FXUS63 KLMK 251044

Area Forecast Discussion
National Weather Service Louisville KY
644 AM EDT Sat Mar 25 2017

...Updated Aviation Discussion...

...Forecast Update...
Issued at 645 AM EDT Sat Mar 25 2017

Minor tweaks made to the hourly POP grids to account for slow
approach of precip today. Leading line of convection really
struggling as it crosses the Mississippi into western Kentucky and
southern Illinois. We have seen better eastward progress down across
Mississippi, and this will likely be the main player in bringing
rain into central Kentucky later today. Looks like the most
significant eastward progress of the precip shield is still on track
for late afternoon/early evening, roughly 21Z-00Z. Could still see a
strong or marginally severe storm in south central Kentucky, but the
window of opportunity before we lose instability will be quite

.Short Term (Now through Sunday)...
Issued at 255 AM EDT Sat Mar 25 2017

Deep southerly flow continues to draw unseasonably warm and
increasingly moist air into the Ohio Valley, ahead of a closed and
stacked low pressure system over Oklahoma. The low will lift NE
across Missouri today and tonight, with the warm conveyor belt
slowly translating eastward across Kentucky. As is often the case,
hi-res models continue to show a slower trend, so will further delay
POPs for today as this system takes its sweet time. Likely POPs
today now appear to be limited to the late afternoon hours and areas
west of I-65. Strong warm advection and slower arrival of precip
should allow max temps to climb into the mid/upper 70s, with some
bust potential coming into play if rain arrives a couple hrs earlier
than advertised.

Still looking at categorical POPs tonight as the negatively-tilting
upper trof axis pushes in. Timing with the diurnal minimum in
instability will limit severe potential, but could see a few strong
storms as the initial convection pushes into south-central Kentucky
early this evening.

Upper low slowly makes its way into the Great Lakes on Sunday, so
will hang on to lingering high POPs through the day as we remain
under the cold pool with ample low-level moisture. Not expecting
much organization, so coverage at any given time will be scattered
but most locations should get measurable precip at some point.

.Long Term (Sunday night through Friday)...
Issued at 255 AM EDT Sat Mar 25 2017

Pattern remains fairly progressive through the week, with a series
of bowling-ball lows ejecting out of the Southwest and being guided
ENE across the Ohio Valley, over the top of flat ridging in the
southeast CONUS.

Shortwave ridging will provide a break in the action Sunday night
into Monday morning, but the next system quickly arrives late
Monday. Steepening mid-level lapse rates will provide decent
instability, so we could see a few strong storms if they arrive
closer to the heat of the afternoon. Likely POPs into Monday
evening, with precip chances lingering into Tue as the sfc trof
hangs back behind the departing low center.

Will see shortwave ridging aloft on Wednesday, but models disagree
on whether a sfc boundary will hang up over the Ohio Valley.
Therefore we'll hang on to a slight chance for precip on Wednesday.

Next system comes out of the Plains Thursday night, give or take 12
hrs or so. Bottom line is that it will rain at some point late in
the week, but confidence in the timing is limited by model
discrepancies, including potential phasing between the northern and
southern streams. Overall pattern will keep temps solidly above
climo through the period, with very mild nights due to the moist air


.Aviation (12Z TAF Update)...
Issued at 640 AM EDT Sat Mar 25 2017

VFR weather is expected today, but winds will have some impact. Low-
level wind shear remains a concern over the next few hours, until we
can mix out toward 13-14z. KLVX VAD wind profile shows 45-50 kts of
wind out of the south at 2 kft. Beyond 13z, surface winds are
forecast to gust to 25-30 kts into the afternoon.

A wrapped-up low pressure system continues to spin off to our west,
and precipitation is still expected to hold off until the late
afternoon and evening hours. Scattered showers and thunderstorms are
expected near BWG by 21z. A few stronger storms are possible late
this afternoon and evening, mainly near BWG. Brief heavy rain and
strong winds would be possible in a strong storm.

Rain showers will become more widespread with some embedded thunder
this evening into the overnight hours. MVFR ceilings/visibilities
are likely late tonight into Sunday morning as the low levels
finally saturate.




Short Term.....RAS
Long Term......RAS
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