Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 300151
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
951 PM EDT Mon Jun 29 2015

...Forecast Update...
Issued at 950 PM EDT Mon Jun 29 2015

Convection is a little slower to move out of southern KY than
previously forecast.  Therefore, updated the forecast to keep
thunderstorms going down in the Lake Cumberland region for a few
more hours.  Also have a small arcing line of convection from
central IN down into northern KY.  These storms may glance our
southeastern IN counties and the northern Bluegrass region.  We
still expect these storms to die out later this evening with the
loss of heating.  For this reason, have increased PoPs slightly
across our far northeastern sections.

Otherwise, rest of the forecast remains generally intact.  Current
thinking is that fog will be our main concern overnight.  This is
especially true down across central and southern KY where afternoon
rains have made for a rich moisture laden atmosphere.  Fog is likely
to start develop after midnight and become most dense between 3-8 AM
local time.

Issued at 830 PM EDT Mon Jun 29 2015

After coordination with SPC and WFO JKL and ILN, have gone ahead and
drop the remaining portion of Tornado Watch #369.  We still have
some lingering convection down across our southern KY counties.
This activity should continue to diminish over the next hour or so
with the loss of daytime heating and instability.

Will probably do one more update after the storms in southern KY
exit the region.  Looking ahead to the overnight period, we expect
partly cloudy skies with some patchy fog developing.  The fog could
be dense in some locations, especially those that saw rainfall this
afternoon.  For now, have painted in the grids some fog mainly south
of the WK and BG Parkways.  Fog would likely be most prominent
between 3 and 8 AM EDT.

Issued at 735 PM EDT Mon Jun 29 2015

Did a quick update to drop a large chunk of Tornado Watch #369.
Basically clear out much of the northeast and central sections of
the watch, but did leave our southern tier of counties in for the
time being.  Based on current radar trends and coordination with SPC
we`re likely to drop the rest of the watch in the next hour or so.

Issued at 617 PM EDT Mon Jun 29 2015

Thunderstorms continue to move eastward across the region.  Most
storms have cleared the I-65 corridor. However, more upscale growth,
most likely related to approaching short wave impulse coming up out
of AR is helping fuel convection across southern KY.  Coordination
with SPC had us expand Tornado Watch #369 southward to cover this
activity.  An isolated spinup is possible down across southern KY
for the next few hours, but feel wind damage and large hail will be
the primary severe weather threats.

Elsewhere, some additional convection has fired behind the main
convective line.  This activity extends from Cincinnati
southwestward to near Bardstown.  This will move east and affect the
Bluegrass region over the next few hours.  Rainfall amounts have
been impressive with 1-2 inch reports in the southern Bluegrass and
down toward the Lake Cumberland region.  This has resulted in some
minor flood issues and a number of flood advisories are in effect
this evening.

As convection pushes south and eastward out of the region, we will
be dropping the watch from NW to SE.

.SHORT TERM (Now through Wednesday)...
Issued at 325 PM EDT Mon Jun 29 2015

The synoptic pattern this afternoon features northwesterly cyclonic
flow aloft over the Ohio Valley, with an upstream ridge across the
western CONUS.  This will set the stage for PV anomalies to dive
southeast through the flow aloft, bringing a couple of chances for
thunderstorms in the short term period.

The first round of storms has already developed this afternoon.
They have formed mainly along confluence bands and along the main
synoptic cold front which is now pushing across the Ohio River.
Dewpoints pooling in the upper 60s along the front coupled with some
diurnal heating has pushed MLCAPEs to 1000-2000 J/kg.  However,
latest WV imagery shows the main shortwave and kinematics aloft have
pushed to the east of the area.  This has led to rather meager
effective shear values of only 20-30 knots.  This marginal
deep-layer shear coupled with only weak convergence along the
boundaries will likely limit storm severity quite a bit, with only
an isolated storm or two likely to reach severe limits.  There
appears to be a very marginal tornado risk, but that will be mainly
northeast of the LMK CWA where winds remain locally backed.  Latest
observations show winds have veered substantially from SDF to FFT,
so think any tornado threat will be limited to the northern
Bluegrass where winds remain the most backed helping to enlarge
low-level hodographs.  The main threat in the strong to locally
severe storms will be damaging winds to 60mph and hail to the size
of quarters.  Another threat will be very heavy rainfall.  Bowman
Field in Louisville saw an inch of rain in about 20 minutes when a
storm passed through there, which may lead to some localized minor
flooding.

