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FXUS61 KRLX 200806
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
Issued by National Weather Service Pittsburgh PA
406 AM EDT Thu Sep 20 2018

.SYNOPSIS...
Upper level ridge crosses today. A strong cold front arrives
Friday, but then stalls over southern portions of the area over
the weekend, with waves into next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 405 AM Thursday...

High pressure drifts east of the area today and tonight, as
upper level ridging crosses. The upper ridge also ends up east
of the area by dawn Friday.

The atmosphere remains unseasonably warm and humid, which lends
itself to instability in the heat of the day. This is maximized
over the middle Ohio Valley this afternoon, mainly west of the
Ohio River, where PW values are progged to peak near 1.75 inches
in a northwest to southeast oriented axis, that then lifts
north of the area, and through the upper Ohio Valley, tonight.
Placed a slight chance for afternoon thunderstorms interior east
central Ohio, which lines up with the SWODY1.

Also continued the slight chance for afternoon and evening
thunderstorms over the higher mountainous terrain per elevated
heat source, but with an increased time window.

Any convection that does pop settles down tonight, and an
increasing gradient behind exiting high pressure should limit
fog considerably, compared with this morning.

Temperatures and dew points continue to reflect the unseasonably
warm and humid air mass. Stayed near the high end of the
guidance envelop on highs today. Liked the slightly warmer idea
off the HIRESarw near the western slopes of the mountains on
lows tonight, on downslope south to southeast flow.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY/...
As of 420 PM Wednesday...

Deep SW return flow will pump moisture into the region on Friday
out ahead of an approaching cold front. Expect a warm muggy
day Friday, with convection possibly starting to pop up out
ahead of the front by later in the afternoon across our Northern
SE Ohio Counties. Best dynamics still look like they will remain
to our north with this system, however still moderate to strong
SW flow aloft and modest instability, especially in the late
afternoon and early evening, means there will be potential at
least for our far northern forecast area to see severe storms.
This will likely all be determined based on the timing of the
front Friday evening. Severe threat will increase if it speeds
up than what current projections are showing and the threat will
extend further south as well.

The front will make it only as far south as Central to possibly
Southern West Virginia and stall there through the remainder of
the weekend. This will be the focus for more shower and storm activity
on Saturday as well.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 420 PM Wednesday...

Stalled surface front and associated shower and storms will
remain in the area through at least late Monday or into Tuesday.
An isolated flash flood threat will persist through this period,
especially with any training storms.

Conditions could get interesting with the approaching upper
trough by mid week, depending on where its best dynamics end
up. Earliest indications place the cold front associated with
the trough passage in the Wednesday to Thursday timeframe.
Depending on the speed of this front/trough, significant
rainfall and flooding could become an issue, but too early to
say for sure at this time.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
As of 215 AM Thursday...

Boundary layer winds were light enough to allow decoupling, and
quickly converging temperatures and dew points, which, in turn,
have allowed dense valley fog to begin forming. The only
question is whether boundary layer winds pick up enough to start
thinning the fog before dawn, so stayed away from a persistent
1/4SM FG forecast for now, allowing for variability instead, but
still predominantly IFR until dawn. BKW may again go MVFR in
mist.

The post-sunrise mixing will then result in fog dissipation by
14Z or earlier Thursday morning, briefly lifting into stratus
before mixing out altogether.

High pressure will bring a VFR Thursday once the morning fog is
gone. As that high moves east tonight, increasing southerly flow
on its back side should preclude fog in all but the deeper
valleys of the eastern mountains of WV, and even EKN may not
get any worse than MVFR Thursday night.

Low clouds will start to form along the eastern slopes of the
mountains on the south to southeast flow overnight, lift on
Thursday, with a pop up afternoon shower or thunderstorm
possible, but lower once again Thursday night. This is not
expected to impact BKW at this time.

Light east to southeast surface flow overnight will become
light south on Thursday, and then light south to southeast
Thursday night. Light north to northeast flow aloft overnight
will become light west to southwest before dawn Thursday, light
southwest Thursday afternoon, and then pick up a bit from the
southwest Thursday night.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z FRIDAY...

FORECAST CONFIDENCE: High.

ALTERNATE SCENARIOS: Timing of fog development and duration may
vary overnight.

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                         THU 09/20/18
UTC 1HRLY       07   08   09   10   11   12   13   14   15   16   17   18
EDT 1HRLY       03   04   05   06   07   08   09   10   11   12   13   14
CRW CONSISTENCY  L    L    L    L    L    H    L    L    L    L    L    L
HTS CONSISTENCY  L    L    L    L    L    H    L    L    L    L    L    L
BKW CONSISTENCY  L    L    L    L    L    L    L    L    L    L    L    L
EKN CONSISTENCY  H    H    H    H    H    H    L    L    L    L    L    L
PKB CONSISTENCY  H    H    H    H    H    H    L    L    L    L    L    L
CKB CONSISTENCY  L    L    H    H    H    H    L    L    L    L    L    L

AFTER 06Z FRIDAY...
IFR possible in SHRA/TSRA late Friday or Friday night, and then
at times in rain over the weekend, and on through Monday.

