Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 060510
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
110 AM EDT Mon Jul 6 2015
...Updated Aviation Discussion...
Updated at 930 PM EDT Sun Jul 5 2015
Last of the showers are ending. Winds are fairly light across the
area, and many spots have dewpoints in the upper 60s, close to or
below current forecast lows. Have bumped up fog wording to areas for
many locations, though think it will still be patchy in the
Louisville metro thanks to a late afternoon drop in dewpoints.
Guidance is not calling for dense fog at this point, perhaps because
of lingering moisture in the low levels that could generate some
cloud cover. Will hold off any dense fog products, but overnight
crew may have to go with them as we see how visibility and cloud
trends go overnight.
.SHORT TERM (Now through Monday Night)...
Issued at 257 PM EDT Sun Jul 5 2015
Water vapor imagery this afternoon shows a well defined circulation
in the upper level flow over eastern Kentucky. At the surface low
pressure is centered near the KY/VA border. The majority of the
showers this afternoon will be across east central Kentucky where
light to moderate rains continue. There could be a few stronger
showers around the Lake Cumberland area. However, for the most part
these should only produce brief heavy rainfall and are not expected
to cause any additional flooding issues. Therefore have decided to
cancel the Flash Flood Watch this afternoon. Short term models also
have isolated to scattered showers developing across southwestern
portions of south central KY this afternoon. These should wane by
All of the rain should move out of the area by early evening. The
overnight hours are expected to be dry with light to calm winds and
partly to mostly cloudy skies. With plenty of low level moisture,
some patchy fog may develop across the region, so have added that in
to the forecast.
Southwesterly flow will set up tomorrow ahead of a cold front which
will begin to approach the region tomorrow night. There will be
little in the way of large scale forcing tomorrow. However,
relatively unstable soundings and a very weak upper level
disturbance moving through the flow could spark isolated showers
and/or thunderstorms. Rain chances will be on the increase late
Monday night as the cold front nears from the northwest.
Temperatures Monday are expected to be on the warm side with highs
in the mid to upper 80s. Lows tonight and tomorrow night will be in
the upper 60s to lower 70s.
.LONG TERM (Tuesday through Sunday)...
Issued at 300 PM EDT Sun Jul 5 2015
Tuesday still looks to be the wettest day in the long term period as
a front drops southeast into the Ohio Valley. Although the
strongest mid to upper level flow should remain to our north, there
may be enough 0-6 km bulk shear to produce some strong storms with
gusty winds. Storm strength will also depend on available
instability. While models are showing some, it may be difficult to
build much if we start the day cloudy with an initial round of
showers/storms. Will need to watch the evolution/timing of this
weather system in coming days.
For mid week, the front looks to stall over our region initially
with uncertainty still in how quickly a SE CONUS ridge will work
into the Ohio Valley and just how strong it will get. Most mid
range models continue to support shortwaves riding along the
boundary producing multiple rounds of showers/storms Tues night/Wed.
By Wed night/Thurs, most models indicate that the boundary will be
far enough north, to result in lesser POPs. Even the recent, wetter
outlier (the Euro) has trended drier on its 12Z run. However, the
door is still open for diurnally based convection peaking during the
afternoon/evening hours. This pattern looks to potentially hold
through the weekend with daily POPs. If the recent drier
model consensus holds, at least some dry periods during the
overnight hours might be added to the forecast beyond mid week.
Temperatures will generally range through the 80s for highs for
Tues-Thurs with lows in the upper 60s/lower 70s. As the ridge
builds into the Ohio Valley, it will bring a warmer airmass
resulting in high temps in the mid 80s to lower 90s for Fri-Sun with
lows in the lower 70s.
.AVIATION (06Z TAF Update)...
Issued at 105 AM EDT Mon Jul 6 2015
Minor restrictions to vis already showing up in LEX and BWG, and
that will be our challenge overnight. Calm winds, clearing skies,
and plenty of low-level moisture all support fog formation. However,
the night is very short, there is some slightly drier air trying to
filter in, and even the usually pessimistic NAM MOS guidance isn`t
hitting it that hard. Other bit of uncertainty in LEX is how much of
an influence the lingering mid-level clouds associated with the
upper low will be. All that said, will initialize with MVFR
visibilities and go with at least a TEMPO IFR for a few hrs around
daybreak. SDF is already a bit drier and always more mixy, so will
stay unrestricted there.
Should mix out any fog/stratus by late morning, with light SW winds
and just diurnal cu expected for the rest of Monday. Any return of
precip Monday night is a low probability, and most likely beyond the
valid TAF period.