Convection should quickly dissipate as it pushes east this evening.
The night will be mainly dry, with just some passing mid/high
clouds.  There could be some fog especially where rain falls today,
but the passing clouds coupled with at least some light surface flow
should keep the fog from becoming too dense.

Tuesday will be a very similar setup to today.  The only difference
is there appears to be a better trough axis swinging through, which
may help to add a bit more vigor to updrafts.  Therefore, once again
expecting strong to marginally severe storms to fire in the
afternoon hours, capable of locally damaging winds and hail to the
size of quarters.  Expect the best coverage across the northeastern
CWA where the better forcing will coexist with more favorable
diurnal timing.  Highs Tuesday will be similar to today, with
readings expected in the low to mid 80s.  Tuesday night will dry
out, with lows in the mid to upper 60s.

.LONG TERM (Wednesday Night through Monday)...
Issued at 329 PM EDT Mon Jun 29 2015

Overall hemispheric pattern is characterized by a 6 wave pattern
aloft.  Three anchor lows, one out over the Aleutians, one over
Hudson Bay, and one out near Iceland will continue to drive the
pattern.  The overall pattern is very much an -AO/+PNA pattern which
looks to result in the ridge west, trough east pattern across NOAM
to continue.  With our region in the northwest flow, we will have to
watch for several pressure perturbations move through within the
flow.  The global models are in good synoptic agreement here and
generally are tracking the perturbations well.  The first looks to
arrive Wednesday and into Thursday, with yet another coming in
Friday/Saturday.  The models do have some placement issues with the
actual tracks, as the GFS is a little north with the Euro being a
bit more south.  In any case, rounds of showers and thunderstorms
are pretty much a given throughout the upcoming week.   Precipitable
water values will start off rather low early in the period and then
rapidly increase from mid-week onward with values well over 2
inches.  Thus, repeated rounds of thunderstorms are likely to result
in hydrologic/flooding issues as we close out the week.  Storms
could be strong at times...especially in the afternoon during peak
heating and peak instability.  Damaging winds, torrential rains and
marginal hail would be the main threats with any strong storm.

As for the upcoming holiday weekend, the pattern is not expected to
change all that much.  The models do forecast another wave in the
train to come through the region.  However, timing issues are going
to be key as to whether or not we`ll see a washout for the weekend.
For now, plan on staying above climatologically PoPs for the weekend
until timing issues can be resolved.  This should occur by the
Thursday/Friday time frame...so stay tuned.   By late in the weekend
and into early next week, there is a bit of a signal suggesting that
some height rises may develop and move in from the west.  Overall,
we`re not totally buying into this signal just yet, given the
configuration of the hemispheric pattern which would continue to
support the NW flow aloft pattern over the Ohio Valley.  Thus,
climatologically PoPs will be featured in the upcoming forecast at
this time.

As for temperatures, the stormy pattern and upper level flow will
likely keep afternoon highs below climatologically values.  Latest
blend of consensus model guidance keeps highs in the upper 70s to
the lower 80s for much of the week.  As a broadbrush, yeah, that may
work out fine, though I do think some pockets of higher temps may be
realized at times.  This would be especially true across southern
KY.  Overnight lows will remain mild too, with lows in the upper 60s
to around 70.  Some moderation in temperatures may occur late this
weekend and into early next week with highs returning to the upper
80s to around 90.

&&

.AVIATION (00Z TAF Update)...
Issued at 715 PM EDT Mon Jun 29 2015

Convection continues to push south and east across the region this
evening.  KLEX will still see some convection through about 30/01Z
and then things will dry up.  KSDF/KBWG look to be done with
precipitation for the night.  Expect VFR conditions to continue this
evening and into the early overnight hours.   MVFR visbys will be
possible overnight at KLEX and KBWG.  Right now, plan on keeping
things at MVFR, but we could see IFR conditions due to fog for a
time (probably between 30/08-12Z).  VFR conditions are expected
tomorrow with gusty southwest winds.

&&

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

$$

Update.........MJ
Short Term.....KJD
Long Term......MJ
Aviation.......MJ




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