Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 221859
Area Forecast Discussion
National Weather Service Louisville KY
259 PM EDT Sat Apr 22 2017
.Short Term...(This evening through Sunday night)
Issued at 230 PM EDT Sat Apr 22 2017
Surface analysis reveals a 1010mb low over northern Mississippi,
with a warm front draped across central Tennessee up into extreme
southeastern Kentucky. Air mass south of the warm front has remained
relatively unstable and warm, with temperatures in the mid 70s
across parts of southern and middle Tennessee. Meanwhile, north of
the warm front in our region, temperatures have remained cool
through the entire day, with upper 40s currently across areas along
and north of I-64, to mid 50s down toward south-central Kentucky
near the Tennessee border. Breezy northeasterly winds along with the
rain showers make it feel even colder outside. Air mass north of the
warm front has remained relatively stable, although SPC mesoanalysis
does show some elevated instability south of the Cumberland Parkway.
Isolated to scattered thunderstorms will be possible this afternoon
along and south of the Cumberland Parkway, and a few storms could
produce some small hail and gusty winds. Expect the more robust
convection to stay along and south of the warm front where the
better instability remains.
Showers and isolated thunderstorms will continue through the
afternoon, with activity beginning to settle down after 21z for most
areas. The exception to this will be near the Lake Cumberland
region, where scattered to numerous showers will continue late this
afternoon into the evening due to its proximity to the warm front
and surface low. Some mesonet sites near that area have already
picked up over an inch of rain today, however, most of that rain has
fallen over a 6-12 hour period, so flooding has not been a concern
so far. Will continue to keep the flash flood watch going through
the evening since this area will have the potential to see some
heavier showers/storms for the next several hours.
Strong ULL begins to take shape over the lower TN/AL/MS on Sunday,
and models project wrap-around precipitation on the northern end of
the low to impact parts of the region. Will see a sharp cut-off
between the clear skies and clouds/precipitation from the ULL, as
southern Indiana looks to be mostly dry and sunny tomorrow, while
central/southern Kentucky will see clouds and rain showers. Best
chances for rain Sunday will generally be south of the Cumberland
ULL begins to move into Georgia Sunday night, taking with it the
clouds and precipitation. Clearing skies should allow overnight
temperatures to fall into the 40s.
.Long Term...(Monday through Saturday)
Issued at 250 PM EDT Sat Apr 22 2017
By Monday, 500mb ULL over the southeastern US begins to move up the
east coast as broad ridging builds into the region. Tuesday and
parts of Wednesday look to be dry and warm under this ridge.
Cold front approaches from the west Wednesday night into Thursday
morning, and medium to long range guidance have a line of showers
and storms developing ahead of the front. While low level moisture
(upper 50s to low 60s dewpoints) and strong deep layer shear (0-6km
~50-60kts) will be present, lapse rates are rather dismal, and
instability looks to be marginal at best. As such, severe weather
potential seems very limited for this timeframe.
Long range models begin to diverge on solutions beyond Thursday, but
generally show warm temperatures and unsettled weather with showers
and thunderstorms possible Friday through the weekend.
.Aviation...(18Z TAF Issuance)
Issued at 107 PM EDT Sat Apr 22 2017
Complicated and complex forecast in the front half of the forecast
period as several waves of showers and low clouds will move through
the terminals. In the near term, band of showers near the I-65
corridor will affect KSDF and KBWG at the beginning of the period
and then will affect KLEX about an hour or so later. Ceilings and
visibilities will likely remain predominantly low end MVFR with some
occasional drops to IFR (especially at KLEX). In general, we expect
ceilings in the vicinity of KSDF to be quite variable through the
afternoon...especially in between shower bands passing
through. Surface winds will remain out of the northeast at 10-12kts
with some gusts in the 17-20kt range.
Latest model data continues to suggest improving cigs/vsbys at KSDF
later this afternoon. Current thinking is that we should start to
see improvement in the 22/2030-21Z time frame. Over at KLEX and
KBWG, conditions will likely linger in the low end of the MVFR range
through the overnight hours. Winds at all the terminals will remain
out of the northeast but wind gusts will not be an issue. Speeds
overnight look to be in the 4-8kt range.
KY...Flash Flood Watch through late tonight for KYZ075-078-081-082.