-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRLX 011951
AFDRLX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
251 PM EST SUN DEC 1 2013

.SYNOPSIS...
APPROACHING SYSTEM BRINGS CLOUDS AND LIGHT PRECIPITATION TONIGHT
AND MONDAY. WARMING RESUMES MID WEEK AHEAD OF A LARGER SYSTEM. IT
SLOWLY CROSSES LATE WEEK AS A COLD FRONT. COLDER SATURDAY.

&&

.NEAR TERM /THROUGH MONDAY/...
NO MAJOR CHANGES WERE MADE TO THE PREVIOUS FORECAST. FRONTAL
BOUNDARY AT 18Z ASSOCIATED WITH LOW ACROSS THE GREAT LAKES
STRETCHED SOUTHWEST ACROSS CENTRAL INDIANA INTO SOUTHERN IL. THIS
FRONT WILL MOVE INTO OHIO LATER TONIGHT...AND FINALLY INTO
SOUTHEAST OHIO/VICINITY OF OHIO RIVER AROUND 12-15Z MONDAY...WHERE
IT WILL EVENTUALLY WASH OUT. INCREASING LOW LEVEL MOISTURE WITH
THIS APPROACHING FRONT...AS WELL AS A WEAK SHORTWAVE MOVING
THROUGH THE AREA ON MONDAY...WILL CREATE A SLIGHT CHANCE TO CHANCE
OF POPS ACROSS MUCH OF THE CWA. MUCH OF THIS PRECIPITATION WILL BE
IN THE FROM OF RAIN...HOWEVER...THERE COULD BE SOME PATCHY
FREEZING RAIN/DRIZZLE ACROSS PARTS OF THE NORTHERN MOUNTAIN ZONES
LATE TONIGHT/EARLY TOMORROW. NOT THINKING THERE WILL BE MUCH IN
TERMS OF COVERAGE OF FZRA...AS SURFACE TEMPERATURES WILL BE
BORDERLINE FREEZING AND PATCHY IN COVERAGE...AS WELL AS A LACK OF
SIGNIFICANT MOISTURE. IN FACT...THE LACK OF MOISTURE ABOVE ABOUT
800MB AND THUS LACK OF MOISTURE IN THE CRYSTAL GROWTH ZONE WILL
PREVENT SNOW OR A MIX.

MADE LITTLE CHANGES TO THE TEMPERATURES FOR THE PERIOD...AND
CONTINUED TO HUG THE COLDER SIDE OF GUIDANCE ON MONDAY DUE TO THE
EXPECTED CLOUDY CONDITIONS.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
-- Changed Discussion --
DYNAMIC WEAKNESS ASSOCIATED WITH TROUGH AXIS AND WEAK BAROCLINIC
ZONE TRANSITIONS ACROSS THE OH VALLEY MONDAY NIGHT AS CYCLOGENESIS
TAKES PLACE OFF THE CAROLINAS. WEAK FORCING SHOULD BE ENOUGH TO
SUPPORT CONTINUATION OF LIGHT SHOWER ACTIVITY WITH LOW CHC POPS.

ON TUESDAY AND WEDNESDAY THE FORECAST AREA FALLS UNDER SHORTWAVE
RIDGING AND SOUTHERLY FLOW AT THE SURFACE. THIS WILL HELP ADVECT
WARMER AIRMASS ACROSS THE MIDLANTIC STATES. AS NEXT FRONT
APPROACHES FROM THE WEST...SURFACE GRADIENTS INCREASE AND MORE WARM
AIR ADVECTION TAKES PLACE IN EARNEST ON WEDNESDAY. BOTH THE GFS
AND ECMWF ARE RUNNING ABOUT 6 TO 12 HOURS FASTER WITH EASTWARD
MOVEMENT OF THE FRONT DEPENDING ON WHICH MODEL YOU SELECT. THESE
SOLUTIONS ARE MORE OR LESS IN LINE WITH ENSEMBLE FORECASTS. THE
NAM IS SLOWER AND MORE OF AN OUTLIER TO THE OVERALL MODEL SUITE.
THEREFORE GAVE GREATER DEFERENCE TO THE EURO AND GFS SOLUTIONS.
THE RESULT IS TO BRING AN INCREASE IN POPS FROM THE NORTHWEST BY
LATE WEDNESDAY AFTERNOON WHICH IS A FEW HOURS EARLIER.

FORECAST MIN TEMPS FOR MONDAY NIGHT INDICATE THERE IS NOT MUCH
SPREAD IN GUIDANCE. THE VALUES ARE ALSO FAIRLY CLOSE TO INHERITED
FORECAST. THE SPREAD OF MODEL GUIDANCE INCREASE WEDNESDAY WITH
INCREASING UNCERTAINTY WITH HOW MUCH WARM AIR ADVECTION TAKES
PLACE. NUDGED VALUES TOWARD NUMBERS CARRIED BY GFS AND ECMWF. MET
GUIDANCE LOOKED TO BE ON THE COOL SIDE FOR WEDNESDAY WITH LESS
PREFRONTAL WARMING SHOWN IN ITS GUIDANCE VALUES.
-- End Changed Discussion --

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
MAIN FEATURE THIS PERIOD IS A WAVY COLD FRONT THAT CROSSES THE AREA
AS A LARGE BUT PROGRESSIVE TROUGH THE MIDDLE CONUS.

