051
FXUS63 KLMK 170221
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1021 PM EDT Thu May 16 2024

...Updated Forecast...

.KEY MESSAGES...

*   Widespread showers and storms Friday and Saturday, with locally
    heavy rain possible Friday morning.

*   Drier Sunday and Monday with well above normal temperatures.

*   Showers and storms return Tuesday and Wednesday.

&&

.UPDATE...
Issued at 1021 PM EDT Thu May 16 2024

The forecast looks on track for tonight as focus shifts to the next
wave for the overnight. Current water vapor imagery shows a
shortwave out over the lower Missouri River Valley that will eject
out into our region later tonight/early tomorrow. Meanwhile, this
shortwave will be able to draw on a PWAT maximum (partially from the
southern stream system) situated over the mid Mississippi/lower
Ohio/Wabash River valleys. This should allow for some efficient
rainfall producing convection, however mid level lapse rates are
expected to remain quite poor. Current mesoanalysis has values
around 5.5 C/km and forecast soundings also show an unimpressive mid
level profile. Nevertheless, seeing some lightning upstream with
current convection so can`t rule out some embedded thunder overnight
into the morning. Most of our activity is expected to be across
southern IN, north central and west central KY. Activity associated
with the southern stream wave really doesn`t arrive in our SW until
around sunrise or so.

Previous Update...
Went ahead and added some measurable pops (~20%)
to our NE CWA along and north of I-64 through sunset. Have had some
isolated to widely scattered showers pop up over the last 1-2 hours,
and these will steadily push east through the evening. Latest AMDAR
soundings out of SDF do show a decent instability profile through
the lowest half of the atmosphere, however a weak inversion around
H4-H5 really hurts mid level lapse rates. So, expect showers to
struggle above 15 K feet. Can`t rule out a lightning strike, however
we haven`t seen any yet, and think that the threat is relatively low
given that mid level inversion/poor mid level lapse rates.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 309 PM EDT Thu May 16 2024

We will remain under the influence of a split flow aloft as we end
the week. The northern stream will work a shortwave trough out of
the Upper Midwest and through the Great Lakes tonight into tomorrow.
This will slowly push a weak sfc cold front currently over the Upper
Mississippi Valley into the Wabash Valley/Ohio Valley by tomorrow
morning. Mesoanalysis this afternoon shows an axis of strong
moisture advection stretching from Mississippi Delta into central IL
with PWATS of around 1.50" located over the Missouri Bootheel. Radar
mosaic over the region shows an area of showers/storms ahead of the
sfc boundary over central IL working to the east-northeast. While
most of our area will remain under the influence of weak sfc high
pressure this afternoon into the early evening, isolated shower or
thunderstorm is possible this afternoon, mainly across southern IN
along the I-64 corridor and west of I-65.

Mid-level vort max associated with the southern stream, will eject
out of eastern TX and meet up with the northern stream trough axis
along the Ohio River later tonight into early tomorrow morning. A 30-
35kt low-level 850mb jet along the trough axis will help provide
additional lift for elevated showers and thunderstorms initially for
southern IN and north central KY after midnight towards daybreak
tomorrow. The southern vort max arrives by 10-12z tomorrow morning
increasing showers and storms further south across the KY/TN border.
Showers and storms become more scattered towards the afternoon as
the vort energy quickly works east northeast later morning/early
afternoon. Main impact from these showers/storms will be heavy rain
that could lead to localized flooding. Excessive rain outlook from
WPC continues to highlight areas west and along I-65 in KY in a
slight risk for flash flooding. Forecast QPF amounts for tonight
into tomorrow ranges from 0.75" to a little over an inch while
current 1 hour FFG is around 1.50".

As for the severe threat, I agree with the current day 2 outlook
from the SPC with a general thunder over central KY. Model soundings
have limited instability as the best dynamics will be focused over
the southern US.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Issued at 309 PM EDT Thu May 16 2024

Positively tilted upper trof will slowly lift out of the Red River
Valley beginning Friday night, but the emphasis is on slowly, as it
will take its sweet time and only reach the southern Appalachians by
Sunday. Unsettled weather will prevail for at least the first half
of the weekend, with PWATs around 1.5 inches through at least late
Saturday. Brief heavy downpours and localized flooding will be the
main hazards. Mid-level winds and deep-layer shear are maximized
Friday evening, but very weak lapse rates will preclude potential
severe wx. Also a decent amount of bust potential on Saturday as, at
some point, the upper trof axis will slip to our east, but the
cyclonic curvature in the flow does not lend any confidence to a dry
forecast.

Showers may linger east of Interstate 65 Sunday as the system slowly
pulls away, but overall it`s looking drier for Sunday-Monday in our
position between systems to our east and west. Temps turn quite warm
under shortwave upper ridging. Could see another day of unseasonable
warmth on Tuesday as the next incoming system is trending a bit
slower. Best chance for showers and storms is Tuesday night and
Wednesday, and while this activity could become more organized, any
threats are still very conditional at 6 days out.

&&

.AVIATION /00Z TAFS THROUGH 06Z SUNDAY/...
Issued at 747 PM EDT Thu May 16 2024

Conditions are currently VFR across the region, with generally light
and variable winds noted. Expecting largely VFR conditions through
this cycle, although with a couple of caveats. 1.) BWG is expected
to have a period of MVFR ceilings and possibly reductions in
visibility, mostly 11 AM CDT and after tomorrow. 2.) The other sites
could briefly see a vis reduction to MVFR in any stronger shower or
storm later tonight or tomorrow, but confidence is low in any one
location at any one time given the spotty nature of expected
coverage. Can`t rule out some brief MVFR ceilings, but overall more
confident in ceilings staying in the lower VFR range through
tomorrow with the northern TAF sites. Overall, this is a pretty low
confidence forecast, especially with timing/placement of any
stronger shower or storm from later this evening through tomorrow.

&&

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

&&

$$

UPDATE...BJS
SHORT TERM...BTN
LONG TERM...RAS
AVIATION...BJS