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000
FXUS63 KLMK 191725
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
125 PM EDT SUN MAY 19 2013

...Updated Aviation Discussion...

.Forecast Update...
Issued at 1145 AM EDT Sun May 19 2013

Convection this morning across south-central Kentucky was on the
northern side of a weak warm frontal boundary. These storms produced
quite a bit of lightning, very heavy rain, and small hail. Activity
is diminishing with outflow moving in all directions away from the
old convective complex. Can see the outflow on radar and satellite
heading north toward the Ohio River. This may trigger new
development. However, an upper-level ridge axis and associated
capping is moving in from the west-northwest. This is evident in the
capping of cumulus across portions of western Kentucky. This will
continue to push east through the day. With this in mind, believe
the best chance for any additional isolated to scattered convection
will be across south-central Kentucky northeastward through the Blue
Grass, where capping aloft is less. Made a few adjustments to
near-term forecast to align with observations and blend with the
afternoon forecast, which looks on track.

&&

.Short Term (Now - Monday)...
Issued at 258 AM EDT Sun May 19 2013

The upper level low that has helped plague the area with scattered
showers and a few storms over the weekend is now located over SE
Kentucky. Meanwhile, a weak warm frontal boundary is situated from
central MO to central TN. This brings the boundary across western
Kentucky where some scattered to broken mid level clouds reside.
There are also some very light returns that are resulting in
sprinkles at best near the surface. Models have been depicting light
QPF with this boundary for several days, however think that even the
light QPF is overdone and may go with just some scattered sprinkles
through the morning hours across the southwest CWA, into the central
CWA. Otherwise, expect a dry morning. Will have to continue to
monitor fog development, with some locally dense spots possible. A
few obs have gone down to a half mile at times already. Do think
that the scattered to broken upper level clouds will hurt fog
potential some as we near dawn, so will only mention in the HWO
unless conditions warrant a more significant product.

The upper low is forecast to wobble over eastern Kentucky today
while an upper level ridge axis builds over central and western
portions of the state. A nice subsidence inversion looks to
accompany this ridge as evidenced on forecast soundings across the
western two thirds of the CWA by afternoon. Therefore, will only
keep iso-scattered (30%) pops in the eastern CWA this afternoon
where ridge does not build in until tonight. Will go dry across
western portions of the state as any potential precipitation with
the warm front should be shunted by the inversion. Will see partly
to mostly cloudy skies by afternoon as diurnally driven cu develop,
however will see a warm up. Look for low to mid 80s west and around
80 east.

Any lingering showers or storms will die off with the loss of
heating this evening. Upper ridge will hold over the area keeping
things dry. A light southerly flow will encompass the area which
should keep temps mild so only expecting lows in the mid and upper
60s. Also think the noticeable gradient winds will keep fog
formation potential in check.

Upper ridge axis will hold through the day on Monday as well,
continuing to keep the CWA dry. Will see a continued increase in
temperatures as H85 temps in jump up around 18 C with only partly
cloudy skies and steady SSW wind. Will go nearer the slightly cooler
NAM guidance in the mid and upper 80s. MAV guidance is going with
upper 80s and low 90s in many spots, but with the amount of
greenery, recent rainfall, and at least scattered cu, hard to
imagine we will get that warm. Just an interesting note, a high in
the low 90s at SDF on Monday would put the record of 91 (1934) in
jeopardy. Right now the forecast calls for 89. Stay tuned.

.Long Term (Monday night - Saturday)...
Issued at 257 AM EDT Sun May 19 2013

A stacked upper low over the mid-Missouri valley at the start of the
long term will slowly drift to the east to the Great Lakes by
Thursday morning and then get absorbed into a deep upper trof
sweeping through southeast Canada.  Correspondingly at the surface,
low pressure will advance from South Dakota to Michigan, pulling its
cold front through the Ohio Valley sometime Thursday or Thursday
evening.  Meanwhile, a large dome of high pressure over the Atlantic
will pump Gulf of Mexico warmth and moisture northward ahead of the
approaching storm system.  The result will be unseasonably
warm, muggy conditions with shower and thunderstorm chances.

Although the best chances for severe storms on Tuesday will remain
to our west, we could still see some strong pulsers here in the
afternoon or evening.  A few strong storms will again be possible on
Wednesday as the Plains system approaches.  Total totals and SWEAT
numbers are actually higher on Tuesday, likely due in part to
steeper mid level lapse rates.  Progged surface instability is also
stronger on Tuesday.  However on Wednesday there will be better
upper level divergence along with a 5H speed max and stronger 850hPa
winds as well.  Wednesday also should have higher 1000-850 RH, which
could serve as moisture to fuel storms but may also cause greater
cloud cover and, as a result, decreased insolation and less surface
based instability.

Canadian high pressure will invade from the north Friday/Saturday,
bringing much drier and cooler air to the region.

Tuesday will be the warmest day of the long term with afternoon
readings peaking in the middle and upper 80s.  Greater RH and shower
coverage on Wednesday should limit high temperatures to around 80.
Thursday through Saturday we`ll enjoy highs in the 70s.

&&

.Aviation (18Z TAF Issuance)...
Issued at 125 PM EDT Sun May 19 2013

A weak upper low continues to meander around east Kentucky today,
with a weak frontal boundary across the Tennessee Valley. These two
disturbances will provide focus for isolated to scattered showers
and storms through the afternoon. Will continue with just scattered
shower coverage around LEX with isolated thunder. VFR conditions
will prevail through the afternoon and evening hours with a steady
SSW wind between 5 and 10 mph. Fog may become a concern again once
again tonight. However, surface winds are expected to stay up a bit,
which could limit fog, particularly dense fog, production.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
KY...NONE.
$$


Update...........MJP
Short Term.......BJS
Long Term........13
Aviation.........MJP