FXUS61 KRLX 221110
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
600 AM EST TUE DEC 22 2009
.SYNOPSIS...
BRIEF LIGHT SNOW OR FLURRIES WITH WEAK UPPER AIR DISTURBANCE TODAY
IN MAINLY NORTHERN PART OF THE AREA. DRY TONIGHT THROUGH THURSDAY
MORNING. LOW PRESSURE SYSTEM LATE THIS WEEK INCLUDING THE HOLIDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
DESPITE SURFACE HIGH PASSING OVER THE AREA...THERE IS STILL SOME
SENSIBLE WEATHER TO FORECAST TODAY. BRIEF TROPOPAUSE FOLD...DOWN TO
ALMOST 400MB...COMES THROUGH TODAY ALONG AXIS OF MINOR Q VECTOR
CONVERGENCE. THIS FEATURE IS MORE STRONGLY REPRESENTED VIA THESE
FIELDS IN CURRENT MODEL RUNS COMPARED TO PREVIOUS ONES. THAT BEING
SAID...IT IS STILL A FAIRLY WEAK DISTURBANCE THAT PASSES WITH A DRY
BATCH OF AIR BETWEEN THE BOUNDARY LAYER AND ABOUT 800MB. SO ANY
SNOWFLAKES THAT PASS THROUGH WILL BE VERY LIGHT IF ANY. DESPITE NO
QPF SHOWING IN RAW MODEL OUTPUT /EXCEPT FOR CANADIAN MODEL/...WILL
RESPECT THE UPPER LEVEL DYNAMICS AND UPSTREAM RADAR TRENDS TO
INCLUDE CHANCE OF LIGHT SNOW IN NORTHERN ZONES...AND AT LEAST SOME
SCATTERED FLURRIES IN ROUGHLY THE CENTRAL THIRD OF THE AREA.
ALSO...AND THIS IS NOT A BIG SURPRISE GIVEN THE VERY FAST FLOW
ALOFT...THIS FEATURE APPEARS TO BE AHEAD OF THE MODEL
PACE...ESPECIALLY COMPARED TO PREVIOUS RUNS. FORECAST WAS ADJUSTED
ACCORDINGLY...TO BE QUICKLY IN-AND-OUT OVER THE COURSE OF MID
MORNING THROUGH EARLY AFTERNOON...WITH VERY LITTLE ACCUMULATION IF
ANY.
AS WITH THE LAST COUPLE DAYS...MAV/MET TEMPERATURES APPEAR A LITTLE
TOO MILD GIVEN SNOWPACK FOR MOST OF AREA...AND CLOUD COVER. WENT
CLOSE TO THE BIAS CORRECTED SREF INSTEAD FOR HIGHS TODAY. FOR
TONIGHT...BOUNDARY LAYER MOISTURE TRAPPED UNDER SURFACE RIDGE...WILL
KEEP CLOUD COVER AROUND FOR MOST OF THE AREA...WHICH WILL ALSO LIMIT
DROP OFF IN TEMPERATURES. MOST LOCATIONS SHOULD BE AT OR SLIGHTLY
ABOVE MAV/MET LOWS FOR TONIGHT.
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
ALL MODELS HAVE NEXT STRONG LOW PRESSURE SYSTEM AFFECTING OUR AREA
LATE THURSDAY INTO CHRISTMAS DAY FRIDAY. MODEL TIMING DIFFERENCES IN
THE SPEED OF THE SYSTEM HAVE BEEN GREATLY RESOLVED...WITH THE
GENERAL TREND TO GO WITH A SLOWER SOLUTION. THE TRACK OF THIS SYSTEM
WILL BE WELL TO THE WEST...UNLIKE THE LAST SYSTEM...AND WILL LIFT
NORTH NORTHEAST FROM THE SOUTHERN PLAINS THURSDAY INTO THE UPPER
MISSISSIPPI VALLEY ON CHRISTMAS DAY. THIS WILL PUSH A WARM FRONT
NORTHWARD ACROSS OUR REGION THURSDAY NIGHT...FOLLOWED BY A COLD
FRONT FROM THE WEST CHRISTMAS DAY.
THIS SCENARIO WILL PUT MOST OF OUR AREA ON THE MILD SIDE WITH RAIN.
