Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 201530 AAA

National Weather Service Jackson KY
1030 AM EST Mon Feb 20 2017

Issued at 1030 AM EST MON FEB 20 2017

14z sfc analysis shows high pressure slipping off to the northeast
as low pressure develops over the High Plains. Mostly clear skies
and plenty of low level moisture led to the development of dense
fog early this morning. This has now cleared up for most locations
and the SPS & NPW for these were allowed to expire at 10 am.
Temperatures are currently in the mid 40s to lower 50s for much of
the area with a few places still in the lower 40s where the fog
was last to clear. These all will climb nicely into the mid and
upper 60s this afternoon thanks to ample sunshine and light winds
turning more to the south with time. Dewpoints, meanwhile, are
generally in the middle 40s under mainly just some high clouds.
Have updated the forecast to account for the clearing of the fog
and to fine tune the temperature rise this morning toward the
afternoon highs. These updated grids have been sent to the NDFD
and web servers along with a freshening of the ZFP and HWO - as
well as a cancellation statement for the dense fog advisory.

UPDATE Issued at 709 AM EST MON FEB 20 2017

Elected to expand the Dense Fog Advisory south along the
Interstate 75 corridor into the Lake Cumberland region as
widespread surface saturation has been persistent near Monticello
with Somerset also seeing visibilities decrease. Other isolated
spots also seeing near or below 1/4 mile visibilities, including
Middlesboro and the Big Sandy Regional Airport. Will let this and
the Special Weather Statement ride through 10 am for now.


.SHORT TERM...(Today through Tuesday)
Issued at 400 AM EST MON FEB 20 2017

Areas of dense fog will continue across eastern Kentucky this
morning, with widespread 1/4 mile or less visibilities nearer the
Interstate 64 corridor down toward Mountain Parkway where surface
saturation has occurred more easily due to cooler temperatures and
lack of boundary layer mixing Sunday. Fog will undoubtedly impact
other locales across eastern Kentucky this morning, but not seeing
widespread 1/4 mile or less visibilities at this time south of a
West Liberty to Irvine line. Big Sandy and Monticello Regional
Airports have seen periods of dense fog, so may have to eventually
expand the Dense Fog Advisory farther south this morning if this

Following turbulent mixing and fog dissipating by mid morning,
tranquil weather will be in the offing for Washington`s Birthday as
deep layer subsidence dominates eastern Kentucky. Bands of cirrus
will move overhead downstream of a rather narrow upper trough
spanning the Canadian Prairies to Mexico. Well above normal
temperatures will be in store as 850 mb thermal ridging approaches
the Tennessee and Ohio Valleys, but a stout low level subsidence
inversion below 900 mb will preclude this from being fully mixed to
the surface. Nonetheless, highs should still top out in the mid-
upper 60s with a few readings in the 70s possible near and south of
Hal Rogers Parkway.

Patchy fog will be possible tonight, mainly in the valleys where
crossover temperatures will be closer to being reached, as high
pressure nudges east downstream of the approaching upper trough. Low
temperatures look to bottom out in the upper 40s to low 50s on
ridges and closer to the mid 40s in valleys. Lowering clouds will be
on the increase through the day Tuesday as low pressure encroaches
upon the Bluegrass. Isolated to scattered rain showers will develop
later into the afternoon, but not expecting much in the way of
appreciable precipitation through Tuesday afternoon as the northern
segment of the trough dampens through the Ohio Valley.

.LONG TERM...(Tuesday night through Sunday)
Issued at 400 AM EST MON FEB 20 2017

The extended period looks like it will be fairly active, with
periods of precipitation expected Tuesday night and Wednesday,
Wednesday night through Thursday night, and Friday through Saturday.
The models were in pretty good agreement regarding timing of weather
systems across the region toward the end of the week and into the
upcoming weekend. The best chances for rain look to be Tuesday night
and Friday night into Saturday. The model data is suggesting the
possibility of some thunderstorms Thursday into early Thursday
evening, and again Friday into early Friday night. A strong cold
front is forecast to move across the at the end of the week, so will
need to closely monitor the model data for the possibility of strong
storms Friday afternoon and evening.

Temperatures are still expected to be well above normal through out
the extended. High temperatures are still forecast to max out in the
upper 60s on Wednesday and Thursday. Friday looks to be the warmest
day of the week by far, with highs in the upper 60s and lower 70s
expected on that day. Highs on Saturday and Sunday should be
considerably cooler, owing to the intrusion of much cooler air into
the region behind the cold front that will pass through the area on
Saturday. Max readings over the weekend are expected to be in the
50s. Nightly lows will also be quite unseasonable, with min values
forecast to drop only into the low to mid 50s Tuesday night through
Thursday night. Once the cooler air settles over the area this
weekend, we could see lows in the 30s Sunday and Monday mornings.
Saturday will mark the transition from one air mass to another, with
lows in the low to mid 40s expected that morning.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)

Fog and subsequent visibility restrictions continue to be the
primary concern of note this morning. SYM/SJS are seeing VLIFR
visibilities, while SME and LOZ may see deteriorating conditions
at times over the next couple of hours. Valley fog may eventually
creep up toward JKL as well as mixing ensues this morning, but
this should be short-lived if it does ascend the ridge. All
remaining fog will mix out by mid-late morning as heating/mixing
commence and VFR conditions return with nothing more than some
high clouds streaming in. East/southeast winds will remain light
near or below 5 mph through today and tonight.




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