Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 290352
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1153 PM EDT Wed Jun 28 2017

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

&&

.SYNOPSIS...
Issued at 315 PM EDT Wed Jun 28 2017

The drier, cooler, mild spell ends today as warmer and more humid
unsettled stormy pattern locks in for much of the coming week.

A weak shortwave in the Upper Midwest today spawning convection
nearby will progress east across southern Canada in the coming
days. Meanwhile, a broader upper level low pressure circulation
across western Canada with troughing into the northern Rockies
will move steadily east and sweep several weak short waves through
its broader cyclonic flow.  The upshot of the Upper Midwest and
western west Canadian circulations will be periods of showers and
thunderstorms Thursday on into next week. A brief lull between
the two systems will offer a dry period late Saturday into Sunday.
No day should be a complete wash-out, and storm timing for the 4th
of July may be mainly daytime hours, but lots of uncertainty
exists for timing that far out. In the upcoming period we will
experience periods of sunshine interspersed with cloudy and stormy
periods. Over the coming week rainfall totals will average 1 to 2
inches.

Relative to recent days we will be warmer and much more humid
through the next week, actually more typical temperature and
humidity for summer.

&&

.NEAR TERM /Tonight/...

Issued at 315 PM EDT Wed Jun 28 2017

A warmer night is in store as southwest winds remain up and
humidity noticeably higher with dewpoints close to 60. Current
convection beginning to fire up across Iowa may reach our
northwest counties late tonight and thus current POPs may need to
be adjusted for that.


&&

.SHORT TERM /Thursday through Saturday/...

Issued at 315 PM EDT Wed Jun 28 2017

Thursday, aforementioned showers and storms that progress
across northern Illinois may still be in play across our
northern counties and progressing east with upper level zonal
flow. Like today, this convection should dissipate in late morning
leaving the entire forecast area rain free. Like today, with some
cloud debris, northern counties temperatures will be on a slower
rise while sunnier southern counties see a steady climb to the
upper 80s. Speaking of a climb, dewpoints will work there way into
the mid and upper 60s as strong southwest flow pumps in moisture
laden air to our southwest. For temperatures, a blend looked good
and was followed with cloudier north ending up in the mid 80s and
sunnier south upper 80s.

Thursday night...the surface trough will have sagged a little
further southeast into central illinois and northwest Indiana. As
daytime instability begins convection, and the nocturnal jet
strengthens and keeps it going, more storms will be trekking east
toward Indiana. Odds favor the surface boundary and storms
staying north of us, but a few model solutions suggest this
boundary and storms could sag south towards I-70 overnight, so
have thus carried that threat. Not much of a cool down as
dewpoints hold in the upper 60s and min temps near 70.

Friday...with the expected surface boundary somewhere in our
vicinity, and active convection possibly in the area, a period of
storminess could continue across central Indiana during at least
the morning. A southeast sag of rain could be expected as well into
our southern counties before this area of convection dissipates
and sunshine begins to take hold. With cloudier conditions
prevalent for more of the area for a longer period of time Friday,
and the probability of at least some rainfall for many areas, max
temperatures should top out a category lower or lower 80s north
and middle 80s south.

Friday night into midday Saturday...this will be the period in
which the upper trough will finally sweep the surface trough
across and through our area. It appears likely a pretty solid band
or large clusters of storms should develop Friday evening to our
northwest and sweep across central Indiana Friday night. Some
showers and isolated storms could linger across the east and
southeast into midday Saturday before ridging begins to take over
and improve the weather. Once again a fairly warm and humid Friday
night will be followed by generally lower 80s Saturday.

&&

.LONG TERM (Saturday night through Wednesday)...

Issued at 140 PM EDT Wed Jun 28 2017

Forecast confidence is high through Sunday night, then drops
sharply.

The deterministic models concur Indiana weather will be dominated by
high pressure until Monday, suggesting forecast errors should be
less than 2 degrees for temperatures and less than 10 percent for
POPs.

Monday into Wednesday, the European and American models differ
widely about how frontal systems will impact Indiana.  This leads to
uncertainty with rain chances. POP errors may be 20 percent.

The models do agree fairly well about temperatures staying near
seasonal levels Monday night through Wednesday. Forecast errors
should be mostly 3 degrees or less.

&&

.AVIATION /Discussion for 290600z TAF Issuance/...
Issued at 1153 PM EDT Wed Jun 28 2017

Good confidence that VFR conditions will dominate the majority of
the TAF period, although would not rule out brief MVFR in
thunderstorms, especially at LAF after 15z. IND could also see MVFR
ceilings after 09z Friday per the SREF. Also, expect scattered to
broken diurnal cu after 15z per cu development progs with bases
above 3k feet.

A 40-45 knot low level jet over central Indiana will result in come
low level wind shear through 12z or so. Otherwise, winds will be
south and southwest 10 knots or more with gusts to 20 knots or more
after 15z at LAF.

&&

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

$$

SYNOPSIS...Tucek
NEAR TERM...Tucek
SHORT TERM...Tucek
LONG TERM....JK
AVIATION...MK


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