Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 192307
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
707 PM EDT Sat May 19 2018

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

&&

.SYNOPSIS...
Issued at 350 PM EDT Sat May 19 2018

Scattered storms will move east this evening but return Sunday and
the active pattern of continued chances for showers and storms will
keep on until Tuesday evening. At this point the front and surface
system will finally lift away from the area. After a few dry days,
chances for rain and a few storms could return going into the
weekend. Temperatures will continue to run above normal.

&&

.NEAR TERM /This evening and tonight /...

Issued at 350 PM EDT Sat May 19 2018

Scattered showers and storms can be found on radar across central
Indiana at 330 pm. These continue to push generally ESE bringing
some much-needed rain to the area. Over the next few hours expect
coverage to begin to diminish as this batch of forcing moves off to
the east. Tonight should see dry conditions to start, but then see
increasing chances for rain and some storms as another upper wave
approaches from the northwest and a surface wave does the same from
the southwest. Lower confidence regarding how much of this will
still be together by that point given lack of daytime heating but
enough there to go with chance pops at some point during the
overnight. Think there will be decent cloud cover most of the night
and thus leaned to the warmer end of consensus for lows.

&&

.SHORT TERM /Sunday through Tuesday/...

Issued at 350 PM EDT Sat May 19 2018

Chances for storms will ramp up through the day on Sunday with a
surface wave moving overhead and through the area on a stalled
frontal boundary. Shear will be maximized near the boundary...but
isn`t all that impressive elsewhere. Instability should ramp up, but
this is somewhat dependent on the amount of cloud debris left from
any overnight convection. Thus there is potential for some severe
storm development Sunday afternoon into the evening, but confidence
is still pretty low given the uncertainty.

Sunday night the upper wave will move through and kept pops in the
high chance category during that time. On Monday the surface wave
and front will continue to provide a focusing mechanism for
development, and thus keeping chances for showers and storms in the
forecast over at least the eastern half of the area. Again a warm
moist unstable air mass, so marginal risk for severe seems a good
fit.

On Tuesday the front and surface wave finally lift northeast away
from the area, allowing pops to drop off for all but the eastern
counties.

Temperatures during this period will be highly dependent on where
exactly the boundary sets up and the effect this has on cloud cover.
Thus stuck with the consensus blend but think there could be a much
tighter gradient somewhere in the forecast area than what the
consensus shows.

&&

.LONG TERM /Tuesday night Through Saturday/...
Issued at 235 PM EDT Sat May 19 2018

Models are in good agreement on the overall synoptic pattern which
lends good confidence in the forecast trends.

Models agree that an upper low will develop over southern California
early next week within west coast troughing in advance of an
Aleutians vortex. The upper low will be over the Great Basin at the
start of the long term and then open up as an upper trough and then
arc around an expansive central U.S. upper ridge. The trough is
expected to reach the western Great Lakes by Saturday. This would
suggest a warm and dry pattern through Thursday with increasing
chances of weekend thunderstorms. Blend handles this well.

&&

.AVIATION /Discussion for 200000Z TAF Issuance/...
Issued at 707 PM EDT Sat May 19 2018

VFR conditions expected throughout much of the forecast period.
Low confidence in convective impacts and timing.

Convection has diminished and shifted east of the terminals early
this evening as ridging aloft has spread into the region from the
west. This should keep dry conditions across central Indiana
through the first half of the overnight with just mid and high
level clouds from convection to the southwest of the area.

Forecast becomes much more uncertain from the predawn hours into
the day Sunday. Hi-res guidance early this evening is not handling
the convective complex over western Missouri particularly well
and how this system evolves as it moves E/NE overnight may have a
potential impact in central Indiana...especially during the
predawn hours. Have inserted a VCTS at KLAF but will leave the
other terminals dry at this point with low confidence in impacts.

Heading into Sunday...the frontal boundary will remain in the
region with an upper level wave traversing through the flow poised
to move into the region during the afternoon. Any convection that
does impact the region in the morning may leave higher cloud
debris over the area which could impact later development. With so
much uncertainty...cannot justify anything more than VCTS mention
at all terminals Sunday afternoon and evening at this time. Winds
will be 10kts or less and variable in direction.

&&

.IND WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SYNOPSIS...CP
NEAR TERM...CP
SHORT TERM...CP
LONG TERM....MK
AVIATION...Ryan



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