Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 201345

Area Forecast Discussion
National Weather Service Indianapolis IN
945 AM EDT Thu Apr 20 2017

The NEAR TERM Section has been updated below.


Issued at 334 AM EDT Thu Apr 20 2017

An active and changing pattern is in store for central Indiana for
the next several days. Today a cold front will move through during
the afternoon/evening hours and bring showers and chances for
thunderstorms sweeping through. Cold air will spill in behind the
front for Friday and the weekend as another low pressure system
moves across the Tennessee valley and brings rain to at least
southern parts of central Indiana. Dry conditions build in on
Sunday and last through Wednesday as temperatures warm back into
the 70s to start the work week.


.NEAR TERM /Rest of Today/...

Issued at 936 AM EDT Thu Apr 20 2017

Cold front will move through the area after 17Z bringing showers
and thunderstorms along with it. SPC has removed area from
Enhanced Risk, as the probabilities for damaging winds have
decreased from 30% to 15%. Given that much of the dynamics with
the upper system is moving more north of the area and that much of
our low level flow will be westerly as shown on this morning`s
H85 analysis, the line of storms that will be accomapnied with thr
front may still be accompanied by small hail and gusty winds, but
the threat is not as widespread as originally thought. Still be
necessary to keep tabs on these storms as they move through the
area this afternoon. Sounding from ILX still shows mid-level dry
air between H7 and H5 withe mid level lapse rates of 7C/km which
is sufficient enough to produce strong winds with the storms.


.SHORT TERM /Tonight through Saturday night/...

Issued at 334 AM EDT Thu Apr 20 2017

The cold front will still be moving through the area as tonight
begins so pops will be high in the southeast ahead of the front.
Expect this to move out of the area by around 3z or so and rapidly
drop pops off then, with dry conditions just about everywhere by
6z. By Friday afternoon though pops are increasing from south to
north again as a warm front forms up south of the area and low
pressure moves across the Tennessee valley during the weekend.
While models are in decent agreement on the track of the low, the
cutoff between rainy and dry conditions on Saturday north of the
warm front will be very sharp and still decent uncertainty
regarding where this will set up. Very confident of rain over the
southernmost counties, but low confidence of rain across the
northern counties and only fair confidence along the I-70
corridor. High temperatures Saturday will only reach the mid 50s
and winds will gust to around 25 mph out of the northeast.


.LONG TERM (Sunday through Wednesday night)...

Issued at 334 AM EDT Thu Apr 20 2017

A few rain showers may linger across the far southeastern counties
on Sunday morning as a low pressure system pushes farther southeast.
After that though, high pressure will result in dry conditions
for most of the period. A few isolated showers cannot be
completely ruled out over the northern counties on Tuesday morning
as a warm front enters the area, but otherwise dry conditions can
be expected through Wednesday morning. At that point, a cold
front is progged to move through central Indiana on Wednesday
afternoon, triggering scattered showers through the end of the
extended period. Temperatures will initially start out near
normal, but a weak warming trend will occur through the period.


.AVIATION /Discussion for 201200z TAF issuance/...

Issued at 624 AM EDT Thu Apr 20 2017

VFR at the sites to begin with only some mid and high clouds and
winds of 6-10 kts from 180-220. Winds will increase by mid morning
as the pressure gradient tightens ahead of an approaching cold
front and will see gusts of 20-28 kts during the late morning and
afternoon. Chances for thunderstorms will overspread the sites
from the northwest starting after around 17z at KLAF and moving
over the other sites thereafter. Expect to see conditions drop to
MVFR or worse when thunderstorms are overhead, but will only
include a tempo MVFR group with TSRA mention at this time. Some
potential for severe hail and damaging winds with the
thunderstorms this afternoon/evening but too low confidence to
include higher gusts in the TAFs. The cold front will move through
later this evening and shift winds around to northwesterly and
drop the gusts.




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