-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRLX 210050
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
850 PM EDT Thu Jul 20 2017

.SYNOPSIS...
Convective activity on the increase into the weekend strong
diurnal heat under northwest flow Friday. Frontal system passes
early next week.

&&

.NEAR TERM /THROUGH FRIDAY/...
-- Changed Discussion --
As of 800 PM Thursday...

Sent an update to cut PoPs across the southern two thirds of the
area. Radar images show weakening convection just north of the
area as we loose sun heat. Guidance suggests that a cold front
will stall just north of the area tonight. This could keep the
northern sections under a threat of a shower or two or perhaps a
storm overnight.


As of 230 PM Thursday...

Quite a few changes to the near term forecast. First and foremost is
an MCS that formed last night, which continues to thrive/move east
towards the CWA where daytime heating/unstable conditions have
persisted, despite debris clouds across the area from earlier. Went
ahead and based on timing of day and continued cooling of cloud tops
evident on satellite, and added in a chance of pops across southeast
Ohio and northeast KY zones. In addition, there have been small pop
up showers this morning/early afternoon across the CWA, and think
with the moist unstable conditions, that isold convection cannot be
completely ruled out this afternoon, so went ahead and added at
least a slight chance everywhere this afternoon.

Focus then shifts to later this evening and tonight as a shortwave
moves east across the Great Lakes region, driving a frontal boundary
south into/towards Ohio zones, and possibly sinking southeastward
overnight across the remainder of the CWA, as the flow aloft becomes
more northwesterly. Models are all over the place with this, and
there is a lot of uncertainty in this, particularly considering the
time of day. Went ahead and decided to hang onto a slight chance to
chance pops in the overnight hours. There is also a slight
possibility that some storms in southeast Ohio could be on the
strong side, with 25-40 kts 0-6km bulk shear across the area. SPC
has included a slight or marginal risk across most southeast Ohio
and adjacent WV zones.

On Friday, convection will be on the increase area wide,
particularly if there are any leftover outflow boundaries from
previous night convection. Moisture will also be on the increase
across the area, with dew points climbing a few degrees on Friday.
This will push heat indices into the lower 100s across parts of the
lowlands, and create the need for a heat advisory. The one
concern is whether or not convection and cloud cover will dampen
temperatures a bit. But feel public safety is more of a concern
at this point, and even if the numbers are not quite advisory
criteria, it will still be dangerously hot. In addition, heavy
downpours, and strong gusty winds will be possible with any
convection on Friday.
-- End Changed Discussion --

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 305 AM Thursday...

Frontal boundary sags and stalls over northern portion of the
area Friday night along with plenty of moisture in place.
Showers and thunderstorms a good bet with boundary draped across
the north especially on Saturday with daytime heating. Went
likely pops along front chance pops elsewhere. Warm and muggy
through Saturday night.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 305 AM Thursday...

Low pressure from the plains will finally move eastward across
the great lakes Sunday and Monday. Expect trailing cold front to
pass through the region Monday night, Tuesday time frame. This
will keep the threat of showers and thunderstorms in the
forecast. Cooler and drier high pressure builds in behind the
front Tuesday night into Wednesday. This will bring some relief
in the high temperatures and humidity as temperatures should
average about 10 degrees cooler through Thursday.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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As of 730 PM Thursday...

Diurnal heating and an frontal boundary north of the area are
producing scattered showers and isolated thunderstorms across
extreme northern WV and southern PA this afternoon. Some of
this convection is developing further south affecting PKB and
CKB with short periods of MVFR/IFR. Otherwise, VFR conditions
expected through the period.

Models suggest some cloud cover overnight. This clouds could prevent
fog formation even along the river valleys. Patchy river valley
fog is expected but not widespread to affect the terminals for
an extended period of time.

On Friday, unstable conditions expected with portions of the
area under a marginal risk for severe weather. Brief periods of
IFR/LIFR possible along heavier showers or storms.


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



FORECAST CONFIDENCE: High.

ALTERNATE SCENARIOS: Fog development tonight in question, and
will depend largely on amount of cloud cover 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                                                            FRI 07/21/17
UTC 1HRLY       00   01   02   03   04   05   06   07   08   09   10   11
EDT 1HRLY       20   21   22   23   00   01   02   03   04   05   06   07
CRW CONSISTENCY  H    H    H    H    H    H    H    H    M    M    M    L
HTS CONSISTENCY  H    H    H    H    H    H    H    H    M    M    M    L
BKW CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    L
EKN CONSISTENCY  H    H    H    H    L    L    L    M    M    M    M    L
PKB CONSISTENCY  H    H    H    H    H    H    L    L    M    M    M    L
CKB CONSISTENCY  H    H    H    H    H    H    L    L    L    H    H    M

AFTER 00Z SATURDAY...
IFR possible Friday and Saturday in showers and thunderstorms.
-- End Changed Discussion --

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Heat Advisory from noon to 7 PM EDT Friday for WVZ005>008-
     013>015-024>026.
OH...Heat Advisory from noon to 7 PM EDT Friday for OHZ083-086-087.
KY...Heat Advisory from noon to 7 PM EDT Friday for KYZ101>103-105.
VA...None.

&&

$$
SYNOPSIS...JS/SL
NEAR TERM...ARJ/SL
SHORT TERM...JS
LONG TERM...JS
AVIATION...ARJ