FXUS61 KRLX 260053 CCA
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
753 PM EST WED NOV 25 2009
.SYNOPSIS...
UPPER LEVEL LOW PRESSURE AND ASSOCIATED COLD FRONT ARRIVE ON
THANKSGIVING. COLD NORTHWEST FLOW LEADS TO ACCUMULATING SNOW IN THE
MOUNTAINS INTO FRIDAY NIGHT. HIGH PRESSURE RETURNS FOR THIS WEEKEND.
&&
.NEAR TERM /THROUGH THURSDAY/...
ONLY A FEW UPDATES NEEDED TO THE FORECAST THIS EVENING...MAINLY TO
SKY COVER AND DEW POINT GRIDS. MUCH OF THE CWA HAS CLEARED OUT THIS
EVENING AS DRIER AIR HAS MOVED IN BEHIND THE EXITING COLD FRONT.
HOWEVER...QUITE A BIT OF CLOUD COVER IS OBSERVED OVER THE SE
OHIO ZONES WHERE CLOUDS HAVE ADVECTED BACK IN. CLOUD COVER IS
EXPECTED TO INCREASE OVERNIGHT AS THE UPPER LOW CONTINUES TO MAKE
ITS EASTWARD PROGRESSION TOWARDS THE REGION. ALTHOUGH SKY COVER HAS
CLEARED ACROSS MOST OF THE CWA THIS EVENING...NOT TOO CONCERNED
ABOUT FOG FORMATION AT THIS TIME. WITH THE DRIER AIR IN PLACE...THE
FACT THAT LOCATIONS WHERE CLEARING HAS TAKEN PLACE RECEIVED THE
LEAST AMOUNT OF RAINFALL TODAY...AND THE EXPECTED INCREASE IN CLOUD
COVER AS THE NIGHT PROGRESSES...THINKING WIDESPREAD FOG IS NOT
LIKELY...ALTHOUGH A LIGHT PATCHY FOG CANNOT BE COMPLETELY RULED OUT
ESPECIALLY IN FAVORED RIVER VALLEYS ESPECIALLY IF EXPECTED CLOUD
COVER DOES NOT REFORM AS FORECAST. OVERNIGHT LOW TEMPERATURES MAY
ALSO FALL BELOW PREVIOUS FORECAST IF CLOUD COVER DOES NOT
REFORM...WILL KEEP AN EYE ON THIS FOR NOW AND UPDATE LATER THIS
EVENING IF NEEDED.
PREVIOUS DISCUSSION FOLLOWS...
COLD FRONT MOVING ACROSS CENTRAL WEST VIRGINIA...WITH MAINLY A LINE
OF CU AND A DEWPOINT DROP ACCOMPANYING IT. WRAPAROUND CLOUDS
ALREADY MOVING BACK INTO SOUTHEAST OHIO. CLOUDS OVER THE WEST
VIRGINIA LOWLANDS ARE ABOUT AT THEIR MINIMUM FOR THE NEXT COUPLE OF
DAYS.
FAIRLY IMPRESSIVE H500 CLOSED LOW WILL ROTATE FROM THE MISSISSIPPI
VALLEY INTO THE MIDDLE OHIO VALLEY BY THE END OF TURKEY DAY. MODEL
TIMING APPEARS SIMILAR...WITH WAVE AXIS IN THE GENERAL VICINITY OF
HTS BY 00Z FRIDAY...BUT NAM IS NOTICEABLY DEEPER THAN GFS/ECMWF.
