Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 212022

Area Forecast Discussion
National Weather Service Indianapolis IN
422 PM EDT Sun May 21 2017

The AVIATION Section has been updated below.


Issued at 237 PM EDT Sun May 21 2017

A broad low pressure system over the Upper Midwest and Great Lakes
will remain an active influence for our region this week.

Surface high pressure will bring dry and seasonable weather into
Monday. The upper low will pivot south and east over the Ohio
Valley by Wednesday renewing cloudy and showery weather as early
as Tuesday. This system will finally kick out Thursday as a new
upper low currently in the Gulf of Alaska shifts into the southern
Canadian rockies to renew unsettled weather in our area by
Memorial Weekend.

Temperature blends are decent showing a drop to below normal most
of the week followed by a rebound to normal by week`s end.


.NEAR TERM /Tonight/...

Issued at 237 PM EDT Sun May 21 2017

High pressure building in will bring fair skies overnight. The
stratocumulus shield across northern Illinois may clip our NW
counties this evening. With surface dewpoints across Illinois in
the mid 40s advecting in, and with winds dropping off, minimum
temperatures in the upper 40s to lower 50s appear reasonable.


.SHORT TERM /Monday through Wednesday/...

Issued at 237 PM EDT Sun May 21 2017

High pressure remains in control Monday and Monday night with some
fair weather cumulus Monday afternoon. Model blend temperatures
of lower 70s maxs Monday and middle 50 mins Monday night still
appear good.

By Tuesday and following into Wednesday the Upper Closed Low
rotates southeast and into Indiana. A return of clouds, and
showers, especially Wednesday appear, likely. With cold
temperatures aloft, combined with daytime heating, enough
instability may develop to yield some isolated thunderstorms
Tuesday afternoon and Wednesday afternoon. Blended temperatures
still look pretty good, bottoming out some 10 degrees below normal
Wednesday as the cold upper low moves overhead.


.LONG TERM /Wednesday Night through Sunday/...
Issued at 237 PM EDT Sun May 21 2017

A cool and unsettled weather pattern will continue into the second
half of the work week. Warmer temperatures will return for the
holiday weekend but with the potential for more rain and storms.

Deep upper low will be in the process of amplifying over the Ohio
Valley Wednesday night serving to strengthen the surface low over
the region. This will result in continued chances for rain into
early Thursday...gradually shifting east with the upper trough by
late day Thursday. Conditions will begin to improve from that
point through Friday as good model consensus exists on the upper
trough lifting out to the northeast and being replaced by ridging
aloft. Expect warmer temperatures back into the 70s for Friday
along with a brief respite from the active weather as dry
conditions are expected for most of the day.

Much lower confidence exists with the forecast going into the
holiday weekend as the ridge flattens somewhat in response to
ripples of energy ejecting out from the base of an upper low
developing over the northern Plains. These waves aloft will track
through the upper flow and across the Ohio Valley over the weekend
and interact with a frontal boundary likely to oscillate over the
area. While neither day over the weekend looks to be a
washout...the presence of the boundary and the energy aloft
warrant chance pops for scattered convection both Saturday and
Sunday. Highs over the weekend are expected to be in the 70s to
lower 80s with lows in the 60s.


.AVIATION /Discussion for the 212100Z KIND TAF Update/...
Issued at 420 PM EDT Sun May 21 2017

No significant changes made to the forecast at this time. Previous
discussion follows.

Scattered to broken cumulus cloud decks should climb to be at or
above 3000 feet at issuance time as daytime heating continues.

Wrap around cumulus/stratocumulus field back in Illinois tied with
low pressure over Wisconsin will sweep into western Indiana but
much of it is diurnally driven and should scatter in coverage by
sunset and dissipate by late evening.

Winds near and above 10 knots from WSW this afternoon will drop
under 10 knots by sundown and remain below thereafter.




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