Area Forecast Discussion
Issued by NWS Louisville, KY

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133
FXUS63 KLMK 240525
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
125 AM EDT Fri Mar 24 2017

...Updated Aviation Discussion...

.Short Term...(This evening through Friday night)
Issued at 257 PM EDT Thu Mar 23 2017

A weak vortmax moving through the area today has brought an area of
rain to portions of southern IN and west central KY. It has also
kept temperatures down across portions of the region. This area of
rain will continue to sink southeast across the region this
afternoon, mainly west of a line from Orange County in Indiana to
Russell county in central KY. This rain is expected to move out/
dissipate by the early evening hours.

Dry weather is then expected through at least Friday evening as
upper level ridging builds in. Southerly winds will increase
overnight as the pressure gradient increases across the region.
Gusty southerly winds through the day tomorrow will bring more of a
warm up than we have seen today despite mostly cloudy skies expected
tomorrow. Low tonight will be in the upper 40s to lower 50s as the
southerly winds will keep temps from falling much. Highs tomorrow
will top out in the lower 70s.

A strong low pressure system approaching from the Plains will be the
main weather maker for the weekend. Ahead of this system, a few
showers may move into southern IN during the pre-dawn hours
Saturday. Lows will be relatively warm in the mid to upper 50s on
Friday night.

.Long Term...(Saturday through Thursday)
Issued at 318 PM EDT Thu Mar 22 2017

Saturday - Sunday

A low pressure system will lift from near the KS/MO border on
Saturday morning into the Great lakes region by Sunday afternoon.
With the track of the storms, the region should mainly remain in the
warm sector until Sunday evening when the frontal boundary
associated with the low finally swings through. A couple of rounds
of showers and storms look possible Saturday. The first will be in
the morning Saturday and mainly west of I-65. Another round of
storms looks to develop west of our region and move through Saturday
afternoon and evening. Soundings are more unstable (500-1000 J/kg
MUCAPE) with these storms and low level winds will increase. Some
stronger storms will be possible, though widespread severe weather
doesn`t look likely.

Scattered showers and storms will continue Saturday night and Sunday
as the upper low continues to lift off to the northeast. These look
to lift off to the northeast by Sunday night.

Monday - Tuesday

Another strong low pressure system will approach Monday. The surface
low for this system looks to take just a bit more southerly track
than the one over the weekend, moving just south of the Great Lakes
region through Thursday afternoon. Soundings with this system show
better instability than for the weekend at 1000-1500 J/kg MUCAPE as
temperatures rise into the mid 70s. Again, some strong storms will
be possible Monday afternoon into Monday evening as this system
moves through. Rain will move out Tuesday as a cold front sweeps
through.

Wednesday - Thursday

This time frame should be mostly dry as we sit in between systems. A
few showers may be possible as a weak shortwave moves through, but
widespread precipitation is not expected at this time.

&&

.Aviation...(06Z TAF Issuance)
Issued at 100 AM EDT Fri Mar 24 2017

AMDAR soundings within the past hour over SDF have revealed a 40-
45kt LLJ in the lowest few thousand feet of the atmosphere. Expect
the LLJ to strengthen to 50-55kts, and with winds at the surface
near 10-15kts, expect some LLWS for all TAF sites this morning.
By about 12z-13z, believe there will be enough mixing near the
surface to negate any LLWS mentioning in the TAF. Winds will be
gusty out of the south through the late morning and afternoon.

Model soundings (NAM/GFS/HRRR) show low level moisture increasing in
the 2500-3500ft region of the atmosphere by about 12z for all TAF
sites. If clouds/stratus do form, they will be borderline VFR/MVFR
criteria. For now, will keep forecast BKN/OVC ceilings just above
MVFR levels, but will be monitoring new model data and upstream obs
for signs that MVFR ceilings may develop.

Any low stratus that formed during the morning/afternoon should
begin to dissipate by late afternoon. Wind at the surface will also
begin to die down. Model soundings redevelop a 45kt LLJ tonight, and
with surface winds around 10kts, could potentially have some low-end
LLWS, though not enough to mention in the TAF at this time.

&&

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

$$

Short Term...EER
Long Term....EER
Aviation...DM



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