Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 180029 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
729 PM EST Fri Feb 17 2017

.UPDATE...
Issued at 713 PM EST FRI FEB 17 2017

Dewpoints and relative humidities continue to gradually increase
across the area this evening with most observations now above 30
percent. Hourly grids have been freshened up based on recent
observations and trends. Some of the valley locations have already
decoupled and with the Breathitt Mesonet already at 47, a wider
ridge/valley temperature difference has been included with this
update. Otherwise, high clouds should gradually increase from the
south and southwest overnight as a shortwave begins to approach.
At the same time, the pressure gradient is expected to be
sufficient enough to keep the atmosphere a bit mixed. Even so,
some more sheltered valley locations may reach the upper 30s.

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 339 PM EST FRI FEB 17 2017

Current conditions across eastern Kentucky feature some gusty
southwest winds caused from some decent mixing this afternoon. In
addition to the dry air in place and what has mixed to the
surface, some RH values have dropped into the 20 percent range
along with some decent southwest winds. This in addition to the
very warm air advecting into the area has resulted in some fire
weather concerns which should be coming to an end by 00Z this
evening as RH values recover into the 40 percent range by this
evening.

Tonight, with a ridge passing through, clear skies will remain for
much of the night before some cloud cover ahead of a disturbance
shifting northeast out of the lower MS valley area. Model trends
and observations might suggest a bit drier heading into this
feature than expected so lower pops below likely through Saturday
night. NAM and GFS trends significantly lessened QPF amounts with
this system and Superblend values confirmed this. Therefore, what
measurable precip does fall, will likely be less than a quarter of
an inch across much of the area. In addition, the origin of this
wave being from the southern stream will be lacking any
baroclinicity and so will be looking at very little instability.
As well, the warm trends will continue with high temps in
southwest flow tomorrow rising to well above normal values again.

.LONG TERM...(Sunday through Friday)
Issued at 400 PM EST FRI FEB 17 2017

The models are in pretty good agreement aloft through the first part
of the extended as they all depict the departure of a relatively
weak trough from the southern Appalachians early Sunday followed by
strong ridging through the start of the new week. The apex of this
ridge passes through Kentucky on Monday ahead of a full latitude
trough sweeping east through the Northern and High Plains down to
the Rio Grande Valley. However, its forward/eastward momentum is
slowed on Tuesday as the southern portion drags and starts to close
off while the north part whips into the Great Lakes but also
weakens. The models are not handling this development very well with
the ECMWF the strongest and furthest east with its new Gulf Coast
closed low. The Canadian is slowest while the GFS weakest and
furthest south with its core. Nevertheless the mass of these lower
heights stay in the Gulf - allowing zonal flow to take over to the
north and through Kentucky - with our state dodging a direct impact
from either parts of this system. The bulk of the energy in this
pattern will then be contained north of the Ohio Valley through the
end of the week. However, a strengthening low - especially from the
ECMWF will head for the Upper Midwest with more ridging for the area
ahead of this. Given the model agreement early and some issues later
on will favor a general model blend for the bulk of this forecast.

Sensible weather will feature a continuation of the very warm
conditions through the entire extended portion of the forecast.
Generally highs will be in the mid to upper 60s with lows in the
upper 40s to lower 50s. As seems appropriate for this spate of
spring-like weather we will have a few periods of showers mixed in
the forecast this week - mainly from Tuesday night through
Wednesday and again later Friday. Best chances for significant
rain appears to hold off until next weekend depending on how the
Midwest system develops and moves into the area. Thunder does not
look like a good bet this week, though, as the best upper support
stays well away from the CWA. The main concern through next week
looks to be one of fire weather where limited rainfall and very
warm temperatures appear to be giving eastern Kentucky a jump
start on the season.

Made some small to moderate adjustments, early on, to the
temperatures at night for minor ridge to valley distinctions before
we see a brief CAA pattern midweek. As for PoPs, basically
tightened them up a bit with the dying cold front passing through
Tuesday night.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 725 PM EST FRI FEB 17 2017

Mainly high clouds will increase across the region by the 6Z to
12Z period ahead of a mid level shortwave. However, before 12Z,
the mid clouds should encroach on the Lake Cumberland Region with
clouds thickening and lowering further with low level clouds
moving in from southwest to northeast from then until the end of
the period. Scattered showers are possible mainly from 16Z and
enough saturation may occur for a few periods of MVFR CIGS and or
VIS by the end of the period. Confidence in that occurring was
not high enough to include at this time. Southwest winds will
average 10KT or less through the period.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...JP
SHORT TERM...SHALLENBERGER
LONG TERM...GREIF
AVIATION...JP


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