Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 171459

Area Forecast Discussion
National Weather Service Indianapolis IN
959 AM EST Fri Nov 17 2017

The NEAR TERM and AVIATION Sections has been updated below.


Issued at 306 AM EST Fri Nov 17 2017

The most active part of the forecast will be early in the period
when the upper ridge breaks down and a frontal system impacts
central Indiana. The highest precipitation chances will be tonight
through Saturday as the associated cold front moves through the
forecast area. After that, much cooler and drier air will follow
in the wake of the cold front on Sunday. Another cold front early
in the week will supply an additional shot of reinforcing cold
air, but the best dynamics should keep any precipitation chances
north of the forecast area.


.NEAR TERM /This Afternoon/...

Issued at 943 AM EST Fri Nov 17 2017

Surface analysis late this morning shows strong high pressure in
place over Eastern Ohio and West Virginia. A broad and
disorganized area of low pressure was found across the western
plains states. GOES16 shows a approaching leaf of mid level
clouds...while abundant lower level clouds were still lingering
across the forecast area which forecast builder and CONSSHORT were
not handling well. Water vapor shows a stream of tropical
moisture streaming across California through the Rockies toward
the Central Plains.

Forecast soundings and Time Height sections show a dry column
through the afternoon. Will expect continued increasing clouds
this afternoon as the high cloud continues to stream toward the
Ohio Valley within the flow aloft. Furthermore...high cloud may
prevent much burn off of the pesky lower level clouds. THus
increasing clouds will be the way to go.

Decent warm air advection today on the backside of the high with
southeast winds becoming southerly as the day progresses. Have
trended Highs close to the MAVMOS.

All of this setting the stage for rainfall tonight and Saturday.


.SHORT TERM /Tonight through Sunday Night/...

Issued at 306 AM EST Fri Nov 17 2017

The main focus of the short term period will be shower and
thunderstorm chances early in the period.

As mentioned above, showers will infiltrate central Indiana from
the west by late afternoon as a frontal system approaches from the
Missouri Valley. As upward vertical motion increases after Sat
06Z per time cross sections, so will the chances for thunderstorm
development. As a result, will include mention of thunderstorms in
the forecast at that point and continuing through Saturday along
and ahead of the associated cold front. SPC Day 2 convective
outlook does highlight an area of marginal risk for severe weather
across the southern third of central Indiana as the cold front
encounters some instability. Daytime highs for Saturday are
progged to top off in the upper 50s to mid 60s with dewpoints in
the mid to upper 50s.

Instability and dynamics will begin to wane by Saturday evening
though, and convection will quickly taper off. Forecast soundings
indicate that any lingering moisture on Saturday night will be in
the form of rain, but it looks like moisture will be limited
anyway after Sun 06Z.

Sunday, much cooler and drier air will prevail in the wake of the
aforementioned cold front with highs only in the 30s and lows
dipping into the 20s.


.LONG TERM /Monday through Thursday/...
Issued at 237 AM EST Fri Nov 17 2017

Ensembles in good agreement in suggesting a rather quiet weather
pattern during this period, with little threat for precipitation.

A short wave trough is expected to push across the Great Lakes
around Tuesday, but it appears the better dynamics and deeper
moisture will remain to the north of the forecast area. Will
continue with a dry forecast.


.AVIATION /Discussion for the 171500Z IND Taf Update/...

Some brief MVFR CIGs will be possible this morning...however
trends toward VFR are expected as High clouds are expected to
invade. No other significant changes made.

Previous Discussion Below

/Discussion for the 171200Z TAFS/...
Issued at 534 AM EST Fri Nov 17 2017

Lower than normal confidence in ceiling forecasts today.

Back edge of ceilings around 015 that has been affecting KIND
and occasionally KLAF most of the night, should be moving out of
those areas over the next couple of hours as the low level wind
field veers. However, another area of ceilings from 006 AGL to
around 012 is expanding northward across southern Indiana. Some of
the finer scale model guidance suggests this deck may expand over
the terminals after sunrise, possibly lingering into the early
afternoon, while other guidance suggests this deck will mix out.
Will continue to monitor trends, and make a last minute call on
how to handle this in the forecast.

Otherwise, surface winds 120-140 degrees at 5-8 kts early this
morning are expected to become 150-170 degrees at 10-14 kts
towards midday, with occasional surface gusts 18-20 kts possible
this afternoon. If lower cloud cover comes to fruition, wind
speeds will probably be lower than what is currently expected.




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