Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 280111
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
911 PM EDT Mon Jul 27 2015
Issued at 905 PM EDT Mon Jul 27 2015
Forecast on track for the remainder of the evening and overnight
period. Two boundaries in play right now that have been the focus
for showers/storms this evening. The first lies across northern
Kentucky westward into south central Indiana and Illinois,
associated with the washed out cool front from the past few days.
This line of storms has been rather weak, with very little CG
lightning but also relatively slow moving. The other boundary
stretches from middle Tennessee to southwest Kentucky to east
central Missouri. This convection has been more robust, aided by a
passing upper level disturbance. Areas in between have remained dry.
For the overnight, expecting most areas in the forecast area to stay
dry. North boundary activity should weaken over the coming hours.
Activity to the see is drifting southwest, and may clip parts of the
area. Otherwise, plan on a rather muggy, humid night as readings
only fall into the low/mid 70s. While we`ll have some high clouds
overhead at times, patchy light fog is still expected.
.SHORT TERM (Now through Tuesday Night)...
Issued at 320 PM EDT Mon Jul 27 2015
Upper level shortwaves along the periphery of a ridge over the Ohio
Valley will continue to spark convection in a moist, unstable
environment. Although the ridge keeps building limiting storm
strength and coverage, we are see an uptick in showery activity as
of 1830Z. Many weak boundaries left over from previous convection
exist over our region which will help provide some focus for
showers/storms. Isld to sct showers with isld t-storms will
continue through the evening hours before daytime instability is
lost. These showers/storms will contain locally heavy rainfall at
Later tonight some short range models indicate a complex of
storms may travel SE from central IL/MO into areas west of I-65. It
would be in a weakening phase if it makes it this far southeast.
Also some areas may develop some patchy fog overnight with the light
sfc winds and moist low levels. Low temperatures should range
through the low to mid 70s.
For Tuesday, expect a hot and muggy day. The ridge will be stronger
over our area tomorrow limiting any convection to isld if it can
even get going. Think that most areas should be dry. With
continued dewpts in the 70 to 75 degree range and high temps
reaching the upper 80s to lower 90s, heat indices should top out in
the 100 to 103 degree range mainly along and west of I-65 in KY and
along the Ohio River in Indiana. Therefore will issue an SPS about
the hot, muggy conditions for Tues/Wed (see long term discussion on
Wed heat indices).
Tues night will again be mostly dry with any lingering showers
quickly dying after sunset. Low temps should range through the low
to mid 70s.
.LONG TERM (Wednesday through Monday)...
Issued at 245 PM EDT Mon Jul 27 2015
Main item of interest will be the timing of a front passing through
the region Wednesday to Thursday morning. The NAM favors a
pre-frontal trough coming into the region during peak heating and
forcing good coverage of storms, whereas the GFS keeps a stronger
cap in place and the best forcing in Indiana. The latest SREF would
argue towards the GFS solution and will lean that way as well, with
isolated pops in the east for the daytime period and scattered in
the west, highest in our northwest counties. Also with that
solution, best chance would be with diurnally driven storms.
Beyond that front, dry air comes back into place over the region,
with little in the way of triggers for daily storms. GFS has a
narrow plume of moisture associated with a weak front Saturday
afternoon, but will maintain continuity in the forecast for now and
The warmest day should be Wednesday, just ahead of the front. Heat
indices will reach around 100 or higher along and west of the I-65
corridor. No need for a headline at this point, as the heat is not
atypical of summer. Behind the front, we should see near normal
temperatures the rest of the period.
.AVIATION (00Z TAF Update)...
Updated 715 PM EDT Mon Jul 27 2015
The region will remain in a moist airmass during the TAF period and
combined with subtle surface boundaries and passing upper level
systems, there will be at least a chance of a shower or storm
through the period. However, the setup isn`t overly favorable for
high coverage of storms so will continue with just a VCSH mention
during peak heating. BWG stands the best chance of seeing a storm
during the overnight, though upstream convection may weaken or miss the
airport to the south/west.
Earlier guidance suggested broken MVFR stratus could develop overnight
at SDF/LEX but latest forecasts is trending more scattered. This may
allow some light fog/haze to persist however.
For Tuesday, expecting similar conditions to today, with isolated
pop up showers possible anytime from mid morning onward. Plan on
light/variable winds overnight becoming light/WSW during the day.