HOWEVER...WITH THE TRACK BEING THIS FAR WEST...AND STRONG COLD HIGH
PRESSURE RIDGING SOUTHWARD EAST OF THE MOUNTAINS TO PROVIDE COLD AIR
DAMMING...THE PRECIPITATION MAY BEGIN AS A WINTRY MIX IN THE
NORTHERN AND CENTRAL WEST VIRGINIA MOUNTAINS THURSDAY NIGHT
ESPECIALLY EAST FACING SLOPES. THIS MAY CONTINUE INTO FRIDAY
MORNING...BEFORE THE MILDER AIR FINALLY WORKS IN. THUS...THERE IS A
POTENTIAL FOR SIGNIFICANT ICING...WHICH WILL BE MENTIONED IN
HAZARDOUS WEATHER OUTLOOK AND IMPACT PRODUCTS. IN ADDITION...850 MB
SOUTHERLY LOW LEVEL JET WITH THIS RAIN BAND MAY PROVIDE GUSTY WINDS
ON MOUNTAIN RIDGETOPS THURSDAY NIGHT.
RAINFALL AMOUNTS WITH THIS SYSTEM LOOK TO BE TRENDING DOWN...
GENERALLY AROUND HALF AN INCH NOW. GIVEN THIS DOWNTREND OF
AMOUNTS...WILL HOLD OFF ON ANY MENTION OF WATER PROBLEMS FROM THE
HEAVY SNOW PACK AT THIS TIME. FOR NOW THE BIGGER ISSUE IS ICING
POTENTIAL IN THE NORTHERN AND CENTRAL MOUNTAINS.
COLD FRONT SWEEPS THRU ON FRIDAY...WITH RAIN CHANGING TO POST
FRONTAL RAIN SHOWERS...THEN TO SNOW SHOWERS FRIDAY NIGHT AS COLDER
AIR WRAPS AROUND THE DEPARTING LOW PRESSURE SYSTEM.
&&
.LONG TERM /SATURDAY THROUGH MONDAY/...
FRIDAY NIGHT IS BEGINNING TO LOOK LIKE A MESSY NIGHT AS LATEST
MODELS DO NOT BRING IN THE COLD AIR ALOFT UNTIL AFTER 00Z IN THE
WEST AND 06Z IN THE EAST. WITH THIS IN MIND...APPEARS PRECIPITATION
IN THE MOUNTAINS COULD BE A WINTRY MIX OF RAIN...TO FREEZING
RAIN/SLEET TO SNOW WITH THE PRECIPITATION. ACROSS THE LOWLANDS...
THE PRECIPITATION SHOULD GENERALLY CHANGING TO A MIX OF RAIN/SNOW
AND THEN ALL SNOW. HAVE GONE WITH A NON-DIURNAL TEMP CURVE AS TEMPS
SHOULD NOT FALL ACROSS THE HIGHER ELEVATIONS UNTIL LATER.
THE REGION SHOULD THEN REMAIN UNDER THE INFLUENCE OF AN UPPER LEVEL
LOW...WITH CONTINUED CHANCES OF SNOW SHOWERS THRU THE WEEKEND.
SURFACE HIGH PRESSURE THEN BUILD IN LATE IN THE PERIOD...SHUTTING
OFF ANY PRECIP CHANCES.
GENERALLY USED HPC TEMP GUIDANCE...WITH SOME TWEAKS TO REFLECT
LATEST ENSEMBLE GUIDANCE.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
MOST OF THE AREA WILL BE MVFR THIS MORNING. HOWEVER...SOME OF THE
CENTRAL LOWLANDS WILL HAVE IFR TO EVEN LIFR VIS DUE TO FOG...THOUGH
ABOUT 14Z OR SO. THIS IS BECAUSE SLOWLY MELTING SNOW THE LAST COUPLE
OF DAYS HAS ADDED ABUNDANT MOISTURE TO THE BOUNDARY LAYER...WHICH IS
NOW TRAPPED UNDERNEATH A SURFACE HIGH. ALSO...A BAND OF FLURRIES
WILL IMPACT THE CENTRAL TO NORTHERN PART OF THE REGION MIDDAY
THROUGH AFTERNOON...ALONG WITH CIGS STAYING IN MVFR CATEGORY FOR
MOST LOCATIONS. CONTINUED TRAPPED MOISTURE IN BOUNDARY LAYER LEADS
TO RETURN OF AT LEAST MVFR CONDITIONS AREAWIDE LATE THIS EVENING
THROUGH 12Z WEDNESDAY...WITH SOME LOCATIONS HITTING IFR AGAIN.
AFTER 12Z WEDNESDAY...
SYSTEM IMPACTS AREA THURSDAY NIGHT INTO FRIDAY...WITH RAIN AND
POSSIBLE IFR. FREEZING RAIN ALSO A THREAT IN THE WV MOUNTAINS.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...MDP/JMV
NEAR TERM...MDP
SHORT TERM...JMV
LONG TERM...JSH
AVIATION...MDP
