Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 181652
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1152 AM EST Thu Jan 18 2018

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

&&

.SYNOPSIS...
Issued at 322 AM EST Thu Jan 18 2018

Dry weather with moderating temperatures will be the rule over
central Indiana through Friday night as high pressure shifts to the
southeastern states and the Atlantic, ahead of a Rockies system. The
Rockies system will lift northeast to the Great Lakes during the
early part of next week. Increasing moisture and lift from that
frontal system will bring rain chances to central Indiana starting
Saturday night.

Seasonable temperatures will follow the frontal passage with a
lingering chance of rain or snow through next Tuesday.

&&

.NEAR TERM /Rest of Today/...
Issued at 953 AM EST Thu Jan 18 2018

Clear skies this morning with temperatures at 1430Z generally in
the teens. Low impact day in progress continues through the
remainder of the daylight hours as the region remains under the
influence of broad high pressure drifting through the Tennessee
and Lower Mississippi Valleys. Return flow on the back side of
the high has already developed over the region this morning...and
will strengthen through the course of the afternoon as the surface
pressure gradient tightens. Likely to see gusts approaching 25mph
this afternoon as a result...especially over northern portions of
the forecast area.

Left forecast highs as is as we continue the slow climb out of the
icebox. Should see temperatures top out in the upper 20s and
lower 30s this afternoon with wind chills held down by the breezy
conditions.

Zone and grid updates out.

&&

.SHORT TERM /Tonight through Saturday night/...
Issued at 320 AM EST Thu Jan 18 2018

The main focus for the short term will be on temperatures and then
whether or not we will see any rate late in the period.

Models in good agreement that the southern high will shift to the
southeastern states and Atlantic this weekend. Meanwhile, the
western upper ridge will flatten and moves over the Ohio Valley
Friday night, and an upper low will move over the South. The result
will be prolonged warm air advection. The flow will have a better
Gulf component by Saturday and Saturday night. Models were also
showing increasing isentropic lift on the 300K level. However, model
time secs were slow to moisten the mid levels and were only showing
saturation up to about 800 millibars by Saturday evening. Forecast
Builder starts to bring in slight chance pops to our far southern
counties by Saturday afternoon and small pops over all of central
Indiana by Saturday night. With the dry mid levels, would not be
surprised to see it dry through Saturday night. However, do not
think leaving the small pops in is that bad an idea at this point.

Prior to Saturday, with a dry southwest flow, good confidence in
little cloud cover with moderating temperatures. Low level thermals
suggest highs 5 plus degrees warmer each day which reflects the
regional blend and translates to near normal highs in the middle and
upper 30s Friday and above normal highs in the lower 40s Saturday.
Confidence in temperatures trends is good. Although, confidence in
highs to within a few degrees is moderate at best, especially
Friday,  due to the dying snow pack battling it out with warm air
advection.

&&

.LONG TERM /Sunday through Wednesday/...
Issued at 332 AM EST Thu Jan 18 2018

Ensembles are in good agreement during this period, albeit a little
slower overall with the system expected to affect the area early
next week. An upper trough is expected to move through the area
around Monday, while an associated low pressure system moves into
the Great Lakes.

Will keep PoPs in the forecast for rain on Sunday and Monday to
cover the passage of this feature, with the highest PoPs on Sunday
night and Monday morning, coinciding with the passage of the cold
front.

Given the slower movement of the system, the potential for some wrap
around light precipitation on the back side of the trough to linger
into early Tuesday is increasing, especially over the northern
zones. As a result, will add some chance PoPs for light rain or snow
to the forecast Monday night and Tuesday morning.

&&

.AVIATION /Discussion for 181800Z TAF Issuance/...
Issued at 1152 AM EST Thu Jan 18 2018

VFR conditions expected throughout the forecast period.

High pressure will remain across the Ohio Valley through the
period...maintaining mostly clear skies across central Indiana.
The only issue for aviators this afternoon and evening will be the
potential for gusts in excess of 20kts as the surface pressure
gradient tightens. Gusts will drop off after sunset at all but
KLAF where they are likely to linger well into the overnight.
Borderline low level wind shear potential will exist later tonight
and Friday morning...mainly at KIND and KLAF. Sustained southwest
winds near 10kts will persist at the other terminals through
Friday morning.

&&

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

&&

$$

SYNOPSIS...MK
NEAR TERM...Ryan
SHORT TERM...MK
LONG TERM....JAS
AVIATION...Ryan



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