Area Forecast Discussion
Issued by NWS Charleston, WV

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000
FXUS61 KRLX 201400
AFDRLX

AREA FORECAST DISCUSSION
National Weather Service Charleston WV
1000 AM EDT Thu Jun 20 2019

.SYNOPSIS...
An upper level disturbance and surface cold front cross later
today into tonight. Warm front moves through early this weekend.
Cold front early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 950 AM Thursday...

Updated POPs today based on recent hi-res model runs. Mainly to
add in higher POPs for the decaying area of showers and storms
moving in from the southwest. And then also tried to tighten up
the gradient on POPs this afternoon as the cold front approaches
from the west.

As of 430 AM Thursday...

A broken, weakening band of showers crossing the forecast area
from west to east early this morning, was what remained of
convection last evening out ahead of a cold front out to the
west, and represented the eastern edge of a cool pool in its
wake, over the middle Ohio Valley. These showers will likely
weaken further and fall apart as they move east early this
morning, in tandem with a short wave trough out ahead of the
main short wave driving the cold front out to the west.

In the meantime, showers and thunderstorms were forming along
the southwestern edge of the cool pool, over south central to
southeastern KY and north central to northeastern TN. This area
is likely to increase in area coverage early this morning, on
the nocturnal theta e feed into the cool pool, from the west-
southwest at about 40 kts at h85. This convection will likely
weaken as it moves into the area later this morning, on cloud
top warming and mixing through of the low level jet.

The NAM12 solution of a convection feed back low of around 1000
mb this morning is dismissed, along with similar solutions over
the past few days of a 996 mb low crossing the upper Ohio
Valley. Rather, an existing low near 999 mb over northwest IN
early this morning, will scoot across northern Ohio this
morning, and north central PA later this afternoon and this
evening. The surface cold front, extending southwestward from
the low center and entering western IN early this morning, will
cross IN, OH and KY today, and WV this evening.

Convection will fire up ahead of the advancing cold front, most
likely beneath forcing out ahead of the main short wave trough,
which was digging into lower Mississippi Valley early this
morning. That forcing will traverse the TN Valley this morning,
before moving northeast across WV this afternoon. As such,
convection later this morning and this afternoon is most likely
to fire mainly east of the Ohio River, and so that is where
PoPs are highest.

As the cool pool erodes and moves east today, CAPE is progged
to climb only to 1000-1500 J/kg this afternoon over the middle
Ohio Valley, even less over the central Appalachians, where the
cool pool crosses this morning. However, that is where the best
forcing and bulk shear are progged, as the short wave trough
lifts out of the TN valley. Thus, the thunderstorm strength
potential is muddled today, with a marginal risk east of the
Ohio River depicted by SPC, and just general thunderstorms
forecast in the weaker shear and forcing over the middle Ohio
Valley. However, taller thunderstorms today could turn out
stronger farther west, given the greater CAPE there, and the
proximity of the advancing cold front.

PW values remain up around 1.75 inches across much of the area
today, amid areas of low FFG values, and the Flash Flood Watch
continues through this evening, as any thunderstorms can easily
produce excessive rainfall. Instantaneous rates of 3-5 inches
per hour were not uncommon with the heavier thunderstorms last
evening, amd there were some reports of minor flash flooding
where such storms persisted or redeveloped.

Where mixing is realized today, downward transfer increased
momentum aloft can result in gusty winds even outside of
thunderstorms.

The cold front crosses tonight, followed by a lowering stratocu
deck, along with light rain showers in and near the mountains.
Mixing behind the front will result in gusty winds tonight,
which will then gradually start to wane overnight.

Near term central blends closest to bias corrected guidance and
close to previous forecast for temperatures and dew points,
with highs today limited by the cool pool, and a slightly
cooler and less humid Friday morning on tap, in the wake of the
cold front.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
As of 305 AM Thursday...

