FXUS61 KRLX 040924
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
425 AM EST FRI DEC 4 2009
.SYNOPSIS...
HIGH PRESSURE SCOOTS ACROSS TODAY. LOW PRESSURE TRACKS NORTHEAST
OFF THE EAST COAST TONIGHT THROUGH SATURDAY NIGHT.
&&
.NEAR TERM /THROUGH TONIGHT/...
DRIZZLE CONTINUES EARLY THIS MORNING IN WEAK UPSLOPE FLOW AND
SATURATED LOW LEVELS. DRIZZLE IS LIKELY FREEZING ACROSS HIGH
TERRAIN BUT NOT WIDESPREAD ENOUGH TO WARRANT SPECIAL MENTION.
EXTENDED DRIZZLE INTO THE DAYLIGHT MORNING HOURS TODAY AS UPSLOPE
FLOW GRADUALLY WANES WHILE INVERSION KEEPS LOW LEVEL MOISTURE LOCKED
IN PLACE INTO MIDDAY TODAY.
LOOKS LIKE WESTERN EDGE OF STRATOCU DECK GETS INTO WESTERN EDGE OF
FORECAST AREA BY DAWN...A LITTLE BEHIND DEW POINT GRADIENT.
CLEARING LINE SHOULD CONTINUE SLOWLY E DURING THE DAY BUT ENOUGH LOW
LEVEL MOISTURE REMAINS TO SUPPORT CU FORMING WHERE THE STRATOCU
BREAKS SO CLEARING LINE BECOMES MUCH MORE DIFFUSE.
LOW LEVEL FLOW SWITCHES TO NE SFC VEERING TO SE AND S THROUGH THE
LOW LEVELS FRI NT AS HIGH PRESSURE BUILDS TO THE N AND LOW PRESSURE
SCOOTS FROM THE GULF OF MEXICO TO SOMEWHERE OFF THE SE COAST. IN
RESPONSE...STRATOCU BECOMES REESTABLISHED TONIGHT ON E SLOPES OF
MTNS FIRST AND THEN THROUGHOUT LARGER PORTION OF THE AREA AS H85
FLOW BECOMES SW.
UPPER LEVEL SHORT WAVE TROUGH IS WELL TO THE W OF THE SFC LOW
REFLECTING TILTING OF BAROCLINIC ZONE W INTO THE COLD AIR. WHILE
STRONGEST FORCING IS STILL SHOWN TO BE E OF THE AREA...BROAD BUT
WEAK FORCING OVER FCST AREA WARRANTS INCREASING POPS SE PORTION OF
THE AREA TOWARD DAWN SAT FOR LIGHT SNOW. RAISED SOMEWHAT FROM PREV
PACKAGE WHILE LEANING A BIT FARTHER W AS WELL WITH UP TO ONE HALF
INCH OF SNOW IN VA COUNTIES BY 12Z.
TEMPERATURES WILL NOT MOVE MUCH WITH CLOUD COVER MOST OF THE DAY
TODAY. STAYED WITH ONGOING FSCT FOR THE MOST PART WHICH IS VERY
CLOSE TO WELL CLUSTERED GUIDANCE AND REPRESENTS A SMALL RISE FROM
CURRENT TEMPERATURES. WENT WITH A SOMEWHAT NON DIURNAL TREND FOR
TONIGHT AND RAISED LOWS TO GO ALONG WITH MET AS CLOUDS WILL LIMIT
RADIATIVE COOLING.
&&
.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
MINOR MODEL DIFF REGARDING PLACEMENT OF WEAK CYCLOGENESIS ALONG EAST
COAST ON SAT ALONG WITH TIMING/STRENGTH OF UPR TROF. 00Z NAM CONT TO
BE ON THE WESTERN SIDE OF ENVELOPE REGARDING PLACEMENT OF SFC
LOW...IN RESPONSE TO MORE AMPLIFIED/SLOWER S/W TROF EMBEDDED WITHIN
MEAN TROF. GFS HOWEVER IS MUCH FASTER WITH THE UPR TROF...HENCE THE
ELONGATED SFC WAVE FARTHER OFFSHORE. 00Z GEM GLOBAL/ECMWF OFFER A
SOLUTION CLOSER TO THE NAM AND THATS WHAT WAS USED IN THIS PACKAGE.
THIS WOULD TAKE BULK OF THE QPF WELL EAST OF THE CWA. HOWEVER...THE
S/W TROF THAT SWINGS THROUGH ON SAT BRINGS IT OWN LIFT AND
QPF...WITH THE MODELS TRACKING A STOUT VORT MAX JUST SOUTH OF THE
AREA. MODELS SHOWING GOOD H5-H3 Q VECT CONV WITH THIS...HOWEVER THE
COUPLED FRONTOGENETIC FORCING REMAINS EAST OF THE CWA.
