FXUS61 KRLX 110250
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
946 PM EST THU DEC 10 2009
.SYNOPSIS...
WIND GRADUALLY SUBSIDES THROUGH TONIGHT...AS COLD HIGH PRESSURE
BUILDS IN TO YIELD DRY WEATHER THROUGH SATURDAY. ANOTHER SYSTEM
PASSES SOUTHWEST TO NORTHEAST SUNDAY MORNING. COLD FRONT TUESDAY.
&&
.NEAR TERM /THROUGH FRIDAY/...
NO CHANGES ON EVENING UPDATE.
PREVIOUS DISCUSSION...
VIS SAT AT 18Z WAS SHOWING A DECREASING TREND TO THE STRATOCU OVER
MOST OF THE CWA...WITH THE NORTHERN MTNS CONT TO BE MAINLY OVC. WITH
THE ATMOS CONT TO DRY OUT FROM THE TOP DOWN...EXPECT MOST AREAS TO
CLEAR OUT BY SUNSET. NORTHERN MTNS WILL BE THE LAST TO CLEAR...AND
HELD THEM IN THE CLOUDS UNTIL THE THERMAL TROF PASSES LATER THIS
EVENING. RADAR RETURNS HAVE ALSO DECREASED OVER THE PAST FEW
HRS...WITH MOST OF THE SNOW FLURRY ACTIVITY CONFINING ITSELF TO THE
NORTHERN MTNS AND ADJ COUNTIES.
WIND CONT TO HOWL ACROSS THE AREA THIS AFTN...AS A DEEP MIXING
LAYER/TO ARND H8/ HAS RESULTED IN CONT MOMENTUM TRANSFER OF ARND
30-35KTS ALONG AND WEST OF THE OH RVR...WITH COMMON 25-30KT GUSTS
ACROSS THE LOWLANDS AND MTNS. EXPECT THESE WINDS TO GRADUALLY
DIMINISH FROM WEST TO EAST LATER TONIGHT AS CAA SUBSIDES WITH THE
PASSAGE OF THE THERMAL TROF. THE NORTH MAY HOLD ON TO THE GUSTS
LONGER WITH MODELS INDICATING A NOCTURNAL ENHANCED JET AT H85...WITH
A LOCALIZED 40KT GUST POSSIBLE ALONG THE HIGHEST RIDGE TOPS/SNOWSHOE.
THIS LEADS TO TEMPS AND THE RESULTING CONUNDRUMS FROM THE WIND AND
CLDS. DESPITE IMPRESSIVE H85 TEMPS BOTTOMING OUT NEAR 16C
TONIGHT...AFOREMENTIONED PUFF SHOULD ALLOW AREAS FROM REALIZING
THEIR FULL POTENTIAL REGARDING MINT. ALSO EXPECT ATLEAST A FEW LOW
CLDS TO HANG ARND THE NORTHERN MTNS FIRST HALF OF TONIGHT IN WNW FLOW
BEFORE CLEARING BY DAWN. THIS COULD FURTHER LIMIT THE TEMP FALL
OVER THAT AREA TONIGHT. HAVING SAID THAT...BELIEVE WITH SUCH COLD
H85 TEMPS AND A CLEARING SKY...WENT A HAIR BELOW MAV GUIDANCE
TOWARD THE LOWER END OF REMAINING GUIDANCE. THIS RESULTS IN NOT
MUCH OF A CHG FROM PREV FCST...WITH LWR TO MID TEENS OUTSIDE OF
THE MTNS...AND EVEN A DEUCE HANGING ACROSS SNOWSHOE. USING FCST
TEMPS/WIND LEADS TO APPARENT T IN THE NEGATIVE TEENS RANGE
OVERNIGHT ACROSS THE NORTHERN MTNS...CONT TO WARRANT WIND CHILL
ADV FOR POCAHONTAS AND RANDOLPH COUNTIES.
AFTER A COLD START FRI MORNING...MOST PLACES SHOULD GET INTO THE
LWR-MID 30S...WITH 20S MTNS/UPR 20S EKN. SFC HIGH WILL SLIDE TO THE
SOUTH WITH A SUNNY DAY ON TAP.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
MAIN ITEM OF CONCERN WILL BE STRONG WARM AIR ADVECTION ALOFT
SATURDAY NIGHT INTO SUNDAY MORNING...WHILE COLD AIR AT SURFACE
REMAINS IN THE MOUNTAINS...AND PERHAPS SOME OF THE NORTHERN
LOWLANDS...LEADING TO FREEZING RAIN POTENTIAL IN THOSE LOCATIONS.
LARGE SURFACE HIGH PASSES OVER THE AREA FRIDAY NIGHT THROUGH
SATURDAY MORNING...WITH VERY DRY ATMOSPHERIC COLUMN YIELDING IDEAL
RADIATIONAL COOLING. GENERALLY WENT AT OR SLIGHTLY BELOW COLDEST
TEMPERATURE GUIDANCE FOR LOWS FRIDAY NIGHT...FOLLOWED BY A BLENDING
OF MODELS FOR HIGHS SATURDAY. HIGH CLOUDS WILL BE NOTICED STARTING
TO STREAM IN FROM THE SOUTHWEST SATURDAY AFTERNOON AHEAD OF THE NEXT
SYSTEM.
