Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 231803
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
203 PM EDT Wed Jul 23 2014
...Updated Aviation Discussion...
Issued at 1145 AM EDT Tue Jul 22 2014
Updated the forecast to decrease temps as clouds overspread the area
limiting heating. The cloud cover looks to spread over most of the
region through early afternoon so the threat of any strong wind
gusts/heavy rainfall is somewhat decreasing due to lack of
Issued at 935 AM EDT Tue Jul 22 2014
Updated the forecast to adjust POPs to current radar trends. The
robust t-storm near Vincennes earlier this morning took quite the
turn from SE-S-SW around the western ridge/instability axis. That
cell will stay clear of our area with scattered showers and storms
slowly creeping into our southern Indiana and Bluegrass Kentucky
counties this morning. Overall we should be in a lull with
convection strength remaining low through mid to late morning. Most
short range models indicate a resurgence in storm strength and
coverage by late morning or early afternoon so increased POPs to 50%
for this afternoon into the evening hours. The latest NAM12 has a
decent handle on the overall regional convective picture this
morning with storms reforming over the Ohio Valley this afternoon.
Cloud cover from this morning`s cells may limit instability over
southern Indiana and portions of northern KY for this afternoon.
Soundings in this area seem to favor more of a heavy rain threat
with slow storm motions and a fairly moist profile. Further south
over central KY, more of an isolated damaging wind threat may be
present this afternoon along with brief heavy rainfall. More
instability and dry air pockets in this region will be supportive of
an isolated damaging wind threat.
.SHORT TERM (Now through Thursday)...
Issued at 253 AM EDT Wed Jul 23 2014
An upper wave over Iowa early this morning will be heading
southeast, and weakening, today, reaching the Ohio Valley by this
evening. Meanwhile, a surface cold front stretching from Detroit to
Wichita at this writing will also head southeast and will cross
southern Indiana and central Kentucky this afternoon. As these
systems interact with warm and moist air over the Ohio and Tennessee
Valleys, scattered showers and thunderstorms will break out.
Elevated PWATs with K Indices in the mid 30s suggest locally heavy
downpours will be possible. High freezing levels indicate that hail
will not be a concern, and weak winds aloft will keep the wind
threat limited. The strongest storms will be capable of some
briefly gusty winds though as the heavy rain falls to the ground.
High temperatures today are tricky thanks to the passage of the cold
front and the presence of clouds and scattered convection. Will go
around 90 in Kentucky and the mid to upper 80s in southern Indiana.
After a possible uptick in convective activity in southern Kentucky
this evening, showers and thunderstorms will begin to wane
overnight, and will end over southern Indiana and northern central
Kentucky. Lows will be in the 60s.
Thursday will be a very different day from the previous few days.
Any lingering showers in the Lake Cumberland region should end by
lunch time. Cooler, drier air will work its way into the area on
north breezes of 5 to 10 mph resulting in decreasing clouds, lower
dew points, and a much cooler afternoon. Some spots in southern
Indiana and the Kentucky Blue Grass may not make it out of the 70s,
with highs in the lower 80s elsewhere thanks to Canadian high
pressure centered over Chicago.
.LONG TERM (Thursday night through Tuesday)...
Issued at 320 AM EDT Wed Jul 23 2014
At the start of the long-term period, the Ohio Valley will be seeing
surface high pressure in control but this won`t last long. By this
weekend, a frontal boundary will slowly make its way south toward
the forecast area as surface low pressure tracks from the Plains
into the Great Lakes region, washing out as it moves eastward.
Higher up, ridging attempts to extend its reach further north and
east from beyond the southern Plains but falls just short of
reaching this forecast area. Early next week, a Canadian upper
trough dives south once again across the NE third of the CONUS.
Surface high pressure will take control next Tuesday.
Dry weather with mostly clear to partly cloudy skies is expected
from Thursday night through late Friday. As the aforementioned
surface high loses its grip overhead and allows for low pressure and
a front to inch closer, precip chances increase early Saturday,
particularly across the northern two-thirds of the forecast area.
These precip chances will linger throughout the entire weekend,
although a total washout is not expected. More likely, thunderstorm
activity should be primarily diurnally-driven but given the warm,
moist air advecting in ahead of the front, couldn`t rule out
continued chances through the overnight periods as well. Sunday and
possibly through Sunday night, if models trend the frontal passage
slower, will be the best chances for storms with the fropa. Once the
front clears, the precip chances aren`t over quite yet as that upper
trough swings through and keeps clouds and showers in the forecast,
particularly for locations in the eastern portions of the forecast
area where orographic lifting will be assisting. This pattern looks
similar to that of last week so will continue to monitor to see how
the details of this system play out. From Tuesday onward, high
pressure should clear things out once again and at least briefly
The atypical summer pattern thus far looks to continue through next
week. High temps on Friday will be below normal, ranging from the
low to mid 80s. Highs through the weekend are anticipated to return
to near normal for this time of year, although clouds and precip
could keep temps from climbing into the 90s. Once the front clears
by the end of the weekend, the much cooler than normal temps look to
settle in once again, with highs currently forecast to flirt with
the 80 degree mark on Monday and struggle to reach 80 on Tuesday.
Lows will respond accordingly with the warmest night looking to be
overnight Saturday (low 70s) and the other nights in this time frame
covering the entire 60 degree spectrum, with Thursday night, Monday
night, and Tuesday night all fighting to be the coolest in the
long-term period as a few upper 50s can`t be ruled out in prone
.AVIATION (18Z TAF Update)...
Issued at 200 PM EDT Wed Jul 23 2014
A cold front to our NW combined with an upper level trough will
continue to provide convection chances through tonight. While
BWG/SDF sit in a lull currently with only a few showers around,
storms should redevelop late this afternoon and evening along the
cold front and move toward the terminals. LEX currently has a
t-storm at the TAF site, but should see a lull in convective
activity by around 1830Z. LEX will also get in on the redevelopment
of storms later today according to the latest model data.
Redevelopment of convection later today is dependent on clouds
clearing/thinning along the front which currently they are thinning
in this area fairly quickly. Also some convection has redeveloped
over central Indiana. T-storm chances should cease after the fropa
between 1-4Z. After the fropa we`ll see low clouds build in with
cigs dropping into the low end MVFR or IFR late tonight into
tomorrow morning. Vsbys should drop to MVFR as well. Lingering
showers and drizzle will prevail through the overnight hours.
Conditions will improve to solid MVFR by mid to late morning
Winds will remain WNW this afternoon and evening ahead of the fropa
and then turn NNE behind the fropa between 5-10 kts. Higher winds
may occur in any t-storms.