689
FXUS63 KLMK 271900
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
300 PM EDT Thu Jun 27 2024

.KEY MESSAGES...

*   Shower and storm chances return Saturday through early Sunday.
    Locally heavy rain and gusty winds will be the main threats.
    Above normal temperatures return by early/mid next week.

*   Another period of unsettled weather returns to the region by
    late Wednesday and Thursday.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 259 PM EDT Thu Jun 27 2024

Synopsis...Positive upper height anomalies will continue rising
across the Lower Ohio Valley and Mid Atlantic as a broad ridge
expands over the southern half of the CONUS. Meanwhile, a northern-
stream, shortwave trough will proceed through the Northern Plains as
it slowly weakens. At the surface, high pressure over the Great
Lakes will eject to the east with low pressure and attendant cold
front approaching the Upper Midwest.

This Afternoon & Tonight...Mid-level subsidence and dry airmass have
kept mostly sunny conditions across the area this afternoon.
Satellite imagery shows a fair weather cumulus field developing
northeast to southwest as convective temperatures are met. Highs
this afternoon should top out in the mid to upper 80s with dewpoints
in the 60s, a momentary respite from the intense heat. For tonight,
expect low level clouds to dissipate after sunset, although a steady
increase of high clouds is anticipated based on upper-level
saturation depicted in GFS forecast soundings. As for fog chances,
confidence is low in coverage or intensity of dense fog as upper
clouds would most likely limit radiational cooling.

Friday...Winds will shift from the east-northeast to south-southeast
during the day in response to the ejection of the surface high
pressure and influence of lower pressures associated with the
approaching low and cold front. As a result, theta-e advection will
overspread the area with highs increasing to the upper 80s and low
90s. At the same time, precipitable water values will ascend
slightly over 1.5 inches in the afternoon providing an opportunity
of a low chance of brief showers along the Lake Cumberland region
where shallow moist convergence should be maximized. Nonetheless,
probability of thunder will be rather low as a capping inversion
will exist in the 700-600 mb layer and sufficient dry air lingers in
the mid-levels.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 259 PM EDT Thu Jun 27 2024

Friday Night through Sunday Night..

Could see a few showers/storms Friday evening ahead of weak warm
frontal boundary lifting north of the region.  Silent PoPs still
look good here and a few spots could pick up a little QPF.  Lows will
be warm with readings in the low-mid 70s.

For Saturday, pretty decent shortwave trough axis is forecast to
track from the Midwest through the Great Lakes during the day on
Saturday while pushing into New England by Sunday.  Associated
surface cyclone and southward extending cold front will approach and
slowly move through the region late Saturday and Sunday.  Ahead of
the front, we should still get decently warm on Saturday with highs
warming into the upper 80s to the lower 90s.  With dewpoints in the
upper 60s to lower 70s, this will result in heat indices rising
into the upper 90s and lower 100s.  We`ll have plentiful moisture in
the column Saturday afternoon.  Forecast soundings still show fairly
marginal lapse rates with tall/skinny CAPE profiles along with high
freezing levels.  PWATs from the models still rise to above 2 inches
on Saturday, but overall bulk shear values remain friarly marginal
with 20-25kts expected.  The overall profile would support
convection that would feature warm cloud depths and good
precipitation efficiencies.  Given the weak shear and steering flow,
these storms could be slow moving and lead to a localized flash
flood threat in some areas.  The tall CAPE profile and weak shear
could support a wet microburst threat as well.  SPC has a marginal
risk out for the area which seems appropriate.  Somewhat stronger
shear will be available to our northeast which agrees well with
current Slight risk area.  While overall coverage here may be a bit
sparse, if more convective coverage ends up occurring, the marginal
risk could see an upgrade to a slight at some point.

Frontal boundary looks to push through the region Saturday night
with convection continuing but diminishing in strength as we lose
heating and the PBL stabilizes.  By Sunday morning, the cold front
should be bisecting the region and continuing to push southward, so
precipitation chances will decrease steadily through the day across
southern IN and the northern half of KY.  A few scattered
showers/storms may continue across the south until the front clears.
Most locations should be dry by Sunday evening.  Highs on Sunday
will be cooler with readings in the 85-90 degree range.  Lows Sunday
night will drop back into the low-mid 60s, with some of the valley
and typical good radiational cooling spots dropping back into the
50s.  Not bad for late June/early July.

Monday through Tuesday Night...

A dry period of weather is expected for Monday and Tuesday as the
upper trough axis heads off to the east and upper level ridging
builds back into the area.  Monday will feature below normal
temperatures for much of the region with highs in the low-mid 80s.
The Bluegrass region of central KY may stay a bit cooler here with
upper 70s.  Lows Monday night will be cool as well with most
locations dropping into the upper 50s to around 60 with the cooler
valley locations dropping as low as the lower 50s.  Temps will
rapidly warm back up by Tuesday with highs in the upper 80s to the
lower 90s with overnight lows in the 70s.

Wednesday and Thursday...

Upper ridge axis looks to get a bit more flattened by Wednesday as a
series of waves moves through in the westerly flow pattern across the
northern tier of states.  A cold front will drop into the region
around Wednesday evening bringing a round of showers/storms to the
region.  This front looks to stall out across the Ohio/Tennessee
Valleys by Thursday and could serve as a focus for additional
convective development.  Some strong/severe storms could occur in
the Wed/Thu time frame given that we should have decent instability.
Overall shear still looks to remain marginal with the faster flow
displaced to our north.  However, we still have several days to
watch the overall scenario play out.  Highs during the period will
be in the upper 80s to the lower 90s with overnight lows in the
upper 60s/lower 70s.

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 116 PM EDT Thu Jun 27 2024

Discussion...VFR conditions will continue through this TAF period as
surface high pressure and dry air remain in control. On the other
hand, winds will stay light with a gradual shift from the northeast
this afternoon to the south-southeast tomorrow afternoon. Finally,
today`s mixing and increasing upper cloud cover tonight will limit
radiational cooling and potentially fog formation at the terminals.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.

&&

$$

SHORT TERM...ALL
LONG TERM...MJ
AVIATION...ALL