Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 240518
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
118 AM EDT Fri Apr 24 2015
...Updated Aviation Discussion...
Updated 845 PM EDT Thu Apr 23 2015
No major changes to the forecast through the overnight. Surface high
pressure is quickly building over the area and temperatures should
begin to fall into the 50s and 40s later this evening, then bottom
out in the upper 20s to middle 30s by dawn Friday. Mid/high level
clouds associated with a southern stream system are slowly creeping
northward into far southwest and southern Kentucky per latest IR
imagery. As the cloud cover continues to move northward overnight,
this should preclude widespread frost formation for those areas.
Otherwise, no changes for the frost/freeze headlines.
.SHORT TERM (Now through Friday Night)...
Issued at 300 PM EDT Thu Apr 23 2015
...Frost/Freeze for Tonight...
With a sfc high pressure center moving through southern Indiana and
central Kentucky tonight, strong subsidence and good rad cooling
will result. Sfc winds will go calm or light and variable late this
evening and remain that way through much of the night. We may start
to see a few upper level clouds late but nothing that will hinder
the cooling all that much. With these ideal cooling conditions in
place for tonight, think that a good portion of the area from Paoli,
IN to E-town, KY to Lake Cumberland and portions east should see
sub-freezing temps tonight. For this area, will issue a Freeze
Warning. For locations along a Jasper to Leitchfield to
Tompkinsville line, think that areas of frost will develop as temps
fall into the low to mid 30s with near sfc moisture still plentiful
enough. This area will warrant a Frost Advisory. Debated a Frost
Advisory for Bowling Green and surrounding counties but feel that
with the sfc high moving to eastern KY by 12Z, this area should
start to see temps level off earlier and/or experience a slight rise
in temps by sunrise. Frost/Freeze products will run from 3 AM to 9
AM EDT (2 AM To 8 AM CDT) Friday.
Any frost will quickly dissipate by mid morning as temps rise well
above freezing. For the rest of the day Friday, we`ll see
increasing mid and high level clouds ahead of the next weather
system. Temperatures will be warmer in the low to mid 60s for highs.
Friday night an upper level wave and a weak sfc trough will move
north through the area providing showers and isolated elevated
t-storms. Showers/storms will be most numerous around and after
midnight. Steady moderate to at times heavy rainfall will be
possible as this convection moves through with 0.25 to 0.75 inches
of rainfall possible Fri night. Low temperatures should range from
the lower 40s to lower 50s.
.LONG TERM (Saturday through Thursday)...
Issued at 252 PM EDT Thu Apr 23 2015
...A Chance of Severe Storms on Saturday...
At 12Z Saturday low pressure will be near Kansas City with
widespread showers and thunderstorms along and either side of a warm
front reaching into the Ohio and Tennessee Valleys. The low will
head to the ESE during the day, reaching the lower Wabash Valley by
evening with its warm front extending eastward through southern
Indiana and northern Kentucky. The GFS has been pretty consistent
with this idea for its past five runs, and this morning`s ECMWF has
trended slightly toward the GFS in this regard. Showers and
thunderstorms will continue to be widespread in association with the
South of the front, much of central Kentucky will get into the warm
sector of the cyclone. This area will have the potential to become
very unstable by afternoon with steep mid-level lapse rates and
plenty of CAPE above a low-level cap that should weaken and possibly
disappear. There will be some dry air aloft to help with downburst
potential, and wet bulb zero heights around 8k feet indicate large
hail to be a possibility. There will be enough shear, along with
low LCLs, that we can`t rule out isolated tornadoes, especially in
far southern Kentucky during the early to mid afternoon.
The best chance for severe weather appears to be west of I-65 and
south of the Ohio River, though we`re still a couple of days out so
nothing is set in stone. A lot will depend on the track of the low
and where exactly the warm front and its related convection set up.
Rainfall amounts should generally be in the 1 to 1.5 inch range,
with the heaviest amounts over northern Kentucky and southern
Indiana. Of course, with thunderstorms there can be large
differences from one spot to the next. The sunshine, winds, and
very low dew points of the last few days have really helped to dry
things out, so any flooding issues from this rain would likely be in
the form of localized flash flooding under particularly heavy
Depending on the placement of the warm front, high temperatures on
Saturday could range from the middle 50s in the northern Blue Grass
and southeast Indiana to the middle 70s in southern Kentucky.
The rest of the long term period is quiet and mostly dry. A
southern system moving along the Gulf coast mid-week may throw a few
showers into southern Kentucky Tuesday night and Wednesday.
.AVIATION (06Z TAF Update)...
Updated at 110 AM EDT Fri Apr 24 2015
Benign conditions expected through most of the valid TAF period,
with VFR and light/variable winds settling into SE as mixing
commences mid/late morning. Mid-level ceilings will work in late
afternoon/early evening. Will keep BWG and LEX dry through 06Z Sat,
but we could start to see lowering ceilings and precip moving into
BWG at the very end of the period. However, not enough confidence to
put in for the final hour or two.
Looking into the planning period for SDF, expect high-end MVFR
ceiling/vis as precip develops just before daybreak on Saturday.
Fuel-alternate, if not IFR ceilings are likely later Saturday
morning, but at this point we expect that to happen beyond the valid
period of the TAF.
KY...FREEZE WARNING until 9 AM EDT /8 AM CDT/ this morning FOR KYZ025-
FROST ADVISORY until 8 AM CDT this morning FOR KYZ023-024-026-
IN...FREEZE WARNING until 9 AM EDT this morning FOR INZ076>079-084-
FROST ADVISORY until 8 AM CDT this morning FOR INZ083-089.