Area Forecast Discussion
Issued by NWS Indianapolis, IN

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653
FXUS63 KIND 210417
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1117 PM EST Mon Feb 20 2017

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

&&

.SYNOPSIS...
Issued at 234 PM EST Mon Feb 20 2017

Warm weather will continue through the work week. Chances for rain
arrive late tonight and exit for brief period late Tuesday night
before returning late Wednesday night. A strong low pressure
system will move in to end the week, bringing with it
thunderstorms and chances for severe weather along with strong winds
for Friday. This system will also bring the end of the mild
conditions and usher near normal temperatures back in and chances
for snow or a rain snow mix Sunday night.

&&

.NEAR TERM /Overnight/...
Issued at 1000 PM EST Mon Feb 20 2017

Mid and high level clouds continue to overspread and thicken
across central Indiana as a weakening frontal boundary approaches
from the west. 03Z temps were in the 50s primarily.

Not much change needed for the evening update. Main adjustment was
to back off on pops in the predawn hours as most if not all of the
forecast area is likely to remain dry through 12Z. Model soundings
and RH progs show plenty of drier air still present in the lowest
10-15kft with only modest moistening of the lower levels towards
daybreak and more into Tuesday morning. Hi-res guidance largely
keeping showers currently over the mid Mississippi Valley to the
west and northwest of the forecast area through daybreak with the
only possible exception being across the northern Wabash Valley.
Have backed pops down to only 20 in these areas after 09-10Z with
rain holding off elsewhere until after daybreak Tuesday.

With warm advection ongoing and clouds increasing...it will remain
mild overnight with lows in the 50s. Afternoon forecast had this
well in hand with only subtle adjustments needed.

Zone and grid updates out.

&&

.SHORT TERM /Tuesday through Thursday/...

Issued at 234 PM EST Mon Feb 20 2017

A weak surface front will move through the area on Tuesday and
bring rain chances across the area. Not ample deep moisture so
only looking at light showers and cloudy skies. The showers will
move out by 6z Wednesday and high pressure moves in. Wednesday
should see mostly sunny skies across the area to start the day,
with increasing clouds across the south and east as another wave
passes by to the south. With southwesterly winds and more sunshine
increased temperatures across the north and west 2 degrees from
the initialization. Wednesday night another wave will approach
that will bring in chances for rain that increase during the day
on Thursday. For Thursday made no adjustments to initialization
temperatures with expectation of clouds and precip chances. Even
so, highs in the mid 60s to around 70 still expected.

&&

.LONG TERM.../Thursday night through Monday/
Issued at 156 PM EST Mon Feb 20 2017

Although models have some differences handling a late week and early
weekend system, all suggest it will be an active one with the
potential for strong convection Friday afternoon and evening, along
and ahead of the associated cold front. This will also bring a
change in the well above normal temperatures with seasonable weather
in the wake of the front starting Saturday.

Model instability progs all support thunder chances Thursday night
as a near-stationary front returns north as a warm front. Superblend
has the highest pops over our northern counties Thursday night and
Friday, closer to this front, which seems reasonable. Model CAPEs of
400 to 700 j/kg Friday afternoon and evening along with 50 knot low
level jet and strong upper support warrant SPC day5 outlooked area.

By Saturday, temperatures will be more late February-like with highs
in the 40s per blend looking good based on low level thermal progs
and cloud cover. Could see a few wraparound showers, possibly mixed
with snow north, as the system exits to the northeast. Saturday
night and Sunday look dry. The next chance of precipitation looks to
be Sunday night and Monday as a warm front approaches from the
south. Superblend suggests a trend of rain and snow becoming all
snow and then switching back to rain Monday morning. Confidence on
precipitation type, coverage and amounts are low this far out. But,
warm ground should prevent any significant snow accumulation, and
warming Monday afternoon would melt any that did occur.

&&

.AVIATION /Discussion for 210600Z TAF Issuance/...
Issued at 1117 PM EST Mon Feb 20 2017

VFR conditions expected through early Tuesday afternoon...then
restrictions developing later in the afternoon into the evening.

Mid and high level clouds continue to expand across the Ohio Valley
late this evening ahead of an approaching frontal boundary currently
moving through the mid Mississippi Valley. The front will move into
the region during the day Tuesday...weakening as it arrives. Expect
only scattered showers impacting the terminals on Tuesday with
limited low level moisture present with the boundary.

Lower ceilings will develop by late afternoon and are likely to
linger and lower into the evening as model soundings show a shallow
inversion setting up. Skies will clear late Tuesday night as drier
air builds in with weak high pressure...but presence of the shallow
inversion supports potential for fog once again early Wednesday.

&&

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

&&

$$

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



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