Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 241718
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1218 PM EST Fri Feb 24 2017

...Updated Aviation Discussion...

.Forecast Update...
Issued at 1120 AM EST Fri Feb 24 2017

Not exactly calm before the storm as a tight gradient has cranked
south wind gusts up to 30-35 mph this morning, with record highs
already falling all over the place. Have issued an SPS advertising
frequent 35 mph gusts, and while it wouldn`t be a shock to see a few
places squeeze out a 40 mph gust, that won`t be the prevailing
condition and we don`t want too much headline clutter with the SVR
threat coming later.

Still on track for strong/severe convection mainly during the
evening hours. Hi-res models are slower again with the main line of
storms, and the main question is when the strong cap (+10C at 800mb)
will break. Appears that it will happen between 21-00Z, but when it
does, expect development to happen rapidly as the mid-level lapse
rates will be over 8C/km.

&&

.Short Term...(This afternoon through Saturday evening)
Issued at 250 AM EST Fri Feb 24 2017

...Record February Warmth and Severe Storms Possible Late This
Afternoon and Tonight...

994 mb low moving across northern Missouri early this morning is
forecast to shift northeast toward Chicago early this afternoon. Our
environment, out ahead of the attendant cold front, will be
characterized by record February warmth, likely near 80 at SDF, a
strong mid-level cap, and brisk southerly winds. By 25/00Z, that low
will be into southern Michigan, with the trailing cold front likely
along the Wabash.

Forecast soundings for SDF have that cap breaking down in the 22-01Z
time frame, allowing for some initial convective development,
generally along and west of the I-65 corridor. Given the timing with
peak heating, these cells will have the best chance to grow quickly
and possibly become supercells. Dry near-surface soundings would
tend to limit tornadic potential, but low wet-bulb zeroes indicate
better potential for any rotating cells to generate some hail. As
the cap erodes further, forcing along the front should allow cells
to develop southward, almost as a zipper, and merge into a linear
feature as the general motion of the line heads eastward. Stronger
winds aloft could mix down with any bowing segments along this line.
Also, as the evening progresses, LCL`s drop some and NCAR ensemble
shows an uptick in updraft helicity that may allow for continued
stronger cells within the line, or possible some book-end vortices
along bowing segments. There is a narrow window around 02-03Z where
instability and helicity match up before the former fades. At this
point, that window lines up just east of I-65, but it is still a bit
early to have too much certainty in either location or time, given
the mesoscale nature of the event.

The cold front will blast east overnight, bringing a sudden end to
the record warmth. Any record warm min temperatures for Friday
likely will have to wait till Midnight Friday night for the falling
temperatures. Crashing temperatures in the atmospheric column will
mean a continued large low-level lapse rate through the day
Saturday. Cannot rule out some convective showers developing, with
even a few flakes of snow possibly mixing in north of I-64 during
the morning. Cloud cover likely will stay over the region most of
the day Saturday, keeping highs ?????

.Long Term...(After midnight Saturday night through Thursday)
Issued at 230 AM EST Fri Feb 24 2017

Surface high pressure over the Lower MS River Valley Sat. night will
shift east into the Southeast U.S. Sunday, bringing a start to
another warm up. For the work week, we look to have a broad
southwest flow aloft. Models are struggling with timing impulses
moving within this flow and their subsequent chances for precip.
Opted mostly to maintain the blended model forecast for this period
outside of some minor tweaks.

That forecast calls for Tuesday to be the warmest day, with
temperatures in the 60s.  The best chance for precipitation is late
that day and into Wednesday.

&&

.Aviation...(18Z TAF Issuance)
Issued at 1215 PM EST Fri Feb 24 2017

Gusty south-southwesterly winds will continue through the afternoon
ahead of a cold front moving in tonight. Showers and storms are
expected to fire up along and ahead of the front late this afternoon
into this evening. The bulk of the activity should impact the
terminals after 0Z. The latest guidance has shifted the timing an
hour or two slower than previously forecast, particularly at LEX. A
TEMPO TS group has been added to the forecast to account for this.

In the wake of the cold front, winds will shift to west-
northwesterly. Sustained winds will remain in the 10-15 knot range
with gusts of 20-25 knots.

&&

.Climate...
Issued at 200 AM EST Fri Feb 24 2016

Record temperatures for today. ** indicates current forecast calls
for that record to be tied or broken.

Louisville:
**Feb. 24 record warm low: 56 (1930)
**Feb. 24 record high:     71 (2000)

**All time record February high:   78 (1932, 1887, and 1883)
All time record February warm low: 62 (1954 and 1932)

Lexington:
**Feb. 24 record warm low: 55 (1930)
**Feb. 24 record high:     71 (1944)

All time record February high:     80 (1996)
All time record February warm low: 59 (1890)

Bowling Green:
**Feb. 24 record warm low: 55 (1930)
**Feb. 24 record high:     74 (1875)

All time record February high:     83 (1918)
All time record February warm low: 64 (2008 and 1895)

Frankfort:
**Feb. 24 record warm low: 52 (1930)
Feb. 24 record high:     78 (1996)

All time record February high:     80 (1932)
All time record February warm low: 61 (1954)

* means most recent occurrence, record occurred in previous years as
  well

&&

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

$$

Update...RAS
Short Term...RJS
Long Term...RJS
Aviation...EER
Climate...RJS


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