Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 271719
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1219 PM EST Mon Feb 27 2017

...Updated Aviation Discussion...

.Short Term...(Today through Tuesday)
Issued at 230 AM EST Mon Feb 27 2017

Shortwave trough moving across Missouri this hour is bringing an
area of mid-level moisture across our region early this morning. The
lower levels slowly are saturating, and we will see some light rains
by daybreak and continuing through the morning hours. Deeper
moisture should leave the region around lunchtime, allowing the
shower activity to taper off. Temperatures under the cloud cover
this morning should be warm enough to keep the precip as all liquid.

Monday night, we should solidly be in the warm sector of a storm
system crossing the Central Plains. The GFS and Euro both paint a
large area of light QPF in this sector overnight, whereas the NAM
and generally the GEM keep us dry. That said, the NAM does show some
lift and moisture transport ahead of a low-level jet by daybreak,
similar to but not as deep as the isentropic lift depicted by the
GFS. High-res guidance shows the best chances across Southern
Indiana and North Central Kentucky. All show some elevated
instability as well, so cannot rule out some thunder in this rain
area as well.

Exactly how the morning precip mentioned above plays out will have
some implications on Tuesday afternoon precip development. Hard to
predict cloud cover and boundaries will determine where the best
instability. Given the presumed best chance for precip early
Tuesday, we would then see afternoon development along and south of
the Parkways. The NAM12 shows a couple of cells tracking northeast
in the afternoon in this area, whereas the 3km and 4km NAMs keep any
cells either over Eastern KY or Middle TN.

.Long Term...(Tuesday night through Sunday)
Issued at 230 AM EST Mon Feb 27 2017

...Strong to Severe Storms Possible Tuesday Night and Wednesday...

Severe weather parameters would indicate potential for stronger
storms to occur, should the instability be realized ahead of cold
front initially moving slowly across the Midwest. Wind energy over
our region is intense just above the surface, with 45-55 kt winds at
925 mb Tuesday night and Wednesday. Flow mostly is unidirectional
though, leading to fast-moving storms and some potential for
damaging winds to mix down. Question mark for surface-based storms
is instability, but for now the GFS and NAM are showing around 500
J/kg of CAPE through the night. Potential exists for a little more
with surface heating during the day Wednesday.

Location of cold front will have a factor in inducing lift as well.
Daybreak on Wednesday should see the actual boundary running from
central IN southwest to the MO Bootheel and progressing eastward
rapidly, clearing our region by late afternoon. The NAM is the
outlier here, slowest with the progress of the front, which would
allow us some time to tap into better instability over Lake
Cumberland in the afternoon. For now, have leaned more towards the
majority of the models, but left in a slight chance for storms west
of I-65 Wed. afternoon.

Beyond the midweek system, we have a clipper moving through the
region Thursday night. This system could bring a quick burst of
light snow, especially to points north of I-64. Expect a little
below normal temperatures for the end of the work week, with highs
in the 40s Friday. Then we`ll start a warmup under dry conditions
for the weekend.

&&

.Aviation...(18Z TAF Issuance)
Issued at 1217 PM EST Mon Feb 27 2017

The rain that has been ongoing tonight will lift off to the north
over the next hour or so. Dry weather is then expected through the
afternoon and evening hours. Clouds have begun to break up at BWG
and will likely scatter out at LEX and SDF for a time tonight as
well. Winds through the afternoon will remain out of the south to
southeast.

Another disturbance will move through tomorrow morning. Ceilings
will deteriorate quickly after 08-09Z, dropping to low end MVFR or
IFR. BWG looks to have the best chance to drop to IFR early tomorrow
morning. Showers will develop as well, so have added them into the
forecast. There is a bit of instability, but coverage of
thunderstorms may be on the lower side, so have not mentioned TS at
this time. Winds will increase tomorrow morning and become gusty out
of the south.

&&

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

$$

Short Term...RJS
Long Term...RJS
Aviation...EER



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