Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 252302
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
702 PM EDT Mon Aug 25 2014
...Updated Aviation Discussion...
.SHORT TERM (Now through Tuesday Night)...
Issued at 305 PM EDT Mon Aug 25 2014
Surface high pressure along the mid-Atlantic coast continues, but is
showing just enough weakness over the Ohio Valley to allow a weak
convergence boundary to develop over east central Kentucky. So far
we have seen a few isolated showers and a T-storm or two develop,
but these have been fairly light and short-lived. Expect any further
convection to fade around sunset, if not before.
Tonight should be a carbon copy of last night with warm and muggy
conditions, and some patchy fog, which shouldn`t be dense over most
of the areas but could get fairly thick in the more typical
For Tuesday the upper ridge covering all the southeast CONUS will
strengthen overhead, and some modest mid-level warming and drying
through the column will make it even more difficult to trigger
convection. That said, there is still a hint that storms that
develop on the periphery of the ridge could drop as far south as
southern Indiana. Therefore will introduce a slight chance POP for
that portion of the area Tuesday afternoon. Any precip should
quickly dissipate around sunset. Max temps look similar to today, if
not just a tick warmer. Will end up near MOS consensus, but most
likely on the lower end as the GFS MOS continues with its warm
tendencies. This is only a slight bump up from raw model consensus.
Heat indices will be similar to today in the mid/upper 90s, as any
warmer temps that we see will be offset by slightly lower dewpoints.
.LONG TERM (Wednesday through Monday)...
Issued at 314 PM EDT Mon Aug 25 2014
For the long-term period, the forecast area will be entrenched in a
pattern typical for summer with afternoon/evening storms firing up
and persistent warm, humid conditions. The upper ridge that has been
hanging out across the SE CONUS and affecting the Ohio Valley will
make a SE shift with the 12Z GEM, GFS, and ECMWF agreeing. The
center is projected to position itself in the NE Florida/SE Georgia
area, which will open the door for a trough ejecting out of the
Rockies to swing through the region. The three deterministic models
also have a general agreement on this trough becoming a cut-off low
in the central Plains before phasing into an open wave as it
interacts with the periphery of the stout ridge in the SE. The most
noticeable differences creep into the picture by this upcoming
holiday weekend as the GFS and GEM washes out the low much quicker
than the ECMWF, plowing into this region by late Saturday/early
Sunday. However it ends up playing out, it looks to be a safe bet
that we`ll be in the periphery of the 500mb ridge so shortwaves/vort
maxes riding on through much of the long-term period will keep this
forecast area unsettled.
At the surface, front currently laid out across Wisconsin
south-southwestward into Iowa will be attempting to approach
southern IN/central KY by the start of this forecast period, losing
its stamina the further south it drops. This boundary will still
make an impact by providing a focus for convection on Wednesday,
primarily across the northern half of the forecast area. For
Thursday into Friday, we`ll be on the periphery of the
aforementioned upper ridge to the SE and surface high hugging the
Canadian border, traversing across the northern Great Lakes and into
New England by early Friday. Therefore, precip chances exist as
diurnal heating assists in their development, losing their punch
after sunset each day. By this weekend, the convection will
transition toward being driven by the synoptic conditions, which
look to allow for higher chances across the entire area. Moisture
and instability will be plentiful with the greater shear entering
into the area as well.
Temperatures will remain near normal for this time of year,
generally in the mid to upper 80s and flirting with the 90 degree
mark through the remainder of this work week. Overnight lows will be
in the upper 60s to lower 70s with dewpoints to match. This will
drive heat indices to a few degrees higher than actual highs.
.AVIATION (00Z TAF Update)...
Issued at 702 PM EDT Mon Aug 25 2014
Areas of showers and thunderstorms over northeast Illinois and
central Indiana are diving to the southeast but are weakening and
should continue to do so, posing no real threat to the central
Kentucky TAF sites. The outflow boundary put out by the activity
north of IND will need to be monitored, but it would be very weak by
the time it gets to the Ohio River, if it even makes it that far.
Dew points are lower tonight than last night at SDF/LEX, and even
last night not much fog formed at those locations, so will keep
tonight fog-free there as well. BWG, on the other hand, received
rain this afternoon and did get fog this morning, so will continue
to include early morning fog there.
Isolated storms will be possible again tomorrow afternoon, with SDF
standing the best shot at a stray cell.