&&

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

&&

$$
SYNOPSIS...RH/TRM/MPK
NEAR TERM...RH/TRM
SHORT TERM...MPK
LONG TERM...MPK
AVIATION...TRM

FXUS61 KRLX 200806
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
Issued by National Weather Service Pittsburgh PA
406 AM EDT Thu Sep 20 2018

.SYNOPSIS...
Upper level ridge crosses today. A strong cold front arrives
Friday, but then stalls over southern portions of the area over
the weekend, with waves into next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 405 AM Thursday...

High pressure drifts east of the area today and tonight, as
upper level ridging crosses. The upper ridge also ends up east
of the area by dawn Friday.

The atmosphere remains unseasonably warm and humid, which lends
itself to instability in the heat of the day. This is maximized
over the middle Ohio Valley this afternoon, mainly west of the
Ohio River, where PW values are progged to peak near 1.75 inches
in a northwest to southeast oriented axis, that then lifts
north of the area, and through the upper Ohio Valley, tonight.
Placed a slight chance for afternoon thunderstorms interior east
central Ohio, which lines up with the SWODY1.

Also continued the slight chance for afternoon and evening
thunderstorms over the higher mountainous terrain per elevated
heat source, but with an increased time window.

Any convection that does pop settles down tonight, and an
increasing gradient behind exiting high pressure should limit
fog considerably, compared with this morning.

Temperatures and dew points continue to reflect the unseasonably
warm and humid air mass. Stayed near the high end of the
guidance envelop on highs today. Liked the slightly warmer idea
off the HIRESarw near the western slopes of the mountains on
lows tonight, on downslope south to southeast flow.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY/...
As of 420 PM Wednesday...

Deep SW return flow will pump moisture into the region on Friday
out ahead of an approaching cold front. Expect a warm muggy
day Friday, with convection possibly starting to pop up out
ahead of the front by later in the afternoon across our Northern
SE Ohio Counties. Best dynamics still look like they will remain
to our north with this system, however still moderate to strong
SW flow aloft and modest instability, especially in the late
afternoon and early evening, means there will be potential at
least for our far northern forecast area to see severe storms.
This will likely all be determined based on the timing of the
front Friday evening. Severe threat will increase if it speeds
up than what current projections are showing and the threat will
extend further south as well.

The front will make it only as far south as Central to possibly
Southern West Virginia and stall there through the remainder of
the weekend. This will be the focus for more shower and storm activity
on Saturday as well.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 420 PM Wednesday...

Stalled surface front and associated shower and storms will
remain in the area through at least late Monday or into Tuesday.
An isolated flash flood threat will persist through this period,
especially with any training storms.

Conditions could get interesting with the approaching upper
trough by mid week, depending on where its best dynamics end
up. Earliest indications place the cold front associated with
the trough passage in the Wednesday to Thursday timeframe.
Depending on the speed of this front/trough, significant
rainfall and flooding could become an issue, but too early to
say for sure at this time.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
As of 215 AM Thursday...

Boundary layer winds were light enough to allow decoupling, and
quickly converging temperatures and dew points, which, in turn,
have allowed dense valley fog to begin forming. The only
question is whether boundary layer winds pick up enough to start
thinning the fog before dawn, so stayed away from a persistent
1/4SM FG forecast for now, allowing for variability instead, but
still predominantly IFR until dawn. BKW may again go MVFR in
mist.

The post-sunrise mixing will then result in fog dissipation by
14Z or earlier Thursday morning, briefly lifting into stratus
before mixing out altogether.

High pressure will bring a VFR Thursday once the morning fog is
gone. As that high moves east tonight, increasing southerly flow
on its back side should preclude fog in all but the deeper
valleys of the eastern mountains of WV, and even EKN may not
get any worse than MVFR Thursday night.

Low clouds will start to form along the eastern slopes of the
mountains on the south to southeast flow overnight, lift on
Thursday, with a pop up afternoon shower or thunderstorm
possible, but lower once again Thursday night. This is not
expected to impact BKW at this time.

Light east to southeast surface flow overnight will become
light south on Thursday, and then light south to southeast
Thursday night. Light north to northeast flow aloft overnight
will become light west to southwest before dawn Thursday, light
southwest Thursday afternoon, and then pick up a bit from the
southwest Thursday night.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z FRIDAY...

FORECAST CONFIDENCE: High.

ALTERNATE SCENARIOS: Timing of fog development and duration may
vary overnight.

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                         THU 09/20/18
UTC 1HRLY       07   08   09   10   11   12   13   14   15   16   17   18
EDT 1HRLY       03   04   05   06   07   08   09   10   11   12   13   14
CRW CONSISTENCY  L    L    L    L    L    H    L    L    L    L    L    L
HTS CONSISTENCY  L    L    L    L    L    H    L    L    L    L    L    L
BKW CONSISTENCY  L    L    L    L    L    L    L    L    L    L    L    L
EKN CONSISTENCY  H    H    H    H    H    H    L    L    L    L    L    L
PKB CONSISTENCY  H    H    H    H    H    H    L    L    L    L    L    L
CKB CONSISTENCY  L    L    H    H    H    H    L    L    L    L    L    L

AFTER 06Z FRIDAY...
IFR possible in SHRA/TSRA late Friday or Friday night, and then
at times in rain over the weekend, and on through Monday.

&&

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

&&

$$
SYNOPSIS...RH/TRM/MPK
NEAR TERM...RH/TRM
SHORT TERM...MPK
LONG TERM...MPK
AVIATION...TRM