Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 161702
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
102 PM EDT Tue Sep 16 2014
...Updated Aviation Discussion...
Issued 1222 PM EDT Tue Sep 16 2014
The optimistic cloud forecast seems to be paying off early this
afternoon, as many holes in the clouds are now showing up on the
latest satellite imagery. These clouds will continue to mix out
over the next several hours as we deepen the boundary layer, meaning
most will see some sunshine by later this afternoon. Will have to
keep an eye on temperatures given the sun starting to poke through,
but highs in the upper 60s to lower 70s still seem reasonable.
Issued 1019 AM EDT Tue Sep 16 2014
Updated the forecast this morning to reflect latest precip and cloud
trends. Drizzle from earlier this morning is becoming less
widespread as cloud bases have slowly lifted and drier low-level air
has worked in. The clouds will be slow to mix out late this morning
into this afternoon and have some doubts on how much sun we will
actually see this afternoon. Will continue to mention some peaks of
sun by late this afternoon given the latest forecast soundings and
cross-sections, but that may be optimistic. Updated products are
.SHORT TERM (Now through Wednesday Night)...
Issued at 300 AM EDT Tue Sep 16 2014
A flat 500mb trough will scoot across Ohio late today. High pressure
of Canadian origin will build in behind this trough and bring in
cooler temperatures for today and Wednesday.
At 2 am this morning, a cold front lay across southern Indiana, this
boundary will move southeast of the Ohio River shortly before dawn,
and south of the Commonwealth by early afternoon. Some light showers
currently (@ 2 am) across the Bluegrass will exit by the pre-dawn
hours. However, some light sprinkles or even some patchy drizzle may
arrive post front, and continue through mid-morning.
Low clouds will also arrive behind this front and bring somewhat
dingy weather for a good portion of this morning. Forecast soundings
agree with current satellite imagery in hinting that clearing will
be slow through early afternoon. However, by mid to late afternoon
skies will slowly clear and mostly clear skies are anticipated by
High pressure will settle across Indiana and Ohio tonight and remain
there tomorrow. Winds will become light northerly today and continue
from the northeast overnight, before backing to light northwest
Wednesday afternoon. Even with this morning`s mild temperatures,
highs will only range from the upper 60s north to the lower 70s this
afternoon. Tonight will cool off down into the lower 50s, aided by
lower dewpoints and relatively clear skies. Wednesday`s highs will
reach the lower to mid 70s.
.LONG TERM (Thursday through Tuesday)...
Issued at 310 AM EDT Tue Sep 16 2014
At the beginning of the extended forecast period, we are expecting a
trough east...ridge west pattern across the CONUS. The Ohio Valley
will be west of the trough axis placing our region in a
northwesterly flow initially. However, the multi-model consensus is
consistent in bringing rising heights to the region from late week
and into the weekend as a large ridge moves east out of the Plains.
This ridge may be amplified a bit due to the remnants of tropical
cyclone Odile which will move from the desert SW and into the
Intermountain west by late week.
As the remnants of Odile push further northward into the westerlies,
the will phase with an approaching upper level trough coming through
the southern Rockies. This upper trough is forecast to amplify and
swing eastward into the Ohio Valley by the latter half of the
weekend. Overall, the model solutions have trended slightly
stronger with this upper trough and therefore, we are starting to
see a slightly slower progression of the trough axis aloft.
Previous model runs had this feature swinging through earlier in the
weekend, but that now looks delay into the latter half of Sunday and
perhaps into Monday. As this occurs, a secondary/potent mid-level
PV anomaly is forecast to swing through central Canada and into the
northern Great Lakes. These two features look to phase at some
point resulting in a large powerful trough swinging through the
northeastern US and re-enforcing a large baggy trough over the
eastern half of the US leading into early next week.
With the aforementioned ridge building into the region by mid-week,
dry and increasingly mild weather conditions are expected across our
region. Generally, mostly sunny days and mostly clear nights will
likely result in large diurnal swings in temperatures with overnight
lows in the upper 40s to the lower 50s warming into the lower-middle
70s during the day. Some patchy morning fog will also be possible
in the typical low-lying and fog prone areas. We should see warmer
and more moist conditions return to the region by Saturday as strong
southwesterly flow pushes into the region. Highs in the upper 70s
to the lower 80s look increasingly likely for Saturday given the
anticipated slower arrival of the front. Rain chances will increase
late Saturday and into Sunday as the frontal boundary pushes in from
the west. Showers and thunderstorms will accompany this front as it
pushes through. With the remnant moisture from Odile, some heavy
rainfall will be possible late Saturday through Sunday. Highs on
Sunday should average a little cooler than Saturday due to clouds
and precipitation. Highs will likely warm into the mid-upper 70s.
Cooler and drier air will filter in on Monday with highs mainly in
the 70s. The next real push of cooler air will arrive Monday night
and Tuesday. Lows Monday night will likely drop back into the upper
40s to the lower 50s...but highs by Tuesday will likely struggle to
reach the middle-upper 60s.
.AVIATION (18Z TAF Update)...
Issued at 100 PM EDT Tue Sep 16 2014
MVFR stratus deck continues to erode early this afternoon as some
peeks of sun are now filtering through. This trend will continue
over the next several hours, with KSDF likely going VFR first early
this afternoon, followed by KLEX and KBWG later on. Winds will
remain out of the NNE at 4-8 knots.
Skies will go mostly clear tonight and winds will go calm as a
surface ridge builds in. Will have to keep an eye on dewpoints this
afternoon to see if we can mix drier air down and help avoid fog
potential overnight. Current thinking is that KSDF will remain VFR,
but KLEX and KBWG likely won`t have as much time to mix down their
dewpoint this afternoon resulting in fog development overnight.
Will keep KLEX at MVFR BR for now and hit KBWG hardest with some
IFR vsbys, but confidence in this occurring is rather low given some
uncertainty in the cloud cover and associated dewpoint evolution