GFS HAS A LEAD UPPER LEVEL LOW THAT LIFTS THROUGH THE UPPER GREAT
LAKES TUE NT AND WED WHICH THE OTHER MODELS DO NOT HAVE.  THE GFS
USES THIS FEATURE...AND ITS SFC REFLECTION...TO PUSH A COLD FRONT
INTO THE AREA WED...GIVING RISE TO RAIN SHOWERS.  OTHER MODELS HAVE
UPPER LEVEL RIDGING CROSSING THE AREA WED AFTERNOON AND
EVENING...WHICH WOULD KEEP THE WEATHER DRY THROUGH THEN AND THIS IS
IN LINE WITH WPC THINKING.

THE WPC/CMC/ECMWF SCENARIO THEN BRINGS THE COLD FRONT TOWARD THE
AREA THU...BEFORE BEING HELD UP INTO FRI BY WAVES OF LOW PRESSURE
MOVING UP ALONG IT...BENEATH THE BROAD SW FLOW ALOFT OUT AHEAD OF
THE LARGE MID CONUS TROUGH.  THIS INTRODUCES THE CHANCE FOR RAIN
SHOWERS LATE WED NT...THE CHANCE INCREASING THU TO HIGH CHANCE /
LIKELY FOR THU NT THROUGH FRI.  THIS CAPTURES THE TIME THE MAIN
CORRIDOR OF PRECIPITATION SHOULD BE OVER OR NEARLY OVER THE FCST
AREA...WHILE NOT ATTEMPTING TO TIME ANY INDIVIDUAL WAVES AT THIS
DISTANCE.

INCLUDED THE SLIGHT CHANCE FOR THUNDER FOR MAINLY THE MOUNTAINS
AHEAD OF THE FRONT LATE THU GIVEN HIGHER DEW POINTS AND STRONG FLOW.

THE FRONT PUSHES S AND E OF THE AREA FRI NT...WITH POPS GRADUALLY
WANING FRI NT AND SAT.  AN UNDERCUTTING PATTERN IS LIKELY BEHIND THE
FRONT WITH ADDITIONAL WAVES NOT OUT OF THE QUESTION.  WE MAY NEED TO
KEEP A WATCHFUL EYE ON THE LENGTH OF TIME THIS SYSTEM IS TO IMPACT
OUR AREA PER RAINFALL TOTALS...ALTHOUGH THESE WINDOWS DO TEND TO
NARROW AS THE TIME GETS CLOSER.

BLENDED IN BIAS CORRECTED VERSIONS OF THE ECMWFHIRES AND ADJMEX...AS
WELL AS WPC FOR TEMPERATURES.  HAVE IT MILDER AHEAD OF THE SYSTEM
WED AND THU...WITH A TIGHTER BAROCLINIC ZONE REFLECTED IN FCST HIGHS
FOR FRI.  COLDER...DRIER AIR SHOULD SET IN BY THE END OF THE PERIOD
/SUN MORNING/.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
-- Changed Discussion --
18Z SUNDAY THROUGH 18Z MONDAY...
LOW VFR STRATUS DECK ACROSS THE AREA. WILL REMAIN RELATIVELY VFR
UNTIL AFTER 03-06Z...WHEN SOME LOWERING TO MVFR IS
EXPECTED. SOME LIFTING TO LOW VFR IS EXPECTED AFTER 16Z MONDAY.
PATCHY FREEZING DRIZZLE POSSIBLE MAINLY 06 TO 13Z ACROSS THE
NORTHERN MOUNTAINS. LIGHT SURFACE WINDS FOR THE PERIOD.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z MONDAY...

FORECAST CONFIDENCE: MEDIUM.

ALTERNATE SCENARIOS: MORE WIDESPREAD MVFR...OR EVEN LOCAL IFR CIGS
COULD DEVELOP OVERNIGHT THAN CURRENTLY FORECAST.

EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH:   TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW:    TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.

UTC 1HRLY       20   21   22   23   00   01   02   03   04   05   06   07
EST 1HRLY       15   16   17   18   19   20   21   22   23   00   01   02
CRW CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H
HTS CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H
BKW CONSISTENCY  H    H    H    H    H    H    H    M    H    H    H    H
EKN CONSISTENCY  H    H    H    H    H    H    H    H    H    H    M    M
PKB CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H
CKB CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H

AFTER 18Z MONDAY...
IFR CIGS POSSIBLE MONDAY NIGHT/EARLY TUESDAY...MAINLY ACROSS MOUNTAINS.
-- End Changed Discussion --

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...NONE.
OH...NONE.
KY...NONE.
VA...NONE.

&&

$$
SYNOPSIS...KMC/TRM/SL
NEAR TERM...SL
SHORT TERM...KMC
LONG TERM...TRM
AVIATION...SL