Area Forecast Discussion
Issued by NWS Indianapolis, IN

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989
FXUS63 KIND 291632
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1232 PM EDT Wed Mar 29 2017

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

&&

.SYNOPSIS...
Issued at 227 AM EDT Wed Mar 29 2017

Dry weather is expected today as high pressure over the Great
lakes will depart the region. Meanwhile a powerful low pressure
system over the southern plains will be pushing northeast toward
the Ohio Valley. This system will push into central Indiana late
Wednesday night and Thursday....bringing rain chances along with a
few isolated thunderstorms back to Indiana.

The upper low will remain over the area on Friday...ending the
work week on a wet note.

Dry weather is expected for much of the weekend as high pressure
builds in the wake of the departing low. More showers will return
to the area next work week as yet another low pressure system
arrives in the region.

&&

.NEAR TERM /Rest of Today/...
Issued at 1008 AM EDT Wed Mar 29 2017

Short term models suggest upper wave currently causing showers and
scattered thunderstorms over southwest Illinois and eastern Missouri
will lift northeast towards the southern Great Lakes during the day.
This lift may brush the west central and northwest zones by late
afternoon. Precipitation potential in these areas still looks low as
this upper wave will be fighting a dry easterly flow. Will keep an
eye on this as the day goes by.

Otherwise, this morning`s upper air indicates highs today may be a
touch on the cool side. Will raise the highs a couple more degrees.

Previous discussion follows.

Surface analysis early this morning show High pressure in place
north of the Great Lakes continuing to influence Indiana`s weather
with dry but dirty northeast flow...with an inverted ridge axis in
place across Indiana. Deep and strong low pressure was found over
the southern plains.

Dry weather will continue to expected today as the HIgh to the
north in combination with strong ridging in place aloft provides
subsidence. forecast soundings and time heights show a mainly dry
column...expected for some trapped moisture in the lowest levels
due to an inversion. Time heights and forecast soundings suggest
a slow decrease in lower level RH through the day....thus a few
peeks of sun should work...although high cirrus from convection to
the west will also begin to invade as the upper ridge axis
departs to the east. Thus mostly to partly cloudy. With minimal
warm air advection and dirty NE flow continuing today...will trend
the forecast builder blends cooler by 1-2 degrees.

&&

.SHORT TERM /Tonight through Friday Night/...

Issued at 227 AM EDT Wed Mar 29 2017

Active and wet period expected to begin on late tonight through
Friday evening.

GFS/NAM continue to surge surge a warm front toward Indiana from
the southwest late tonight as the upper low approaches. Forecast
soundings show lower level saturation arriving late tonight. 300K
isentropic surface shows excellent lift and upglide arriving late
tonight and continuing into Thursday with specific humidities over
6 g/kg. Thus will trend pops higher than a forecast builder blend
at least on Thursday.

A second round of storms seem possible on Thursday afternoon as
forecast soundings suggest CAPE near 1000 j/kg by late thursday
afternoon and into the evening. Models suggest a second wave
pushing into the area as the upper low approaches from the
west...with this wave passing across Indiana mainly in the
evening. With rain expected during the morning and early
afternoon...uncertainty on how much instability will be present
is high as heating could be limited. None the less with major
forcing and moisture available with this powerful low...will
trend pops above a mavmos blend on Thursday night. Given the
dynamics possible...isolated severe weather will be possible.

GFS keeps the upper low passing across Indiana on Friday before
allowing the system to exit saturday night. Forecast soundings
continue to indicate a saturated column and good lift will be
expected with upper low in place. Again will trend toward pops
above a forecast builder blend.

By Friday Night the GFS and NAM suggest the system will be
departing and best forcing will be lost as weak high pressure
arrives in its wake. However...forecast soundings indicate trapped
lower level moisture on Friday night along with cyclonic lower
level flow still in place. Thus will keep any low pops suggested
by forecast builder for any stray shower or slowing progression
of this system.

&&

.LONG TERM /Saturday Through Tuesday/...
Issued at 254 AM EDT Wed Mar 29 2017

Models are close enough that the model blend initialization
was accepted for most items.

A break in the frequent chances for rain will occur for the weekend
as high pressure builds in. Some models are trying to sneak some
rain in on Sunday, but confidence is too low to include. Thus
removed the blend`s PoPs Sunday.

Yet another low pressure system will bring more chances for rain
Monday and Tuesday. Models still don`t quite agree on timing and
location, but the threat for rain would still exit for Monday and
Tuesday anyway. Thus left the blend`s PoPs alone then.

Temperatures will remain near average to above average through the
period.

&&

.AVIATION /Discussion for the 291800Z TAFS/...
Issued at 1231 PM EDT Wed Mar 29 2017

Satellite shows area of ceilings 015-025 continuing to drift
westward, affecting the KHUF/KBMG terminals. Based on
extrapolation, it appears these ceilings will scatter out at
those terminals by 291900Z or so.

Otherwise, scattered to broken layers above 050 expected through
the late evening hours, with some potential for ceilings around
050 to begin moving into the KHUF/KLAF areas towards 300600Z.
Surface winds 090-110 degrees at 10-14 kts through the evening
hours. Some surface gusts around 20 kts probable at times this
afternoon, mainly in the KLAF area.

&&

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

$$

SYNOPSIS...PUMA
NEAR TERM...PUMA/JAS
SHORT TERM...PUMA
LONG TERM...50
AVIATION...JAS



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