Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 250828
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
425 AM EDT WED MAY 25 2016

.UPDATE...
The AVIATION Section has been updated below.

&&

.SYNOPSIS...
Issued at 218 AM EDT Wed May 25 2016

Upper disturbances and an increasing moist and unstable atmosphere
will combine to trigger thunderstorm chances today through early
next week.

Temperatures will remain a few degrees above normal through the
period with highs mostly in the lower to mid 80s and lows in the 60s.

&&

.NEAR TERM.../Today and Tonight/
Issued at 218 AM EDT Wed May 25 2016

Focus for the near term will be on thunderstorm chances as well as
temperatures.

Models continue to be in excellent agreement on the major players
with the 00z run.

Currently...showers and thunderstorms were well southwest of our
southwestern counties as a short wave slowly meanders over that
area. This feature could still touch off a few storms overnight in
that area and this morning a little further to the northeast.
However...the main feature today is expected to be another upper
wave moving through the southwest flow aloft...ejected northeast by
a southern California upper low. This upper disturbance should move
into our northwestern counties shortly after 21z per model
blend...including the RAP. This feature will interact with an
increasingly moist and unstable atmosphere...and modest 25 to 30
knot low level flow. Models are forecasting dew points in the lower
60s and mixed layer CAPEs to 1000 j/kg and higher this afternoon.
This should be enough to touch off scattered thunderstorms across
the forecast area. A few storms could be strong...but the SPC day1
outlook is keeping any severe risk just to our west in the even more
unstable air. The thunderstorms should continue through the night as
the upper wave moves through and with at least weak instability
after sunset and a 25 to 30 knot low level jet. Will keep likely
pops going far north...in closer proximity to the upper wave.
Elsewhere...good chance pops look good.

Should see plenty of convective clouds today but should still see
enough sunshine peaking through from time to time to allow
temperatures to reach the lower to mid 80s for afternoon highs.
Meanwhile...with decent cloud cover and southerly winds staying up
around 10 knots...prefer overnight lows at or slightly warmer than
00z MOS in the mid 60s.

&&

.SHORT TERM.../Thursday through Friday night/
Issued at 218 AM EDT Wed May 25 2016

All eyes will continue to be on thunderstorm chances as the Socal
upper low continues to send upper disturbances our way in the
southwest flow aloft even as it moves to the Central Plains Friday
night. Models have been very consistent with this and also with a
modest but persistent moist Gulf flow through the Ohio Valley and
lower Great Lakes on the back side of a Bermuda High and ahead of a
slow moving to stalled Plains frontal system.

Next disturbance in the southwest wavetrain is harder to pick
out...but it looks like a weak impulse will move through the area
Thursday afternoon. As the wave is more subtle...only went with 40
percent pops. However...models are showing a very unstable
atmosphere with CAPES anywhere from 1500-3000 j/kg...depending on
the model. So...with that kind of potential energy...could see some
strong storms with a lot of cloud to ground lightning. Weaker
dynamics preclude organized severe threat...however.

After Thursday...the remainder of the forecast looks pretty much the
same. Although models have a harder time resolving any weak impulse
that far out...each period should see at least one weak wave and
with the atmosphere remaining moist and unstable...will keep 30-40
percent pops going the rest of the way.

It will remain warm and humid and with the air mass unchanged...will
go with a persistence forecast with highs in the mid 80s and lows in
the mid and upper 60s.

&&

.LONG TERM /Saturday through next Tuesday/...

Issued at 222 AM EDT Wed May 25 2016

Ensembles in good agreement with respect to the overall pattern
during the extended. Mean ridging expected over the eastern parts
of the country with troughing over the west.

An upper disturbance is expected to eject into the western Great
Lakes over the upcoming weekend. Will keep chance PoPs in the
forecast for Saturday and Sunday to cover the passage of this
trough.

By early next week, convective potential may tend to diminish and
become more diurnal in nature as heights rise some, however
ensembles suggest a weakness in the upper ridge/cool pocket may
linger over the Ohio valley. For this reason, will continue to
keep some PoPs going through early next week.

&&

.AVIATION /Discussion for the 250900Z IND TAF Update/...

Issued at 425 AM EDT Wed May 25 2016

Low threat for scattered shower activity in the vicinity of the KIND
terminal through the mid to late morning hours as a vorticity center
that originated from convective complex in Missouri yesterday
afternoon moves through. Model data not very bullish with this idea,
and nothing seems to be developing locally so far. Will take out the
shower mention for this morning on the update.

Previous discussion follows.

Mainly VFR conditions through the period. Forecast soundings and MOS
guidance indicates some potential for MVFR fog late during the
overnight at KLAF so brought in 4SM 9-13z there, but fairly low
confidence in this.  Elsewhere increasing clouds should negate any
fog development. HRRR and RAP show scattered showers developing over
southwest Indiana and moving northeast from there around 8-9z , but
time heights and upstream obs don`t show much in the way of
restrictions so kept VFR during that time with a VCSH. Also should
be noted that thus far this has been advertised but has not
developed so again confidence is pretty low. If showers do develop
there could be a lull in activity late morning before some scattered
thunderstorms develop in the afternoon. Kept a VCTS going starting
around 20z at the sites for this, but again with scattered storms
and many places missing out did not add any restrictions with
it.

&&

.IND Watches/Warnings/Advisories...
NONE.
&&

$$

SYNOPSIS...MK
NEAR TERM...MK
SHORT TERM...MK
LONG TERM....JAS
AVIATION...CP/JAS


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