Area Forecast Discussion
Issued by NWS Jackson, KY

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184
FXUS63 KJKL 251724
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
124 PM EDT Fri May 25 2018

.UPDATE...
Issued at 1219 PM EDT FRI MAY 25 2018

The latest GOES-16 visible imagery shows cloud streets of cumulus
developing across much of eastern Kentucky. There have already
been a few showers develop in Pike County, and that trend will
continue this afternoon as instability builds across the region.
Overall the forecast looks on track and only updated to handle
latest obs and trends.

UPDATE Issued at 1006 AM EDT FRI MAY 25 2018

The morning surface analysis shows high pressure has pushed off
to the east. This will continue to allow moisture to stream into
the region and leading to afternoon showers and thunderstorms.
Used this update to blend in the latest obs and trends to the
forecast grids, but otherwise little if any changes needed for
this update.

UPDATE Issued at 645 AM EDT FRI MAY 25 2018

Touched up the grids mainly to add some slight PoPs in the far
southeast and also to include the latest obs and trends. These
have been sent to the NDFD and web servers.

&&

.SHORT TERM...(Today through Saturday)
Issued at 415 AM EDT FRI MAY 25 2018

07z sfc analysis shows high pressure having shifted off to the
east while weak low pressure exists to the south and west of the
area. More clouds have moved through the sky over eastern Kentucky
this night helping to slow the fog developing in the river
valleys - thus far. They did not prevent another ridge to valley
temperature split from developing overnight with readings
currently varying from the low 60s in the sheltered spots to
around 70 on the hills. Dewpoints are up over last night with
values generally in the lower to middle 60s. Winds are light and
variable where they are not calm ATTM.

The models remain in good agreement aloft through the short term
portion of the forecast. They all depict a weakening ridge of
heights over Kentucky this night with a trough approaching from
the northwest. This trough brings with it more in the way of
energy that will strafe by the state into the weekend. At the
same time, an upper low will continue to take shape over the Gulf
of Mexico with its lower heights helping to draw the effects of
the mid level trough more into our area by Saturday. Given the
good agreement among the guidance, will favor a general blend
with a lean on the higher resolution HRRR and NAM12 for finer
scale convective details through the period.

Sensible weather will feature a return of humid and likely stormy
conditions through the start of the weekend. Moisture increasing
from the south and plenty of instability developing will probably
lead to scattered convection developing over the higher terrain
late this morning and into this afternoon. With this, some
expansion back northwest to the rest of the CWA is anticipated.
The convective activity today will be diurnally driven and tail
off with sunset. Higher moisture content and more clouds around
will lead to more uniform temperatures tonight, except maybe in
the sheltered valleys in the northeast where decoupling could
occur, though shower and storm activity may move back in from the
west toward dawn, per the NAM12. Accordingly, expect less in the
way of fog around tomorrow morning for most spots. On Saturday,
the approach of the upper trough and more mid level energy passing
to the north expect to see better coverage of still primarily
diurnally driven showers and thunderstorms. Through this time, PWS
in the range of 1.5 to 1.8 inches suggest a potential for heavy
rains should the showers and storms sit in one place or train very
much. Forecast soundings do indicate that the convection should
be progressive enough to limit this concern, for now.

Again used the CONSShort and ShortBlend as the starting point for
all the short term grids. Did not adjust temperatures much
through the period aside from point specific values and in those
northeast valleys tonight. For PoPs, though, did significantly
raise up the values from the CONSShort through the period owing to
the better chances depicted in both the HRRR and NAM12.

.LONG TERM...(Saturday night through Thursday)
Issued at 300 AM EDT FRI MAY 25 2018

The extended will feature periods of showers and thunderstorms, with
the best chances for storms during the afternoon and evening hours
each day. The wild card during the period will be a possible
tropical system that the models are trying to form at some point.
There is a lot of uncertainty as to when this system may form and
what track it will follow. If this tropical system does indeed form,
which the National Hurricane Center web page is predicting it will,
the track and strength of the remnants of this system may or may not
have some influence on the weather of eastern Kentucky at some point
next week. That being said, generally went with a slightly modified
version of the model blend for precipitation chances and the timing
of precipitation across the area for the middle of next week. In
general, showers and storms will be occurring each day in the
extended, as a series of non tropical weather systems move across
the Ohio and Tennessee valley`s. Temperatures will continue to run
above normal, with daily highs topping out in the low to mid 80s,
and nightly lows in the mid 60s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
ISSUED AT 124 PM EDT FRI MAY 25 2018

Overall the period will be VFR, but some afternoon storms could
lead to localized lower restrictions. This afternoon we have seen
cloud streets of cumulus develop, with some showers developing
among those. Given the coverage will keep the VCTS going for now
and amend as needed. We could see some fog tonight, but that
should be more limited under more sky cover tonight. The coverage
of fog may be more pronounced in locations that receive rainfall
this afternoon, but that will have to be more fine tuned this
evening. The winds will continue to remain light and variable
across the region.

&&

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

$$

UPDATE...DJ
SHORT TERM...GREIF
LONG TERM...AR
AVIATION...DJ



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