FXUS61 KRLX 042037
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
337 PM EST FRI DEC 4 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 SATURDAY/...
MAIN FEATURE OF INTEREST IS SYSTEM MOVING THROUGH SATURDAY WITH SOME
ACCUMULATING SNOW FOR MUCH OF THE AREA. HIGH CLOUDS FROM BAROCLINIC
LIFT ARE ALREADY BEGINNING TO STREAM IN AHEAD OF THE SYSTEM THIS
EVENING.
SURFACE LOW IS SET TO MOVE UP THE COAST SATURDAY MORNING...WHILE
SIGNIFICANT UPPER LEVEL AXIS MOVES THROUGH OUR REGION TOWARDS
MIDDAY. IN BETWEEN...AXIS OF FRONTOGENESIS AT THE 700MB LEVEL
ROUGHLY ALONG OR JUST A HAIR EAST OF APPALACHIANS LATE TONIGHT
THROUGH SATURDAY MORNING...ALONG WITH SIGNIFICANT CONVERGENCE OF Q
VECTORS AT UPPER LEVELS THROUGHOUT THE REGION. SO WHILE DYNAMICS
LOOK FAIRLY GOOD WITH THIS SYSTEM...OUR PRECIPITATION WILL ALMOST
EXCLUSIVELY BE CAUSED FROM MID TO UPPER LEVEL FEATURES. THAT BEING
SAID...SATURATED LAYER WILL INCLUDE THE ENTIRE DENDRITIC GROWTH ZONE
/700-500MB IN THIS CASE...WHERE TEMPERATURES WILL BE 12 TO 18 BELOW
ZERO CELSIUS/.
UPPER TROUGH WILL BE MOVING QUICKLY...WHICH WILL CAUSE A RAPID
DIMINISHING OF PRECIPITATION SATURDAY AFTERNOON. ADD INITIALLY WARM
GROUND TEMPERATURES...ALONG WITH SPEED OF SYSTEM...AND IT APPEARS
THAT SNOW ACCUMULATIONS WILL BE FAIRLY LIMITED. DRY AIR AT LOW
LEVELS WILL PRETTY MUCH PREVENT SNOW CHANCES NORTHWEST OF OHIO
RIVER. 1 TO 3 INCHES ACCUMULATION LOOKS LIKELY FROM SW VA COAL
FIELDS...THROUGH THE WV MOUNTAINS. HOWEVER...FAIRLY WARM GROUND
TEMPERATURES WILL VERY MUCH LIMIT ACCUMULATION ON ROADWAYS. HIGHER
ELEVATIONS...AND EXPOSED SURFACES SUCH AS BRIDGES...WILL BE MORE
VULNERABLE. A WINTER WEATHER ADVISORY HAS BEEN ISSUED FOR SW VA AND
MCDOWELL/WYOMING WV...WHERE ADVISORY CRITERIA WILL BE REACHABLE.
FOR LOW TEMPERATURES TONIGHT...FAVORED A BLENDING OF GUIDANCE WITH
CLOUDS LIMITING AMOUNT OF RADIATIONAL COOLING. HOWEVER...WENT COLDER
THAN MAV/MET FOR HIGHS SATURDAY...ESPECIALLY IN CENTRAL TO EASTERN
CWA WHERE NEW SNOW WILL BE ON THE GROUND.
&&
.SHORT TERM /SATURDAY NIGHT 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 /21Z FRIDAY THROUGH WEDNESDAY/...
LOW MVFR STRATUS WILL PERSIST BECAUSE OF LINGERING LOW LEVEL
MOISTURE EAST OF THE OHIO RIVER THROUGH 20Z...AND EVEN UP TO 00Z IN
THE WV MOUNTAINS. HOWEVER...MAIN FEATURE OF INTEREST IS ALREADY
BEGINNING TO STREAM HIGH CLOUDS ACROSS THE AREA OUT OF THE
SOUTHWEST. WE WILL BE ON COLD SIDE OF COASTAL LOW SATURDAY
MORNING...WHILE AN UPPER SYSTEM WILL ALSO MOVE THROUGH OUR REGION
DURING THE DAY SATURDAY. MOISTENING OF THE ATMOSPHERE SOUTHEAST OF
OHIO RIVER WILL CAUSE LOWERING OF CIGS INTO MVFR DURING PREDAWN
HOURS AFTER 06Z...FOLLOWED BY IFR OR WORSE CIGS AND/OR VIS IN
SNOW...ESPECIALLY 11Z-18Z SATURDAY. WORST CONDITIONS ARE EXPECTED IN
SW VA THROUGH THE MOUNTAINOUS AREAS OF WV. NORTHWEST OF OHIO
RIVER...ONLY MVFR AT WORST FOR CIGS.
AFTER 18Z SATURDAY...
THOUGH SNOW WILL QUICKLY FINISH WITH EXIT OF THE SYSTEM SATURDAY
AFTERNOON...IFR OR WORSE CIGS WILL LINGER IN THE MOUNTAINS UP TO
ABOUT 00Z SUNDAY.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...WINTER WEATHER ADVISORY FROM 5 AM TO 7 PM EST SATURDAY FOR
WVZ033-034.
OH...NONE.
KY...NONE.
VA...WINTER WEATHER ADVISORY FROM 5 AM TO 7 PM EST SATURDAY FOR
VAZ003-004.
&&
$$
SYNOPSIS...CL/MDP/RPY
NEAR TERM...MDP
SHORT TERM...CL
LONG TERM...RPY
AVIATION...MDP
