Area Forecast Discussion
Issued by NWS Charleston, WV

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000
FXUS61 KRLX 262054
AFDRLX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
354 PM EST FRI DEC 26 2014

.SYNOPSIS...
HIGH PRESSURE MAINTAINS CONTROL INTO SATURDAY.  A COLD FRONT CROSSES
SATURDAY NIGHT AND SUNDAY.  A WAVE OF LOW PRESSURE MOVES ALONG THE
FRONT SUNDAY.  DRIER...COLDER AIR SLOWLY BUILDS IN TO CLOSE OUT 2014.

&&

.NEAR TERM /THROUGH SATURDAY/...
SURFACE HIGH PRESSURE CENTERED OVER THE SOUTHEASTERN STATES WILL
SHIFT EAST TONIGHT AND SATURDAY...ALLOWING A CONTINUING SOUTHERLY
FLOW ACROSS THE AREA. WHILE THE AIR REMAINS RELATIVELY DRY IN THE
LOWER LEVELS UNTIL LATER ON SATURDAY...MID TO UPPER LEVEL MOISTURE
WILL BE INCREASING ON BROAD SOUTHWEST FLOW ALOFT AS A PROGRESSIVE
UPPER TROUGH WELL TO OUR WEST SHIFTS EASTWARD. MODELS ARE IN BASIC
AGREEMENT ON THE MASS FIELDS...BUT SATELLITE IMAGERY SHOWS THEY ARE
LIKELY TOO SLOW IN ADVECTING THIS MID TO HIGH LEVEL MOISTURE INTO
OUR AREA. MAIN DEVIATION TO THE MODELS WILL BE TO INCREASE CLOUDS
FASTER LATER TONIGHT AND ESPECIALLY SATURDAY...AND IN TURN GO
SLIGHTLY LOWER ON MAX TEMPS SATURDAY. NEVERTHELESS...TEMPS WILL
STILL BE ABOVE NORMAL SATURDAY DESPITE THE CLOUD INCREASE. THE
ATTENDING COLD FRONT REMAINS WELL TO THE WEST...WITH ONLY A SMALL
CHANCE FOR RAIN OVER FAR WESTERN AND SOUTHWESTERN SECTIONS AT THE
END OF THE PERIOD.

TONIGHT WILL BE TRANQUIL WITH VERY LIGHT WINDS AND INCREASING MAINLY
THIN HIGH CLOUDS...ALLOWING FOR RADIATIONAL COOLING TO DROP
TEMPERATURES BELOW FREEZING AGAIN...BUT NOT AS COLD AS LAST NIGHT.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
PATTERN THIS PERIOD IS CHARACTERIZED BY FAST UPPER LEVEL FLOW
THROUGH A CENTRAL CONUS L/W TROUGH...AND A TENACIOUS BAHAMA HIGH
THAT SLOWLY FLATTENS.  S/W TROUGH MINORS OUT AS IT LIFTS ENEWD OUT
OF THE ROCKIES...AND CROSSES THE GREAT LAKES ON SAT.  SECOND S/W
TROUGH A LITTLE BEHIND THE FIRST ONE AND MORE IN THE SRN
STREAM...ALSO MINORS OUT AS IF LIFTS ENEWD...REACHING THE TN VALLEY
ON SUN AND THEN CROSSING THE APPALACHIANS SUN NT.

THE S/W FIRST DRIVES A SW TO NE ORIENTED COLD FRONT INTO THE AREA
SAT NT...AND THEN THE SECOND S/W PUSHES IT ON THROUGH ON SUN EVEN AS
IT GENERATES A FLAT WAVE ALONG IT.  RAIN SHOULD INCREASE FROM W TO E
SAT NT AS THE FRONT MOVES THROUGH.  THE NAM WAS THE FAST OUTLIER
HERE...LEANED MORE TOWARD THE 09Z SREF...WHICH WAS CONSIDERABLY
SLOWER.

SUNDAY FIGURES TO BE A RAINY DAY THROUGHOUT THE AREA WITH THE
APPROACHING S/W GENERATING THE FLAT WAVE ALONG THE FRONT CROSSING
THE AREA.  THE RAIN ONLY GRADUALLY MOVES OUT OF THE AREA SUN NT AND
MON...AS THE UPPER LEVEL FLOW DOES NOT VEER MUCH BEHIND THE EXITING
S/W TROUGH.  HAVE TOTAL QPF WITH THIS PROLONGED EVENT RANGING FROM
ALMOST AN INCH IN THE MOUNTAINS TO TWO DIMES IN OHIO...OFF RFC AND
IN GENERALLY AGREEMENT WITH THE MODELS...ALTHOUGH THE CMC AND GFS
HINT AT A SECOND MAXIMA ALONG THE OHIO RIVER.

