Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 231906
Area Forecast Discussion
National Weather Service Louisville KY
306 PM EDT SAT JUL 23 2016
.SHORT TERM (Now through Tuesday)...
Issued at 300 PM EDT Sat Jul 23 2016
...Hot and Humid Conditions Continue For the Weekend...
Current visible satellite shows a ridge axis across Kentucky, with
slow flow of the cloud field pivoting around that axis roughly along
a line from Beaver Dam to Elizabethtown to Richmond. There is a
relative minima in clouds along this axis, with clouds puffing up a
little more north and south of it. Convective Initiation tool and
radar mosaic show the best activity over the Appalachians as well as
a few blips in southern Indiana. For the rest of this afternoon,
lowered pops over the Bluegrass and limited the widely scattered
values to our southern border with TN. Expect this activity to wane
with sunset and some pockets of fog to develop overnight, especially
where this rain falls.
As for the heat, as of this writing, SDF briefly poked up to a 102
heat index, with a 93 temperature and a 73 dewpoint. With limited
coverage of storms today, expect a little less coverage of storms
tomorrow, given a similar setup and fewer boundaries out there to
work with. Given the subsequent longer period of sunshine and a
little higher surface dewpoint to work with, will be extending the
heat advisory through Sunday, but tailoring back a few of the
Monday we should see dewpoints inch up another degree or two, but
lower thicknesses due to an approaching trough should limit us from
reaching the higher heat indices of this weekend. Models, are
trending a little slower with the front coming down, so that puts
more of a question mark on pops and heat, especially in our south.
For now, will keep high-end chance pops in the north and go a little
lower down south.
With the slower progression of the front Tuesday, we should end up
with chance-range pops, 30-50%, areawide, with the best focus down
south. The cloud cover should limit temperatures this day to the mid
to upper 80s for highs.
.LONG TERM (Tuesday Night Through Saturday)...
Issued at 221 PM EDT Sat Jul 23 2016
The upper ridge we have been talking about for the past several days
will recenter itself over the western half of the United States
during this period as troffing digs into the east. This suggests a
break from significant heat and increased chances of thunderstorms.
The GEFS QPF plumes are noisy but do show a general trend of daily
convection. The operational run of the ECMWF, with regard to 12-hr
PoPs, is in fairly good agreement with the ensemble mean and are
within 90% confidence bounds for the most part. Precipitable water
values are consistently in the 1.5 to 2 inch range (mostly the high
side of that range) with surface dew points in the lower 70s. Given
all of the above, it makes sense to continue with scattered daily
shower and thunderstorm chances. Chances should increase towards the
weekend as the axis of the upper trof approaches.
Afternoon highs will be typical for this time of year in the 85 to
90 degree range but the expected dew points and our green summer
will keep humidity levels on the uncomfortable side.
.AVIATION (18Z TAF Update)...
Issued at 100 PM EDT Sat Jul 23 2016
Cloud field early this afternoon would indicate the best chance for
storms in the near term to initiate west of Louisville, over
southwest Indiana, and along the KY/TN border. Clouds are fairly
flat over the KLEX terminal this hour. Cannot rule out isolated
storms at each site, but confidence now just high enough to mention
at KBWG. Storm chances will dissipate by mid evening and potentially
get replaced by more fog at KBWG (or any site that sees late
afternoon/evening precip). Otherwise, for Sunday, winds will start
to have a south to southwest component.
KY...Heat Advisory until 8 PM EDT /7 PM CDT/ Sunday for KYZ023>034-
Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for KYZ046-
IN...Heat Advisory until 8 PM EDT /7 PM CDT/ Sunday for INZ076>079-