Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 301720
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
120 PM EDT Tue Jun 30 2015

...Updated Aviation Discussion...

...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
out.

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.

Monday...

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 (18Z TAF Update)...
Issued at 118 PM EDT Tue Jun 30 2015

Thunderstorms will continue to develop this afternoon in a couple of
different areas.  As it stands now, KLEX and KSDF have the best
chance of seeing thunderstorm activity push in from the north later
this afternoon into early this evening.  There stands a bit less of
a chance at KBWG where storms have fired and already pushed to the
east.  In any storm that affects a site, winds will be gusty along
with brief vsby reductions into the IFR range.

Otherwise, convection will come to an end tonight.  There will once
again be a chance of some light fog at KBWG and/or KLEX, but some
incoming clouds from the west may help to limit the fog threat.
Will introduce MVFR vsbys for now.  Otherwise, renewed chances for
showers and storms look to arrive toward the end of the valid TAF
period as yet another system pushes in from the west.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&

$$

Update.........KJD
Short Term.....RJS
Long Term......BJS
Aviation.......KJD




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