Area Forecast Discussion
Issued by NWS Charleston, WV

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000
FXUS61 KRLX 240309
AFDRLX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
1009 PM EST TUE DEC 23 2014

.SYNOPSIS...
LOW PRESSURE MOVES WEST OF THE AREA BUT BRINGS RAIN TONIGHT AND
WEDNESDAY.  COLD FRONT LATE WEDNESDAY WILL BRING GUSTY WINDS.
CHRISTMAS DAY STARTS COLD...CLOUDY...AND WINDY...WITH SNOW SHOWERS.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
10 PM UPDATE...
FCST ON TRACK. DID RAISE DEW POINTS AHEAD OF THE COLD FRONT WED.

715 PM UPDATE...
ADJUSTED TO FASTER TIMING OF THE RAIN OVER THE MIDDLE OHIO VALLEY
THIS EVENING.  ADDED THUNDER TO HTS TRI-STATE AREA WED
MORNING...WITH DEEPENING LOW PRESSURE PASSING TO THE W...AND STRONG
EARLY MORNING LLJ.  MADE SOME ADJUSTMENTS TO WIND GUSTS DURING THE
ADVISORY WED...KEEPING THE GIST AND REASONING OF THE PREVIOUS FCST
WHICH KEYS IN MAINLY ON THE STRONG COLD ADVECTION DIRECTLY BEHIND
THE COLD FRONT... BUT WITH TIMING AND DETAIL ADJUSTMENTS.

PREV DISCN...
MODELS HAVE DEEPENING SURFACE LOW TRACKING NORTHWARD THRU CENTRAL
KENTUCKY AND WESTERN OHIO LATER TONIGHT AND WEDNESDAY. ONCE THE
SURFACE LOW GETS INTO NORTHERN OHIO LATER WEDNESDAY MORNING...IT
WILL SWEEP A STRONG COLD FRONT EASTWARD ACROSS MUCH OF THE AREA
WEDNESDAY AFTERNOON...REACHING THE MOUNTAINS LATE IN THE DAY. WE
LIKE THE SLIGHTLY FASTER GFS WITH THE FRONT...GIVEN THE
STRENGTHENING PRESSURE GRADIENT AROUND THE LOW.

BUT FIRST...MODELS HAVE A BROAD AND DEEP MOIST SOUTHERLY FLOW AHEAD
OF THE LOW...WITH NUMEROUS UPPER DISTURBANCES TRACKING OVER THE
AREA. LOOKS LIKE WIDESPREAD SHOWERS WILL MOVE IN EARLY TONIGHT AND
QUICKLY OVER OVERSPREAD THE AREA. THERE IS SOME QUESTION AS TO IF
AND WHEN THIS BROAD SHIELD OF SHOWERS WILL END BEFORE THE COLD FRONT
STARTS TO TRACK EASTWARD WEDNESDAY AFTERNOON...AS TRACKING OF
EMBEDDED DISTURBANCES IN THE SOUTHERLY FLOW WILL BE VERY DIFFICULT.
PAST EXPERIENCE HAS SHOWN WITH THESE SYSTEMS THAT THERE WILL BE A
TAPERING OFF OF THE SHOWERS BEFORE THE ORGANIZED BAND OF SHOWERS AND
A FEW THUNDERSTORMS MOVE IN FROM THE WEST. THUS...WILL BRING IN CAT
POPS TONIGHT...EXCEPT LIKELY IN THE SHADOW ZONE BETWEEN THE OHIO
RIVER AND THE MOUNTAINS DUE TO SOUTHEAST DOWNSLOPING WINDS...AND
THEN GO CHANCE POPS FROM SOUTH TO NORTH WEDNESDAY MORNING. EXPECT
WELL ABOVE NORMAL TEMPS TONIGHT WITH SOUTHERLY FLOW AND CLOUDS.

FOR WEDNESDAY...WILL TRACK THE STRONG COLD AND ORGANIZED BAND OF
SHOWERS AND STORMS ACROSS THE AREA...REACHING THE OHIO RIVER AROUND
19Z...CENTRAL WV AROUND 21Z...AND ON INTO THE MOUNTAINS BY 00Z.
WHILE THE WESTERLY 850MB WINDS ARE NOT PARTICULARLY IMPRESSIVE
COMING IN BEHIND THE FRONT...THERE IS A REAL STRONG POTENTIAL FOR
DOWNWARD MOMENTUM WITH A VERY IMPRESSIVE COLD ADVECTION SURGE. THIS
IN COMBINATION WITH THE SHOWERS AND STORMS...POSE REAL THREAT FOR
DAMAGING WINDS UP TO 50 MPH ALONG AND JUST BEHIND THE FRONT...SO
THAT A WIND ADVISORY HAS BEEN POSTED FOR EXTREME SOUTHEAST
OHIO...EXTREME NORTHEAST KENTUCKY AND EASTWARD INTO CENTRAL WEST
VIRGINIA WEDNESDAY AFTERNOON.

