Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 241833
AFDJKL

Area Forecast Discussion
National Weather Service Jackson KY
233 PM EDT SUN JUL 24 2016

.UPDATE...
Issued at 233 PM EDT SUN JUL 24 2016

No major changes to the forecast. Hourly temps were running
slightly behind observations. Thoughts were to bump up afternoon
highs just slightly, but diurnal CU field developing over the
area is fairly extensive and should help moderate any additional
rises through the afternoon time frame. Otherwise, brought grids
in line with hourly trends. Isolated showers and thunderstorms
have already begun to fire as well. Nearly stationary cells could
lay down some brief heavy rainfall once they become mature.
However life cycles have been on the order of an hour and rates,
like yesterday have not been impressive being generally less than
2 inches per hour at maturity.

UPDATE Issued at 1025 AM EDT SUN JUL 24 2016

Forecast is in good shape this morning. Very few changes needed to
the grids. However, do plan to freshen up the zones to remove
morning fog. Otherwise it appears to be another hot one.

UPDATE Issued at 753 AM EDT SUN JUL 24 2016

Increasing mid-high clouds moving in downstream of an eroding
convective system should help to somewhat offset rising
heights/thicknesses and negate need for a heat advisory.
Regardless, high temperatures in the low 90s will still lead to
heat indices near the century mark later this afternoon.

&&

.SHORT TERM...(Today through Monday)
Issued at 344 AM EDT SUN JUL 24 2016

A decaying mesoscale convective complex, currently traversing
southwest Michigan into central Indiana, will bring increasing mid
to high clouds to eastern Kentucky this morning. This should
somewhat inhibit full insolation and subsequently negate the need
for a heat advisory. Nonetheless, heat indices will approach and
exceed the century mark once again this afternoon for several
locales. Will be close to record territory at Jackson, but currently
thinking cloud cover may be just enough to keep the record high
temperature of 93 degrees for the date untouched. Regarding
precipitation, southeastward propagating outflow boundary ahead of
said complex of storms may end up being the primary forcing
mechanism for afternoon convection given a lack of any local upper
features. The presence of a lingering and rather diffuse outflow
boundary from prior day activity may also end up sparking a storm
or two, but main lift will reside along newly generated boundary
along with orographic forcing along the higher terrain from the
Cumberland Plateau into southeast Kentucky near the Virginia state
line.

Showers and storms should wane this evening with the loss of daytime
heating. An upper trough swinging through Ontario and Hudson Bay
through the Great Lakes will then push a frontal boundary toward the
Ohio Valley into early Monday, providing a larger forcing mechanism
to focus upon for showers and thunderstorms. Moisture pooling along
the front should send precipitable water values up toward the 1.9 to
2 inch mark, leading to a threat of heavy rainfall by late Monday
afternoon as diurnal heating boosts instability and storm chances.
Additionally, the right entrance region of an associated upper jet
will skirt the Ohio Valley, thus further supporting rising motion.
Gusty winds will also be possible with any storm given precipitation
loading atop shallow drier air beneath cloud bases.

.LONG TERM...(Monday night through Saturday)
Issued at 344 AM EDT SUN JUL 24 2016

Models continue to be in good agreement from Monday night through
midweek, with upper level ridging across the southern half of the
conus, becoming increasingly dampened by shortwaves and troughs that
pass across the northern half of the conus. This will keep much of
the central conus, including the Ohio River Valley in a zonal flow
pattern to start the period, becoming increasingly amplified as a
deeper trough start pushing southward into the region for the second
half of the work week. This deeper troughing pattern will lower
heights across the Ohio River Valley starting Thursday. Then as
shortwaves interact with this trough, expect it to continue
deepening as we head into the weekend. Models continue to show very
good continuity through the entirety of the period with these
features.

The first shortwave to impact the region Monday will bring with it a
surface frontal boundary, which should push into the state Monday
night, before becoming quasi-stationary during the day Tuesday. This
will be the epicenter for convective development Monday night
through Wednesday, with scattered to numerous showers and
thunderstorms through this time frame. Best chances/coverage will be
during the afternoon/early evening with the aid of peak heating.
Instability and lift with these storms will be more than enough to
produce strong thunderstorms, but there will be little in the way of
steering flow, especially with the elongated stationary boundary
across the region. As such, will likely see pulse-natured storms,
but will need to be on the look out for both slow moving and
training storms, which could lead to localized high rainfall amounts
and potential urban or flash flooding.

The frontal boundary will push north of the state Wednesday night,
before deeper troughing and the next shortwave will near the region
from the northwest. This shortwave will produce a surface low
pressure center, which will interact with the surface boundary and
increase its strength. However, as of the latest WPC frontal
analysis, the boundary should remain north of the state through the
remainder of the forecast period, slowly pushing in a more easterly
direction. That being said, additional weak upper level disturbances
will continue to drop into the region from the northwest, deepening
the magnitude of the trough through the weekend. These disturbances,
in addition to continued WAA and moist unstable air south of the
boundary, will continue to spawn showers and thunderstorms
throughout the period, with coverage and storm strength once again
peaking in the afternoon. Winds may increase aloft somewhat during
this time, but are forecast to remain fairly weak in the mid levels,
so concerns for slow moving heavy rain producing cells will
continue.

The loss of mid and upper level ridging combined with daily
convection will help keep our high temperatures close to normal for
this time of the year, generally in the mid 80s. But with dew points
hovering around the 70 degree mark, our weather will remain quite
muggy. Likewise overnight lows will be warm, running a little above
normals in the upper 60s to near 70.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 233 PM EDT SUN JUL 24 2016

Other than some spotty pre-dawn MVFR fog at a few terminals went
with a predominant VFR forecast. Guidance was too pessimistic with
VSBYS and therefore chose to lean closer to persistence. CU field
will linger into the early evening. Will see typical summertime
garden variety pop up showers and thunderstorms across the area
this afternoon as well. However, coverage will not be widespread.
Therefore no plans to mention any thunder at any particular site
until it become evident that a terminal might be affected. Winds
will remain light this afternoon, generally southwesterly around 5
kts or less. Winds will pick up just a bit Monday as a cold front
settles down into the Ohio Valley.

&&

.JKL Watches/Warnings/Advisories...None.

&&

$$

UPDATE...RAY
SHORT TERM...GUSEMAN
LONG TERM...JMW
AVIATION...RAY



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