Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 261341

Area Forecast Discussion
National Weather Service Louisville KY
941 AM EDT THU MAY 26 2016

...Forecast Update...
Issued at 939 AM EDT Thu May 26 2016

Lingering showers and isolated storms across the Bluegrass have
slowly dissipated as LLJ begins to weaken and push to the east. A
nice clear slot resides behind it across central Kentucky and
southern Indiana, with southerly flow and dewpoints in the mid 60s.
Further to the west across central Illinois, a line of storms is
steadily moving east.

Extrapolating this line will put it into southern Indiana and
northern Kentucky by early afternoon. Our air mass should be able to
destabilize with dewpoints in the mid 60s and temps in the 80s. The
past few runs of the HRRR have finally latched onto this line and
brings it across southern Indiana and northern Kentucky. Some of the
other hi-res models have this ideas as well. As a result, increased
POPs quite a bit for parts of the area through the late afternoon.
Will likely need to fine tune or increase POPs further east across
the Bluegrass if this complex holds together across the entire area.

The very weak shear environment will limit severe storms, but
lightning, heavy rain and gusty winds will be a threat.

Issued at 555 AM EDT Thu May 26 2016

MCV loitering about south-central Kentucky has triggered showers and
a few isolated T-storms extending north into the Bluegrass region in
the last 2 hrs or so. The bulk of this precip is sliding into
eastern Kentucky already, but we`re continuing to see a smattering
of showers re-develop behind it. Also saw a few lighter showers over
southwest Indiana, but those are not holding together well at all.

Grids have been tweaked to better capture hourly trends, and hi-res
products will be updated shortly. No update to the zones as the
overall trend for the next 12 hrs is still pretty much unchanged.

.SHORT TERM (Now through Friday)...
Issued at 300 AM EDT Thu May 26 2016

Summertime air mass is now established over the Ohio Valley with
dewpoints into the 60s and precipitable water pushing 1.5 inches.
Upper trof has settled in over the High Plains, with an amplifying
ridge along the East Coast.

This pattern figures to remain fairly stagnant for the next couple
of days, resulting in a continuation of the warm and fairly muggy
conditions that took hold on Wednesday. Even with abundant low-level
moisture, the greatest instability and the favored track for most of
the synoptic-scale upper disturbances will be to our north and west.
Convective potential will be driven largely by whatever
destabilization can occur diurnally, and low-level boundaries that
manage to push in with decaying MCSs from the Plains. Will carry a
20-30 POP with a slight diurnal signal through tonight.

Confidence in model guidance is fairly low, but signs do point to a
dry day on Friday as deep southerly flow may better focus storms
over the Mississippi Valley, leaving us in a relative minimum for
moisture and instability. Will go with a dry forecast for now, but
proceed cautiously. With the dry forecast, would expect Friday to be
the warmer day in the short-term, with upper 80s quite likely
anywhere that sees enough insolation.

.LONG TERM (Friday Night through Wednesday)...
Issued at 300 AM EDT Thu May 26 2016

Unsettled pattern will continue through the Memorial Day weekend,
with warm and muggy conditions and isolated to scattered showers/
storms almost on a daily basis.

Will start out Saturday with the most amplified pattern, but the
upper trof over the Plains tries to lift out, with a fair bit of
bagginess in the flow translating NNE through the Ohio Valley. This
will likely be the most unsettled day of the period, and we`ll carry
the highest POPs but still limit to a 50 percent chance given low
confidence in the timing of any impulses.

As we head into Memorial Day and early next week, the pattern
flattens out a bit. The wild card is the warm core system that is
progged to develop off the Carolina coast. If it gets close and/or
strong enough, subsidence could keep a lid on convection here,
allowing us a dry day but pushing temps close to 90. Otherwise will
see a continuation of the summer pattern, resulting in isolated/
scattered POPs, with the best chances in the afternoon, and temps
running several degrees above normal, especially by night.


.AVIATION (12Z TAF Update)...
Issued at 650 AM EDT Thu May 26 2016

Remnant weak mid-level vortex over central KY has resulted in
development of numerous nocturnal showers and isolated thunderstorms
over our eastern forecast area. Indeed, these have affected LEX with
varying vsbys depending on rainfall intensity. By the start of the
forecast period (12z), the back edge of the showers should be near
LEX, with the showers moving east thereafter. Meanwhile, isolated
showers have developed behind the shortwave over parts of south-
central IN, and latest model trends suggest that isolated showers
could affect SDF or nearby locations this morning, so will include
VCSH. However, conditions should remain VFR.

For this afternoon, this system will be east of the area. Precip
should be at a lull with VFR conditions continuing. However,
isolated thunderstorms could develop in the mid or late afternoon,
with SDF most susceptible. Will also have to watch the later
remnants of the current MCS over MO and whether outflow boundaries
from this convection has any implications on convective development
across our northern area, including SDF. For BWG and LEX, any storms
later today should be isolated so will not include VCTS at this
time, although this will be monitored. Surface winds today will be
south to southwest around 10 kts with gusts 10-20.

Any storms should weaken later this evening with VFR conditions.
However, there light fog could develop at LEX (possibly BWG) near
the end of the forecast period.


.LMK Watches/Warnings/Advisories...


Short Term.....RAS
Long Term......RAS
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