Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 182338
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
638 PM EST Wed Jan 18 2017

.UPDATE...

The Near Term section has been updated below.

&&

.SYNOPSIS...
Issued at 227 PM EST Wed Jan 18 2017

High pressure is expected to move through the Ohio Valley tonight.
A frontal system is expected to move through the local area around
Thursday night. Another frontal system may affect the area over the
weekend and on into early next week.

&&

.NEAR TERM /Rest of This Afternoon and Tonight/...
Issued at 638 PM EST Wed Jan 18 2017

Based on latest hourly numerical guidance and presence of low
level warm advection much of the night, have bumped min temps up a
bit.

Additionally, will carry fog mentions as some of the near term
guidance is quite pessimistic on visibilities overnight. MOS and
LAMP not nearly as bullish on fog potential, but given warm
advection and lingering low level inversion, fog certainly seems
possible. Will monitor through the evening for dense fog
potential. Previous discussion follows.

Issued at 227 PM EST Wed Jan 18 2017

Low cloud cover has held across the area so far, however some
clearing has taken place recently over southwest Illinois and
eastern Missouri. This clearing may reach the far southwest zones
late this afternoon, but more likely it will be later tonight
before significant clearing takes place as a low level inversion
holds.

Low level thicknesses tonight suggest the GFS MOS lows for tonight
look good for the most part, so little, if any, adjustments will
be made.

&&

.SHORT TERM /Thursday through Saturday/...
Issued at 227 PM EST Wed Jan 18 2017

Model data suggest upper trough currently pushing out of the
southern Rockies will eject northeast across the local area
Thursday night. Will bring in PoPs starting Thursday afternoon,
and continue them through Friday morning to cover this feature. It
appears the highest PoPs will occur Thursday night, coinciding
with the best lift. Steeper mid level lapse rates, associated with
the negatively tilted nature of the upper trough, will result in
an elevated risk for thunderstorms mainly late Thursday afternoon
and night.

Next upper disturbance ejecting out of the western trough looks to
move into the southern Plains by Saturday. Will bring chance PoPs
back into the area by Saturday as this next trough approaches.

Progged low level thicknesses generally support the GFS MOS
temperature guidance over the next couple of days. The guidance
highs on Saturday may be a little on the warm side given cloud
cover and precipitation potential. May nudge the highs down a
little in that period.

&&

.LONG TERM (Saturday night through Wednesday)...
Issued at 1257 PM EST Wed Jan 18 2017

There is high confidence the weather will be unusually warm. There
is also high confidence there will be lots of rain, but little or no
chance for snow.

The models all predict Indiana is going to be affected by air from
the Gulf Coast. Besides being warm and humid, this air should have
storm systems embedded in it.

It is too early to be precise about rain timing. POPS for any one
period may need adjusting by 20 percent. Given uncertainty about
precipitation, there is some uncertainty about temperatures.
Possible errors are about 4 degrees. It is very likely readings
will be at least 10 degrees above average most of the time.

&&

.AVIATION /Discussion for the 19/00Z TAFs/...
Issued at 611 PM EST Wed Jan 18 2017

Borderline MVFR/IFR conditions may deteriorate again overnight as
the low level inversion lingers across the area.

HRRR and Short term blends depict very poor visibilities overnight
in fog. MOS and LAMP guidance are significantly less pessimistic,
but with lingering inversion and moist low levels poor conditions
certainly seem possible. Will take most sites down to 1/2SM at least
for this package and monitor evolution of low cloud and visibilities
through the evening.

Ceilings are likely to remain poor through much of the night,
although some breakup of ceilings cannot be entirely ruled out at
the southwest sites.

Winds will be less than 10kt through the period.

&&

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

&&

$$

SYNOPSIS...JAS
NEAR TERM...JAS/NIELD
SHORT TERM...JAS
LONG TERM...JK
AVIATION...NIELD


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