FXUS61 KRLX 270326
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
1021 PM EST THU NOV 26 2009
.SYNOPSIS...
COLD NORTHWEST FLOW BRINGS RAIN AND SNOW SHOWERS...WITH ACCUMULATING
SNOW IN THE MOUNTAINS INTO FRIDAY NIGHT. HIGH PRESSURE RETURNS FOR
THIS WEEKEND. COLD FRONT WITH RAIN MONDAY.
&&
.NEAR TERM /THROUGH FRIDAY/...
COLD FRONT TREKKING ACROSS CENTRAL WEST VIRGINIA AT THIS TIME.
MOISTURE IS LIMITED...BUT VORT LOBE OUT AHEAD HAS ALLOWED SCATTERED
SHRA TO SQUEEZE OUT...ALTHOUGH THERE IS ALSO A LOT OF VIRGA.
MODELS GENERALLY AGREE ON H500 TROUGH SWINGING ACROSS CWA THIS
EVENING. AS WAVE TAKES ON A NEGATIVE TILT OVERNIGHT...IT WILL FEED A
DEVELOPING LOW OFF OF THE ATLANTIC COAST. THESE WILL AID IN A
DEVELOPING DEEP NORTHWEST FLOW COLD ADVECTION PATTERN...AND THUS AN
UPSLOPE SNOW EVENT.
MODELS A LITTLE SLOWER WITH ONSET OF TRUE COLD ADVECTION AND
ATTENDANT PRECIP. AFTER FRONTAL PRECIP DEPARTS...SHOULD START TO
SEE FIRST COLD ADVECTION SHOWERS IN THE WEST AROUND 00Z...AND THESE
WILL ROLL EAST WITH TIME. IDEAL NORTHWEST FLOW PATTERN SETS UP
AFTER 06Z...AND THINK THAT MOST WIDESPREAD PRECIP OCCURS BETWEEN
THEN AND 15Z OR SO. THIS IS ALSO THE TIME OF MAX WINDS...WITH GUSTS
OF 20-30 KNOTS POSSIBLE. INCLUDED BLOWING SNOW MENTION AT THE
HIGHEST ELEVATIONS LATE. WITH H850 TEMPS DROPPING BELOW ZERO EARLY
THIS EVENING...THE HIGHER ELEVATIONS WILL BE SNOW ALMOST FROM THE
START. ACROSS THE LOWLANDS...IT WILL TAKE SOME TIME FOR THE
BOUNDARY LAYER TO COOL AS NOTED ON MODELS SOUNDING AND H925 FIELDS.
THINK IT STAYS MOSTLY LIQUID HERE UNTIL AFTER 06Z...WHEN SNOW WILL
BE ABLE TO MIX IN. MAX POPS ARE LIKELY NOT FAR EAST OF
I-77...CHANCE OTHERWISE. COVERAGE DECREASES SLOWLY AREAWIDE ON
FRIDAY. ALTHOUGH H850 THERMAL TROUGH DOES NOT CLEAR MOUNTAINS UNTIL
LATE AFTERNOON OR EARLY EVENING...MOISTURE STARTS TO SIGNIFICANT
WANE AFTER 18Z.
WARM GROUND AND MARGINAL LOW LEVEL TEMPS MEAN VIRTUALLY NO
ACCUMULATION IN THE LOWLANDS. HIGHER UP...DO NOT FORESEE EXCESSIVE
TOTALS. IDEAL DENDRITIC SNOW GROWTH LAYER OF -12C TO -18C IS
GENERALLY ABOVE THE DEEP MOISTURE FOR THE DURATION OF THE
EVENT...SAVE FOR PERHAPS A BRIEF WINDOW AROUND 09-12Z. CLOUD TOPS
SHOULD STAY AT OR JUST BELOW -10C...SO ICE CRYSTALS WILL BE PRESENT
IN THE CLOUDS...BUT MOISTURE DEPTH IS ALSO NOT GREAT AS IT TOPS OUT
AROUND H750/H700. USED HPC LIQUID QPF TO START AND ENHANCED
ELEVATIONS ABOVE 3000 FEET A BIT. ENDED UP WITH 3-6 INCHES ABOVE
3000 FEET FOR THE 24 PERIOD THROUGH 00Z SATURDAY...WITH 1-3 INCHES
IN OTHER AREAS FROM EKN TO BKW. WITHOUT IDEAL DENDRITIC
GROWTH...EXPECTING A FINER SNOW WHICH SHOULD HELP TO KEEP
ACCUMULATIONS DOWN. GIVEN THESE AMOUNTS DO NOT MEET THE COUNTY
AVERAGE CRITERIA AND THE TIME PERIOD OVER WHICH IT OCCURS...WILL NOT
BE ISSUING AN ADVISORY FOR SNOW AT THIS TIME.
AT OR BELOW THE COOLER MOS TEMPERATURES FOR BOTH TONIGHT AND
TOMORROW IN THIS COLD ADVECTION PATTERN.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
A MUCH COOLER...AND DRIER NORTHWEST FLOW WILL BE IN PLACE ACROSS THE
CWA FRIDAY NIGHT AS THE UPPER LOW CONTINUES TO DEPART TO THE EAST.
