Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 172029

Area Forecast Discussion
National Weather Service Indianapolis IN
329 PM EST Wed Jan 17 2018

Aviation section updated


Issued at 230 PM EST Wed Jan 17 2018

Dry and slowly warming winter weather can be expected the for the
rest of the  work week across Central Indiana. High pressure in
place over the southern Mississippi River Valley will continue to
slowly slide southeast...keeping a warmer and drier westerly flow
of air to Central Indiana.

The next best chance for rain will be late this weekend and early
next work week as a low pressure system approaches from the west.


.NEAR TERM /Tonight/...

Issued at 230 PM EST Wed Jan 17 2018

Surface Analysis early this afternoon shows high pressure in
place over Arkansas...extending through the deep south and into
the Central Mississippi River Valley and Ohio River Valley.
Westerly Surface flow was in place across Indiana and temperatures
were recovering into the teens. GOES16 shows mainly clear skies
and snow cover across Central Indiana...with some high cloud
drifting in from the north. Water Vapor shows a trough aloft
entering the southeastern States while a large and broad ridge was
found across the plains and upper midwest.

Forecast soundings and time heights show a dry column again
tonight with subsidence in place. This should be expected on the
lee side of the strong broad ridge aloft upstream. However the
story tonight will be warm air advection. GFS and NAM show
excellent warm air advection from the NW as the dome of cold air
associated with the high to the south departs eastward. 850mb
temps look to soar above freezing by 12Z...which should result in
a slow warm up for us. Thus will trend toward a mostly clear and
warmer highs...trending lows at or above the forecast builder


.SHORT TERM /Thursday through Saturday/...

Issued at 230 PM EST Wed Jan 17 2018

Models continue to suggest a quiet weather pattern during this
time. The GFS and NAM suggest that the broad ridge aloft over the
plains and upper midwest will slowly push eastward through
Saturday and very gradually flatten out. This should keep Indiana
protected from any passing short waves within the flow
aloft...deflecting them to the north. Through Saturday...warm air
advection continues within the lower levels with 850MB temps
reaching near 4c by 12Z Friday and 7C by 12Z Saturday. The surface
high to the south is also expected to drift east of Florida by
Saturday...which will allow warmer and more moist gulf air return
to Central Indiana. Forecast soundings and Time heights remain
quite dry during this period...failing to show much in the way of
saturation. An exception to this is the GFS forecast soundings on
Saturday which suggest some low level saturation mainly due to
warm air advection. At this time...confidence in that is low given
our very dry air mass. Thus will take a wait and see approach for
now. Overall, will aim for partly cloudy days and mostly clear
nights during this period...with temperatures at or above the
forecast builder blend given the warm air advection.


.LONG TERM /Saturday Night through Wednesday/...
Issued at 116 PM EST Wed Jan 17 2018

The long term portion of the forecast will be significantly warmer
as the west coast ridge breaks down and shifts eastward across the
country. This will allow a trailing trough axis to push into the
Rockies Saturday and induce cyclogenesis in the lee of the Rockies.
Warm advection and isentropic lift out ahead of this developing low
will necessitate low pops for rain showers early in the weekend,
with chances increasing into early next week as a well developed
low pressure system pushes northeast through the Great Lakes and
drags a cold front through the area. The vast majority of
precipitation with this system will fall as rain, although it may
turn cold enough with the wrap around precipitation behind the
cold front for a few light snow showers.

Blended initialization handled things well and few significant
changes were required.


.AVIATION /Discussion for the 172100Z IND TAF Update/...

VFR conditions continue. No significant changes to the ongoing
TAF. High Pressure south of Indiana continues to dominate the

Previous Discussion Below

/Discussion for the 17/18Z TAFs/...
Issued at 1211 PM EST Wed Jan 17 2018

VFR through the period.

Surface high pressure will be the dominant feature this TAF
period. As a result, expect mostly clear skies, and winds
generally around 230-250 less than 10KT. No significant
obstructions to visibility expected.




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