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000
FXUS63 KLMK 190957
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
557 AM EDT SUN MAY 19 2013

.Forecast Update...
Issued at 556 AM EDT Sun May 19 2013

A broken line of thunderstorms has blossomed over central Tennessee
this morning, however the bulk of the precipitation should remain
south of the state border. Do have mention of an isolated
thunderstorm possible along the southern tier or two of counties
this morning. Otherwise, the only other concern is with transient
patches of dense fog. Scattered mid low/mid level clouds are
limiting more widespread fog formation, however local obs and
webcams are showing enough patches to warrant a Special Weather
Statement. Visibilities may be reduced over short distances,
especially near bodies of water, sheltered valleys, and spots that
received recent rainfall. Conditions should improve by 9 AM EDT/8 AM
CDT.

&&

.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 (06Z TAF Issuance)...
Issued at 1255 AM EDT Sun May 19 2013

The upper low that has plagued the area with scattered showers is
now over SE Kentucky. Meanwhile, an upper level ridge axis is
centered over the Mississippi Valley and will progress eastward
toward the the TAF sites through the period. Will watch a weak
boundary stretched across the Tennessee Valley work northeastward
overnight, however only expect scattered to broken clouds around 3-5
K feet with the feature, and perhaps a few very light rain showers
near BWG. Impacts would be negligible. Of more concern, will be the
potential for fog under mostly clear skies and calm winds early on.
Will stick with a fairly low confidence forecast of MVFR
visibilities through dawn at BWG/LEX, before improvement. At this
point, thinking convection will be minimized at the TAF sites later
this afternoon as the upper level ridge axis moves overhead and mid
level cap keeps storms at bay. Will not mention any precipitation at
this point. Otherwise, expect scattered to broken VFR clouds with a
more noticeable SSW wind around 10 mph in the afternoon.

&&

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


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