HOWEVER...A FEW UPSLOPE SNOW SHOWERS WILL CONTINUE TO LINGER FRIDAY
NIGHT/EARLY SATURDAY OVER THE NORTHERN MOUNTAIN ZONES IN THE NW
FLOW. THESE WILL TAPER OFF BY LATE SATURDAY MORNING...AS A RIDGE OF
HIGH PRESSURE BUILDS INTO THE REGION...AND THE FLOW BECOMES MORE
WEST TO SOUTHWESTERLY. GUSTY WINDS WILL CONTINUE TO REMAIN ACROSS
THE HIGHER TERRAIN ON SATURDAY AS LLJ REMAINS IN PLACE.
OTHERWISE...EXPECT DRIER AND WARMER CONDITIONS ACROSS THE CWA FOR
THE WEEKEND. SUNDAY LOOKS TO BE THE WARMEST DAY OF THE EXTENDED...AS
SOUTHERLY FLOW INCREASES IN ADVANCE OF THE NEXT SYSTEM...WHICH WILL
MOVE INTO THE FORECAST AREA LATE SUNDAY EVENING/EARLY
MONDAY...BRINGING A RETURN OF RAIN SHOWERS.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
ALL THE MODELS HAVE NORTHERN STREAM FLOW DOMINATING EARLY NEXT WEEK.
PER HPC...WE ARE FOLLOWING THE OPERATIONAL ECMWF FOR DETAILS AS
OTHER MODELS...ALONG WITH MUCH OF THEIR ENSEMBLES...HAVE TRENDED
TOWARD THIS MOST CONSISTENT ECMWF...WHICH SHOWED THIS SCENARIO
FIRST.
THIS ACCEPTED SCENARIO HAS A COLD FRONT IN THIS NORTHERN STREAM
MOVING STEADILY ACROSS THE OHIO VALLEY ON MONDAY...EXITING THE
MOUNTAINS BY MONDAY NIGHT. MODELS SHOWING A GOOD SLUG OF MOISTURE
AND MILD AIR AHEAD OF THIS FRONT...BUT INSTABILITY REMAINS ALMOST
NIL. THUS...EXPECT A GOOD SLUG OF RAIN MONDAY...WHICH BEING ON THE
LAST DAY OF NOVEMBER WILL LIKELY ERASE OUR POTENTIAL DRIEST NOVEMBER
ON RECORD. WITH MUCH OF THE RAIN BEING POST FRONTAL...HAVE CONTINUED
POPS MONDAY NIGHT...AND INTO TUESDAY MORNING IN THE MOUNTAINS. LOOKS
LIKE ENOUGH COLD AIR ALOFT COMES IN FOR SOME CHANGEOVER TO SNOW
SHOWERS IN THE HIGHER ELEVATIONS OF THE NORTHERN WEST VIRGINA
MOUNTAINS LATER MONDAY NIGHT AND EARLY TUESDAY...WITH LITTLE
ACCUMULATION. THEN...LOOK FOR A BREAK WITH HIGH PRESSURE BUILDING
ACROSS ON TUESDAY AND TUESDAY NIGHT.
MEANWHILE...WHILE THE NORTHERN STREAM HAS MOVED RIGHT ALONG...
SOUTHERN ENERGY IN THE FORM OF A CLOSED UPPER LOW HANGS BACK OVER
THE SOUTHERN PLAINS EARLY NEXT WEEK. THIS SOUTHERN SYSTEM IS THEN
PROGGED TO LIFT NORTHEASTWARD TOWARD THE OHIO VALLEY WEDNESDAY AND
THURSDAY...AS A NEW POWERFUL NORTHERN STREAM SYSTEM DIVES INTO THE
PLAINS STATES. THIS WILL BRING ANOTHER SURGE OF MILD AIR AND A GOOD
SLUG OF MOISTURE FOR RAIN DURING WEDNESDAY INTO THURSDAY TO OUR AREA.
&&
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
COLDER AIR PUSHING INTO THE AREA THROUGH THE OVERNIGHT ON GUSTY W
FLOW WILL RESULT IN CIGS LOWERING TO MVFR AND THEN IFR ESPECIALLY IN
THE MTNS...WHERE SNOW SHOWERS WILL COMMENCE EARLIEST AND BE MOST
NUMEROUS. THE PERIOD OF MOST NUMEROUS SNOW SHOWERS WILL BE THE LATE
OVERNIGHT HOURS THROUGH THE MORNING HOURS FRI...OR ABOUT 06Z-18Z
FRI. IFR VSBY IN SNOW IS LIKELY DURING THIS TIME.
DURING THE DAY FRI...THE FLOW WILL BECOME A BIT MORE WNW AND REMAIN
SOMEWHAT GUSTY MOST OF THE DAY. CIGS WILL LIFT THROUGH MVFR LATER
FRI MORNING AND THEN TO VFR DURING FRI AFTN. IN THE MTNS...CIGS
WILL REMAIN LOW MVFR AS IFR VSBY BECOMES LESS FREQUENT IN FAVOR OF
MVFR OR BETTER.
FLOW ALOFT WILL BE STRONG OUT OF THE WNW.
AFTER 06Z SATURDAY...
NO SIGNIFICANT IFR CONDITIONS ARE EXPECTED AT THIS TIME.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...CL/SL/JMV
NEAR TERM...CL
SHORT TERM...SL
LONG TERM...JMV
AVIATION...TRM
