129
FXUS61 KRLX 272034
AFDRLX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
315 PM EST FRI NOV 27 2009
SYNOPSIS
COLD NORTHWEST FLOW SNOW SHOWERS WILL WIND DOWN TONIGHT. HIGH
PRESSURE RETURNS FOR THIS WEEKEND. COLD FRONT WITH RAIN MONDAY.
A LOW PRESSURE SYSTEM WITH MORE RAIN WEDNESDAY AND THURSDAY.
NEAR TERM /THROUGH SATURDAY/
VORT LOBE HAS ROTATED OUT OF CWA...AND REMAINING SNOW SHOWERS ARE
BEING DRIVEN PURELY BY NW FLOW. ACCUMULATIONS ARE BASICALLY NIL IN
THE LOWLANDS...AN INCH OR TWO IN THE MOUNTAINOUS COUNTIES...AND 3-4
INCHES AT THE HIGHEST PEAKS SUCH AS SNOWSHOE. H850 THERMAL TROUGH
DOES NOT PULL OUT OF MOUNTAINS UNTIL 06Z TONIGHT OR SO. HAVE
CATEGORICAL POPS ALONG THE NW SLOPES TO START...WANING TO CHANCE BY
THAT THERMAL TROUGH PULLOUT. ANOTHER INCH OR TWO POSSIBLE HIGH
UP...SAY ABOVE 2500 FEET...WITH LESS THAN AN INCH ELSEWHERE AT MOST.
WEST OF THE MOUNTAINS...MOISTURE THINNING SHOULD LEAD TO A SLOW
DECREASE IN CLOUD COVER. EXPECTING MAINLY CLEAR SKIES BY 12Z WEST
OF THE MOUNTAINS.
EXPECT SNOW TO CEASE BY 12Z SATURDAY. HIGH PRESSURE NOSES IN FROM
THE SOUTH AND SOUTHWEST TO PROVIDE PLENTY OF SUNSHINE DURING THE
DAY. FORESEE A SILENT WARM FRONTAL PASSAGE DURING THE DAY...WITH
H850 TEMPS REBOUNDING BACK TO +6/+8C BY 21Z. THIS WILL ALLOW HIGH
TEMPS TO REBOUND BACK TOWARDS SEASONABLE LEVELS.
RAN WITH A GENERAL MET/MAV BLEND FOR LOWS TONIGHT. LIKED A TWEAKED
BIAS-CORRECTED SREF GRID FOR SATURDAY HIGHS...AGAIN AS A GOOD MOS
COMPROMISE.
SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/
FIRST HALF OF THE SHORT TERM WILL CONTINUE TO REMAIN DRY UNDER THE
INFLUENCE OF HIGH PRESSURE AT THE SURFACE AND ALOFT. SATURDAY NIGHT
STILL LOOKS TO BE A NIGHT OF GOOD RADIATIONAL COOLING...ALTHOUGH
HIGH CLOUDS WILL BEGIN TO INCREASE IN ADVANCE OF THE NEXT SYSTEM.
SUNDAY WILL BE THE WARMEST DAY OF THE EXTENDED DESPITE AN INCREASE
IN CLOUD COVER THROUGHOUT THE DAY...AS SOUTHERLY FLOW INCREASES IN
ADVANCE OF AN APPROACHING COLD FRONT. THIS COLD FRONT...AND
ASSOCIATED PRECIPITATION WILL BEGIN TO MOVE INTO THE WESTERN EDGE OF
THE CWA AROUND 06Z...AND EXIT THE CWA AROUND 18Z...WITH MUCH OF THE
PRECIPITATION BEGINNING TO TAPER OFF BEHIND THE FRONT AS DRIER AIR
MOVES INTO THE REGION. MUCH COOLER AIR WILL ALSO MOVE INTO THE CWA
BEHIND THE FRONT...WITH MODEL SOUNDINGS AND THICKNESSES SUGGESTING
PRECIPITATION TURNING TO SNOW OR A RAIN/SNOW MIX OVER THE HIGHER
ELEVATIONS BY MONDAY EVENING. ANY ACCUMULATIONS THAT DO OCCUR WILL
BE LIGHT AS THE GROUND SHOULD STILL BE RELATIVELY WARM...AND DUE TO
THE OVERALL DECREASE IN MOISTURE BEHIND THE FRONT.
LONG TERM /MONDAY 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 /19Z FRIDAY THROUGH WEDNESDAY/
SNOW SHOWERS ARE NOW BEING MAINLY DRIVEN BY COLD NORTHWEST FLOW.
THEY WILL CONCENTRATE IN THE HIGHER ELEVATIONS THROUGH THE EARLY
EVENING HOURS. EKN...AND PERHAPS BKW...MAY BRIEFLY TOUCH IFR FROM
TIME TO TIME. WEST OF THE MOUNTAINS...BRIEF MVFR AT WORST. GUSTY
NW WINDS OF UP TO 20 KNOTS WEST OF THE MOUNTAINS AND 30 KNOTS HIGHER
UP WILL ALSO CONTINUE. SNOW SHOWERS WILL MAINLY SHUT OFF BY
MIDNIGHT...WITH MVFR CIGS LINGERING THROUGH MIDNIGHT OR SO.
MOISTURE DECREASE WILL LEAD TO THINNING CLOUDS OVERNIGHT...ALONG
WITH DIMINISHING WINDS. BY 12Z...SKC WEST OF THE MOUNTAINS WITH A
VFR CEILING PERHAPS LINGERING IN THE MOUNTAINS...WHICH WILL BREAK UP
DURING THE MORNING.
AFTER 18Z SATURDAY...
NO SIGNIFICANT IFR CONDITIONS ARE EXPECTED AT THIS TIME.
RLX WATCHES/WARNINGS/ADVISORIES
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.
SYNOPSIS...CL/SL/JMV
NEAR TERM...CL
SHORT TERM...SL
LONG TERM...JMV
AVIATION...CL
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