898 
FXUS61 KRLX 172045
AFDRLX

Area Forecast Discussion
National Weather Service Charleston WV
445 PM EDT Tue Oct 17 2017

.SYNOPSIS...
Dry high pressure with cool mornings and warm afternoons, with
temperatures moderating through the weekend. A cold front 
crosses on Monday.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 440 PM Tuesday...

Opted to add the remaining coal field counties to the frost
advisory. Fog limiting the diurnal trend is a concern, however
per reports on social media there were some areas that got 
frost last night despite the fog...and forecast lows for tonight
are lower than last night. Not everywhere will frost, but enough
frost is expected that an advisory seems warranted.

As of 235 PM Tuesday...

A clear sky dominates much of the Ohio Valley and central
Appalachians this afternoon. Dewpoints are running a bit below
guidance at some locations which this leads to the frost 
conundrum overnight. With high pressure overhead amid a dry 
airmass, expect a quick fall in temps this evening. Using this 
afternoon's dewpoints as a base and knocking a few degrees off
guidance in our colder spots, we have elected to hoist a frost 
advisory for much of the area. The exception being the northern
and central mountains where we ended the growing season today. 
Within the advisory area, expect dense main stem river valley 
fog to form once again, which will likely keep frost from 
forming in our more populated urban centers. I tried to hit this
thinking in the headline reiterating areas away from main stem 
rivers and urban centers more likely to receive frost.

Surface high shifts to the east on Wednesday with a s/w trof
approaching from the west in the afternoon. Given the dry
airmass in place at all levels, expect no impacts from this, 
with barely a cloud in the sky again. Highs were derived from 
met/mav/nbm blend which sends afternoon temps back above normal 
amid lowering RH values.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 230 PM Tuesday...

A sfc high pressure will extend from the adjacent coastal 
waters of the Mid Atlantic, east and south into WV Wednesday 
night. The high center shifts overhead as it strengthened 
controlling the weather conditions. Very dry conditions 
expected through Friday night.

Minimum RH values will dip into the 20s in parts 
of the area Wednesday afternoon, with 30s again widespread 
Thursday afternoon, becoming more confined to the mountains for 
Friday afternoon.

By Saturday night, the high drifts east as an approaching cold
front tightens the pressure gradient to pump moist and warmer
air into the area under southwest flow.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 230 PM Tuesday...

High pressure continues in control on Saturday through Sunday
night. Will have to monitor each afternoon after mixing could
bring low RH into the mid 30s. An increase in southwest flow is
expected as the front approaches. An upper level trough and 
surface cold front to cross from the west Sunday night into 
Monday. Models are in agreement with the timing of FROPA as an 
upper level through passes through. 

After drying out behind the front Monday night, the slowing, 
deepening upper level trough over the area spells lots of 
clouds, and the chance for showers into Tuesday.

Guidance suggests a warming trend through Sunday, followed by 
temperatures falling back to normal early next week.

&&

.AVIATION /21Z TUESDAY THROUGH SUNDAY/...
As of 340 PM Tuesday...


High pressure remains in control through the taf period with
light flow surface and aloft. IFR and VLIFR valley fog 
developing again tonight after 06Z at most terminals, with 
perhaps the exception of KHTS/KBKW. Fog will dissipate in the 13
to 14Z time frame with VFR conditions areawide thereafter. 

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z WEDNESDAY...
     
FORECAST CONFIDENCE: Medium.
     
ALTERNATE SCENARIOS: Less fog may develop tonight than currently
forecast. 

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       21   22   23   00   01   02   03   04   05   06   07   08
EDT 1HRLY       17   18   19   20   21   22   23   00   01   02   03   04
CRW CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    M
HTS CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    M
BKW CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    M
EKN CONSISTENCY  H    H    H    H    H    H    H    H    L    L    L    M
PKB CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    M
CKB CONSISTENCY  H    H    H    H    H    H    H    H    H    H    H    M

AFTER 18Z WEDNESDAY...
Dense valley fog possible each morning this week.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Frost Advisory from 2 AM to 9 AM EDT Wednesday for WVZ005>011-
     013>020-024>034-039-040-515-517-519-521.
OH...Frost Advisory from 2 AM to 9 AM EDT Wednesday for OHZ066-067-
     075-076-083>087.
KY...Frost Advisory from 2 AM to 9 AM EDT Wednesday for KYZ101>103-
     105.
VA...Frost Advisory from 2 AM to 9 AM EDT Wednesday for VAZ003-004.

&&

$$
SYNOPSIS...ARJ/30
NEAR TERM...MZ/30
SHORT TERM...ARJ
LONG TERM...ARJ
AVIATION...30