Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 010659
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
259 AM EDT Mon May 1 2017

.UPDATE...
The LONG TERM Section has been updated below.

&&

.SYNOPSIS...
Issued at 205 AM EDT Mon May 1 2017

A cold front will exit Central Indiana this morning...bringing an
end to the heavy rain threat across Central Indiana Today.
However...large and deep low pressure will be moving through Iowa
and Wisconsin...and continue to bring chances for light showers to
Central Indiana late this afternoon and Tonight.

A break from the rain is set to arrive on Tuesday as weak high
pressure builds across the area. This will keep dry weather in
place until early Wednesday.

By Wednesday afternoon and Thursday...yet another low pressure
system is expected to be pushing through the Ohio
valley...bringing more chances for rain to the state along with
cool temperatures.

&&

.NEAR TERM /Today/...

Issued at 205 AM EDT Mon May 1 2017

Surface analysis early this morning shows deep low pressure in
place over Kansas and Missouri with broad cyclonic flow in place
across the region. Radar shows the associated cold front
approaching Indiana early this morning...just along the Wabash
near 1AM....and lifting northeast with the flow. Radar shows sct
showers along and ahead of the front. GOES-R imagery shows a dry
slot intruding in to the system over Western Kentucky and Central
Illinois.

Models continue to suggest that the deep low to the northwest will
move ever slowly to the northeast. By 12Z...cold front should have
propagated east of the forecast area...allowing the dry slot to
arrive across the area. This should lead to some dry weather this
morning and early afternoon...and perhaps even some sunshine.
However the GFS and NAM both suggest by late this afternoon and
evening...wrap around moisture associated with the low slowly
moving Northeast once again will arrive in Central Indiana.
Forecast soundings show the arrival of trapped stratocu along with
convective temps in the lower 50s. NAM time heights show good
lower level moisture and weak lift. Given this and the cyclonic
flow will trend toward some low chc pops this afternoon.

Wind will also be a concern today. 850mb surface shows a 40knt LLJ
working across Indiana this afternoon within the arrival of the
dry slot. With a good pressure gradient in place along with some
mixing due to allowed daytime heating...wind gusts near 40 mph
will be possible. For now...expect sustained winds to remain less
than 30 and out of advisory criteria...however a windy spring day
is expected. Furthermore...give the arrival of cooler air...will
trend highs cooler than the MAVMOS.

&&

.SHORT TERM /Tonight through Wednesday Night/...

Issued at 205 AM EDT Mon May 1 2017

GFS and NAM continue to show wrap around moisture associated with
the low to the northwest lingering across Central Indiana this
evening. Time heights and forecast continue to show lower level
saturation. Although this should bring an end to any gust
conditions...low chc pops will still be needed for the stray
showers or drizzle that will be possible with weak lift in the
area. Models suggest the moisture shield finally begins to lift
north by 12Z Tuesday as the associated upper low pulls into
Ontario. A forecast builder blend will work fine on lows.

GFS And NAM suggests zonal flow develops on Tuesday through early
Wednesday aloft with little in the way of dynamics. Weak high
pressure looks to remain in place at the surface. Forecast
soundings show a mainly dry column and Time heights hint at
subsidence. Thus will trend toward a dry forecast...with partly
cloudy skies and use a forecaster builder blend.

Changeable weather returns on Late Wednesday...as the GFS
suggests a moderate short wave pushing out of the Central Plains
into the Ohio Valley. An associated low pressure system looks to
set up over Missouri along with a warm front stretching eastward
across Kentucky. Forecast soundings indicate a saturating column
as these features begin to arrive on Wednesday night. Thus will be
ramping up pops on Late wednesday and wednesday night.

&&

.LONG TERM /Thursday Through Sunday/...
Issued at 257 AM EDT Mon May 1 2017

Ensembles in good agreement during this period. A deep long wave
upper trough initially over the Midwest on Thursday is expected to
drift slowly east, reaching the eastern parts of the country by next
Sunday. This upper trough will be accompanied by a rather strong
surface low, which is progged to move through the Ohio/Tennessee
Valley around Thursday.

Will keep PoPs in the forecast from Thursday into next Saturday to
cover the passage of this feature, with the highest PoPs on
Thursday. Ensembles suggest the maximum rainfall axis with this
system may be over or near the local area, so this system will have
to be watched for heavy rain potential.

Ensembles suggest this system will be far enough east by next Sunday
to go dry by that time.

&&

.AVIATION /Discussion for 010600Z TAF Update/...
Issued at 106 AM EDT Mon May 1 2017

Restrictions expected within rain and storms through the
predawn. MVFR ceilings likely to return by late day.

Low pressure will track northeast into the Great Lakes overnight and
enable a cold front to swing across the forecast area during the
predawn hours. Periodic chances for showers and thunderstorms will
continue to impact the terminals until the front passes...with MVFR
and possibly IFR restrictions within any of the heavier rain.
Southerly winds will gust to 25kts at times.

Once the front moves through...should see clouds scatter with a
brief period of clearing expected around daybreak as a well
pronounced dry slot passes across the region from west to east.
Clouds will begin to fill back in through the course of the day as
the cold pool associated with an upper low spreads into the area.
Model soundings and RH progs indicate ceilings could slip into the
MVFR category by late day into the evening although confidence
remains low at this point. The primary impact to aviators will be
the strong wind gusts from the southwest...possibly approaching 35
to 40kts at times in the afternoon. Could see a few light showers
develop as well later in the day increasing in coverage during the
evening as a wave aloft rotates around the base of the upper low.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 8 AM EDT this morning for INZ021-028>031-
035>049-051>057-060>065-067>072.

&&

$$

SYNOPSIS...Puma
NEAR TERM...Puma
SHORT TERM...Puma
LONG TERM....JAS
AVIATION...Ryan



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