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Forecast Discussion for Indianapolis, IN

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000
FXUS63 KIND 190140
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
940 PM EDT Mon Oct 18 2021

.Forecast Update...
Issued at 940 PM EDT Mon Oct 18 2021

Surface analysis late this evening shows strong high pressure in
place over TN and KY...with an associated ridge extending north
across eastern Indiana to the Great Lakes. GOES16 is unable to
detect any clouds within the state. Aloft...a large ridge was in
place over the Mississippi Valley...resulting in NW flow aloft over
Indiana and subsidence. Dew points were mainly in the mid 40s.

Overall the forecast remains in good shape. The strong high and
associated subsidence is expected to remain in place across Indiana
overnight...perhaps moving slightly east. Subsidence will remain
across the area. Forecast soundings and time heights continue to
shows a dry column through the night. Only minor adjustments made to
the low temps in the usual cooler spots.

&&

.Short Term...(This evening through Tuesday night)
Issued at 300 PM EDT Mon Oct 18 2021

Ridging will continue to keep central Indiana dry through the short
term...as the dome of high pressure to our south drifts to the
southern Appalachians, all the while blocking Gulf moisture while
providing subsidence amid the lower levels.  The associated mid-
level ridge axis will slowly settle over the Mid-West by Tuesday
night... although modest subtropical moisture will stream over the
Mid-West through the PM hours Tuesday courtesy of the southwest flow
from the southern Plains.  Therefore, placid mid-autumn weather will
continue through early Wednesday, with the only noteworthy change
being generally SCT clouds occupying the skies over central Indiana
Tuesday afternoon and early evening.  The generally modest gradients
through the boundary layer will keep sustained winds under 10 knots,
with the flow backing slightly from west-southwest to south-
southwest as the surface high slides to the east. A few gusts may
reach 15 knots across northwestern counties Tuesday afternoon.

Temperatures will moderate slightly compared to recent days given
the weak southwesterly advection.  Overnight lows will trend from
the mid-40s tonight to the upper 40s Tuesday night...although
temperatures Tuesday will again peak near 70F under ample high
clouds.

&&

.Long Term...(Wednesday through Monday)
Issued at 300 PM EDT Mon Oct 18 2021

A pleasant start to the extended on Wednesday will transition to a
cooler and eventually more unsettled pattern through the weekend as
ridging aloft is first shifted east...then replaced by a deep upper
low near James Bay that will eventually amplify the upper flow by
Saturday and Sunday as it drops southeast into New England.

The ridge will be centered across the region to start on Wednesday.
A quick moving upper low in tandem with a surface wave will track
out of the central Plains and through the lower Great Lakes
Wednesday night into Thursday. This will bring a cold front across
the forecast area late Wednesday night into early Thursday...with a
narrow window for showers and perhaps a few rumbles of thunder. Not
expecting widespread precipitation accompanying the front with
limited moisture advecting into the region ahead of the boundary and
marginal forcing aloft. Presence of a stronger 850mb flow Wednesday
night though should be enough to generate an axis of weak
instability ahead of the front. High pressure will return to the
region behind the front on Thursday with highs slipping back into
the 60s.

By Friday however...the aforementioned upper low to our north will
begin to exert its influence over the eastern half of the country
with gradual amplification of a broad trough. The passage of a
subtle upper level wave Friday afternoon and evening will aid in
this process...and may have just enough lift associated with it to
generate a few light showers. Cyclonic flow aloft for the weekend
will bring periodic clouds and cooler temperatures to the Great
Lakes and Ohio Valley.

Potential growing for a soaking...cool rain by Sunday into Monday as
a warm front aligns across the region. At this stage...model
discrepancies exist with respect to location and timing of the
boundary.  Additionally...presence of a strong high pressure to the
north could shift the boundary further south away from central
Indiana. Will carry chance pops at this point but not ready to go
any higher with precip chances for the reasons mentioned above.

&&

.Aviation...(00Z TAF Issuance)
Issued at 628 PM EDT Mon Oct 18 2021

IMPACTS:
- VFR through the TAF period
- Light to calm winds overnight. Winds will be 5-10 knts and from
the south after 191500Z.

DISCUSSION:

VFR conditions will continue this evening under mainly clear skies.
Strong high pressure over KY along with an associated ridge of high
pressure over Indiana will provide clear skies and subsidence
through the period. Winds will become southerly on Tuesday as the
high drifts east of Indiana.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

Update...Puma
Short Term...AGM
Long Term...Ryan
Aviation...Puma

Previous Forecast Discussions may be found at
NWS Indianapolis, IN (IND) Office Forecast Discussions.
(Click 'Previous Version' there to view past versions successively.
Some may differ only in time posted.)

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