Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 270554
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
154 AM EDT Thu Apr 27 2017

.UPDATE...
Issued at 154 AM EDT THU APR 27 2017

HRRR/RAP are trending towards thunder being limited to the
southern half of the area as instability remains limited across
the north and east. This is in line with current trends in
convection upstream as the lightning activity has been retreated
southward across western Kentucky. Also, with models fairly
consistent on measurable rainfall occurring this morning,
increased pops to categorical to cover the rain this morning. Also
tweaked temperatures to reflect higher temperatures on the ridges
and to bring in a quick temperature drop to the upper 50s as the
rain sets in this morning. Looks like that rain will push towards
I-75 by 8 am this morning, then across the rest of the area by 11
am. Rain should come to an end by early afternoon.

UPDATE Issued at 1054 PM EDT WED APR 26 2017

The latest HRRR and other CAMs remain in decent alignment with
latest radar trends. These models still bring showers and perhaps
a few thunderstorms into the Lake Cumberland region by 11Z to 12Z.
This line could even slow down some, as the upper level trough
does take on a more negative tilt. The next issue tonight will be
valley temperatures, and did opt to lower from previous forecast
given the latest trends. However, it will be tricky to time the
actual low given the cloud cover moving into the region. Overall
think we could still be looking at a 10 degree split from the
ridges to the valleys. Otherwise, gravitated grids to latest obs
and trends.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 300 PM EDT WED APR 26 2017

The short term portion of the forecast will feature above normal
temperatures and a period of showers and storms on Thursday. A
fast moving cold front is forecast to move across the Ohio and
Tennessee valley regions during the day on Thursday. The
precipitation should begin moving into our southwestern and
western counties early Thursday morning, and should be exiting the
area early Thursday evening. The latest model data is suggesting
that instability should be elevated across the region, which would
help mitigate any threat of severe weather. However, wind decent
wind shear may exist tomorrow while the front is passing through,
so an isolated severe storm with damaging wind gusts cannot be
ruled out at this time. With precipitation and extensive expected
to spread across the area tomorrow, temperatures will not be able
to warm nearly as much as they have the past couple of days, but
we should still highs max out in the low to mid 70s, which is
still slightly above normal for this time of year. Low
temperatures the next two nights should be in the 50s and 60s
tonight, and in the 50s tomorrow night.

Southerly winds will begin to pick up and become gusty overnight
and tomorrow, as the front approaches and the regional pressure
gradient strengthens. Isolated gusts of 15 to 20 mph cannot be
ruled out.

.LONG TERM...(Friday through Wednesday)
Issued at 333 PM EDT WED APR 26 2017

Southwest flow will be in place aloft across eastern Kentucky
Friday through the weekend with ridging off the southeast coast
while a deep trough gets carved out over the central CONUS. At the
surface, a quasi-stationary frontal boundary located initially
along the Ohio River will sag south into the area Friday night.
After a dry and warm day on Friday, shower/thunderstorm chances
increase overnight Friday night, especially over the Bluegrass and
Gateway regions which will lie closest to the boundary. Models
indicate decreasing instability and shear parameters during the
night so severe weather is not a major concern.

Forecast models lift the warm front to our north Saturday into
Sunday placing our area firmly in the warm sector and likely
capped from much if any convective development, although cannot
rule out a shower or storm completely. Temperatures will warm well
into the 80s both days, along with dewpoints in the 60s, making
it feel very summer-like. Showers/storm chances then increase
quickly Sunday night into Monday morning as the potent storm
system wraps up and tracks into the Great Lakes, forcing a cold
front across the local area. Models show quite the wind field
accompanying the frontal passage so despite unfavorable timing and
insignificant instability, will have to monitor this system
closely for a strong wind threat as the front passes through.

The front quickly clears the area on Monday leaving behind a
cooler, less humid airmass. After a brief respite Monday night and
Tuesday, both the GFS and ECMWF indicate another shot at
showers developing by the middle of next week as an open wave
drops into the central CONUS, renewing southwest flow aloft over
our area.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
ISSUED AT 154 AM EDT THU APR 27 2017

Low level wind shear will continue just ahead of an approaching
cold front overnight. As the front moves on through, a complex of
showers and a few thunderstorms will push east across the area. In
the wake of this activity and the front, we may see a brief period
of MVFR cigs. These MVFR cigs will return to VFR this afternoon
with VFR conditions remaining for the rest of the TAF forecast
period.

&&

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

$$

UPDATE...KAS
SHORT TERM...AR
LONG TERM...ABE
AVIATION...KAS



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