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Area Forecast Discussion (AFD)

Issued by Jackson, KY (JKL)

FXUS63 KJKL 161829 AAA

National Weather Service Jackson KY
229 PM EDT Mon Sep 16 2019

Issued at 229 PM EDT MON SEP 16 2019

The forecast continues to be on track early this afternoon.
Current temperatures across the area range from the upper 80s to 
lower 90s, generally within a degree or so of forecast highs. Will
also leave in the slight chance PoPs through early this evening,
with a few echoes continuing to show up on radar. Updates have
been sent.  

UPDATE Issued at 1155 AM EDT MON SEP 16 2019

The forecast remains on track thus far. A weak mid-level
disturbance, as seen on the latest water vapor imagery, is
currently dropping south across the Ohio Valley. Some mid-level
cloudiness has been maintaining across northern Kentucky, with
even a few short-lived showers popping up from time to time. As
the disturbance works further southeast later today. The
combination of heating as well as this weak forcing will pose a
small threat for showers and thunderstorms across portions of
eastern Kentucky. The current temperatures are generally running
somewhat behind the forecast; however, given the ongoing dry
conditions in place, would rather stick with the current forecast
highs, as readings will likely catch up as we move into the 
afternoon hours. For now, will just freshen up the hourly 
temperatures to account for this slightly cooler start. Updates 
will be out shortly. 

UPDATE Issued at 750 AM EDT MON SEP 16 2019

Hourly grids were freshened up based on observations and trends.
This led to no substantial changes at this time. 


.SHORT TERM...(Today through Tuesday)
Issued at 430 AM EDT MON SEP 16 2019

Early this morning, an upper level ridge was centered in the
vicinity of the Arklatex region with the axis of the ridge
extending north through the MS Valley region. Meanwhile a trough
extend from the Canadian Maritimes into the northeastern Conus and
portions of the Atlantic. Meanwhile, Hurricane Humberto was
located east of the southeast US Coast and moving away from the
southeast Conus. Further west a trough was moving into the western
Conus. Locally, a few mid and high level clouds were passing
across the region in the northwest flow between the upper ridge 
centered to the southeast of the Commonwealth and the upper trough
to the northeast. Also moving through this northwest flow is a
shortwave moving through the Great Lakes. Valley temperatures 
have dropped as much as about 35 degree from highs on Sunday with 
mid to upper 50s observed in the valleys and lower 60s on the 
ridges and in the more open terrain locations. The airmass remains
dry, especially the further southeast in the CWA and below 700 mb
with a 41 dewpoint recently observed on top of Black Mtn near 
4100 ft MSL. At the surface, high pressure is centered across the
Appalachian region. Further north a frontal zone extended from the
mid Atlantic states and into the Great Lakes to MS Valley and 
then west and north across portions of the Plains. A wave of low 
pressure associated with the shortwave working through the Great 
Lakes was tracking along the boundary. 

Today and into tonight, initial valley fog should lift and
dissipate through around 9 AM EDT. Otherwise, the axis the upper 
trough to the northeast of the area, the ridge centered in the 
Arklatex to midsouth region and the trough moving into the western
Conus will all move east. Some subtle height falls are expected 
this afternoon. At the same time, the previously mentioned sfc 
wave of low pressure will track toward WV while the trailing cold 
front will approach the OH River this morning before dropping into
the Commonwealth this afternoon and evening. The subtle height 
falls, an increase in sfc dewpoints as well as PW increasing from 
the current values of about 0.8 inches near the VA border and 1.1
inches in the far northwest to 1.2 inches southeast to around 1.5
to 1.6 inches by afternoon and evening will yield at least a 
cumulus field and mid level clouds. A few stray showers or perhaps
a rumble of thunder cannot be ruled out, mainly in the more 
northwestern and western locations. In these more western and 
northwester locations, dewpoints should climb to the mid to upper 
60s, and this combined with upper 80s to lower 90s temperatures 
may be sufficient that the cap could be broken in a couple of 
locations there. The bulk of the region, especially the more 
southeastern locations where it has been very dry since late July 
are expected to remain dry. Slight chance pops were used generally
north of a Monticello to London to Jackson to Paintsville line 
from mid afternoon to early evening.

As the boundary drop southeast of the area tonight, slightly
higher dewpoints/a more moist airmass will linger with high
pressure at the sfc building back in and the upper ridge centered
to the west of the area remaining dominant. Cumulus should
decrease through the evening with mostly high clouds passing by
tonight. Light winds should be favorable for perhaps a bit more
coverage of valley fog as compared to what is occurring this

Tuesday, the upper ridge axis will remain in place west of the
area with northerly flow aloft. Passing high clouds are expected
with some generally shallow cumulus developing in the afternoon.
The atmosphere should remain too capped for any shower development
even in the higher terrain despite some model runs that develop
this. Temperatures will remain very warm for mid September, but
should average 2 to 3 degrees lower than today.

.LONG TERM...(Tuesday night through Sunday)
Issued at 335 AM EDT MON SEP 16 2019

The extended portion of the forecast begins on Tuesday night with
high pressure remaining the dominant weather feature across the
region. Upper level ridging will continue to intensify over the
Ohio Valley throughout the extended period. This will prevent any
systems from moving through the region. Furthermore, a strong and
expansive area of surface high pressure will be located to our NE,
but encompassing much of the state and moving southward throughout
the period. This will eventually introduce some llvl southerly
flow into the region by late next week and into the weekend. With
the introduction of this moisture, models have been trying to
bring in a boundary and associated precip by the Monday and
Tuesday range. However, there have been some inconsistencies with
this in the GFS runs. Additionally, the Euro has not been in
agreement with this trend. It is very possible the drought
conditions will persist past next week barring any tropical
influence. Highs will be in the upper 80s to around 90 each day.
Strong subsidence and light winds will allow temperatures to cool
quickly overnight. Overnight lows will be in the mid 50s to low
60s each night, with coldest temperatures in the deepest valleys. 


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)

An approaching weak cold front will allow for the potential of some
isolated convection across the area through early this evening. 
Given the limited areal coverage, will continue to leave out this 
mention at any TAF sites. Model guidance suggests some fog/low 
clouds building in between 06 and 12z. For now, included some MVFR
fog at KSYM, KSME, and KLOZ generally between 09 and 13z. Given 
the ongoing dry conditions, do not feel confident going with any 
worse conditions for now. Any fog will burn off by 13z, with some 
diurnally driven cumulus popping up once again by early Tuesday 
afternoon. Winds will average around 5 kts or less, generally 
veering to the north to northeast through the period.