NOT MUCH TO POINT AT FOR THE SURFACE WITH THIS NEXT SYSTEM...OTHER
THAN COLD AIR DAMMING FROM SOUTHEAST UPSLOPE AGAINST THE
MOUNTAINS...PROLONGING SUBFREEZING TEMPERATURES UNTIL AFTER
PRECIPITATION BEGINS. THIS SYSTEM WILL BE DRIVEN FROM THE UPPER
LEVELS. AXIS OF 700-750MB FRONTOGENESIS ZIPS SOUTHWEST TO NORTHEAST
THROUGH THE AREA SUNDAY MORNING...WITH TROPOPAUSE FOLD DOWN TO 350MB
AND 300-500MB Q VECTOR CONVERGENCE FOLLOWING BEHIND. QUESTIONS NOW
ARE TIMING AND HOW PHASED THESE FEATURES WILL BE /NAM FOR INSTANCE
HAS A SIGNIFICANT GAP/. AS I SEE THE LATEST ECMWF COME IN...LATER
SHIFTS MAY NEED TO SPEED ONSET OF PRECIPITATION LATE SATURDAY
NIGHT...IF FASTER TREND CONTINUES IN MODELS. WARM WEDGE-BASED WINTRY
MIX APPEARS LIKELY IN THE MOUNTAINS AND PERHAPS FOR A SHORT TIME IN
THE NORTHERN LOWLANDS. SPEED OF THE WHOLE SYSTEM WILL LIMIT OVERALL
ICE ACCUMULATION...BUT POTENTIAL FOR MORE THAN A TENTH OF AN INCH
ICE EXISTS IN THE NORTHERN MOUNTAINS...ESPECIALLY GREENBRIER VALLEY
REGION. AT THIS TIME IT APPEARS MOST OF LOWLANDS WILL BE WARM ENOUGH
FOR PLAIN RAIN...HOWEVER...WE MAY HAVE TO CONSIDER POSSIBILITY OF
THE COLD GROUND ITSELF PROMOTING SOME INITIAL ICING DESPITE AIR
TEMPERATURES...BECAUSE OF PRIOR ARCTIC AIR MASS.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
FORECAST WAS GENERALLY BASED ON HPC THINKING. A COLD FRONT WILL
PUSH EAST LATE MONDAY NIGHT/EARLY TUESDAY...WITH HIGH PRESSURE
SLOWLY BUILDING IN.
AS FRONT APPROACHES...MODELS INDICATE A WARM LATER WILL SPREAD NORTH
ACROSS THE REGION....SO PRECIP TYPE SHOULD DEPEND ON SURFACE TEMPS.
RAIN SHOULD PREVAIL WITH SOME AREAS OF FREEZING RAIN ACROSS THE
NORTHERN MOUNTAINS AS WELL AS PERRY COUNTY OH AT 12 UTC TUESDAY.
PRECIP SHOULD THEN TURN TO ALL RAIN AS THE SFC TEMPS WARM TUESDAY
AFTERNOON BEFORE TURNING BACK TO SNOW TUESDAY NIGHT.
PRECIPITATION SHOULD THEN GRADUALLY ACROSS THE LOWLANDS TUESDAY
NIGHT INTO WEDNESDAY. HOWEVER...SNOW SHOWERS SHOULD CONTINUE ACROSS
THE MOUNTAIN COUNTIES INTO THURSDAY AS NORTHWEST FLOW DEVELOPS.
PRECIPITATION CHANCES SHOULD THEN INCREASE ACROSS THE ENTIRE AREA
THURSDAY AS A MID-LEVEL SHORTWAVE APPROACHES.
GENERALLY WENT BELOW HPC NUMBERS FOR HIGHS FOR MONDAY/TUESDAY...AS
GUIDANCE WAS ON THE HIGH END OF THE ENSEMBLE NUMBERS...OR EVEN ABOVE
IT. OTHERWISE...MADE TWEAKS TO GUIDANCE TO MATCH UP BETTER WITH
NEIGHBORING OFFICES.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
03Z FRIDAY THRU 00Z SATURDAY...
VFR MOSTLY CLEAR THRU THE PERIOD. GUSTY WEST WINDS CONT ACROSS THE
MOUNTAINS TONIGHT...WITH GUSTS UP TO 35KTS POSSIBLE AT THE HIGHEST
ELEVATIONS. ELSEWHERE...WINDS SUBSIDE BUT STILL MODERATE AT
TIMES...ESPECIALLY NORTH.
AFTER 00Z SATURDAY...
IFR POSSIBLE IN RAIN SATURDAY NIGHT AND SUNDAY.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...WIND CHILL ADVISORY UNTIL 10 AM EST FRIDAY FOR WVZ046-047.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...JSH/MDP/30
NEAR TERM...JMV
SHORT TERM...MDP
LONG TERM...JSH
AVIATION...JMV