PREFER THIS WEAKER SOLUTION...WHICH WILL KEEP THE PRE-UPSLOPE
PRECIPITATION RATHER LIGHT. TONIGHT...AS H850 TEMPERATURES LEAK
DOWN WITH TIME...EXPECT A STRATOCUMULUS DECK TO MOVE IN/REFORM WITH
SLOWLY LOWERING CEILINGS. NEXT SURFACE BOUNDARY...WITH MORE OF A
COLD PUNCH THAN THE FRONT TODAY...APPROACHES THE WESTERN CWA BORDER
BY 12Z. MAY SEE ISOLATED SHRA ARRIVE BEFORE THEN ACROSS THE
NORTHWEST THIRD OF CWA. FRONT TRUDGES ACROSS ON THURSDAY. WHILE
H850 TEMPS FALL BELOW ZERO FAIRLY EARLY ON...THE BOUNDARY LAYER IS
SLOWER TO FOLLOW. THUS...IN THE COLD ADVECTION-CREATED SHOWERS
BEHIND THE BOUNDARY...THINK SNOW CHANGEOVER WILL BE MAINLY CONFINED
TO THE RIDGES ABOVE 3000 FEET ON THURSDAY AFTERNOON. ACCUMULATION
WILL ALSO HOLD OFF UNTIL AFTER THEN. DEEPER NORTHWEST FLOW WILL
ALSO BE SETTING UP...AS PRECIP STARTS THE TRANSITION TO A NORTHWEST
UPSLOPE EVENT.
WENT A DEGREE OR TWO ABOVE MET/MAV TEMPERATURES FOR
TONIGHT...FOLLOWING THE BETTER-PERFORMING SREF GRIDS. AT OR A TOUCH
BELOW MET/MAV FOR THANKSGIVING WITH COLD ADVECTION/CLOUDS. DO NOT
THINK COLD INTRUSION IS STRONG ENOUGH FOR A NONDIURNAL TEMPERATURE
TRACE.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
NOTWITHSTANDING DIFFERENCES IN THE DETAILS...STRONG UPPER TROUGH
DIGS INTO THE AREA THU NT AND THEN LIFTS OUT FRI THRU FRI NT. SFC
RESPONSE IS W TO EVENTUALLY WNW MODERATE UPSLOPE FLOW DURING THIS
TIME. COLD ADVECTION IN THIS FLOW THU NT CEASES FIRST THING FRI.
CRYSTAL GROWTH IS ALSO BEST THU NT AS MOISTURE BECOMES SHALLOW
FRI...BUT STILL DEEP ENOUGH TO SUPPORT THE PRESENCE OF CRYSTALS IN
CLOUD. BEST DYNAMICS SET UP E OF THE AREA AS UPPER SYSTEM CLOSES
OFF OVER THE NORTHEASTERN STATES...POSSIBLY RATHER NEAR THE COAST.
USING OROGRAPHIC LIFT TOOLS TO ENHANCE QPF AND THEN CARIBOU TOOL
FOR SNOW RATIO...CAME UP WITH 5 TO 9 INCHES ACROSS THE HIGHEST
WINDWARD TERRAIN...MOSTLY THU NT AND FRI WITH THE HIGHEST 12-HR
VALUES THU NT WHEN CRYSTAL GROWTH AND THEREFORE SNOW RATIO IS BEST.
WITH COUNTY AVERAGES NEAR OF BELOW ADVISORY CRITERIA AND SIMILAR TO
PREV FCST...OPTING TO LEAVE SNOW ACCUMULATION OUT OF HWO FOR NOW
WHILE RETAINING IMPACT IN RWS.
NOT MUCH CHANGE WAS NEED TO TEMPERATURES AS THEY WERE CLOSE TO
LATEST GUIDANCE. TEMPERATURES USUALLY PAN OUT NEAR OR JUST ABOVE
THE HIGHEST GUIDANCE IN A PATTERN LIKE THIS ESPECIALLY GIVEN THE
GROUND IS STILL WARM...NEAR 50F HERE AT RLX. DID MAKE SURE HIGHER
TERRAIN WAS COLD ENOUGH IN RELATION TO LOW LEVEL MODEL FIELDS WITH
H85 VALUES OF -6C TO -8C.
WARM ADVECTION TAKES OVER SAT ON STRONG THOUGH DRY SW FLOW. RAISED
TEMPERATURES TOWARD LATEST MEX GUIDANCE OUTSIDE NORTHERN MTNS AS
LARGER THAN NORMAL DIFFERENCE BETWEEN HTS AND EKN APPEARS LIKELY.
&&
.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
HIGH PRESSURE WITH DRY WEATHER AND A WARMING TREND FOR THE WEEKEND
IS EXPECTED.
