Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 241602

Area Forecast Discussion
National Weather Service Louisville KY
1202 PM EDT Wed May 24 2017

...Forecast Update...
Issued at 1155 AM EDT Wed May 24 2017

Showers have been fairly widespread for the last few hrs over
central Kentucky, but a mid-level dry slot has punched in from the
south and precip is eroding in between I-65 and I-75. Minimal
thunder so far, but will have to watch for this dry slot to
destabilize through the afternoon as a 997mb surface low over Middle
Tennessee lifts NNE into the Commonwealth. Instability, or potential
lack of it, will be the limiting factor in severe wx as sfc winds
will be backed ahead of the low. SPC Slight Risk has expanded as far
west as Paris, Lexington, and the Highway 127 corridor from Danville
to Jamestown. Between the shear profile and low LCL heights,
potential for brief tornadoes is certainly on the table.

Potential threats are fairly well covered by the going forecast, and
with categorical POPs in play, most adjustments have been a matter
of precip timing.

.Short Term (Now through Thursday)...
Issued at 325 AM EDT Wed May 24 2017

...Widespread Rain Today, A Few Strong Storms East of I-65

An interesting setup will unfold through the day, and could
ultimately yield a threat for strong storms and a few mini-
supercells around the I-75 corridor by this afternoon and evening.

A closed upper low will drop south into the mid Mississippi River
Valley by this evening. Meanwhile, a secondary shortwave will race
up through the Tennessee Valley and into our region by this
afternoon. The associated surface low is expected to move up the I-
75 corridor. This will create a locally veered wind profile as
surface winds with the northward advancing triple point back beneath
a 30 knot low level jet. Forecast soundings show a favorable
hodograph to support rotating storms, however the big question will
be whether we are able to destabilize ahead of these conditions late
morning and early afternoon. Given the degree of expected cloud
cover, confidence will stay low in the overall strong storm threat
but wanted to note the potential if the modest instability offered
by some of the models is realized. Like the SPC outlook of the
slight and marginal categories, and the tornado probs. Will also
note how low LCL`s will be, which would help the tornado threat a
bit if robust updrafts are able to develop. Will have to monitor the
potential destabilization in our east as we move through the day. I-
65 and westward should expect widespread showers and a few rumbles
of thunder. Some of the showers could be heavy at times given the
moist column, and some of the CAM`s suggest localized rainfall
amounts around 1 inch.

Otherwise, highs today will struggle under the heavy cloud cover and
precipitation. This will put us about 10 degrees below normal values
for this time of year. Look for the mid and upper 60s in most spots.

The deep upper low will sit over the tri-state (IN/KY/OH) confluence
tonight with a mid level dry slot likely drying out southern KY for
some of the overnight. Meanwhile, scattered to numerous showers
should continue near the low center over southern IN and north
central KY. Look for lows in the mid 50s.

One final shortwave rotates through the parent low on Thursday,
bringing numerous showers with it. Highs won`t make it out of the
60s east and barely into the 70s west.

.Long Term (Thursday night through Tuesday)...
Issued at 325 AM EDT Wed May 24 2017

...Warmer for the Memorial Day Weekend with MCS activity Possible...

Thursday Night - Friday...

Progressive shortwave ridging will bring a brief dry spell and much
warmer conditions by Friday. After a chilly Friday morning in the
mid 50s, highs on either side of 80 will be a couple degrees above
climo for this time of year. Do have to keep a slight chance of a
shower or storm in across southern IN Friday afternoon as a weak
disturbance slides in behind the departing upper ridge axis.

Memorial Day Weekend...

A frontal boundary looks to develop somewhere over or near the
region for the weekend, with scattered showers and storms developing
along it through Saturday. Temperatures will depend on where the
boundary sets up, but will go with highs in the low 80s for
Saturday. By Saturday night into Sunday, a strong trough develops
over the central and northern Plains with an associated surface low
developing ahead of it. Most models agree this low will track to our
NW up into the Great Lakes, keeping us warm and unstable. As better
forcing arrives Saturday night into Sunday, more widespread showers
and storms are expected. Depending on ultimate frontal boundary
position and how much we destabilize, some stronger storms may be

Cold front looks to pass through Sunday night, with a mid level dry
slot bringing drier conditions into Memorial Day. Lows will be back
around the 60 degree mark for Sunday night, followed by highs around
80 on Monday. Some wrap around showers may move back into southern
Indiana by later Monday as a deep upper low spins over the northern
Great Lakes.


Another chance for showers arrives Tuesday as shortwave embedded in
the parent trough rotates through our region. A few T-storms may be
possible by Tuesday afternoon, with highs in the upper 70s to 80


.Aviation (12Z TAF Update)...
Issued at 649 AM EDT Wed May 24 2017

Precipitation shield continues to advance northeastward this morning
and will overspread the I-65 corridor in the next few hours.  This
will result in showers developing at KSDF and KBWG.  Ceilings look
to fall at KBWG with IFR ceilings possible starting around 24/16Z.
KSDF looks to remain MVFR, but some temporary drops to IFR will be
possible from lunchtime into the afternoon hours.  Showers will
arrive a little later over in the KLEX area.  Expecting some
destabilization to occur later this morning and have added in some
thunderstorms to the TAF mainly between 24/17Z and 25/01Z.  Also of
note, expect winds to pick up as the pressure gradient increases
across the region.  Winds look to be pretty gusty this evening with
sustained winds of 12-15kt and gusts up to 20kts at times.




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