Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 240520

Area Forecast Discussion
National Weather Service Louisville KY
120 AM EDT Wed May 24 2017

...Updated Aviation Discussion...

.Forecast Update...
Issued at 1039 PM EDT Tue May 23 2017

Showers and thunderstorms from earlier have tapered off. The next
few hours should be quiet until showers move in west of I-65 toward
morning. We received a report of fog in Henry County where a
thunderstorm passed through earlier, and KK24 (Jamestown) has been
reporting fog as well. Went ahead and put patchy fog into the
forecast in the east where rain fell earlier this evening and winds
will remain nearly calm overnight.

Issued at 546 PM EDT Tue May 23 2017

Breaks in the CI/AC have allowed instability to increase over
southeastern portions of central Kentucky ahead of surface low
pressure east of Nashville. A corridor of slightly negative LI and
SBCAPE near 1000 east of I-65, combined with some deep moisture
convergence and a weak pool of slightly cooler temperatures aloft,
has led to thunderstorm development west of Lake Cumberland. The
storms will move to the northeast and should begin to weaken as the
sun continues to lower.

Grids and related products have been updated for the thunderstorms.


.Short Term (Now through Wednesday Night)...
Issued at 330 PM EDT Tue May 23 2017

...Much Cooler and Rainy Overnight and Wednesday...

A deepening upper low over Iowa will dive south to Missouri
overnight. Meanwhile, the southern stream shortwave that brought a
few light showers to the Lake Cumberland region this morning will
continue exiting to the northeast. Still can`t rule out an isolated
light shower over the SE CWA this evening. Otherwise, the vast
majority of folks will stay dry this evening under partly to mostly
cloudy skies.

Steady pressure falls continue across the area this afternoon as a
broad area of low pressure develops. Scattered showers and a few
thunderstorms have developed along a weak cold front from IL down
into MO. East of the Mississippi, this activity will track to the

In addition to the upper low dropping south, a vigorous shortwave
currently over the Red River Valley is forecast to swing around the
base of the trough to Dixie by 12z. This wave then swings due north
into the Ohio Valley tomorrow as it wraps into parent circulation.
The result will be rapid pressure falls and widespread rain over
central KY and southern IN very late tonight through Wednesday
morning. Some of the latest hi-res guidance would suggest we could
see an MCV develop and track north through east-central KY, with an
associated threat for localized gusty winds. Isolated storms will be
possible, especially by mid to late morning. Another risk is minor
flooding, particularly in areas that received heavy rainfall over
the weekend (Washington and Scott counties in Indiana).

Model thicknesses and widespread rain suggest highs remaining in the
60s for Wednesday. Rain will likely become more scattered by late
afternoon or the evening, but isolated to scattered showers will
continue overnight. Lows will fall into the low to mid 50s.

.Long Term (Thursday through Tuesday)...
Issued at 345 PM EDT Tue May 23 2017

...Chilly Weather Thu...
...Warmer for the Memorial Day Weekend with MCS activity...

As the upper low spins overhead, a shot of wrap-around moisture will
bring more widespread showers once again Thursday morning. Shower
activity could remain more scattered across the southwest.
Temperatures will remain well below normal with highs in the mid 60s
to low 70s. Instability will be limited, but much cooler air aloft
could result in some graupel or pea-size hail.

Friday is a brief warmup as shortwave ridging crosses the region
with thicknesses supporting upper 70s to low 80s with sunshine.
Clouds will be moving in late in the day though.

A warm front will lift out of AR/OK and move to near IND-CVG by Sat
morning. Depending on where this sets up is critical to the POPs.
Mid-level waves ejecting through WSW flow aloft along this boundary
should lead to MCS development for the holiday weekend, but the
precise location of the boundary will change the rain and
temperature forecast significantly. Blended guidance remains below
the likely range for rain and thunderstorms over the weekend, so
will maintain current forecast.


.Aviation...(06Z TAF Issuance)
Issued at 119 AM EDT Wed May 24 2017

Latest guidance suggests that rain showers will continue to develop
in both coverage and intensity overnight.  The axis of precipitation
looks to develop out over near the MS River over the next few hours
and then rapidly spread into the KSDF and KBWG terminals around
dawn.  KLEX which had some rain earlier this evening, will likely
see some patch fog develop in the pre-dawn hours. Cigs/Vsbys will
remain mainly VFR overnight with ceilings lowering toward dawn.
Periods of rain and low ceilings look likely for Thursday across the
region.  For the most part, most locations look to stay solidly MVFR
due to rain and low clouds with KBWG seeing the highest risk of IFR
ceilings during the late morning and into the afternoon hours.




Short Term.....EBW
Long Term......EBW
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