695
FXUS63 KLMK 130704
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
304 AM EDT Tue Aug 13 2013
.SHORT TERM (Now through Wednesday)...
Issued at 245 AM EDT Tue Aug 13 2013
A couple of fronts are headed our way today. The first is slower
moving and stretches roughly from Lake Erie right to our northern
row of counties. The second has a more noticeable dewpoint
difference and is located between Central Michigan and southern
Wisconsin. Expect the first front to bring a wind shift into the
Ohio River area in the next few hours, but the main drier air with
the second front will not get here until this afternoon.
With a continued moist airmass in place ahead of the first front, we
are seeing lines of showers/embedded thunder continue to develop
early this morning. Will continue to watch for training of heavier
cells, but that watch should end soon, as that second front brings a
great rest of the work week forecast.
Highs today will depend on who can see the most sunshine. Most
places will stay cloudy, keeping readings around 80. The northern
forecast area has the best chance to break out behind the front, but
north winds should temper the extra sunshine and keep readings in
the lower 80s. Tonight, a steady north wind will keep us from ideal
radiational cooling, but lows should fall into the 50s for most
everyone. Then Wednesday under full sunshine and a north/northeast
wind highs look to rise only to the mid/upper 70s. Dewpoints may
drop into the mid 40s across the north, very low for mid August!
.LONG TERM (Wednesday Night through Monday)...
Issued at 300 AM EDT Tue Aug 13 2013
Upper air pattern will undergo a transition during the extended
period from troughing centered over the eastern Great Lakes (which
has been the prevailing pattern almost all summer) to a more typical
mid-summer pattern in which flat zonal flow retreats well north of
the Canadian border. However, this latter zonal flow won't really
become established until Monday or Tuesday of next week.
A very dry and unseasonably cool airmass will already be in place
across the Great Lakes and the Lower Ohio Valley by Wednesday
evening. By late Wednesday, high pressure of Canadian origin is
forecast to lie near Chicago, with a ridge axis extending southeast
toward West Virginia. Clear skies and light winds will allow for
almost perfect radiational cooling early Thursday, and some
remarkably cool (for mid-August) overnight lows are expected for
early Thursday morning. Some lows may dip below 50 across some of our
typically colder rural locations!
Expect mostly clear skies with very comfortable temperatures and
humidities through Friday morning as high pressure settles overhead.
Highs both Thursday and Friday will hover not too far from 80. Lows
early Friday morning will reach the mid 50s.
For Saturday and Sunday, surface high pressure will move over New
England, with ridging extending southwest over the Ohio
River. Winds will stay quite light through the weekend, mostly from
an easterly direction. A weak upper level disturbance will slide
south across Missouri late Friday and will establish a weak 500mb
trough across southern Illinois, which will basically stay in
place through Sunday.
Isolated to scattered showers and thunderstorms are expected to our
east over the southern Appalachians on Friday, this convection may
re-develop a bit farther west Saturday and Sunday as light easterly
winds at the surface combine with relatively cool 500mb highs to
bring moderate afternoon and evening instability each day. This
convection will not be as widespread nor produce the heavy downpours
that some locations experienced over this past weekend. They will
also tend to develop during the afternoon and diminish during the
evening hours. Overall expect partly cloudy skies this weekend with
relatively cool highs in the lower to mid 80s with overnight lows in
the 60s. Think that each afternoon, scattered thunderstorm coverage
will be greatest across our southeastern counties and most sparse
across southern Indiana.
&&
.AVIATION (06Z TAF Update)...
Issued at 1205 AM EDT Tue Aug 13 2013
Did an early round of updates to the TAFs as HRRR is indicating some
low cloud development in the wake of last night's rains. KHNB is
coming in with these low clouds and think they will invade points
farther east as the night goes on. For now have gone with low-end
MVFR cigs, with worse conditions at KLEX by daybreak. Would not be
surprised to see some lower ceilings, but will introduce into the
TAFs for now and see how trends go the rest of the early morning.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&
$$
Short Term........RJS
Long Term.........JSD
Aviation..........RJS