TEMPERATURES WILL BE WELL ABOVE NORMAL TONIGHT AND WEDNESDAY AHEAD
OF THE FRONT...BEFORE FALLING OFF. SINCE THE COLD ADVECTION BEGINS
LATER WEDNESDAY AFTERNOON...HAVE CHOSEN NOT TO GO WITH A NON
DIURNAL TEMPERATURE CURVE.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
STRONG GRADIENT AFTER COLD FRONT EXITS CHRISTMAS EVE AND COULD SEE
SOME WIND GUSTS IN THE ADVISORY CRITERIA CONTINUING INTO THE EVENING
HOURS BEFORE DYING DOWN TOWARDS MIDNIGHT.

MODELS IN AGREEMENT WITH UPPER TROF SWINGING THROUGH
CHRISTMAS DAY. COLD AIR WILL BE WORKING IN  WITH H850 TEMPS
FALLING BETWEEN -3 TO -6 BY 12Z. COULD SEE ANY RAIN...MIX AND
CHANGE TO SNOW BRIEFLY IN SE OH TOWARDS DAYBREAK WITH A MIX
ELSEWHERE. RAIN AND SNOW MIX WILL CHANGE TO ALL RAIN TOWARDS LATE
MORNING AS TEMPS RISE. UPSLOPE MIX TO ALL SNOW IN THE HIGHER
ELEVATIONS OF THE MOUNTAIN COUNTIES WILL CONTINUE INTO THE
AFTERNOON. LITTLE OR NO SNOW ACCUMULATION IS EXPECTED.

HIGH PRESSURE WILL START TO BUILD INTO THE AREA CHRISTMAS NIGHT
AND INTO FRIDAY. DRY WEATHER AND CLEARING SKIES ARE ON TAP.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
HIGH PRESSURE EXITING TO THE EAST EARLY IN THE LONG TERM. MODELS
THEN HAVE SOME DISCREPANCIES GOING FORWARD. ECMWF HAS HAD A STRETCH
OF RATHER LACKLUSTER PERFORMANCE IN THE LONG TERM RECENTLY...SO
WHILE NOT DISCOUNTING IT COMPLETELY...DID PUT MORE WEIGHT ON THE GFS
WHILE BLENDING. THIS BRINGS A MOISTURE STARVED COLD FRONT THROUGH
SATURDAY...AND THEN A SECOND SURFACE WAVE RIDES UP THE FRONT SUNDAY
INTO MONDAY. GFS HAS THIS WELL SOUTH AND EAST OF CWA...WITH THE
EASTERN THIRD OF THE CWA BEING CLIPPED BY THE NW FRINGE OF THE QPF
FIELD. FOR COMPARISON...THE ECMWF IS MUCH FARTHER WEST WITH THE
SECOND WAVE.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
MILD S TO SE FLOW DOMINATES MOST OF THE PERIOD...THE STRENGTH OF THE
FLOW INCREASING AS A STRONG COLD FRONT CROSSES FROM THE W.  RAIN WAS
ALREADY AFFECTING THE MIDDLE OHIO VALLEY AND THE EASTERN SLOPES OF
THE CENTRAL APPALACHIANS...IN RESPONSE TO LOW PRESSURE STILL DOWN
OVER THE CENTRAL GULF STATES.  THAT LOW WILL INTENSIFY RAPIDLY WHILE
MOVING N RAPIDLY...REACHING THE TN VALLEY BY DAWN WED...AND CENTRAL
MICHIGAN BY 00Z THU...CHRISTMAS EVE.

RAIN WILL CONTINUE TO EXPAND ACROSS THE AREA OVERNIGHT...BRINGING
WIDESPREAD MVFR CIGS AND VSBYS...STARTING FROM THE OHIO VALLEY AND
THE SOUTHERN COALFIELDS EARLY ON...SPREADING RAPIDLY N TO COVER THE
ENTIRE AREA BY 08Z.  IFR VSBY IS MOST LIKELY IN THE WV
MOUNTAINS...AND ALONG AND W OF THE OHIO RIVER OVERNIGHT...WHILE IFR
CIGS ARE MOST LIKELY IN THE WV MOUNTAINS...MAINLY THE EASTERN
SLOPES...BY 06Z.

