Area Forecast Discussion
Issued by NWS Charleston, WV

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FXUS61 KRLX 271454
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
1054 AM EDT Thu Apr 27 2017

.SYNOPSIS...
A cold front crosses late today and this evening. Weak high
crosses Friday morning. A front sags into the area and then
retreats this weekend. A stronger cold front crosses Monday.

&&

.NEAR TERM /THROUGH TONIGHT/...

As of 1050 AM Thursday...

Surface analysis shows pre-frontal pressure trough, over central
KY this morning. Just to the west lies a vigorous cold front
approaching from the west. The past few radar scans show a line
of convection forming up in vicinity of Lexington KY. Expect
this line to continue to progress to the east today. Moderate
instability and shear profiles support linear convection with
some multicellular development with gusty winds being the main
threat. Current forecast trends on track with only minor tweaks
made to forecast.

As of 545 AM Thursday...

Showers and thunderstorms are likely today, as a cold front
approaches from the west-southwest.

The front was just east of the Mississippi River early this
morning, with convection ahead of it along the nose of a jet max
through the base of an upper level short wave trough, pushing
into eastern Tennessee early this morning.

The cold front is progged to move through late this afternoon
and this evening, as the short wave trough lifts through the
middle and upper portions of the Ohio Valley. Meanwhile, the jet
max approaches, but remains mainly southwest of the area
through tonight. All of this places the timing of the showers
and thunderstorms moving west to east across the area squarely
on today, with the forcing weakening late.

CAPE is progged to reach 1500 J/kg ahead of the front. Deep
layer shear is impressive, exceeding 80 kts in the 0-8km layer,
but the effective inflow layer is limited by a relatively
stable layer about h9-h9, thus limiting the effective bulk
shear. Midday through mid afternoon across central and eastern
portions of the forecast area appear to carry the best potential
for strong wind gusts and small hail.

Clearing takes place behind the cold front tonight, as high
pressure builds in toward dawn. Fog is likely to form toward
dawn as the boundary layer becomes calm, with low clouds
possible in the mountains.

Adjusted temperatures today to get highest values ahead of
precipitation. Faster timing of the front, and associated
precipitation result in slightly lower highs than previous
forecast. Lows tonight are close to latest guidance as well as
previous forecast.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
As of 545 AM Thursday...

High pressure Friday, with dry and warmer conditions, with warm
frontal boundary lifting north across the region. The warm frontal
boundary will linger across the Ohio Valley during the weekend, with
periods of showers and thunderstorms, particularly across parts of
southeast Ohio, with heavy downpours expected. In addition, some of
the storms could be on the strong side late Friday night/early
Saturday, with strong winds the primary threat, particularly across
western zones. A slight risk is in place across parts of northeast
KY, with a marginal risk across western 1/3 of CWA. Warm frontal
boundary will continue to lift north over the weekend as upper
trough across central U.S. continues to deepen. Showers and
thunderstorms, along with increasing heat and humidity can be
expected over the weekend as a result.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
As of 545 AM Thursday...

Cold frontal boundary associated with the system will push through
the region Monday and Monday night, with additional rounds of
showers and thunderstorms, some of which will be heavy at times.
Still a bit too early to pinpoint/determine any severe threat.
Behind the front, cooler and unsettled weather takes hold for
Tuesday, followed by another system by mid week.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
As of 700 AM Wednesday...

MVFR fog in the Tygart Valley will dissipate first hour of the
forecast.

A cold front approaching from the west is likely to bring
showers and thunderstorms from west to east across the area late
this morning through this afternoon. So far have coded VCTS /
CB at this distance, but any thunderstorm can bring IFR
conditions. Strong wind gusts and hail are also possible.

Timing of the showers and thunderstorms is generally 16-21Z
west, and 18-23Z east, although the actual window of
precipitation should be no more than 3 or 4 hours at any one
site.

Clearing will take place behind the cold front tonight, although
MVFR stratocu may linger in the mountains, and fog may form
late. IFR is coded for CRW 09Z and EKN 11Z, when MVFR stratocu
breaks up.

South to southwest will be around 10 kts and gusty ahead of the
cold front today, and then light west to southwest behind the
cold front tonight, becoming calm overnight. Moderate south to
southwest flow aloft today will become light to moderate
southwest tonight.

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

FORECAST CONFIDENCE: Medium to high.

ALTERNATE SCENARIOS: Timing and coverage of showers and storms,
and associated MVFR or worse conditions, may vary today.
Formation and then breakup of MVFR stratocu behind the cold
front tonight may vary, as may fog formation late. Fog
formation may depend upon dissipation of stratocu in the
mountains.

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       15   16   17   18   19   20   21   22   23   00   01   02
EDT 1HRLY       11   12   13   14   15   16   17   18   19   20   21   22
CRW CONSISTENCY  H    H    H    H    M    H    H    H    H    H    H    M
HTS CONSISTENCY  H    H    M    H    H    H    H    H    H    H    H    M
BKW CONSISTENCY  H    H    H    H    H    M    L    H    H    L    H    L
EKN CONSISTENCY  H    H    H    H    H    H    M    H    L    H    H    L
PKB CONSISTENCY  H    H    H    H    M    H    H    H    H    H    H    M
CKB CONSISTENCY  H    H    H    H    H    M    L    H    H    H    H    M

AFTER 12Z FRIDAY...
IFR fog possible Friday morning.

&&

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

&&

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


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