Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 162021

Area Forecast Discussion
National Weather Service Indianapolis IN
420 PM EDT Fri Mar 16 2018

The AVIATION Section has been updated below.


Issued at 326 AM EDT Fri Mar 16 2018

A low pressure system will move from the Mississippi Valley to the
Ohio Valley on Saturday. This system will bring widespread
precipitation to central Indiana tonight and early Saturday. Areas
near and north of Interstate 74 will see a wintry mix with mainly
freezing rain. Meanwhile, areas south of Interstate 74 will see just

High pressure will bring dry weather to the area Saturday night into
Sunday night. Then, a southern system will result in a wintry mix
starting early next Monday. Finally, dry weather will follow for the
middle and late parts of next week as high pressure moves in.

Look for below normal temperatures through Saturday, above normal
temperatures Sunday and Monday and then below normal temperatures
for the middle part of next week.


.NEAR TERM /Rest of Today/...
Issued at 1043 AM EDT Fri Mar 16 2018

High clouds are slowly expanding into the region from the west
this morning ahead of the low pressure tracking through the
central Plains. 1430Z temps remained chilly...running from the
upper 20s to mid 30s.

Not much need to change the forecast for the rest of the day.
Cloud cover will continue to steadily increase through the course
of the day as the low tracks east. The initial surge of moisture
will arrive in the lower Wabash Valley by late day and while a
stray shower or sprinkle cannot be entirely ruled out...not
overly excited in precip potential prior to 00Z with such a dry
airmass present over the region. Model soundings indicate that
boundary layer saturation will likely take well into the evening
over the forecast area.

Nudged winds and temps up just a bit based on current trends.
Otherwise...the current forecast is in very good shape.

Zone and grid updates out.


.SHORT TERM /Tonight through Sunday night/...
Issued at 326 AM EDT Fri Mar 16 2018

The main concern for the short term will be overnight and Saturday
morning, when freezing rain will be possible over northern and
eastern sections of the forecast area as a low pressure system moves
into the middle Mississippi Valley and then Ohio Valley on Saturday.
The 00z NAM looked to be a slow outlier, otherwise 00z model blend
looked good and suggests areas near and north of a New Castle to
Anderson to Lafayette line could see precipitation start off as or
switch to a wintry mix of rain or snow this evening. However, after
06z, as the precipitation becomes widespread and increases in
intensity, top down method suggests the main precipitation type in
this area will be freezing rain. Forecast builder and WPC suggest
our far northeastern counties could see over a tenth of an inch of
ice. That said, above normal road temperatures and barely below
freezing forecasted temperatures tonight lend low confidence to icy
roads. Thus, will stick with a Special Weather Statement to handle
things as opposed to a Freezing Rain Advisory. If the models come in
colder with their 12z runs, this would increase confidence in icy
roads and thus an advisory could still be needed with the afternoon

High confidence that the precipitation will be ending from northwest
to southeast Saturday afternoon. Any linger wintry precipitation
will change back to rain by Noon. After that high confidence in dry
weather through Sunday under the influence of high pressure. Can not
rule out light rain far southwest overnight Sunday night as another
low pressure system moves into the central Plains. That said,
confidence is low.

After a cool start to the weekend, low level thermals and increasing
sunshine support temperatures returning to normal on Sunday.


.LONG TERM /Monday Night through Friday/...
Issued at 239 PM EDT Fri Mar 16 2018

Astronomical Spring may be on the calendar to start Tuesday.
Actual Spring weather on the other hand will remain elusive
through the extended as much of the eastern Midwest...and eastern
U S for that matter...remain under a deep upper trough. Unsettled
and chilly weather will dominate through the period with multiple
opportunities for wet snow over parts of the area.

A cutoff upper low will track across the central Plains and into
the Ohio Valley by Tuesday...and serve as the initial catalyst for
the transition back into a cold and unsettled pattern. The blocky
upper level flow will amplify yet again with the upper low
becoming absorbed by a deepening upper trough set to encompass
much of the eastern part of the country next week. A strong
surface wave will accompany the cutoff upper wave bringing
primarily rain to central Indiana through Tuesday.

Once the wave reemerges as a strong coastal low Wednesday...
colder air will be drawn into the region on the back side of the
system with the potential for an elongated period of rain/snow mix
or potentially all snow lasting into early Thursday as upper level
energy holds back across the Ohio Valley. It still remains
premature to consider wintry impacts...but signs continue to grow
that parts of central Indiana are likely to experience a late
season winter storm that could bring light snow accumulations...
especially Tuesday night into Wednesday.

Highs Tuesday through Thursday are only expected to be in the 30s
and 40s with subtle warming into the middle and upper 40s by
Friday as the upper trough departs off to the east.


.AVIATION /Discussion for the 162100Z KIND TAF Update/...
Issued at 420 PM EDT Fri Mar 16 2018

No significant changes made to the forecast at this time. Previous
discussion follows.

VFR conditions will continue through the evening. MVFR ceilings
will develop overnight into Saturday with periodic drops to IFR as

High pressure will shift away to the east through the rest of the
day as a surface low tracks through the central PLains.
Progressively deeper mid and high level moisture will overspread
the region into the evening...but the presence of easterly flow
will maintain dry conditions through the lowest 10-15kft into the

Model soundings indicate more substantial saturation of the
boundary layer will take place overnight with precipitation
developing after midnight at the terminals. Precip type issues
should not be a problem at any of the terminals with greater
impacts focused northeast of KIND and KLAF. Will carry prevailing
rainfall through daybreak Saturday with scattered light showers
lingering well into the afternoon as the low tracks through the
lower Ohio Valley. The bigger impact to operations Saturday will
be the lower ceilings...likely dropping to 1000-1500ft with the
potential to occasional dip into IFR category. Winds will remain
easterly through the forecast period.




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