Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 031032

Area Forecast Discussion
National Weather Service Louisville KY
632 AM EDT TUE MAY 3 2016

...Updated Aviation Discussion...

.SHORT TERM (Now through Wednesday)...
Issued at 330 AM EDT Tue May 3 2016

...Showery and Cooler Through Mid Week...

An upper trough with several vort maxes rotating through will
dominate the short term forecast period. This will result in a
showery and cooler than normal period of weather.

Current water vapor imagery shows the next feature dropping into the
upper Wabash River Valley at this hour, with some very light showers
slowly dropping through central IN. Previous forecast and current hi
res models agree that isolated to widely scattered showers will drop
into southern IN around daybreak and slowly pivot through our region
mainly along and north of I-64 through the day, then into central KY
by late afternoon. Moisture is not very deep, so will go with low
chances for measurable rain. Under mostly cloudy skies and steady NW
surface wind, temperatures will struggle. Expect highs only in the
low to mid 60s in many spots.

Isolated light rain showers will linger in the Blue Grass region
through the evening hours, with a lull in precipitation elsewhere.
Will forecast a dry period in the pre-dawn hours, however this will
be short-lived ahead of a potent Vort diving into the region for
Wednesday. Lows tonight should be in the upper 40s.

Anomalous upper low dives toward our region through Wednesday, and
will be the focus for numerous rain showers and scattered
thunderstorms in the afternoon. Given mid level lapse rates and very
low freezing levels (6-7 K feet), some hail is possible in
thunderstorms Wednesday afternoon. If a few breaks in the clouds are
realized during the afternoon, then potential for a few marginally
severe hailers isn`t out of the question. In addition, any surface
heating will result in better potential to mix into stronger winds
aloft in the afternoon. Will forecast gusts up to around 25 mph for
now, but deeper mixing could warrant gusts over 30 mph. Again, the
limiting factor at this time appears to be cloud cover. Expect highs
in the low to mid 60s.

.LONG TERM (Wednesday Night through Monday)...
Issued at 330 AM EDT Tue May 3 2016

Wednesday Night - Thursday...

Anomalous closed upper low will be sliding through the region
Wednesday night and Thursday, with enough lingering moisture to
squeeze out isolated to widely scattered showers in our east. As one
would expect with anomalous upper low, temperatures will be well
below normal under heavy cloud cover and steady cold advection. Lows
Wednesday night should drop into the 40 to 45 range, with highs on
Thursday mostly in the mid and upper 50s. Spots near Bowling Green
should sneak into the low 60s.

Thursday Night - Friday Night...

The overall upper pattern slowly slides east to end the week, with
closed upper low spinning over the mid Atlantic Coast and upper
ridge axis sliding to the central CONUS. This will put the Ohio
Valley under enough influence of high pressure to return dry
conditions and begin to warm up a bit. Thursday night lows will
still be chilly in the low to mid 40s. Friday highs will mostly be
in the low 70s under mostly sunny skies and increasing
heights/thicknesses. Friday night lows will be slightly milder
in the low 50s.


Upper ridge axis breaks down on Saturday in response to a shortwave
moving into the Great Lakes region. The trend with this features is
stronger/faster to the point where it could have a minimal impact on
the Saturday evening forecast along and north of the Ohio River.
Data suggest that enough moisture could pool ahead of a surface
frontal boundary sagging into our area to produce isolated to widely
scatterd showers or a storm. This tends to be overdone by models a
lot of the time, especially when moving into an antecedent dry
airmass. That being said, the faster trend is worth noting/watching.
Overall, the Saturday forecast will be dry with highs around 80.
We`ll be watching for a few showers across southern IN by late
afternoon and early evening.

Saturday Night - Monday...

The Ohio Valley will be situated under persistent NW flow aloft
between central CONUS ridge axis and New England troughing to end
the weekend. The aforementioned frontal boundary will stall over or
near our area nearly parallel to the upper flow. With this feature
in the area, expect that isolated to scattered showers and a few
storms will be possible, mainly each afternoon and evening.
Temperatures are always tricky when trying to nail down the exact
position of a frontal boundary, but with most of the region expected
to be on the warm side, upper 70s and low 80s seem reasonable.
Southern IN would have the best shot at mid 70s for highs.


.AVIATION (12Z TAF Update)...
Updated at 619 AM EDT Tue May 3 2016

Latest IR imagery and GOES-R MVFR/IFR probabilities show an area of
IFR stratus across southwest to central Indiana slowly dropping
south into north central Kentucky. This will most likely impact SDF
and LEX through the morning hours with low ceilings. There are some
visibility restrictions but feel the main aviation challenge is
ceilings. Expect this deck to continue for a few hours but slowly
lifting as the initial upper level system passes the area.

Plan on light west/northwest winds today and mostly VFR conditions
this afternoon and evening. Isolated to widely scattered showers are
possible but will continue to leave out of TAF.


.LMK Watches/Warnings/Advisories...


Short Term........BJS
Long Term.........BJS
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