Scientific Forecaster Discussion
fxus63 klmk 280527
Area forecast discussion
National Weather Service Louisville Kentucky
127 am EDT sun may 28 2017
..updated aviation discussion...
issued at 1019 PM EDT Sat may 27 2017
Severe Thunderstorm Watch #276 was allowed to expire at 10 PM EDT.
Periods Severe Thunderstorm Watch #280 remains in effect until midnight
CDT. In addition, the Flash Flood Watch will remain in effect.
Focus has mainly shifted to a Hydro threat for the time being,
however will still have to watch upstream mesoscale convective system over the MO bootheel
and NE Arkansas. The bulk of this activity should slide south of the
cwa, but some impacts to the remaining Severe Thunderstorm Watch are
possible with lead convection.
Issued at 700 PM EDT Sat may 27 2017
Multiple rounds of convection are still expected this evening and
into the overnight hours. The latest models indicate each round
should continue to sink southward as the night wears on. Still the
models have been too quick to push convection southward and
convection has been running mostly west-east along the best
instability gradient. So overall the forecast trends towards models
but not as quickly with overall convection moving southward. There
are many convective boundaries across the area currently as well
which complicates movement of individual storms and storm complexes.
Overall feel the worst severe threat for the next few hours will be
south of a line from DuBois County, in to Lincoln County, Kentucky. This
area still has the best instability and dcape. Flash flooding will
be a concern as well as some areas see multiple T-storms this
evening and overnight.
Severe watch #276 is in effect through 10 PM EDT tonight with a periods
severe watch #280 to highlight the area over south central Kentucky of
best chances for concentrated damaging winds. Flash Flood Watch
remains in effect for much of central Kentucky through Sunday.
Short term (now through Sunday night)...
issued at 323 PM EDT Sat may 27 2017
..severe weather chances continue through Sunday...
For the remainder of the afternoon into the evening hours a Severe
Thunderstorm Watch is in effect. The capping from this morning has
eroded and the region has become rather unstable with 3000+ j/kg of
SBCAPE across central Kentucky and just a bit less across southern in.
Dcape values are highest across north central Kentucky and southern in
while shear is highest across south central Kentucky. Storms are expected
to continue to develop in this environment through the afternoon and
into the evening. Damaging winds and large hail will be the main
threats this afternoon. Lightning could also be a concern for anyone
participating in outdoor activities as well as very heavy rainfall.
The scattered storms from this afternoon and evening should diminish
and push off to the east this evening. The attention then turns to
the overnight hours and the mesoscale convective system that will be moving out of MO. The
models are still struggling with the evolution and eventual path of
this system as well as how strong it will be by the time it nears
the forecast area. The area most likely to see damaging winds looks
to be southwest central Kentucky. The storms should begin to move into the
forecast area around midnight or just after and push eastward
through the overnight hours. They will begin to weaken as they move
in, and become more scattered in nature, particularly across north
central Kentucky and southern in. The main threat overnight will be
damaging wind gusts. However, heavy rain could also lead to some
localized instances of flooding as well, so will keep the Flash
Flood Watch going.
Storms will be moving out during the morning hours on Sunday. There
should then be a relative lull in the precipitation through the
afternoon in the wake of the overnight system. The severe potential
for late Sunday afternoon/evening is somewhat dependent on how the
atmosphere recovers. Models do show moderate instability developing
again during the afternoon. Most of the mesoscale models show storms
developing again late afternoon into the evening hours across
southern in as a cold front moves in. These storms do have the
potential to become strong to severe if the instability does develop
with strong winds and hail possible. However, this is somewhat
conditional. These storms should move through during the evening
into the early overnight hours. We will then dry out towards dawn on
Long term (monday through saturday)...
issued at 330 PM EDT Sat may 27 2017
Memorial Day will be dry with clouds clearing out during the day.
Temperatures will top out in the upper 70s to lower 80s. A frontal
boundary will work into the region Monday evening. A few models try
to develop some showers along this boundary, but they look to dry up
as they move into southern in, so have kept the forecast dry for now.
A trough will set up across the eastern Continental U.S. And remain in place
through much of the week. In addition, there will be a quasi-
stationary frontal boundary that may be in the vicinity as well.
Weak disturbances rotating through the upper level flow will bring
off and on chances for showers and storms through the week. However,
it will certainly not be a washout all week. High temps through the
week will be in the upper 70s to lower 80s with lows in the upper
50s to lower 60s.
Aviation...(06z taf issuance)
issued at 125 am EDT sun may 28 2017
Brunt of the heavier thunderstorms now well south of the region,
with one wave of rains about to move into central Kentucky. Best chance
for lightning will be down in bwg in the next 3-4 hours. After that
we will see a brief lull before the next better storm chances come
later this afternoon ahead of a cold front. Winds will pick up from
the southeast ahead of this front by late morning. Some of these
storms could be stronger with gusty winds and hail. Storm chances
should end by late evening.
Kentucky...Flash Flood Watch through this evening for kyz027>030-034>036-