Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 191048

Area Forecast Discussion
National Weather Service Louisville KY
648 AM EDT Tue Sep 19 2017

...Updated Aviation Discussion...

.Forecast Update...
Issued at 634 AM EDT Tue Sep 19 2017

Updated the forecast to include higher coverage of Pops in the high
likely and categorical (70-80%) range across southern IN and
northern KY. A current look at radar shows increasing coverage and
think that most spots will see a few thunderstorms. Each storm will
be capable of plenty of cloud to ground lightning and brief heavy
rainfall. This wave of showers and storms will steadily push east
through the morning into the early afternoon, gradually weakening as
it does so. Then, some redevelopment back along and east of I-65 is
possible through the remainder of the afternoon and evening.


.Short Term...(Today through Wednesday)
Issued at 305 AM EDT Tue Sep 19 2017

A few morning fog issues to contend with, mainly down where we saw
rainfall yesterday evening. Obs around Bowling Green have gone down
around a 1/2 mile at times, however extensive cloud cover and mixy
near surface winds should be enough to mitigate any widespread
problems. Will continue to monitor through the morning hours.

A shortwave trough will slowly pass through the Ohio River Valley
today into tonight. A weak surface low can also be noted with this
feature, but the overall reflection is pretty weak. Expect scattered
to numerous showers and storms ahead of the disturbance from west to
east as we move through the day. A bit concerned that coverage is
overdone by the models, as has been the case early this morning.
Nevertheless, the triggering combined with a modestly unstable
airmass should be enough for decent coverage. Looking at forecast
soundings and expected PWAT values around 1.8, do think that some of
the slow moving storms could put down locally heavy rainfall. Main
concern would be ponding of water for any commute that is affected.

Today`s highs will struggle (relative to what we`ve been seeing) a
bit under fairly extensive cloud cover. Expecting mainly low 80s,
although a few spots that see more sun could see mid 80s.

Showers and storms should diminish to mainly just isolated coverage
in our east by this evening as the shortwave pushes east. Lows drop
into the mid 60s, and we`ll likely have to deal with more fog issues
through the overnight. Will go ahead and mention patch fog.

Upper ridging begins to build into the area through Wednesday,
however a continued unsettled airmass could still yield an isolated
shower or storm. Look for highs in the mid to upper 80s.

.Long Term...(Wednesday night through Monday)
Issued at 308 AM EDT Tue Sep 19 2017

Strong upper ridging will hold over the eastern half of the CONUS
during the extended, bringing mostly dry conditions and above normal
temperatures. The biggest question will be whether isolated
diurnally driven showers and storms will be able to develop under
the influence of the strong ridge. An early look at forecast
soundings doesn`t show much in the way of a subsidence inversion
that you would otherwise expect under this pattern, so suppose we
could kick off an isolated shower or storm with local
effects/heating any afternoon or evening. Overall though, the lack
of any defined triggers will make the main messaging about the above
normal temps.

A look at 850mb temps and 1000-850mb thicknesses reveal that high
temps should stay fairly consistent through the extended, only
fluctuating a degree or two each day. Overall, temps might be
slightly "cooler" by the late weekend/early next week as the ridge
slowly weakens. Still, most readings should be in the mid to upper
80s which is about 10 degrees above normal for this time of year.
Will tend to lean on the high side of guidance considering how
efficiently we`ve warmed under good heating conditions recently.
Plus, any climo based guidance would tend to work against
anomalously warm patterns this time of year, and likely be too low.
Wouldn`t be surprised to see some 90 degree readings late this week,
especially if you consider BWG got to 89 yesterday under 16-17 C 850
temps. Stay tuned...

Min T`s will mostly be in the mid to upper 60s by late this week,
and then in the low to mid 60s as we move through the weekend.


.Aviation...(12Z TAF Issuance)
Issued at 647 AM EDT Tue Sep 19 2017

Cluster of showers and embedded thunderstorms will move eastward
across the forecast area this morning.  This will affect mainly the
KHNB/KSDF and KBWG terminals early in the period and KLEX by mid to
late morning.  This activity will then push to the east and some
improvement in conditions will be seen in the afternoon.  Some
isolated to scattered convection will be possible through the
afternoon and evening, but coverage looks to be fairly scattered at
this point.  Winds will primarily be out of the southwest today at 5-
8kts.  Convection is expected to diminish by sunset with light and
variable winds developing.  Some patchy fog is likely again tonight,
especially in areas that see rainfall today.




Short Term...BJS
Long Term....BJS
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