Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 260337

Area Forecast Discussion
National Weather Service Indianapolis IN
1137 PM EDT Thu May 25 2017

The AVIATION section has been updated below.


Issued at 219 PM EDT Thu May 25 2017

Low pressure over Ohio will exit the region tonight....allowing a
weak area of High pressure over the plains states to build across
the Ohio valley. This will bring dry weather to much of Indiana
through Friday morning.

A quick moving low pressure system is expected to push across the
southern Great Lakes on late Friday. This may result in a shower
or a thunderstorms mainly across the northern parts of the State
on Late Friday afternoon and evening. The departing low will leave
a lingering frontal boundary across the area for Saturday. This
feature along with a passing upper level weather disturbance may
generate showers and storms on late Saturday afternoon and
Saturday Night.

Dry weather should return on Sunday morning as the upper level
weather disturbance departs. However A cold front is poised to
push toward Central Indiana by late afternoon on Sunday and
chances for more showers and storms will return.

In the long term another weak cold front will move our way late
Monday night and early Tuesday and high pressure over the northern
plains will build southeast towards Indiana towards the middle of
next week.


.NEAR TERM /Rest of Tonight/...

Issued at 950 PM EDT Thu May 25 2017

Latest hi-res satellite data shows clouds have diminished across the
southwest forecast area with a band of clouds across the northeast
half of the area. This band will diminish some, but the latest
trends indicate that at least part of it will remain for a while.

Additional clouds will move in late tonight ahead of the next system
moving in. Thus overall expect a partly cloudy night.

As a surface ridge moves in, winds will continue to diminish. With
at least some clearing, expect some patchy fog to develop. Have
added this to the forecast.

Temperatures look good with only minor tweaks made.

Previous discussion follows...

Surface analysis early this afternoon shows low pressure in place
across Western Ohio. A weak Ridge of high pressure was found
across Missouri and Iowa. GOESR visible bands showed extensive
cloud cover across Indiana...associated with the low. Cool
Cyclonic NW flow was in place across Indiana which was caught
between these two systems.

Models remain in good agreement that the low pressure system is
expected to depart northeast this evening...reaching NY state near
midnight. This will allow the ridging toward the west to build
across Indiana and diminish the cyclonic flow by then. Thus will
trend to decrease cloudiness through the evening hours as the low
departs. Forecast soundings reflect this as drying and subsidence
is found within the column. Thus will try for a decreasing
cloudiness trend.

Weak warm air advection is expected overnight as the cold pool
associated with the departing low exits. However without strong
mixing expected and variable cloud cover...feel there is not
advantage to sway from the blend on lows.


.SHORT TERM /Friday through Sunday/...

Issued at 219 PM EDT Thu May 25 2017

Active weather is poised for Central Indiana during this period.
Friday should start out rather quiet as the models suggest High
Pressure and subsidence exiting the area in the morning
associated with the quick moving ridge of High pressure. GFS and
NAm suggest a quick moving short wave pushing across Northern
Illinois and Michiana Friday Night. Best moisture and forcing
remains across the northern parts of  the state. Across Much of
Central Indiana...forecast soundings suggest mid level capping and
unreachable convective temperatures in the 80s. THus will contain
pops on Friday afternoon and Friday evening...mainly to the
northern parts of the forecast area. Will follow the blend on

Forcing aloft on late Friday night and on Saturday is lost as the
quick moving short wave departs to the east. this should result in
dry weather for the start of Saturday and Into the afternoon. No
further dynamics appear to pass aloft on Saturday. However the
previous convection on Friday night appears to lay out a weak
boundary that sags across Central Indiana on Saturday. Forecast
soundings on Saturday afternoon are quite steep...showing CAPE
over 4000 j/kg with reachable convective temperatures near 80.
however 700mb are quite close to 10C by 00Z Sunday. Thus there
remains some uncertainty if convection will develop. Better
chances will persist farther south of the I-70 corridor...closer
to the ohio River where instability is better. Nonetheless...will
include pops on Saturday afternoon and evening for possible
convection...with best chances across the far southern parts of
the forecast area. Given the amount of instability should the cap
be broken...severe storms would be a reasonable wager.

Model suggest convection across the region will end overnight on
Saturday and moisture profiles begin to dry out. Aloft...little
support for additional development appears available on Sunday Indiana looks to be between two systems. GFS shows a
broader...more organized wave and dynamics over Iowa...Missouri
and Illinois...poised to push across the area by mid to late
afternoon. Forecast soundings showing much less instability in
place ahead of this system...and the arrival of high cloud.
Forecast soundings suggest reachable convective temperature in
the middle 70s. Thus will include pops mainly in the late
afternoon with the arrival of the dynamics from the west combined
with max heating.

Again a blend on temps will work nicely.


.LONG TERM /Sunday Night Through Thursday/...
Issued at 219 PM EDT Thu May 25 2017

Ensembles in fairly good agreement on the main weather features
during this period. Upper troughing is expected to drift east
through the Great Lakes through the early parts of next week, with
the flow flattening out towards the middle of the week.

Ensembles suggest an upper disturbance rippling through the Great
Lakes trough may move through the area either Monday or Tuesday of
next week, with the majority leaning towards Tuesday. Will keep
some chance PoPs going for Monday and Tuesday to cover this feature.

Some of the ensembles are quite aggressive in ejecting an upper low
of the southwestern deserts into the local area later next week.
Would like to see more continuity with this feature. For now, will
keep next Wednesday and Thursday mainly dry and monitor trends.


.AVIATION (Discussion for the 260600Z TAF Issuance)...
Issued at 1137 PM EDT Thu May 25 2017

MVFR visibilities expected to develop overnight, then quickly return
to VFR by 13Z. MVFR ceilings may develop after 00Z, especially west.

Dissipating lower clouds and lightening winds should allow for some
MVFR fog to develop overnight. This will burn off quickly with VFR
returning by 13Z. Some cumulus and mid/high clouds will then rule
the daylight hours, with perhaps some lower clouds moving back in
after 00Z.

There will be some scattered convection Friday afternoon and
evening, especially near KLAF. Will include a VCTS mention there.




NEAR TERM...Puma/50
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