Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 290701
Area Forecast Discussion
National Weather Service Louisville KY
301 AM EDT Wed Mar 29 2017
.Short Term (Now through Thursday Night)...
Issued at 247 AM EDT Wed Mar 29 2017
...Increasing Confidence in Severe Weather Chances Thursday/Thursday
An upper level shortwave ridge and a surface high centered north of
the Great Lakes will give us a dry day today. Though there will be
some clouds in the sky we should still see enough sunshine to attain
high temperatures ranging from the mid 60s in southern Indiana to
the lower 70s in southern Kentucky and urban Louisville.
Tonight low pressure will intensify and become better organized as it
moves from Oklahoma to Missouri. Severe convection will be ongoing
ahead of the low and its cold front but should stay to our west.
Can`t rule out a few warm advection showers/storms making it into
western sections of central Kentucky and southern Indiana after
midnight, but the main storminess will be off to our west from
Arkansas to the mid Mississippi Valley. Lows will be in the 50s
though will go above guidance especially in the west as the surface
low`s warm front surges north across the region.
On Thursday the 5H low will move over the Ozarks as the surface low
moves to western Illinois by evening. Severe storms to our west
tonight will weaken as they move into the Ohio Valley Thursday
morning. Regeneration of storms to our west will then take place in
the afternoon as the atmosphere destabilizes and mid/upper level
winds increase ahead of the cold front extending from the low to the
Louisiana coast. By late afternoon/early evening in the LMK CWA
surface LI will be around -4C with CAPE peaking around 1000 J/kg,
with about 40kt of 0-6km bulk shear. The best chances for supercells
will be west of I-65 in the late afternoon and evening, with a
possible transition to bowing line segments as the convection
proceeds eastward across central Kentucky and southern Indiana
Thursday night. All severe weather modes are possible, with the best
chance of a tornado west of I-65 where 0-1km EHI values will be 1-2
m2/s2. WBZ heights around 8k` indicate a possibility of large hail.
Will go above guidance for temps Thursday afternoon ahead of this
dynamic system, with a MaxT of 75-80.
.Long Term (Friday through Wednesday)...
Issued at 300 AM EDT Wed Mar 29 2017
Friday the surface low discussed in the Short Term will travel
roughly from Chicago to Cleveland with wrap-around moisture and a
trailing surface trough touching off light rain showers in the Ohio
Valley. Cold air will remain sequestered well to our north, though,
with highs Friday in the 60s.
The weekend looks dry and pleasant as a long surface ridge
stretching from Hudson Bay to the Gulf Coast slides across the area.
Highs both days should be in the 60s with lows in the 40s...right
around normal for the beginning of April.
By Monday morning the next strong springtime surface low will be in
the vicinity of the Arklatex and will head northeast into the Ohio
Valley Monday night. Right now the main threat of severe weather
with this system is painted to our south over Dixie. However, the
past couple of systems have had a tendency to trend northward, so
we`ll have to keep an eye on this one. It should be noted that the
models are still trying to get a handle on this system. The EC has
had very little run-to-run consistency and the GFS and GEM have only
been showing the closed surface low for the last two or three runs.
The upper trof associated with the system is still out over the Gulf
of Alaska this morning. So, forecast adjustments can be expected.
Temperatures early next week will likely be near or just above
.Aviation (06Z TAF Update)...
Issued at 1250 AM EDT Wed Mar 29 2017
Main concern is ceilings trends through mid-morning. Current
satellite imagery and observations show blanket of MVFR to low-end
VFR ceilings just along/north of Ohio River. Recent trends show
saturation is winning out across central Kentucky, and the TAF sites
are expected to see a 2-3 kft stratus ceiling develop within the
next couple of hours. Some lowering below fuel-alternate levels is
possible at LEX and BWG.
While some patchy fog is possible through sunrise, a stout 15-20 kt
northeast wind at about 1000 ft, per latest RAP soundings, should
keep visibility from lowering much below 3-5 miles.
Stratus should linger through mid-morning then begin to lift to VFR
and then scatter by early afternoon. A tightening pressure gradient
will keep easterly flow steady at about 10 to 12 kts through the
afternoon. Meanwhile, later in the TAF period, mid/high clouds will
begin to work in from the west.