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FXUS63 KIND 211713
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1213 PM EST Wed Feb 21 2018

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

&&

.SYNOPSIS...
Issued at 336 AM EST Wed Feb 21 2018

A cold front will slowly drop southeast across Kentucky and
Tennessee today. The front will stall and return north over central
Indiana Thursday night and then another cold front will sweep
through late in the weekend. The fronts will interact with a plume
of tropical moisture and result in periods of rain and flooding
through the weekend.

Save a small chance of rain or snow over the area Monday night, high
pressure will provide a relief from the rain Sunday afternoon
through the middle of next week.

Temperatures will be falling through the 40s and 30s today behind
the cold front. But then, they will return to slightly above normal
by Thursday and well above normal by Friday.

&&

.NEAR TERM /Rest of Today and Tonight/...
Issued at 910 AM EST Wed Feb 21 2018

At 9 am, radar loop shows light rainfall across all but the far
northwestern counties of central Indiana. Temperatures range from 33
degrees at Lafayette to 48 at Seymour, with the cold front already
to the southeast of the area and temperatures in the 30s making
their way southeast across the area on northwesterly winds. Rain
will continue, with the back edge of the rainfall slowly progressing
through the area. Made some minor adjustments to PoPs based on this
slightly slower progression, but overall result was not significant.
Temperatures will fall over the southeast counties over the next few
hours and elsewhere should hold pretty steady through the day in the
mid 30s. Skies will remain cloud covered. Previous discussion about
tonight follows...

Models in good agreement that an impulse, currently over
southeastern Texas, in the persistent southwest flow aloft, will
lift northeast over central Indiana tonight. With tropical moisture
plume still over the area, should see more decent rains, mainly
south of Interstate 70. Blend QPF is bringing up to three quarters
of an inch to those areas tonight. Also of concern, is areas north
of Terre Haute, Indianapolis and New Castle late today and tonight,
where model soundings support a mix with freezing rain or snow. That
said, warm ground and less low level moisture there should make it a
little to no impact event there.

Some thought about issuing a Flood Watch for the southern counties
tonight, but with them being dry of late, should be able to hold off
for later in the week and weekend, when more high QPF is expected.

High confidence temperatures will fall through the 40s and 30s today
in the wake of the front in good low level cold air advection setup.
Blend overnight lows in the 30s look good as well with clouds around.

&&

.SHORT TERM /Thursday through Friday night/...
Issued at 336 AM EST Wed Feb 21 2018

POPs will be the main focus for the short term.

Should see a brief break in the rain Thursday afternoon and evening.
Then, a wave will move along the cold front and allow it to return
north over the area as a warm front. With tropical moisture and
upper waves in southwest flow still in play, should see more
widespread rain starting overnight Thursday night through Friday
night and into the long term. Will likely need more flood headlines
for this period.

With the front moving north, confidence is high temperatures will
warm back to well above normal by Friday.

&&

.LONG TERM /Saturday through Tuesday/...
Issued at 327 AM EST Wed Feb 21 2018

The wet and active pattern will continue through Sunday morning
before high pressure and a relaxed flow regime aloft provides a
much needed break with dry and mild weather for early next week.

The heavy rain and flooding threat will continue Saturday as the
frontal boundary lays out across central Indiana with surface wave
rippling along the boundary. A final and more significant surface
wave is poised to swing through the area Saturday night into
Sunday morning. The op GFS continues to hold serve with an
intensifying low pressure system aided by a strengthening
negatively tilted upper trough and while it remains the strongest
with the surface wave Saturday night...it is gradually gaining a
bit more support from other models. This would bring a greater
convective potential Saturday night and possibly the threat for a
low topped squall line with stronger winds along and ahead of the
cold front overnight Saturday.

Potential for an additional 1 to 2 inches of rain with locally
higher amounts Saturday and Saturday night with precip water
values once again rising to climatological maxes for late
February. Taking into account expected rainfall through Friday this
will only exacerbate flooding concerns into the weekend...
especially for rivers and streams...and in lowland and poor
drainage areas.

Drier weather will build in behind the front Sunday with high
pressure taking over across the Ohio Valley and lower Great Lakes
through the first half of next week. Temperatures will remain mild
for early next week with highs primarily in the 50s.

&&

.AVIATION /Discussion for 211800z TAF issuance/...

Issued at 1206 PM EST Wed Feb 21 2018

Low end MVFR/high end IFR to start at the sites due to ceilings.
Short range models show improvement to ceilings to MVFR during the
afternoon/early evening (even VFR possible at KLAF) as rain moves
out to the east/southeast. Tonight the front will make its way
north again and bring more rain and IFR ceilings to the sites.
Winds will shift from NNEly around to ENEly during the period and
should remain about 6 to 14 kts throughout.

&&

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

$$

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