NEVERTHELESS...EXPECTING ANOTHER SHIELD OF PCPN TO BREAK OUT ACROSS
THE WESTERN PIEDMONT/APPALACHIANS. TOP DOWN METHOD RESULTS IN ALL SN
EVERYWHERE...WITH SUFFICIENT MOISTURE/OMEGA IN THE DENDRITE GROWTH
ZONE. THE FLAKES WILL ALREADY BE FLYING IN THE SOUTHERN COAL
FIELDS/SW VA BY 12Z. THE SN WILL QUICKLY OVERSPREAD THE REMAINDER OF
THE MTNS AND EASTERN PORTIONS OF THE LOWLANDS SAT MORNING. THERE
WILL BE SOMEWHAT OF A SHARP GRADIENT...WITH NOT MUCH ALONG AND WEST
OF THE OH RVR. CODED UP CAT POPS FOR THE MTNS...WITH LKLY EXTENDING
WEST TO A LINE FROM WILLIAMS-CHARLESTON-CLARKSBURG. AGAIN...NOT
EXPECTING MUCH OF ANYTHING OH RVR AND POINTS WEST. THE SN WILL TAPER
OFF FROM SW TO NE SAT AFTN AS THE S/W TROF QUICKLY MOVES OUT AND SFC
HIGH BUILDS IN FROM THE WEST. CALCULATED SN AMTS VERY CLOSE TO PRVS
FCST...WITH A COUPLE INCHES FOR THE MOUNTAINS...DWINDLING TO A
COATING NEAR CHARLESTON/WILLIAMSON/CLARKSBURG. HIGHLIGHTED IMPACTS
IN RWS. ADVISORY CRITERIA NOT EXPECTED TO BE MET FOR MOST
AREAS...EXCEPTION BEING SW VA/WYOMING/MCDOWELL...WHERE CRITERIA IS 2
INCHES. DAY SHIFT WILL NEED TO TAKE A CLOSER LOOK TO DETERMINE IF
ANY HEADLINES NEED HOISTING FOR THAT AREA. FRESHENED UP HWO FOR
THOSE AREAS.
A CLEARING SKY FROM WEST TO EAST SAT NIGHT COURTESY OF SFC HIGH.
COULD BE A FEW CIRRUS STREAMING IN FROM THE WEST TOWARD DAWN SUN.
OTHERWISE AN IDEAL RADIATIONAL COOLING SETUP ON TAP.
SHOULD BE A DECENT DAY ON SUN WITH ONLY MID/HIGH CLDS AS FLOW TURN
SW AND WAA COMMENCES AHEAD OF NEXT S/W TROF. THIS TROF WILL PASS
NORTH OF CWA INTO AREA OF CONFLUENCE...WITH A WEAK FRONT PASSING
THROUGH ON MONDAY. MAINTAINED SCHC POPS IN FOR THIS. TEMP PROFILES
INDICATE THERE COULD BE SOME WET SNOW IN ANY PCPN MON SE OH...WITH
SHRA BY THE TIME IT REACHES KANAWHA VALLEY.
FOR TEMPS...UNDERCUT GUIDANCE FOR MAXT SAT EASTERN HALF OF CWA WITH
THE SN. SHOULD STAY BELOW FRZ ACROSS THE MTNS ON SAT...PERHAPS
GETTING A DEGREE OR TWO ABV FRZING KANAWHA VALLEY. MID 30S EXPECTED
OH RVR/SE OH. WITH GOOD RADIATIONAL COOLING AND EXPECTED SNOW COVER
EASTERN HALF OF CWA...UNDERCUT ALL GUIDANCE FOR MINT SAT
NIGHT...WITH OH RVR AND WEST A TICK OR TWO BELOW. WENT MID/UPR TEENS
MTNS...NEAR 20 EASTERN LOWLANDS...LWR 20S POINTS WEST. ON SUN TEMPS
REBOUND INTO LWR 40S IN THE LOWLANDS....WITH 30S ACROSS THE MTNS.
INSERTED A RIDGETOP/VALLEY SPLIT FOR MINT SUN AS WAA WILL BE
COMMENCING. MOST PLACES OUTSIDE OF THE MTNS WARM INTO THE MID 40S ON
MON...A FEW DEGREES LOWER THAT GUIDANCE.
&&
.LONG TERM /TUESDAY THROUGH THURSDAY/...
MODELS IN FAIRLY DECENT AGREEMENT WITH THE GENERAL PATTERN THROUGH
THIS PERIOD. WILL FOLLOW A BLEND OF THE ECMWF AND ECMWF
ENSEMBLE...WHICH IS FAIRLY CLOSE TO THE GFS. THIS BRINGS A WEAK COLD
FRONT THROUGH ON MONDAY...WITH A MUCH STRONGER SYSTEM ON WEDNESDAY.
THE SYSTEM ON WEDNESDAY MOVES TO THE WEST OF THE REGION...SO EXPECT
RAIN IN ADVANCE OF THIS SYSTEM. THE AIR BEHIND THE COLD FRONT SEEMS
PLENTY COLD ENOUGH FOR SNOW SHOWERS WEDNESDAY NIGHT INTO THURSDAY.
&&
.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
WIDESPREAD STRATOCUMULUS CEILINGS AT 2 TO 3 KFT BKN TO OVC IN LOWER
ELEVATIONS EXCEPT ABOVE 3 KFT OHIO RIVER W...AND AROUND 1 KFT OVER
MOUNTAINS THROUGH 12Z. SPOTTY DRIZZLE...FREEZING DRIZZLE...LIGHT
SNOW OVER THE MOUNTAINOUS COUNTIES INCLUDING EKN TO BKW...VSBY COULD
BE 3 TO 5 MILES OVER HIGHEST TERRAIN THROUGH 12Z FRI.
AFTER 12Z FRI THROUGH 06Z SAT...CLOUDS BECOMING SCT W TO BKN E AND S
AROUND 4 KFT AND VSBY UNRESTRICTED.
AFTER 06Z SATURDAY...
IFR POSSIBLE IN LIGHT SNOW SATURDAY IN THE MOUNTAINOUS COUNTIES.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...TRM/30
NEAR TERM...TRM
SHORT TERM...30
LONG TERM...RPY
AVIATION...TRM
