Area Forecast Discussion
Issued by NWS Charleston, WV

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000
FXUS61 KRLX 211109
AFDRLX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON WV
708 AM EDT SUN SEP 21 2014

.SYNOPSIS...
A COLD FRONT CROSSES THIS AFTERNOON.  AUTUMN HIGH PRESSURE BUILDS IN
MONDAY NIGHT...AND THEN DOMINATES THE WEATHER OVER THE AREA THROUGH
MUCH...IF NOT ALL...OF THE REMAINDER OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
700 AM UPDATE...
SLOWED PRECIPITATION DOWN FURTHER STILL...BUT FCST OTHERWISE REMAINS
ON TRACK.

PREV DISCN...
CONVECTION AHEAD OF A COLD FRONT CROSSING IN AND IL EARLY THIS
MORNING STRUGGLING TO PUSH E AS INITIAL S/W TROUGH LIFTS OUT.  AS A
RESULT...CONVECTION HAS BECOME INCREASINGLY CONFINED TO AN AXIS JUST
AHEAD OF THE FRONT.  AS A RESULT...SHOWERS DO NOT REACH THE UPSTREAM
/W/ EDGE OF THE FCST AREA UNTIL CLOSE TO DAYBREAK.

MODELS ESPECIALLY NEAR TERM MODELS INSIST THE PRECIPITATION MOVES
QUICKLY E ACROSS FCST AREA TODAY IN RESPONSE TO SECOND S/W TROUGH
WHICH ALSO LIFTS OUT THIS MORNING...SO THIS PRECIPITATION MAY AGAIN
STRUGGLE TO HOLD TOGETHER.  POPS EVENTUALLY COME CLOSER IN LINE WITH
PREV FCST AS FRONT AND WHATEVER DIURNAL HEATING WE CAN ACHIEVE
CONVERGE ON THE FCST AREA THIS AFTERNOON BENEATH DIFFLUENT UPPER
LEVEL FLOW AND FALLING HEIGHTS.  SO NAM DYNAMICS SUGGEST AT LEAST
TWO BANDS OF CONVECTION SWEEPING ACROSS WHILE WRFARW FOR EXAMPLE
SUGGESTS SEVERAL.

SEP HEATING AND CLOUD COVER EARLY ON WILL LIMIT INSTABILITY BUT
CYCLONIC FLOW ALOFT HELPS PUSH MID LEVEL /H85-H7/ LAPSE RATES TO
6-7C/KM.  FLOW IS ALSO MARGINAL WITH 30 KTS AT H85 AND 40 KTS MID
LEVEL MEAN AND 60 KTS AT H5.  WILL BE DIFFICULT BUT NOT IMPOSSIBLE
TO CONVERT THIS TO DAMAGING WIND AT THE SFC BUT ISOLATED STRONGER
GUSTS ARE POSSIBLE.  THINK ANY DAMAGE IS MINOR AND ISOLATED ENOUGH
FOR NO MENTION IN HWO AND NEAR TERM FCST.

H7-H5 LAPSE RATES ARE LOWER OWING TO A STABLE LEVEL THERE SO HAIL IS
NOT LIKELY DESPITE FREEZING LEVELS AS LOW AS 10 KFT AGL AND THE 60
KTS AT H5 WILL BE HARD TO TAP.  SPC KEEPS PROBABILITIES AT 5 PERCENT
ON BOTH IN A SEE TEXT.

BRIEF CLEARING TAKES PLACE LATE TODAY AND TONIGHT IN THE WAKE OF THE
FRONT...BUT CLOUDS INCREASE AGAIN OVERNIGHT IN THE CYCLONIC LOW
LEVEL FLOW BENEATH THE POST FRONTAL INVERSION.  CLOUD AND FLOW
SHOULD PRECLUDE DENSE FOG TONIGHT ALTHOUGH SOME POST RAIN MIST AND
LIMITED VALLEY FOG ARE LIKELY.