THERE IS MUCH DIVERSITY IN THE MODELS IN HANDLING THE LOW PRESSURE
SYSTEM AFFECTING OUR AREA EARLY NEXT WEEK. WHILE ALL THE MODELS
SPLIT THE ENERGY TO SOME DEGREE IN THE HIGHLY AMPLIFIED UPPER TROUGH
THAT APPROACHES US FROM THE WEST...THE PREFERRED SOLUTION PER
HPC...WHICH IS SUPPORTED BY MAJORITY OF ENSEMBLES...WOULD BE THE
OPERATIONAL ECMWF. THIS MODEL HAS THE NORTHERN PORTION OF THE UPPER
TROUGH AND ASSOCIATED COLD FRONT MOVING RIGHT ALONG...WHILE SOUTHERN
ENERGY CLOSES OFF OVER THE SOUTHERN MISSISSIPPI VALLEY BY TUESDAY.
THIS SCENARIO THEN HAS THE COLD FRONT CROSS OUR AREA MONDAY AND
MONDAY NIGHT...THEN STALLING OVER THE SOUTHEASTERN STATES TUESDAY. A
SURFACE WAVE ALONG THE FRONT WITH THE SOUTHERN ENERGY THEN LIFTS
NORTH AND EAST TOWARD THE MID ATLANTIC STATES FOR MID WEEK.
THIS ACCEPTED SOLUTION WOULD HAVE THE BULK OF THE RAIN WITH THIS
FRONT COMING ACROSS MONDAY AND MONDAY NIGHT...FOLLOWED BY SCATTERED
POST FRONTAL RAIN SHOWERS MAINLY SOUTHEAST TUESDAY. GOOD INFLUX OF
MOISTURE WILL BRING A GOOD SLUG OF RAIN...BUT INSTABILITY FOR
THUNDER REMAINS LOW. RAIN THEN WORKS BACK NORTHWARD WITH THE FRONTAL
WAVE ACROSS AT LEAST THE EASTERN HALF OF WEST VIRGINIA WEDNESDAY.
TEMPERATURES WILL BE QUITE MILD AHEAD OF THE FRONT MONDAY. COLD AIR
INTRUSION BEHIND THE FRONT WILL TEMPERED BY THE SOUTHERN SYSTEM
LIFTING UP FOR MID MEEK. THUS...TEMPERATURES WILL FALL BACK TO NEAR
NORMAL BEHIND THE FRONT...WITH SOME REALLY COLD AIR WAITING FOR THE
MID WEEK SYSTEM TO MOVE OUT.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS EXPECTED FOR MUCH OF THE NIGHT...HOWEVER...CIGS WILL
LOWER BACK TO LOW VFR/MVFR TOWARDS EARLY MORNING AS MOISTURE STARTS
TO INCREASE AGAIN. THEY WILL THEN HOVER AROUND THE 3000 FOOT
BOUNDARY INTO THE AFTERNOON...BEFORE LOWERING AGAIN THURSDAY NIGHT.
-SHRA ARE POSSIBLE AFTER 12Z...PARTICULARLY ACROSS NORTHERN WEST
VIRGINIA AND SE OHIO...CREATING BRIEF LOW VFR/MVFR CONDITIONS AS A
COLD FRONT MOVES INTO THE REGION. FRONTAL BOUNDARY WILL BE ALONG
OHIO RIVER BY 12Z...AND ACROSS THE HIGHER TERRAIN OF WEST VIRGINIA
BY 00Z. EXPECT GUSTY WINDS BEHIND FRONTAL PASSAGE...PARTICULARLY
THURSDAY NIGHT. RAIN WILL CHANGE TO SNOW OR A RAIN SNOW MIX AT
ELEVATIONS ABOVE 2500 FEET AFTER 21Z. STRONG SW WINDS ALOFT.
AFTER 00Z FRIDAY...
IFR CONDITIONS EXPECTED AFTER 00Z FRIDAY IN RAIN/SNOW OR SNOW SHOWERS.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...CL/TRM/JMV
NEAR TERM...SL/CL
SHORT TERM...TRM
LONG TERM...JMV
AVIATION...SL
