Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 280154
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
954 PM EDT Wed Aug 27 2014
Issued at 950 PM EDT Wed Aug 27 2014
Convection has pretty much dissipated over central Kentucky and
southern Indiana. A few isolated cells west of Bowling Green, and in
Indiana just west of Tell City, where greater moisture pooling along
the surface boundary continues. Will hang onto isolated POPs just a
bit longer along our western boundary, but otherwise this update
will remove the POPs for the rest of the night.
Issued at 820 PM EDT Wed Aug 27 2014
Weak sfc trof continues to press southward across central KY, with
scattered storms persisting but on a clear weakening trend. Expect
the remaining convection to dissipate within the next hour or so as
daytime heating is lost, but confidence is limited by the couple of
storms that remain fairly healthy over southwest Indiana. Current
isolated to scattered wording seems to have a good handle on the
situation now, but expect to update the forecast in an hour or so to
refine where isolated T-storms might linger a bit deeper into the
.SHORT TERM (Now through Thursday Night)...
Issued at 315 PM EDT Wed Aug 27 2014
A healthy cu field has developed in a moist, unstable atmosphere
this afternoon. An upper level ridge was over the region with a
weak sfc boundary located near the Ohio River. Instability along
with the boundary has created enough lift for a few showers over
southern Indiana as of 245pm. Expect isld-scattered showers and
some t-storms to continue to develop through the evening hours over
southern Indiana and central Kentucky. Soundings indicate
plentiful CAPE but meager wind fields so any storms that develop
should be limited in strength. However dry low levels and steep low
level lapse rates may be enough to force a few windier showers and
storms with wind gusts up to around 40 mph. Convection should
decline after sunset with the loss of day time heating.
The front should continue to make slow progress southward tonight
with patchy light fog developing during the pre-dawn hours. Low
temps tonight should hold in the upper 60s and lower 70s.
For Thursday, the weak sfc front will drift into south central
Kentucky providing the best focus for afternoon showers and storms
there. These storms will be similar to today in strength and
coverage peaking during the late afternoon/evening hours. It is a
bit unclear if storms will diminish completely Thurs evening or
continue on throughout the overnight night hours Thurs as a
shortwave moves into the region possibly prolonging convective
activity. For now will remain conservative and diminish POPs by
midnight Thurs night with the next chance for rain on Friday (see
long term discussion).
Temps Thurs should be slightly cooler than today in the 84-92 degree
range with the coolest temps north of the front. Low temps should
range from the mid 60s to low 70s Thurs night.
.LONG TERM (Friday through Wednesday)...
Issued at 323 PM EDT Wed Aug 27 2014
The tenacious upper ridge across the SE CONUS will have shifted off
the FL/GA coast by the start of this forecast period with meridional
flow dominating. Southerly flow will advect in copious amounts of
moisture by this upcoming holiday weekend with PWATs looking to
reach toward and exceed the 2 inch mark. Previously advertised upper
low swinging through the central Plains late this week will phase
into the mean flow as it takes a northeasterly turn toward the Great
Lakes. Its remnants will bring height falls to the region over the
weekend and with the upper ridge no longer in the picture, zonal
flow will return by the start of the new week but with
shortwaves/perturbations traversing through overhead. This all
equates to another unsettled period with precip chances nearly every
day. This isn`t to say that everyone will see rain each day, but
just that chances exist, especially over the weekend.
The frontal boundary mentioned above (in the short-term section)
will be lifting north across the forecast area on Friday, setting
the stage for WAA and serving as a focus for convection. Have gone
with slight chance on Friday as the day will be the start for warm,
moist air advecting in but won`t have been quite enough to drive too
much convection other than pop-ups that will been diurnally driven
and isolated, such as what has been seen thus far this week. PoPs
will be much higher for Saturday and Sunday with convection
potentially more organized, given the greater synoptic push. As
alluded to already, PoPs continue into the new week with a secondary
focus for convection Monday into Tuesday as another frontal boundary
dives down from the NW. Depending on the speed of the front, could
begin to see some drying out by the middle of next week with
potentially a reprieve from the typical summer heat and humidity
that has enveloped the region lately.
Highs on Friday look to be the warmest of the long-term as they
reach near to slightly above normal - upper 80s to low 90s with
dewpoints in the upper 60s to around 70. We`ll then see the full
spectrum of 80s for the remainder of the period with variations due
to precip and cloud cover. Lows will range from the mid 60s to low
70s with the warmest overnight period looking to be Saturday night
as cloud cover moderates temperatures and WAA in full swing.
.AVIATION (00Z TAF Update)...
Issued at 650 PM EDT Wed Aug 27 2014
Weak surface trof has fired convection from the SDF area to north of
LEX this afternoon. LEX TAF was updated for the line of storms, and
SDF continues to deal with convection in the area, but at this point
it appears that should push on to the south before the valid TAF
time. Storms should fade quickly after sunset, well before anything
works into BWG.
Main challenge overnight is fog potential. BWG is largely a
persistence forecast from last night and is consistent with
guidance. Will go to MVFR around midnight, with a few hrs of IFR vis
around daybreak. Confidence is a bit lower in LEX, where it remains
to be seen how much rain falls. With the expectation of rain and
decent model agreement, will follow the MOS lead and include IFR
visibility around daybreak. Even SDF could get in on reduced vis
given the late-day storms. Look for MVFR for much of the night, but
heat island effects should keep vis from tanking.
Weakening boundary will be south of the terminals on Thursday, so
expect VFR conditions with diurnal cu and light east winds.