Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 272108
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
505 PM EDT Mon Mar 27 2017

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

&&

.SYNOPSIS...
Issued at 327 PM EDT Mon Mar 27 2017

An active forecast period is expected for Central Indiana as
several troughs and ridges rotate through the area. The first
system is currently approaching the forecast area and is expected
to produce showers and thunderstorms this evening and tonight.
After that, weak ridging will result in dry conditions for mid-
week, but another system will approach from the southwest on
Wednesday night. This will keep high rain chances in the forecast
through the end of the week along with the threat for additional
thunderstorms. At that point, the pattern will almost repeat again
with a dry period for the weekend followed by another system late
in the extended period.

&&

.NEAR TERM /This Evening and Tonight/...

Issued at 327 PM EDT Mon Mar 27 2017

The main focus of the near term will be the severe threat with
approaching low pressure system.

Latest analysis indicates an area of low pressure over eastern
Missouri with a cold front extending into the Southern Plains and
a warm front draped across IL/IN/OH. This matches well with the
latest radar mosaic, which is showing ongoing convection across
western portions of Kentucky and Tennessee. Latest LAPS data is
showing a sharp cut-off between high instability and the more
stable environment over central Indiana. Highest CAPE values are
confined to Kentucky and northern Tennessee with values in the
1100 to 1600 J/kg range, decreasing drastically farther north.
Much the same for helicity values and LI, which are favorable for
supercell development but confined to areas south of the forecast
area. As a result, high confidence in severe threat remaining
south of the forecast area.

Nonetheless, some non-severe thunderstorms could make their way
into Central Indiana this evening, and the thunderstorm threat is
expected to diminish altogether after midnight with just
lingering rain showers at that point. Overnight lows are expected
to be in the upper 40s/low 50s.

&&

.SHORT TERM /Tomorrow through Thursday/...

Issued at 327 PM EDT Mon Mar 27 2017

Rain showers will end from west to east very early tomorrow
morning, and then dry conditions will prevail through Wednesday
evening as ridging strengthens aloft.

Focus then turns to the next system, which will start impacting
Central Indiana on Wednesday night. This system will take almost
the same exact path as the near term system, approaching from the
southwest. Inserted mention of thunderstorms with this forecast
issuance starting Wednesday night across the southwestern
counties, spreading northeast across the forecast area on
Thursday. As of now, any severe threat with this system is
expected to stay south, but this could change quickly with any
shifts in the path.

Temperatures through the period will be in the 60s, increasing to
the low 70s by Thursday as warm advection increases with
aforementioned system. Meanwhile, overnight lows will generally be
in the 40s with some 50s across the southern counties.

&&

.LONG TERM /Thursday night through Monday/...

Issued at 220 PM EDT Mon Mar 27 2017

Timing of showers will be the main focus for the long term.

The general weather pattern will remain the same through the long
term with alternating Pacific upper lows and ridges. Each upper low
will dive southeast across dessert southwest and southern Plains and
then lift northeast over the Ohio Valley.

Thursday night will start off with the first upper low over the
Ozarks. It will open up and move east over the Ohio Valley on
Friday. Southerly flow along and ahead of the associated frontal
system will bring deep moisture and some instability to the area as
well as synoptic forcing. Thus, expect widespread showers and a few
thunderstorms from Thursday night through Friday. An upper ridge
will follow and should keep the weather quiet from early Saturday
through Sunday morning. Then, the next in the upper train will bring
shower chances back to central Indiana by Monday.

Low level thermal progs and expected cloud cover support slightly
above normal blend temperatures with highs in the mid 50s to mid
60s.

&&

.AVIATION /Discussion for the 27/2100Z TAF Issuance/...

Issued at 505 PM EDT Mon Mar 27 2017

Threat for thunderstorms will increase at the sites over the next
couple of hours, and should see an increase in coverage by 22-23z as
well. Uncertainty in how far north and west it will get, so HUF and
LAF may wind up avoiding it. Will go less bullish at those sites and
move timing back a bit. Still expect conditions to deteriorate to
MVFR this evening and possibly even IFR overnight with some fog
formation. Meanwhile, winds will be southeasterly for most of the
TAF period, then shift to the north behind the aforementioned low
pressure system. Sustained speeds will generally be 5 to 10 kts
outside of any convection.

&&

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

$$

SYNOPSIS...TDUD
NEAR TERM...TDUD
SHORT TERM...TDUD
LONG TERM....MK
AVIATION...TDUD/CP



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