTEM...MODELS SHOW A GOOD UPSLOPE SNOW EVENT. IF MODELS HANG ON TO
THIS SOLUTION...EVEN THE LOWLANDS COULD SEE SOME ACCUMULATIONS.
&&
.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
STRATOCUMULUS CEILINGS AT 2 TO 4 THSD FT BKN-EKN-CKB WITH LAYERS
ABOVE. MID CLOUDS THICKENING QUICKLY THROUGH 09Z WITH LIGHT SNOW
REACHING GROUND LNP TO CRW AND BKW BY AROUND 08Z...SPREADING QUICKLY
N TOWARD EKN CKB AND W TO HTS AND EVEN PKB BY 12Z. CEILINGS AOB 1
THSD FT 12Z TO 18Z OVER MOUNTAINS AND VSBY BLO 3 MILES IN SNOW. HTS
TO PKB CORRIDOR ON WESTERN FRINGE OF ANY LIGHT SNOW WITH VSBY
OCCASIONALLY 3 MILES AND CEILINGS 2 TO 4 THSD FT 12Z TO 18Z. COULD
GO IFR VSBY EVEN THERE AT TIMES.
LIGHT SNOW EXITING QUICKLY 18Z SATURDAY TO 00Z SUNDAY WITH CLEARING
REACHING OHIO RIVER NEAR 00Z. CEILINGS LIFTING TO 2 TO 3 THSD FT
BKN TO OVC AND VSBY NR 5-6 MILES IN LINGERING LIGHT SNOW SHOWERS EKN
VCNTY.
AFTER 06Z SUNDAY...
IFR IN RAIN POSSIBLE TUESDAY NIGHT INTO WEDNESDAY.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...WINTER WEATHER ADVISORY FROM 4 AM EARLY THIS MORNING TO 7 PM
EST THIS EVENING FOR WVZ033-034.
OH...NONE.
KY...NONE.
VA...WINTER WEATHER ADVISORY FROM 4 AM EARLY THIS MORNING TO 7 PM
EST THIS EVENING FOR VAZ003-004.
&&
$$
SYNOPSIS...KTB/CL/MDP/RPY
NEAR TERM...KTB
SHORT TERM...CL
LONG TERM...RPY
AVIATION...TRM
