Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 191820
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
220 PM EDT Thu Oct 19 2017

.UPDATE...The SYNOPSIS...NEAR TERM AND SHORT TERM sections have been
updated below.

&&

.SYNOPSIS...
Issued at 220 PM EDT Thu Oct 19 2017

High pressure will provide dry and warm weather through Saturday.
Then, a pair of low pressure systems will bring wet weather to
central Indiana late weekend and into next week. The second cold
frontal passage will bring much cooler weather to the area by next
Tuesday.

&&

.NEAR TERM /Tonight/...

Issued at 220 PM EDT Thu Oct 19 2017

An upper ridge will build over the area tonight as surface high
pressure expands from the southern states to the eastern Great
Lakes. Model time sections were showing a very dry column except at
the upper levels of the atmosphere. Thus, good confidence there will
no more than some passing cirrus and overnight lows in the upper 40s
to lower 50s per the blend.

&&

.SHORT TERM /Friday through Sunday/...

Issued at 220 PM EDT Thu Oct 19 2017

High confidence in warm and dry weather through Saturday as surface
high pressure moves slowly eastward across the eastern states. Then,
a change is in store as a frontal system is expected to move just
west of central Indiana Sunday afternoon. The 12z ECMWF has now
caught up with the faster 12z GFS. They both bring the cold front to
near a Rockford to St. Louis line by 12z Sunday. The deepest
moisture and best lift both arrive Sunday per similar model output.
That supports the likely to categorical blend pops on Sunday.
Meanwhile, blend small pops west overnight Saturday night look
reasonable as well. Confidence in overall trend is high if not exact
timing. Also, good confidence in temperature trends with above
average highs in the lower and middle 70s through Sunday.

Models were hinting there could be some weak elevated instability
over parts of the area Saturday night and Sunday. However, at this
time, feel the limited instability is not enough to mention thunder.

&&

.LONG TERM /Sunday through Thursday/...

Issued at 327 AM EDT Thu Oct 19 2017

Big changes coming to the region early to mid-week.

Models are in good agreement in sharp, high amplitude mid/upper
level trough entering the center of the CONUS Saturday night into
Sunday morning. Mid/upper level low is expected to develop over
the southern Plains/lower MS Valley region creating a split flow
over the Ohio Valley. This feature is expected to continue
eastward through the southern states as its kicker in the form of
a another high amplitude trough moves into the upper Great Lakes
southward into the mid MS Valley on Monday. By Tuesday evening
a mid/upper level low will develop over the IL/IN/OH region.

Large band of light/moderate rain will be moving into the region
by Sunday afternoon ahead of the first strong cold front, as a
surface low develops in association with the lower MS Valley
trough, around southeast MO/southern IL. Moderate low level flow
of up to 40 kts will run northeast ahead of the front enhancing
moisture/warm advection into the area. Thus, expect that
strong/severe weather be possible south of Indiana, but will
increase the impact of moderate/locally heavy rain across parts
of central IN into Sunday night.

Second strong cold frontal boundary is expected as it drops
southeast Monday night and as a strong mid/upper level jet stream
drops southward over the northern high Plains then eastward over
the Tennessee Valley, bringing with it the coolest air of the
season. Cloudy, rainy weather will continue to be the main
impacts along with occasional gusty winds with the frontal passage
Monday going into Tuesday.

The temperatures will be mild to start the week on Sunday with
highs in the low-mid 70s and lows in the mid 50s Monday morning,
then dropping into the mid 50s for highs Wednesday with lows in
the low 40s throughout the region Wednesday morning, and upper
30s/lower 40s Thursday morning.

&&

.AVIATION /Discussion for 19/18Z TAF Issuance/...

Issued at 1245 PM EDT Thu Oct 19 2017

VFR conditions expected through the TAF period.

High pressure will remain in place through the period with clear
skies expected. Isolated patchy fog may be present tomorrow
morning across eastern and southern Indiana, but should stay clear
of the terminals. Winds will generally be southwesterly at 6-8
kts.


&&

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

$$

SYNOPSIS...MK
NEAR TERM...MK
SHORT TERM...MK
LONG TERM....DM
AVIATION...White



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