Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 230003

Area Forecast Discussion
National Weather Service Louisville KY
803 PM EDT Sat Apr 22 2017

...Updated Aviation Discussion...

...Forecast Update...
Issued at 523 PM EDT Sat Apr 22 2017

Given recent radar trends, have dropped PoP chances from the
forecast across much of southern Indiana and north-central KY for
this evening.  Recent satellite imagery shows some scouring of
cloudiness across southern IN and portions of NC KY.  In fact, we`re
probably going to see a bit of sunshine across this region which may
result in high temperatures spiking in the next hour or so given the
higher sun angles.  Winds will remain gusty out of the northeast
this afternoon as we get some additional mixing.  These winds will
come down toward sunset, but the evening will still be a bit breezy
at times, especially across south-central KY where the pressure
gradient remains elevated.

We will assess the late afternoon runs for further forecast
adjustments.  If drier forecasts look increasingly likely, we will
likely drop the flood watch for far southern KY later this evening.

.Short Term (Now 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 (00Z TAF Update)...
Issued at 750 PM EDT Sat Apr 22 2017

Will maintain VFR for tonight at SDF/LEX. The stratus is expected to
move slowly south as drier air advects in via northeast winds. Winds
may stay up around 8-11 kts overnight. Winds are expected to pick up
slightly after 13z Sunday, with occasional gusts to around 20 kts.

MVFR stratus will remain across southern KY, including BWG. Shower
development looks likely again on Sunday as deeper moisture wraps
around the upper low. Expect ceilings/visibility to lower at BWG,
and a period of IFR is possible. MVFR looks more likely at LEX, with
IFR staying south of there.


KY...Flash Flood Watch until 6 AM CDT Sunday for KYZ075-078-081-082.



Short Term.....DM
Long Term......DM
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