A warm front marks the return of higher humidity through the
column after a brief stint in a low POP forecast. Looking at
the thicknesses and layer moisture, the warm front will make
only slow progress through the CWA Friday through Saturday. The
upper level flow will be nearly parallel to this warm front, so
there will be a possibility of convection running southeastward
along the boundary Friday night and Saturday night. Even though
the warm front should make a full push through the region, the
northwest flow aloft looks somewhat active for the duration of
the short term after Friday, particularly for the western CWA.
The rises in the 500mb heights will signal a modest warm up that
will be affected by clouds and convection, but temperatures
should end up slightly above normal for the max values this
weekend. The standard threats for downpours and some gusty
winds in storms will be present.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
As of 305 AM Thursday...

The upper level pattern becomes progressive again, with the
ridge passing early next week and the next trough axis in line
behind it. Expect frontal passage right now in the late Monday
night/Tuesday time frame, and will of course need to watch the
convective threats for as it does so. Some discrepancies in the
long term models give a lower confidence for this timing.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
As of 650 AM Thursday...

A cool pool has overspread the area early this morning, in the
wake of a dying, curved line of convection that rolled through
overnight. The last of these showers will move out of the CKB-
EKN area first thing this morning. However, the cool pool
spells MVFR stratocu at times most TAF sites this morning, that
should lift later this morning.

Showers, with a few embedded thunderstorms, were moving
northeast out of southern KY, and toward the Tug Fork area.
These showers and thunderstorms will cross the Tug Fork, and
then start dying as they approach HTS, CRW and BKW later this
morning.

Showers and thunderstorms are likely to fire up this afternoon,
out ahead of a cold front approaching from the west, that will
cross this evening. Still only coded the CB / VCTS mention, as
cool pool clouds and the showers affecting the area this
morning, will affect heating, and thus when and where the
thunderstorms will fire. However, any thunderstorm today can
bring brief IFR conditions, along with strong wind gusts.

An MVFR cloud deck will set in behind the front tonight, that
will lower to IFR overnight. MVFR visibility in light showers
tonight is most likely in and near the mountains, where IFR ceilings
develop earliest.

Light southwest surface flow early this morning will increase
to around 10 kts today, with gusts of 20 to 25 kts. Surface
flow will become west to northwest behind the front tonight,
and remain gusty initially, before gradually diminishing
overnight tonight. Moderate southwest flow aloft today will
become moderate northwest tonight.

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

FORECAST CONFIDENCE: Medium.

ALTERNATE SCENARIOS: Timing of MVFR restrictions under stratocu
may vary this morning. Amendments may be needed for showers and
thunderstorms today, especially this afternoon into this evening.
Gusty winds will vary today. Timing of lowering ceilings
tonight may vary.

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       12   13   14   15   16   17   18   19   20   21   22   23
EDT 1HRLY       08   09   10   11   12   13   14   15   16   17   18   19
CRW CONSISTENCY  H    L    M    M    H    H    H    H    H    H    H    H
HTS CONSISTENCY  H    M    L    H    H    H    H    H    H    H    H    H
BKW CONSISTENCY  H    H    H    H    H    M    H    M    H    H    H    H
EKN CONSISTENCY  H    H    H    M    H    H    H    H    H    M    M    M
PKB CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    M
CKB CONSISTENCY  M    H    H    H    H    H    H    H    H    H    H    M

AFTER 12Z FRIDAY...
IFR in stratus possible Friday morning, especially in and near
the mountains. Brief IFR possible in showers and thunderstorms
this weekend.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Flash Flood Watch until 8 PM EDT this evening for WVZ005>011-
     013>020-024>034-039-040-515-516.
OH...Flash Flood Watch until 8 PM EDT this evening for OHZ066-067-
     075-076-083>087.
KY...Flash Flood Watch until 8 PM EDT this evening for KYZ101>103-
     105.
VA...Flash Flood Watch until 8 PM EDT this evening for VAZ003-004.

&&

$$
SYNOPSIS...26/TRM
NEAR TERM...TRM/MZ
SHORT TERM...26
LONG TERM...26
AVIATION...TRM


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