Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 301505

1105 AM EDT Tue Jun 30 2015

...Forecast Update...
Issued at 1103 AM EDT Tue Jun 30 2015

A rather complex convective evolution appears on tap for this
afternoon.  Latest WV imagery depicts northwesterly flow across the
Ohio Valley, through which a couple of compact shortwaves were
traveling through.  It appears one of these compact waves is now
entering southern KY, which has resulted in an uptick of cu
development there over the past hour or so.  The latest HRRR is
suggestive this activity will grow in coverage through the early
afternoon hours.

Further north, there appears to be a boundary/weak cold front
associated with a remnant MCV across portions of western OH
southwest into east-central IN along which some cu and associated
showers have recently developed.  Convection could develop along
that early this afternoon, but not quite sure how far southwest this
will extend into the LMK CWA.  What seems a bit more certain is that
convection will develop further north of this area in response to
yet another wave diving through the flow.  If this occurs, this
activity may be a bit later in getting into the northern LMK CWA
(21-23Z and after).  These scenarios will bear watching over the
next few hours.  Any storm that develops could be strong to locally
severe.  Effective shear values will only be 20-30 knots, but wet
bulb zero heights of only 10-11k feet will promote a hail threat in
the stronger multicell cores.  Damaging wind will also be possible
in the strongest storms given steep low-level lapse rates and drier
air around 750mb.

.SHORT TERM (Now through Wednesday)...
Issued at 325 AM EDT Tue Jun 30 2015

A shortwave, noted on early morning water vapor imagery, is sparking
off a few elevated storms across southern IL. These are on track to
reach our western CWA before daybreak, so have added in some rain
chances. Main feature should be another another shortwave, now over
central Wisconsin. This feature is sparking storms over east central
Illinois. Expect lift associated with this system to reach our
northern counties by late morning. Clearing ahead of it should allow
for some heating and subsequent storm development.

The early onset of precip may make it difficult for storms to get
too strong. Still, soundings indicate some potential for near-severe
downbursts as well as wet bulb temperatures a little lower than
Monday, leading to perhaps some hail reports.

With loss of heating, we should see coverage of storms diminish.
Then expect an MCS to develop over the MO/IA region overnight and
head southeast toward our region for Wednesday morning and leading
to likely rain showers/storms through the day. Given the cloud
cover, expect temperatures to be cooler for Wednesday, compared
today`s highs in the low to mid 80s.

.LONG TERM (Wednesday Night through Monday)...
Issued at 327 AM EDT Tue Jun 30 2015

Overall upper pattern will continue to feature ridging across the
western CONUS, with varying amplitude troughing over the eastern
CONUS. The combination of embedded disturbances within the NW flow
aloft over the Ohio River Valley, and a quasi-stationary frontal
boundary in the vicinity will continue to bring rounds of showers
and storms through the weekend. While models generally agree on the
pattern, main challenges will be timing of individual perturbations
within the NW flow over the Ohio River Valley, and with positioning
of a frontal boundary that stalls out somewhere near or over our CWA
to end the week and through the weekend. Current data would suggest
that 2-3 inches of rain will be possible across central and southern
KY through early next week. Locally higher amounts can`t be ruled

Wednesday Night - Sunday Night...

Sensible weather under this pattern through the end of the week will
feature rounds of showers and t-storms associated with individual
disturbances and peak heating. Given conditional destabilization
each day and general enhancements in deep layer shear with each
disturbance, a risk of severe storms will be possible south of where
the boundary sets up. As has been the case, localized damaging winds
and very heavy rain will be the main threats along with marginally
severe hail and lots of cloud to ground lightning. Overall, models
have trended a bit further south with placement of synoptic features
which will put the focus for heaviest rain and most activity over
central and southern KY.

High temperatures during this time will generally be characterized by
upper 70s and low 80s, dependent on thunderstorm activity and
placement of the synoptic boundary each day. Lows each night will
generally be in the mid and upper 60s.


As we start the new work week, upper pattern looks to flatten out a
bit as southern CONUS ridging pumps up. This would likely bring an
increase in temperatures/humidity with a continued active pattern as
more disturbances dive through the flow. Highs during this time will
likely begin to rise to the 85-90 range.


.AVIATION (12Z TAF Update)...
Issued at 645 AM EDT Tue Jun 30 2015

Do have some reduced visibilities in the KBWG/KLEX corridor. These
should improve over the next hour or two.  Next up will be rain
chances. Expect scattered storms to start developing by late
morning, with best coverage in the mid to late afternoon. Tried to
time the tempo groups with the highest rain chances in the public
forecast, with chance for gusty winds and at least MVFR conditions
at KLEX/KSDF. Winds will become variable as storms dies down this
evening. Cannot rule out additional fog Wednesday morning, but that
will depend on timing and location of today`s storms.




Short Term.....RJS
Long Term......BJS
Aviation.......RJS is the U.S. government's official web portal to all federal, state and local government web resources and services.