Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 212345

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

The AVIATION Section has been updated below.


Issued at 306 PM EST Wed Feb 21 2018

Wet pattern continues into early Sunday as a series of short waves
ride northeast from Texas up and across the Ohio and Tennessee
Valleys. Rainfall episodes tonight into early Thursday, Thursday
night into early Friday, and again Saturday and Saturday night
will in combination produce 2 to 5 inches of rainfall across the
area, especially south of I-70. High pressure will clear things
out Sunday and bring dry weather into midweek next week.

Temperatures will remain above normal through the next seven days
with tonight and Thursday the coolest in this period.


.NEAR TERM /Tonight/...

Issued at 306 PM EST Wed Feb 21 2018

As the next short wave lifts out to our southwest, the rain area
will expand northward overnight across central Indiana. Rain
amounts over one inch are projected by both the NAM and GFS for
our southern counties which appears reasonable. Given that these
areas have just today started into the rain and that stream
levels are normal there, we do expect a rise in rivers and
ponding in the usual low lying areas but do not anticipate
significant flooding issues.

Further north from Lafayette to Tipton and Muncie, temperatures
will be approaching freezing overnight and thus the precipitation
expanding north will likely be a mix of snow with mostly rain.
Should air temperatures reach freezing a light glazing of ice may
occur on above ground surfaces. At the moment the ground is much
warmer than the air and the likelihood of the ground reaching
freezing by tomorrow morning is pretty low. Will issue a special
weather statement to cover that possibility but at the moment that
does not appear to be a problem.

Forecast lows are near guidance in the lower 30s north and upper
30s south.


.SHORT TERM /Thursday through Saturday/...

Issued at 306 PM EST Wed Feb 21 2018

Wave 1 exits the area Thursday morning. Again a wintry mix of
precipitation may continue into the first few hours after
daybreak before temperatures are no longer an issue. Temperatures
near guidance were followed ranging from maxs near 40 in the north
to near 50 in the south.

Wave 2 enters the picture Thursday night. Confidence in rain
amounts and the axis of heaviest rain is low given differences
between available models. A lean towards a compromise between the
models with a rain maximum axis between I-70 and the East Fork
White River looks best. Rain amounts from this wave near one inch
appear in line.

The final wave arrives Saturday with strong dynamics and continued
thrust of abnormally high moisture and with it, another inch of
rainfall by Sunday but this axis appears more likely to shift back
to our northern counties.

Thus the current flooding in the Upper Wabash will have a respite
from heavy rains into Saturday while the White and East Fork White
receive the brunt of rains tonight and Thursday night. The end
will result in river flooding, possibly major flooding, for some
stretches of the rivers.

As referenced in the synopsis, the period Thursday through
Saturday will remain warmer than normal with forecast temperatures
a blend of available model data.


.LONG TERM /Saturday night through Wednesday/...

Issued at 213 PM EST Wed Feb 21 2018

As the long term begins, an upper wave is moving through central
Indiana. There is some instability with this pretty strong upper
system and surface cold front moving through, so included a thunder
mention. Rain could be heavy Saturday night until frontal passage,
with plenty of Gulf moisture to work with advected north on a strong
low level jet.

Once the front and upper trough pass through the area, dry weather
will move in to end the weekend and start next week. Broad upper
ridging slowly builds over the central and eastern U.S. during this
time. The GFS shows a weak upper wave sliding through to the north
on Monday, but right now that feature looks weak enough to only
result in a little increase in cloud cover if that. The next chance
for precipitation arrives at the end of the forecast period (Tuesday
night/Wednesday) as a front stretches east from the plains.

Temperatures will run above normal through the period, with 50s
for highs and 30s for lows throughout in the flatter flow regime.


.AVIATION /Discussion for the 22/00Z TAF Issuance/...

Issued at 633 PM EST Wed Feb 21 2018

MVFR/IFR conditions will continue throughout the TAF period as
rain remains in the area. Currently, heaviest rain is confined to
the southeast of TAF sites. However, rain will spread back north
tonight keeping conditions at MVFR/IFR levels. Meanwhile, winds
will generally be northeasterly at 5 to 10 kts.


Winter Weather Advisory from 11 PM this evening to 10 AM EST
Thursday for INZ021-028>031-035>043.



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