A DRY SLOT WILL CAUSE THE RAIN TO BREAK UP INTO SCATTERED SHOWERS
DURING THE DAYLIGHT MORNING HOURS WED...WITH CONDITIONS IMPROVING TO
VFR FROM S TO N...EXCEPT FOR MVFR CIGS LIKELY HOLDING ON ALONG THE
EASTERN SLOPES OF THE WV MOUNTAINS.  A NEW BAND OF SHOWERS AND
POSSIBLE THUNDERSTORMS WILL MOVE W TO E ACROSS THE AREA WED
AFTERNOON...AS THE STRONG COLD FRONT PUSHES INTO THE AREA.  THIS
WILL BRING A RETURN OF MVFR CONDITIONS...WITH LOCAL IFR POSSIBLE IN
HEAVIER RAIN.

CIG CONDITIONS WILL LIKELY LAG VSBY WED AFTERNOON...WITH MVFR VSBY
MOST LIKELY WITH THE RAIN...AND THEN MVFR CIGS MOST LIKELY FOLLOWING
THE PASSAGE OF THE COLD FRONT...ALTHOUGH ALSO STILL HANGING ON ALONG
THE EASTERN SLOPES OF THE WV MOUNTAINS.

LIGHT E TO NE SFC FLOW THIS EVENING WILL BECOME LIGHT E TO SE
OVERNIGHT...AND THEN STRENGTHEN FROM THE S TO SE ON WED...WITH GUSTS
INCREASING TO 20 KTS BY WED AFTERNOON...EVEN NEAR 30 KTS ON THE
HIGHER  RIDGES.  THE STRONGEST WIND GUSTS ARE EXPECTED AS THE FRONT
CROSSES.  THE FRONT WILL REACH ABOUT A CRW-PKB LINE BY 00Z
THU...WITH GUSTS OF 30 KTS OR MORE MOST LIKELY IN THE STRONG COLD
ADVECTION RIGHT BEHIND THE COLD FRONT...CODED UP FOR HTS AT THE END
OF THE TAF PERIOD.  MODERATE S FLOW ALOFT OVERNIGHT WILL BECOME
STRONG S FIRST THING WED MORNING...AND THEN SHIFT TO SW BEHIND THE
FRONT ALOFT...WHICH WILL BE ABOUT CO-LOCATED WITH THE SFC COLD
FRONT...LATE WED.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z THURSDAY...

FORECAST CONFIDENCE: MEDIUM.

ALTERNATE SCENARIOS: IFR CONDITIONS MAY BE MORE WIDESPREAD OVERNIGHT
IN AREAS OF HEAVIER RAIN AND FOG.  TIMING OF CHANGING CONDITIONS
WITH THE DRY SLOT AND THEN THE COLD FRONT MAY VARY ON WED.

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.

DATE                                                                 WED
UTC 1HRLY       00   01   02   03   04   05   06   07   08   09   10   11
EST 1HRLY       19   20   21   22   23   00   01   02   03   04   05   06
CRW CONSISTENCY  H    H    H    H    H    M    H    H    H    H    M    M
HTS CONSISTENCY  H    M    M    M    M    L    M    H    H    H    H    H
BKW CONSISTENCY  H    H    H    H    H    M    H    H    H    H    L    L
EKN CONSISTENCY  H    H    H    H    H    M    H    H    H    L    H    H
PKB CONSISTENCY  H    H    H    M    M    M    M    M    M    H    H    H
CKB CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    H

AFTER 00Z THURSDAY...
IFR IN CLOUDS POSSIBLE IN THE HIGHER ELEVATIONS OF THE MOUNTAINS WED
NT INTO THU.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...WIND ADVISORY FROM NOON TO 10 PM EST WEDNESDAY FOR WVZ005>011-
     013>019-024>026.
OH...WIND ADVISORY FROM NOON TO 10 PM EST WEDNESDAY FOR OHZ066-067-
     075-076-083>087.
KY...WIND ADVISORY FROM NOON TO 10 PM EST WEDNESDAY FOR KYZ101>103-
     105.
VA...NONE.

&&

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







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