Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 040102
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
902 PM EDT Fri Jul 3 2015
Updated at 900 PM EDT Fri Jul 3 2015
Convection continues to move slowly across the region. Despite
rather poor mid-level lapse rates, a saturated atmosphere combined
with broad scale synoptic scale lift associated with mid-level vort
swinging through the region is resulting in efficient rainfall
producing convection. The deep westerly flow will continue to allow
these convective clusters to train over central/southern KY for the
next few hours. However, a very gradual diminishing trend in
intensity is expected later on as the boundary layer cools and the
synoptic scale ascent pushes eastward and away from the region.
Back edge of the convection is pushing toward the Ohio River, so
have lowered PoPs a bit across our southern Indiana counties only,
but have significantly raised PoPs across central/southern KY for
the next several hours. Current thinking is that most widespread
rainfall will affect areas mainly south of the Parkways in KY, but a
secondary line will push through the Bluegrass region as well.
Overall, we believe convective trends should really come down after
midnight local time.
Flash Flood Watch continues for much of the region. Did allow our
far northeastern Indiana counties to clear out of the watch at 800
PM. Rest of the forecast elements look good at this time, with just
some minor adjustments needed.
.SHORT TERM (Now through Saturday Night)...
Issued at 304 PM EDT Fri Jul 3 2015
...Flash Flood Potential Continues Through Tonight...
A 5H shortwave trof reaching from the Great Lakes to the southern
Plains will sweep slowly eastward tonight. As this disturbance
encounters very moist, slightly unstable air it will generate
scattered showers and storms. Coverage should slowly decrease
overnight as instability decreases, but we may hold on to at least
scattered showers through the night thanks to that wave as well as a
broad synoptic surface boundary and local boundaries from earlier
convection. Because the ground is so wet, and considering the
rainfall rates we saw this afternoon, after chatting with JKL have
decided to extend most of the Flash Flood Watch through tonight. As
coverage decreases, we may be able to cancel it early. Speaking of
which, we will let the northeast corner of the LMK CWA (Scott IN,
Jefferson IN, and Trimble KY) expire at 8pm as previously scheduled
since that area has had time to dry out today plus the better
chances for heavier downpours are south of there. Thanks to ILN for
Tomorrow moisture will not be as deep as the upper wave sweeps much
of the RH to the south and southeast. As we destabilize over the
course of the day some showers and storms may still pop up,
especially across the Lake Cumberland region, but coverage will be
less than what we saw today. High temperatures will be pretty nice
for Independence Day, generally in the 80 to 85 degree range.
Shower/storm coverage will continue to decrease Saturday night as
temperatures fall into the middle 60s by morning.
.LONG TERM (Sunday through Friday)...
Issued at 257 PM EDT Fri Jul 3 2015
A weak upper level trough will be over the region at the beginning
of the long term period. This trough will slowly shift off to the
north and east through Monday. At the surface we will be in between
high pressure to the east and a low pressure system to the west.
There should be a relative lull in showers and thunderstorms Sunday
through Monday night. The best chance for rain will be across the
southeastern portion of the forecast area. However, these storms
will be scattered at best. In addition, Sunday night still looks
like it should be dry. Highs through this period will be in the mid
80s with lows in the upper 60s to lower 70s.
A shortwave trough will swing into southeastern Canada and the Great
Lakes region by Tuesday. A cold front will approach the lower Ohio
Valley Tuesday, bringing with it a greater chance for storms. This
front will stall out across the forecast area and will serve as a
focus for storms through the end of the work week. In addition, a
couple of weak waves will ride along this front. Scattered to
numerous storms can be expected through Thursday night in
association with these disturbances. A few strong storms may be
possible with this activity, but the main concern could become
flooding once again as grounds are already saturated from rounds of
rain this week.
Highs look to be a bit cooler this week with temps topping out in
the lower to mid 80s. Lows will range from the mid 60s to lower 70s.
.AVIATION (00Z TAF Update)...
Issued at 710 PM EDT Fri Jul 3 2015
Several bands of convection continue to move across the region this
evening. Surface frontal boundary lies just north of the Ohio River
with yet another mid-level wave pushing through the region. Expect
convection to diminish this evening and into the overnight hours as
the upper wave moves eastward and the frontal boundary sinks further
south into KY. Will continue to go with vicinity showers/storms at
the terminals this evening and taper things down toward midnight
Ceilings are expected to lower during the overnight hours. For now,
we plan on MVFR ceilings, but some temporary IFR ceilings can`t be
ruled out. Some light fog may also develop...especially at KLEX and
KBWG. Surface winds look to remain generally light and variable
tonight and then shift to the northwest on Saturday as the frontal
boundary pushes further south into KY.
KY...FLASH FLOOD WATCH until 8 AM EDT /7 AM CDT/ Saturday FOR
IN...FLASH FLOOD WATCH until 8 AM EDT /7 AM CDT/ Saturday FOR INZ076-