FXUS63 KLMK 250513

Area Forecast Discussion
National Weather Service Louisville KY
113 AM EDT Wed Apr 25 2018

...Updated Aviation Discussion...

.Forecast Update... Issued at 949 PM EDT Tue Apr 24 2018

Upper level low will continue to move slowly eastward overnight.
Plenty of low level cloud cover will be seen along with scattered
areas of light rain and drizzle. Main area of drizzle and light
rain will be found across the west late this evening and this should
shift into the eastern sections overnight. Overnight lows in the
lower 50s still look good for tonight. Did a quick refresh of the
short term grids. This resulted in very little change to the
overall forecast.


.Short Term...(This evening through Wednesday night)
Issued at 340 pM EDT Tue Apr 24 2018

The upper low that has persisted the last couple of days across
central Kentucky is becoming more disorganized this afternoon
(less vertically stacked in nature). There is a diffuse middle and
upper level circulation centered between Bowling Green and Glasgow
Kentucky with the main surface low displaced over South Carolina
with an inverted trough extending northward into eastern Kentucky
and West Virginia.

There has been some entrainment of drier air from the south and
southeast around this circulation that may help overturn some
lower level higher theta-e air. Given the sharp vorticity
gradients and potential for some insolation, will keep the
small mention of thunderstorms across the southeast part of the
WFO LMK forecast area. There has been intermittent moderate rain
showers over parts of Monroe and Cumberland counties near the
Kentucky-Tennessee border, but updrafts have not been organized
enough to support charge separation for thunderstorm development
at this time. The potential will still be there through this

Anticipate a diurnal downturn in convective activity late this
afternoon and this evening. Persistent cloud cover and light winds
tonight will limit any significant drop in temperatures
overnight and mitigate any fog development.

Going into Wednesday, the upper low will be slow to move along the
mid-Atlantic coast. With high pressure slowly building in,
steering currents will be too weak to completely scour out the
deeper layer moisture. Will keep skies mostly cloudy for tomorrow
and tomorrow night. The diurnal amplification around the upper low
should support some isolated showers along the eastern edge of the
WFO LMK forecast area.

No real significant changes made in the short term from the
previous package. The NAM-WRF and RAP guidance seem to have a good
fit on the convective trends associated with the upper low this
afternoon and this evening.

.Long Term...(Thursday through Tuesday)
Issued at 340 PM EDT Tue Apr 24 2018

An upper level shortwave diving through the Central Plains/Middle
and Lower Mississippi Valley on Wednesday will skirt through the
Tennessee Valley on Thursday. As this shortwave moves southeast,
it will amplify across the southeast U.S., bringing some moisture
and enough instability northward to generate some showers for
mainly the southern 1/2 of central Kentucky mainly Thursday and
Thursday evening.

Another progressive, but weaker shortwave will follow on the heels
of the aforementioned shortwave (that is forecast to produce
showers on Thursday) leading to a small chance for rain on Friday
afternoon. Any shower development will likely occur during the
peak heating/greatest potential for instability associated with
the shortwave.

Beyond Friday, and through the remainder of the forecast period,
large scale high pressure is expected to dominate the region. This
will finally allow the region to dry out and bring temperatures
closer to seasonal normals expected in late April and early May.

In addition to the regionally blended model guidance
initialization, the ECMWF and Canadian numerical guidance was
preferred for the longer range forecast solution with respect to
temperatures and weather.


.Aviation...(06Z TAF Issuance)
Issued at 113 AM EDT Wed Apr 25 2018

Main challenge is ceilings and possible visibility restrictions in
fog through the morning hours. Low stratus continues across the
area, but is slowly moving east/southeast. Back edge will clear HNB
and BWG through 08z, while SDF and LEX likely to stay overcast
through sunrise. With clearing skies and light winds behind stratus,
fog is a concern. There is already some lower vsbys developing west
of HNB, so will need to watch for the possibility of fog becoming
dense at HNB and BWG early this morning.

Otherwise, plan on the stratus to gradually lift/scatter through the
afternoon hours as drier air works into the region. LEX will be last
to improve. Winds will remain light and out of the northwest to




Short Term...WFO PAH
Long Term....WFO PAH
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