Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 030506
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
106 AM EDT Fri Jul 3 2015

...Updated Aviation Discussion...

...Forecast Update...
Updated at 910 PM EDT Thu Jul 2 2015

Convection has continued to wind down this evening with the loss of
heating.  Still seeing some locally heavy rainfall across the
northern side of the Louisville Metro area.  This activity should
diminish over the next few hours.  Heavy rainfall across southern
Kentucky has abated for the time being.  However, additional
convection continues to develop over western KY which may move into
the Bowling Green areas and points southwest in the next few hours.
Severe weather threat continues to look low at this point.  However,
the main threat will be heavy rain and flash flooding.  Will be
keeping the Flash Flood Watch going for the overnight and Friday
time frame as additional rounds of showers and storms will be
possible later tonight and Friday as a weather system pushes through
the region.

Updated at 556 PM EDT Thu Jul 2 2015

Several areas of convection continue to move slowly across the
region.  The first one of note is the one across southern Kentucky.
This line of storms continues to move off to the southeast and will
train over areas that saw rain earlier.  Heaviest rain with these
bands has been from near Hartford (Ohio County) down through near
Columbia (Adair County).  One to three inches of rainfall has
occurred with this line this afternoon.  This is water falling on
already saturated grounds from earlier rains.  Thus, a couple of
flash flood warnings have been hoisted down across southern KY.

A couple of other bands of convection are trying to get going.  One
is up across the northern Bluegrass with a second one just south of
the Bluegrass Parkway (stretching from southern Hardin county down
to Casey County).  These storms are not severe, but are producing
torrential rainfall as they slide eastward.

Some additional convection is trying to develop upstream across
southern Indiana.  We`ll continue to monitor those storms this
evening.

.SHORT TERM (Now through Friday Night)...
Issued at 250 PM EDT Thu Jul 2 2015

...Flash Flooding Possible Through Friday Across Southern Indiana
and Central Kentucky...

As of mid-afternoon, a surface analysis showed a weak area of low
pressure across southern Missouri while a stationary boundary lies
west to east from southern Illinois into southern Indiana and
northern Kentucky. A pool of very moist air lies along this feature
characterized by dewpoints in the upper 60s to low 70s and light
southwesterly winds.

For the remainder of this afternoon and into this evening, the patch
of clearing clouds across southwest into south-central KY has
resulted in modest amounts of instability across the area. Daytime
heating is also bringing 1000 to 2000 J/kg of SBCAPE to the area. In
the presence of 20 to 30 kts of deep layer shear, scattered
thunderstorms that do develop will have the potential to put down
some gusty winds. The two areas likely to see greater coverage of
showers/storms is 1) along the Ohio River in the vicinity of the
stalled boundary and 2) closer to south-central Kentucky which has
had the most clearing/destabilization.

Water vapor imagery shows that another upper level disturbance will
arrive later this evening through early Friday morning, which will
push the surface low and front through the region. Additional
showers and thunderstorms are expected to spread across the area.

Main threat through Friday morning is flash flooding thanks
to torrential rainfall. PWATs are running 1.5 to 2.0 inches with
relatively high warm cloud depths. Soil moisture is running high
thanks to a couple weeks of higher than normal rainfall and
especially across some areas after last night`s rainfall. Lowest
flash flood guidance pockets are across southern Indiana and
south-central Kentucky. The flash flood watch continues and was
expanded/extended for the area. For more details, see the Hydrology
section below.

Diurnal temperature ranges will be low as clouds/rain keep highs
below normal and lows on the mild side. Sided with the higher
performing model consensus, putting highs in the mid 70s to around
80s and lows in the upper 60s.

.LONG TERM (Saturday through Thursday)...
Issued at 310 PM EDT Thu Jul 2 2015

Saturday/Saturday Night...

An upper trough axis should move east through the area shunting a
sfc boundary to the south of the Ohio River.  It`s still in question
as to how far south the boundary will settle on Sat and that may be
a determining factor on where convection fires later in the day.
The latest trend in mid range models has been to push the boundary
into south central KY or TN.  However, the latest NAM keeps it a
little farther north.  Still will keep the southern trend going and
limit precip chances to 30-50% Sat afternoon.  Scattered
convection is likely to continue into the evening hours before
diminishing after midnight.  With fairly meager wind profiles and
ridging building into the region Sat night, feel that storms will
generally stay below severe limits.  At this point it is fairly
difficult to pinpoint exactly who will and won`t see convection Sat
afternoon/evening.

As for temperatures, highs should be quite pleasant in the upper 70s
to lower 80s.  Low temperatures Sat night should be in the mid 60s.

Sunday/Monday...

Upper level ridging should work into the region for Sun helping
suppress convection both Sun/Mon.  Soundings indicate good capping
over the Ohio Valley for the beginning of the week, so will trend
POPs downward even making Sun night dry.  Any storms that do develop
should stay on the weak side.  Temperatures will be on the increase
as thicknesses increase over the region.  Highs should range through
the low to mid 80s both Sun/Mon with Monday being the warmer day.

Tuesday - Thursday...

The next weather system will approach our area Tuesday bringing
potentially several rounds of showers and storms for mid week.
Another sfc front looks to become stalled over the Midwest with
rounds of storms occurring daily as various waves ride along the
boundary.  The 12Z Euro looks quite wet leaving the boundary nearly
stationary over our area for much of mid week.  The 12Z GFS wobbles
the boundary a little more and wouldn`t be quite as wet as the
Euro.  High temps look to remain at or slightly below normal while
low temps will remain at or slightly above normal.

&&

.AVIATION (06Z TAF Update)...
Issued at 105 AM EDT Fri Jul 3 2015

Should remain convectively quiet overnight, with the only
uncertainty stemming from weakening storms near the KY/TN border.
Given the weakening trend, will keep that out of BWG overnight. Main
issue in the overnight will be fog. BWG is likely to be most
problematic given heavy rainfall earlier in the day, and proximity
to the nearly stationary boundary. Primary limiting factor is cloud
cover, and we expect it to be more of a stratus than fog event. Will
go IFR ceiling, with vis right on the IFR/MVFR borderline. Similar
philosophy in LEX due to less antecedent cloud cover, but will keep
SDF as a fuel-alternate MVFR for now.

After that, convective timing becomes the main challenge. Will jump
on board with the hi-res models, which all seem to fire convection
around mid-afternoon. However, confidence is not high enough in a
direct impact, so at this time will carry VCTS/CB mentions.
Extensive and persistent cloud cover will keep MVFR ceilings in
place, with only SDF remaining above fuel-alternate thresholds.

T-storm chances taper down late enough in the evening that we`ll not
add the extra line in BWG and LEX for just the final hour or two.
Will show the SDF planning period dry from midnight onward, but with
ceilings back down to fuel alternate.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...FLASH FLOOD WATCH through this evening FOR KYZ023>043-045>049-
     053>057-061>067-070>078-081-082.

IN...FLASH FLOOD WATCH through this evening FOR INZ076>079-083-084-
     089>092.

&&

$$

Update.........MJ
Short Term.....ZT
Long Term......AMS
Aviation.......RAS





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