THE COLUMN MAY GET JUST COLD ENOUGH TO SUPPORT SNOW SFC AND ALOFT ON
THE BACK SIDE OF THE PRECIPITATION SHIELD OVER THE MIDDLE OHIO
VALLEY MON MORNING...AND IN THE WV MOUNTAINS VERY LATE MON...AS THE
PRECIPITATION DIMINISHES TO A FEW SHOWERS AND / OR DRIZZLE THERE.
THERE MAY BE A BRIEF OPPORTUNITY FOR SLEET OR FREEZING RAIN IN THE
TRANSITION IF SUFFICIENTLY COLD AIR ARRIVES AT THE SFC BEFORE WE
LOSE THE WARM NOSE ALOFT.  THESE PRECIPITATION TYPES MAY EVENTUALLY
NEED CODED IN EXPLICITLY DEPENDING UPON HOW MODELS RESOLVE CURRENT
DIFFERENCES WITH TIMING AND THERMAL STRUCTURE.

USED MAINLY NAM BASED SOURCES FOR TEMPERATURES...EXCEPT LATE MON
WHERE THE INFLUENCE OF COLDER MODELS WAS ALLOWED IN.  THE NAM DOES
NOT SUPPORT SNOW IN THE MOUNTAINS THROUGH 84 HRS.  IN THE
MEANTIME...TEMPERATURES WILL BE STEADY OR SLOWLY FALLING SUN OVER
THE MIDDLE OHIO VALLEY...IN THE WAKE OF THE FRONT.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
OVERALL A FAIRLY QUIET LONG TERM PERIOD. HAVE POPS TAPERING OFF
MONDAY NIGHT AS MOISTURE DEPARTS. BRING BACK IN SOME SLIGHT CHANCE
POPS IN THE MOUNTAINS FOR LATE TUESDAY AND TUESDAY NIGHT WITH 850MB
TEMPERATURE TROUGH AND WEAK 500MB SHORTWAVE TROUGH SLIDING THROUGH.
HIGH PRESSURE NOSES IN FOR WEDNESDAY AND THURSDAY. BOTH GFS AND
ECMWF SHOWING A SYSTEM MOVING OUT OF THE LOWER MISSISSIPPI VALLEY AT
THE END OF THE WEEK...SO DO START INCREASING POPS RIGHT AT THE END
OF THE PERIOD. BLENDED NEW WPC GUIDANCE INTO PREVIOUS FORECAST FOR
TEMPS...AND THEN WENT JUST A TOUCH COOLER ON LOWS.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
18Z FRIDAY THRU 18Z SATURDAY...
HIGH PRESSURE DOMINATES THRU 12Z SATURDAY WITH VFR CONDITIONS UNDER
MOSTLY CLEAR SKY TO SLOWLY INCREASING HIGH CLOUDS.

MID TO HIGH LEVEL MOISTURE WILL INCREASE FROM THE WEST AND SOUTHWEST
SATURDAY WITHIN A LONG FETCH OF SOUTHWESTERLY FLOW ALOFT...BUT WELL
AHEAD OF THE NEXT UPPER DISTURBANCE AND ATTENDING COLD FRONT.
SO...BECOMING VFR CEILINGS AOA 8000 FEET MAINLY WEST BY 18Z...WITH
NO PRECIPITATION EXPECTED. WINDS WILL GENERALLY BE LIGHT FROM THE
SOUTH AND SOUTHWEST.

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

FORECAST CONFIDENCE: HIGH.

ALTERNATE SCENARIOS: NONE.

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       18   19   20   21   22   23   00   01   02   03   04   05
EST 1HRLY       13   14   15   16   17   18   19   20   21   22   23   00
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    H    H    H    H    H
EKN CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H
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 SATURDAY...
IFR POSSIBLE IN RAIN SUNDAY INTO MONDAY.

&&

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

&&

$$
SYNOPSIS...TRM/JMV/MZ
NEAR TERM...JMV
SHORT TERM...TRM
LONG TERM...MZ
AVIATION...JMV





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