FXUS61 KRLX 281711
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
1211 PM EST SAT NOV 28 2009
.SYNOPSIS...
HIGH PRESSURE THIS WEEKEND. A COLD FRONT BRINGS RAIN LATE SUNDAY
NIGHT AND MONDAY. HIGH PRESSURE RETURNS TUESDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
JUST SOME TWEAKS TO THE FORECAST. LAST OF LOW CLOUDS SHOULD
DISSIPATE OVER THE NORTHERN MOUNTAINS OVER THE NEXT COUPLE OF
HOURS...LEAVING CRYSTAL CLEAR SKIES AREAWIDE FOR THE AFTERNOON.
TWEAKED TEMPERATURES DOWN A DEGREE OR TWO IN HIGHER ELEVATIONS WHERE
THERE IS SNOW COVER...AND RAISED THEM A BIT IN THE WEST IN THIS
DRIER AIRMASS.
&&
.SHORT TERM /SUNDAY THROUGH TUESDAY/...
STRONG COLD FRONT STILL ON TRACK FOR A SUNDAY NIGHT ARRIVAL AS
SURFACE LOW SKIRTS THE SOUTHERN GREAT LAKES. TIMING OF THE FRONT
DEFINED BY NAM FRONTOGENESIS IN THIS DYNAMIC SYSTEM. NORTHWEST FLOW
SETS UP ONCE AGAIN IN THE WAKE OF THE FRONT...WITH THE MID AND UPPER
LEVELS DRYING OUT MUCH QUICKER THAN THE LOW LEVELS. WILL SEE TYPICAL
UPSLOPE AREAS REMAINING OVERCAST THROUGH MONDAY NIGHT...WITH GRADUAL
CLEARING TUESDAY AS SURFACE HIGH PRESSURE PASSES TO THE SOUTH AND
EAST. LONGEVITY OF THE NORTHWEST FLOW COULD RESULT IN SOME LIGHT
SNOW ACCUMULATIONS ACROSS THE HIGHER ELEVATIONS TO THE EAST THROUGH
MONDAY NIGHT AS COLDER AIR FILTERS IN. UPPER LEVEL TROUGH AXIS WILL
PASS BY TUESDAY MORNING AS THE FLOW GRADUALLY TURNS MORE ZONAL BY
THE END OF THE SHORT TERM FORECAST PERIOD.
USED BIAS CORRECTED SREF AND MOSGUIDANCE TEMPERATURE BLEND AS A
STARTING POINT FOR MAX AND MIN T VALUES. TEMPERATURES WILL DROP
BELOW NORMAL BEYOND MONDAY BEHIND THE COLD FRONT.
&&
.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
HAVE TRIMMED BACK SCATTERED POST FRONTAL RAIN AND SNOW SHOWERS TO
MAINLY MOUNTAINS MONDAY NIGHT...AS ALL MODEL GUIDANCE IS MORE
PROGRESSIVE. ANY SNOW ACCUMULATION WILL BE VERY LIGHT AND MAINLY
ABOVE 2000 FEET BEFORE ENDING BY 12Z TUESDAY. HIGH PRESSURE THEN
BUILDS IN FOR TUESDAY WITH DRY AND COOL CONDITIONS.
THE NEXT BIG ISSUE CONCERNS THE FUTURE OF THE SOUTHERN STREAM UPPER
LOW THAT WILL HAVE BEEN LEFT BEHIND OVER THE SOUTHWESTERN U.S. EARLY
NEXT WEEK. THE TRACK AND SPEED OF THIS RATHER POTENT SYSTEM DEPENDS
ON THE NEXT NORTHERN STREAM SHORT WAVE DIVING OVER THE WEST COAST
UPPER RIDGE. THE MAJORITY OF OPERATIONAL AND ENSEMBLE GUIDANCE HAS
THIS ENERGY DIVING INTO THE PLAINS AND AMPLIFYING INTO A DEEP UPPER
TROUGH OVER THE CENTER OF THE NATION BY THURSDAY. THIS ACCEPTED
SCENARIO LIFTS THE SOUTHERN STREAM LOW PRESSURE SYSTEM NORTHEASTWARD
THROUGH THE OHIO VALLEY WEDNESDAY AND THURSDAY. THE OPERATIONAL
ECMWF WAS USED FOR DETAILS IN THIS ACCEPTED SCENARIO. THE GFS
CONTINUES TO BE AN OUTLIER IN PROGRESSING THE NORTHERN STREAM SYSTEM
MORE EASTWARD AND THUS FORCING THE SOUTHERN UPPER SYSTEM TO OUR
SOUTH.
THUS...EXPECT A WARMING TREND WITH INCREASING RAIN CHANCES WEDNESDAY
INTO THURSDAY...WITH SOME COLDER AIR COMING BACK IN BEHIND THE
SYSTEM BY FRIDAY.
&&
.AVIATION /18Z SATURDAY THROUGH WEDNESDAY/...
VFR THROUGH THE PERIOD. P6SM SKC THROUGH 12Z...AFTER WHICH SOME
CIRRUS WILL BEGIN TO STREAM IN AHEAD OF THE NEXT WEATHER SYSTEM.
ONLY ITEM OF NOTE IS LOW LEVEL WIND SHEAR AFTER 06Z...WITH WINDS OF
25-30 KNOTS JUST ABOVE DECOUPLED BOUNDARY LAYER.
AFTER 18Z SUNDAY...
BRIEF PERIODS OF IFR POSSIBLE ALONG COLD FRONT SUNDAY NIGHT INTO
MONDAY.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
&&
$$
SYNOPSIS...26/ARJ
NEAR TERM...CL
SHORT TERM...26
LONG TERM...JMV
AVIATION...CL
