Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 181633
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1133 AM EST Wed Jan 18 2017

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

&&

.SYNOPSIS...
Issued at 216 AM EST Wed Jan 18 2017

High pressure over Missouri will push east across the Ohio Valley
today and tonight. This will result in dry weather today and
tonight across Central Indiana...with above normal temperatures.

By Thursday afternoon...the High pressure systems will have exited
to the east while a Low pressure system and warm front approach the
Wabash Valley from the southwest. This will bring yet another shot
of warm air to central Indiana along with showers and perhaps a
Thunderstorm Thursday night into Friday morning.

As the low departs to the north on Friday...Warm southerly winds are
expected to provide well above normal temperatures...with mostly
cloudy skies.

More Active weather with above normal temperatures look in store for
the weekend as quick southwest flow in place aloft pushes several
upper level weather disturbances across the Ohio Valley.

&&

.NEAR TERM /Rest of Today/...
Issued at 950 AM EST Wed Jan 18 2017

Widespread low clouds across the area late this morning, under a
strong inversion noted on this morning`s upper air. May see some
breaks in the low clouds by mid to late afternoon, but it appears
significant clearing probably won`t happen until later tonight.

Will nudge down the highs today about a category, especially over
the southern zones, due to expected cloud cover today.

Previous discussion follows.

Surface Analysis early this morning shows high pressure in place
over Missouri. IR Images show extensive cloudiness on the north side
of the high...stretching from Indiana to Western Missouri.
Water Vapor Imagery shows a quick SW flow in place with a tropical
plume surging across eastern texas into the Tennessee Valley. A
quick moving short wave over over NE Indiana...exiting rapidly.

Main forecast challenge today will be clouds. The high pressure
system is expected to build across Indiana today and tonight.
Ridging aloft is expected also. Furthermore...forecast soundings
show a very dry column as do the Time height sections. Both suggest
however that lower level saturation will linger across the area
through the day. Thus given the latest satellite trends will keep
much of the day cloudy...but trend toward a few peaks of sun late in
the day as the High builds along with subsidence in the column.
Given the expected clouds will keep temps close or slightly below
superblend.

&&

.SHORT TERM /Tonight through Friday night/...

Issued at 216 AM EST Wed Jan 18 2017

Quiet weather is expected to continue tonight as the models suggest
the surface high and ridging aloft pushing across the state.
Again...time heights and forecast soundings suggesting a dry column
and will expect some clearing as forecast soundings show breaks in
the lower level saturation. Thus partly cloudy should work with a
blend on Temps.

On Thursday...the high will be departing to the east along with the
ridging aloft. Meanwhile the models suggest a deep upper low
developing across the Central Plains and pushing an embedded short
wave toward the Ohio Valley within the SW flow aloft. Forecast
soundings quickly become saturated by late Thursday afternoon.
Meanwhile the GFS shows excellent isentropic lift on the 295K GFS
surface...with specific humidities surging to Over 8 g/kg into
Thursday Night. Furthermore Time Heights show a deeply Saturated
column with strong lift as this negatively tilted short wave
approaches.
Thus will ramp up pops this Thursday afternoon and Thursday Night as
these dynamics pass. Forecast soundings only show elevated
convection possible...thus a rumble of thunder cannot be ruled out
but TStorms are not expected to be widespread. Will trend Highs on
Thursday at or above a blend given the very strong warm air
advection...and trend Thursday night lows toward expected wetbulbs.

On Friday and Friday Night...the GFS and NAM suggest progressive SW
in place aloft...but little arriving in the way of forcing.
Forecast soundings suggest a mainly dry column Friday and Friday
Night...but do keep some lingering lower level moisture in place
trapped beneath a weak inversion. Meanwhile strong warm air
advection will be in place on Friday and Friday Night with 850mb
Temps surging toward spring like values of 7-8C. Thus given the warm
air and gulf flow...expect some clouds from time to time.
Partly Sunny to Mostly cloudy should work fine. Again given the warm
air advection will stick close or slightly above superblend on Highs
and lows.

&&

.LONG TERM /Saturday Through Tuesday/...
Issued at 223 AM EST Wed Jan 18 2017

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

An upper level and associated surface low will keep frequent chances
of rain across the area through the long term.

Of course there are some minor differences in timing and location of
rain, but the initialization is a good compromise.

Temperatures will remain well above average with no cold air poised
to move in with the upper system.

&&

.AVIATION /Discussion for the 181800Z TAFS/...
Issued at 1133 AM EST Wed Jan 18 2017

Widespread ceilings 005-008 AGL linger across the area under a
strong low level inversion. Should see ceilings gradually rise
above IFR to around 010-015 by mid afternoon as boundary layer
warms a bit. Patchy drizzle through early afternoon may produce
areas of MVFR visibility restrictions as well.

Short term model guidance suggests ceilings may scatter out at the
KHUF/KBMG/KLAF terminals after 190400Z or so, but with low level
inversion holding, this may be too quick.

Surface winds 240-260 degrees at 8-10 kts this afternoon will
gradually back around to 200-220 degrees at 5-7 kts after sunset.

&&

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

$$

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



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