Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 242323
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
723 PM EDT Sun May 24 2015

...Updated Aviation Discussion...

.SHORT TERM (Now through Monday Night)...
Issued at 301 PM EDT Sun May 24 2015

A subtle warm front has lifted north of our CWA, with a surge in
deeper moisture over our western CWA showing up on SPC mesoanalysis
and visible satellite. Will continue to keep a 20% chance of a
shower or storm through the afternoon across western tier or two of
counties. Soundings do appear to show a mid level inversion around
15 K feet, which could be a limiting factor for any development.
Otherwise, temperatures are on track to top out in the low and mid
80s and south winds will continue to gust up around 20-25 mph at
times.

Steady S flow will continue overnight with increasing mid and upper
clouds. Expect fairly mild lows as a result, only bottoming out in
the upper 60s and low 70s in most spots. The far east may bottom out
in the mid 60s around Midnight, before potentially climbing a bit
toward dawn.

A 40-50 knot low level jet will ramp up over the area tonight
underneath the right entrance region of a weak upper jet. The
moisture transport and weak forcing associated with this will allow
for increasing shower/storm chances across our west toward dawn.
Expect whatever is ongoing at daybreak to slowly progress east and
weaken as it does so. Precipitation chances for the rest of the day
will then be dependent on the morning convection and any
redevelopment along differential heating, likely focused more across
our eastern CWA. More subsident and worked over airmass to the west
is expected to have less coverage and a few breaks in the clouds
possible. Can`t rule out a stronger storm or two as 0-6 km shear
should be between 25-30 knots, which is marginally sufficient for a
multicell cluster. However, instability is expected to be fairly
meager 1000 J/Kg or less, so not expecting severe. Main threat will
be brief heavy downpours and gusty winds. Gradient winds themselves
will be quite steady with gusts up around 25 mph possible.

High temperatures will be tricky, but generally thinking the west
will have some trouble recovering from morning convection so will
keep them in upper 70s. Meanwhile, the east will have some time to
heat up so will go with low 80s.

Scattered convection mainly in the east should wane in the evening
hours, with a relative lull through the first part of Monday night.
However, expect isolated to widely scattered shower/storm chances to
again get going toward dawn. Another mild night is in store with
lows in the 65-70 range.

.LONG TERM (Tuesday through Sunday)...
Issued at 300 PM EDT Sun May 24 2015

Not too much change in the overall extended forecast period with
this forecast issuance.  We`ll see the upper level ridge break down
and shift to the eastward on Tuesday which will allow a mid-level
wave to push into the region.  This should result in widespread
shower and thunderstorm development.  Moisture profiles indicated
that we`ll see relatively deep saturation so heavy rainfall looks to
be a good possibility.  Wind fields aloft are strong, but
instability looks to be questionable given anticipated morning
convection.  Thus, think overall severe weather threat is rather
marginal at this time.  However, if we did see some breaks in the
clouds in the afternoon, we could attain sufficient instability for
strong convection.  This will be something to watch over the next
few days.   It will be rather breezy on Tuesday due to the pressure
gradient, so winds of 15-20 mph with gusts up to 25 mph will be
possible.  We did keep temps down slightly for Tuesday based on
expected cloud cover.  Highs in the upper 70s to the lower 80s still
look reasonable.

By Wednesday, main forcing looks to be to our east, with a slightly
drier atmospheric profile.  Diurnally driven convection looks likely
with iso-sct convection in the afternoon/eve.  Temperatures easily
climb into the upper 70s to lower 80s, with overnight lows in the
lower-middle 60s.


For the remainder of the work week, some upper level ridging will
try to build back into the region.  Flow aloft weakens slightly, so
overall progressive pattern looks to slow down a bit.  Typical of a
summertime pattern, we`re likely to see scattered diurnally driven
convection during the afternoon hours.  Highs should be a little
warmer with low-mid 80s in most areas with overnight lows in the
60s.

As we head into the weekend, model guidance reveals the typical day
6-7 spread in their solutions.  Upper level ridging looks to hold
into Saturday as a stronger trough moves out of the Intermountain
west.  This looks to pose a risk of additional showers/storms
Saturday afternoon, with much better chances of precipitation
holding off until Sunday.  Highs Saturday look to warm into the 80s
again, but will be a bit cooler on Sunday with highs in the upper
70s to around 80.

QPF amounts for the period look to be rather excessive out to our
west with the main bulk of precipitation extending from Texas
northeastward into the Midwest.  As mentioned above, our main
precipitation chances look to come on Tuesday and Sunday.  QPF
amounts of 2-3 inches will be likely over the coming week.  The
higher amounts will be out across the west, and the lower bounds out
over the east.  This rain, falling over the week looks to be spaced
out enough to preclude hydrologic issues at this time.

&&

.AVIATION (00Z TAF Update)...
Updated at 720 PM EDT Sun May 24 2015

VFR conditions will persist through the night and into Monday
morning as moist southerly flow continues. SSE winds have lost their
gustiness with the loss of heating, but will remain near 10 kt
through the night with a tightening gradient and strengthening
low-level jet. That LLJ will become a bigger concern after midnight,
with 40-45 kt expected to build down to 1500-2000 ft AGL. It`s a
marginal and somewhat low-confidence forecast, given the lack of a
strong inversion to focus the speed shear, but will keep the
previous forecast of LLWS developing around midnight for SDF and
BWG.

By mid-morning LLJ will mix out and we`ll start to see gusts again
in the 20-25 kt range. Showers and storms will become enough of a
factor in SDF and BWG to warrant a period of VCTS late in the
morning. Expect these to decay by early afternoon, but we could see
late afternoon re-development, mainly in LEX given the moist and
boundary-rich environment. Ceilings could go into MVFR, but will
keep it solidly above fuel-alternate thresholds.

&&

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

$$

Short Term........BJS
Long Term.........MJ
Aviation..........RAS




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