MET AND MAV WERE A LITTLE HIGHER THAN PREV FCST ON TEMPERATURES BUT
MADE JUST S SLIGHT MOVE IN THAT DIRECTION.  THE TIMING ON HIGHS WILL
VARY BASED ON THE MOVEMENT OF THE FRONT...BASICALLY EARLY E AND LATE
W BUT DETAIL DIFFICULT TO CODE.  MOVED TOWARD HIGHER GUIDANCE
TONIGHT WITH THE TYPICAL SLOWER PUSH OF COOLER AIR TOWARD THE
MOUNTAINS.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
COLD FRONT TO THE EAST OF THE AREA AT THE BEGINNING OF THE
PERIOD...WITH UPPER TROUGH PUSHING EAST ACROSS THE CWA. STILL
EXPECTING QUITE A BIT OF STRATUS LINGERING ACROSS THE CWA FOR AT
LEAST THE FIRST PART OF MONDAY...WITH SOME LINGERING LIGHT
PRECIPITATION POSSIBLE MONDAY MORNING. OTHERWISE...HIGH PRESSURE
WILL GRADUALLY BUILD IN FROM THE WEST...WITH A GRADUAL
CLEARING/DRYING TREND. WARMER TEMPERATURES EXPECTED BY TUESDAY INTO
WEDNESDAY...AS UPPER HEIGHTS BUILD ACROSS THE EASTERN U.S. EXPECT A
RIDGE/VALLEY TEMPERATURE SPLIT TUESDAY NIGHT/WEDNESDAY MORNING.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
NOT MUCH GOING ON AS THE SURFACE HIGH CONTINUES UNDER A DEVELOPING
EASTERN U.S. UPPER RIDGE. THIS WILL BRING DRY AIR WITH LOTS OF
SUNSHINE FOR THE REMAINDER OF THE WORK WEEK. THE RESULT HERE WILL BE
A LARGE RANGE IN DIURNAL TEMPERATURES...BUT A DEFINITE WARMING TREND
FROM HIGHS IN THE 60S MONDAY TO AROUND 80 BY FRIDAY.

&&

.AVIATION /10Z SUNDAY THROUGH THURSDAY/...
ANY REMAINING VALLEY FOG WAS BEING SCOURED OUT EARLY THIS
MORNING...AS CLOUD AND WIND WERE INCREASING IN RESPONSE TO A COLD
FRONT APPROACHING FROM THE W.

THE FRONT WILL LIKELY BRING SHRA/TSRA TO THE OHIO RIVER NEAR
15Z...CRW AND CKB 16Z AND THE MOUNTAINS 16-17Z.  THERE WILL BE ABOUT
A 5 HOUR PERIOD AT MOST SITES DURING WHICH SHRA/TSRA ARE POSSIBLE
AND IT WILL LIKELY COME IN TWO OR THREE BROKEN BANDS.

THE FRONT WILL CROSS THE MIDDLE OHIO VALLEY AROUND 00Z AND THE
MOUNTAINS 01-02Z.  STRATOCU FOLLOWING THE FRONT THIS EVENING WILL
LIKELY BE 4-5 KFT MIDDLE OHIO VALLEY AND MVFR 2-3 KFT
MOUNTAINS...BUT LOWER TO MVFR LOWLANDS OVERNIGHT AND EVENTUALLY AOA
1-2 KFT...WITH IFR IN THE MOUNTAINS...BY 12Z MON.  POST-RAIN MVFR
MIST MAY FORM AS WELL OVERNIGHT TONIGHT...BUT THE FLOW SHOULD REMAIN
STRONG ENOUGH FOR ALL BUT IFR FOG IN A FEW BETTER SHELTERED VALLEYS.

SW SFC FLOW TODAY...A BIT GUSTY THIS AFTERNOON...WILL BECOME  W TO
NW BEHIND THE FRONT LATE THIS AFTERNOON AND THIS EVENING...A BIT
GUSTY INITIALLY.  LIGHT TO MODERATE W TO SW FLOW ALOFT MOST OF TODAY
WILL BECOME MODERATE NW TONIGHT.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z MONDAY...

FORECAST CONFIDENCE: MEDIUM.

ALTERNATE SCENARIOS: CONDITIONS IN SHRA/TSRA TODAY WILL VARY AS MAY
MVFR STRATOCU CIGS FOLLOWING THE FRONT TONIGHT AND MVFR MIST AND IFR
CIGS IN MOUNTAINS TOWARD DAWN MON.

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       11   12   13   14   15   16   17   18   19   20   21   22
EDT 1HRLY       07   08   09   10   11   12   13   14   15   16   17   18
CRW CONSISTENCY  M    M    H    H    H    H    M    H    H    M    M    M
HTS CONSISTENCY  M    M    H    M    M    M    M    M    M    M    H    H
BKW CONSISTENCY  H    M    M    M    M    M    M    H    H    H    H    H
EKN CONSISTENCY  L    L    L    M    M    M    M    H    M    M    M    M
PKB CONSISTENCY  M    M    H    M    M    M    M    M    M    M    H    H
CKB CONSISTENCY  M    H    H    H    H    H    H    H    H    M    M    H

AFTER 12Z MONDAY...
IFR STRATUS POSSIBLE MON MORNING...ESPECIALLY IN THE MOUNTAINS.  IFR
VALLEY FOG POSSIBLE TUE MORNING...ESPECIALLY ALONG RIVERS AND IN
BETTER SHELTERED VALLEYS.

&&

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

&&

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





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