Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 220534
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1234 AM EST Wed Feb 22 2017

...Updated Aviation Discussion...

.Short Term (Now through Wednesday Night)...
Issued at 255 PM EST Tue Feb 21 2017

Upper low working its way along the Gulf Coast continues to feed
moisture north into the Tennessee and Ohio Valleys. Scattered light
rain showers are spreading through south-central Kentucky, while the
more solid band of rain focused by a northern stream system remains
north of our CWA in Indiana.

Expect coverage to continue to increase through this evening as the
two streams try to phase, but precip amounts will be quite light, on
the order of a tenth of an inch with isolated quarter inch amounts.
Best chances will be east of I-65 where we will go likely.

Deeper moisture exits by morning, but that could clear us off just
enough to set up fog. At this point will just mention patchy fog
roughly from daybreak to mid/late morning, mainly in southern
Indiana and roughly one tier of counties south of the Ohio River.
Not going to get carried away with dense fog just yet, as cloud
cover holding on would limit any fog. Lingering showers from the
Bluegrass to Lake Cumberland will exit Wednesday morning. Otherwise
unseasonable warmth continues Wednesday into Wednesday night under
weak ridging aloft and a sloppy SW low-level gradient.

.Long Term (Thursday through Tuesday)...
Issued at 255 PM EST Tue Feb 21 2017

Unseasonably warm weather continues Thu-Fri under deepening SW flow
ahead of a broad western CONUS trof. A few warm advection showers
possible on Thursday with the warm front, but will keep POPs low
given the lack of focus until it is farther north over
Illinois/Indiana. Thu night min temp forecast is working the high
end of guidance, but in the pre-frontal SW flow regime it might be
difficult to get below 60.

Most interesting part of the forecast is Friday into Friday night as
a very dynamic system gets organized with the surface and upper low
becoming stacked over the Upper Midwest, and a strong cold front
pushing through the Ohio Valley. What we can say with confidence is
it will be quite breezy with at least near-record warmth Friday
afternoon. Forecast highs generally in the mid 70s are conservative,
but reasonable if there is substantial cloud cover. More sunshine
and slower fropa could allow temps to approach 80.

Models are trending slower with fropa, which would end up more at
the diurnal min in instability. At this time, the greatest SVR
threat is likely to our north and west, but not far enough to write
off SPC`s Day 4 Slight Risk. Even with storms in a weakening state,
wind fields are strong enough to support at least isolated damaging
winds, mainly over southern Indiana and north-central Kentucky.

Strong cold advection on Saturday will mean minimal recovery in
temps, with daytime readings struggling to crack 50. Otherwise look
for a cloudy and blustery day under the cyclonically curved flow.
High pressure builds in for Sunday, so we will have a dry day with
temps near climo. After that look for a period of active weather,
with a quick-hitting but weak system bringing light precip Sunday
night, and then milder but unsettled weather by Tuesday ahead of a
slow-moving cold front.

&&

.Aviation (06Z TAF Update)...
Issued at 1233 AM EST Wed Feb 22 2017

Closed upper low will move SE to the Gulf of Mexico overnight, and
we will gradually lose deeper moisture as this occurs. As a result,
precipitation will gradually end at the TAF sites over the next few
hours. However, the main concern will be lower ceilings and fog
potential as we move toward dawn and the mid morning hours.

Already seeing ceiling/vis categories drop into the MVFR range under
light and variable winds. Still expect that ceilings will drop below
fuel-alternate for a time toward dawn, possibly down to IFR at LEX.
Expect vis to stay in the MVFR range, although a brief period of IFR
is also possible, especially at LEX.

Improvement should occur by mid to late morning, with a return to
VFR ceilings and visibility. A light south wind will take hold with
dry conditions persisting thereafter. May run into more ceiling/vis
problems tomorrow night, but will nail that down at a later issuance
due to low confidence.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&

$$

Short Term........RAS
Long Term.........RAS
Aviation..........BJS


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