Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 171755
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1255 PM EST Sun Dec 17 2017

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

&&

.SYNOPSIS...
Issued at 310 AM EST Sun Dec 17 2017

Mid/Upper level trough over the ARKLATEX region on recent
satellite imagery is moving slowly northeast this morning toward
the lower OH Valley region. Surface analysis shows a
quasistationary frontal boundary lying E-W across northern IN.

&&

.NEAR TERM /This afternoon/...

Issued at 1000 AM EST Sun Dec 17 2017

Surface analysis late this morning shows a warm front stretching
across Northern Indiana...ahead of low pressure over Iowa. Radar
shows an area of rain fall in the wake of the warm front over SW
Indiana...pushing northeast within the flow. These light rain
showers are expected to push across Central Indiana over the next
2-4 hours...producing minimal rainfall amounts. HRRR also
suggests this propagation. Time heights reveals good moisture and
lift passing across the area near 18Z. THus have fine tuned the
pops a bit to account for rain showers over this time period.

As for temperatures...trended slightly cooler than the previous
forecast with expected clouds and rain through the
afternoon...particularly across the Wabash Valley and points
southwest of Indianapolis where the previous forecast appears too
warm.

&&

.SHORT TERM /Tonight through Tuesday/...

Issued at 310 AM EST Sun Dec 17 2017

As weakening low pressure moves across southern IN then off to the
east, low clouds and some light rain/drizzle should remain
from cooler air circulating around the backside of the low. Given
the rain producing wet ground and low clouds with light winds,
have collaborated with keeping low clouds, drizzle and fog across
the region for tonight into early Monday morning. Would expect the
possibility of some dense fog especially across urban areas where
the wet comparatively warmer ground is covered by the cooler air
on the backside of the surface system/trough in low levels. This
may impact morning commute on Monday morning before skies
gradually clear by afternoon.

Area will be between systems going into Tuesday as a strong
frontal boundary will be across the Great Lakes westward over
southern WI/northern IL, and a shortwave trough moving in the
southern branch over south central TX. Southwest surface flow
over the southern Plains is forecast over are area providing some
clouds but temperatures in the low-mid 50s for Tuesday providing
the best day in the week before the cooler air to the north drops
into the area.

&&

.LONG TERM /Wednesday through Saturday/...
Issued at 307 AM EST Sun Dec 17 2017

Extended models indicate a somewhat zonal upper flow Wednesday and
Thursday will become more amplified towards the weekend as a strong
upper trough digs first into the upper midwest and then the great
lakes. Quiet and mild weather will occur Wednesday and Thursday as
an area of low pressure track`s east across the deep south. It now
appears that any precipitation from this will will remain to our
south.

Models indicate an area of low pressure over the central plains
Thursday will track across the upper midwest Friday and into the
great lakes and a trailing cold front will move east across Indiana
Friday night.  Models indicate rain will be possible by Friday
changing to light snow Friday night and then ending.  This seems
reasonable given the above pattern.

Superblend temperatures are least 5 degrees too cool Thursday night
and will raise them to better match MOS and HPC values.  This change
will keep precipitation all liquid Friday morning.  Otherwise...only
minor tweaks made to superblend temperatures in other periods.

&&

.AVIATION /Discussion for the 171800Z Tafs/...

Issued at 1255 PM EST Sun Dec 17 2017

VFR conditions are expected this afternoon. Overnight...a
deterioration to MVFR and then IFR is expected.

Radar shows rain showers associated with a warm front passing
across the Indianapolis area. These will lift to the north by late
this afternoon. Time heights show best moisture and forcing
leaving the area by this afternoon. However the warm and
relatively moist southwest flow will remain across Indiana and
the Ohio valley overnight. This will weak flow of warm and moist
air will allow for the development of Fog overnight and low
clouds. Forecast soundings and Time height sections show saturated
lower levels with minimal forcing aloft through Monday morning.
Thus a trend toward MVFR And IFR will be expected with the
developing inversion overnight.

As heating and mixing resumes on Friday...improvement to MVFR or
better will be expected toward 18Z Monday.

&&

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

$$

SYNOPSIS...DM
NEAR TERM...Puma
SHORT TERM...DM
LONG TERM....JH
AVIATION...JP


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