Area Forecast Discussion
Issued by NWS Indianapolis, IN

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000
FXUS63 KIND 282100
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
400 PM EST Tue Feb 28 2017

.UPDATE...
The SYNOPSIS...NEAR TERM and SHORT TERM Sections have been updated below.

&&

.SYNOPSIS...
Issued at 330 PM EST Tue Feb 28 2017

Severe storms expected to develop and move through central
Indiana later tonight and during the overnight, with potential for
tornadoes, large hail and damaging winds. The threat will continue
into Wednesday morning until a cold front moves through to bring
it to an end. Small chances for rain or snow will be off and on
Wednesday night through Friday night for parts of the area, but a
warmup will come for the weekend. More rain chances arrive to end
the weekend and start the work week.

&&

.NEAR TERM /Tonight/...

Issued at 330 PM EST Tue Feb 28 2017

Forecast focus is on severe weather expected tonight-both the
threats and the timing. Incredible dynamics are coming into place
over the area with a strong upper jet and low level jet forecast
to come into phase tonight over the Ohio Valley. While instability
could be a somewhat limiting factor given the timing during the
night and no sunshine today, moisture return has been ample on
southerly flow and dewpoints in the 60s are already making their
way into central Indiana. The vertical shear profiles are
extremely favorable for rotating storms, and LCLs and LFCs are
sufficiently low to not impede tornado development.

Best estimate on timing of severe potential for the area at this
point is starting around 9pm in the western counties, 10-11
central and midnight or so east. Initially more discrete cells
are anticipated that could possibly morph into a line as they
move across the area, but some models are also indicating they may
keep their more discrete nature. There is also potential after
this first batch of storms that another may come behind them in
the form of a squall line ahead of the cold front.

Given the shear profiles, the tornado threat will continue through
the overnight hours, along with potential for very large hail and
damaging winds.

Also of note...southern counties received a couple of rounds of
showers and thunderstorms already today, with around an inch of
rain or more in some locations. With another couple of rounds
moving through tonight and ample moisture, see potential for
flash flooding and have issued a flash flood watch for that area.

&&

.SHORT TERM /Wednesday through Wednesday night/...

Issued at 330 PM EST Tue Feb 28 2017

Thunderstorms should be ongoing across the area to start the day
on Wednesday. A threat for severe storms will continue ahead of
the cold front which should somewhere in the forecast area at 12z
Wednesday morning. The threat should quickly come to an end by
around 15z or so as model consensus has the front east of the area
12-18z, depending on your model of choice, with the GFS faster and
the NAM slower. Given the time of day and waning instability
threat should be for damaging winds mainly as the aforementioned
ongoing storms start to fade in intensity.

Storm chances move out by Wednesday afternoon, and rain showers
should be exiting as well. An upper wave moving in from the north
will bring some rain chances transitioning to rain/snow mix over
to snow in the north and central parts of the forecast area early
evening into Wednesday night. No accumulation expected.

&&

.LONG TERM /Thursday through Tuesday/...

Issued at 145 PM EST Tue Feb 28 2017

A clipper type system could move through the Great Lakes Thursday
afternoon and night bringing chances for precip to much of the
area. Temperatures look warm enough Thursday afternoon for rain,
but a mix with snow could occur Thursday evening before
transitioning to all snow from north to south during the night.
Little to no accumulation expected.

Another clipper system will move through Friday night and could
bring chances for snow showers to the northern counties. Again
little to no accumulation expected.

Warmer air arrives Saturday and temperatures well above normal
then expected through Tuesday. Sunday night a front system will
approach and keep rain chances in the forecast through Monday
night.

&&

.AVIATION /Discussion for 282100z TAF issuance/...

Issued at 324 PM EST Tue Feb 28 2017

Delayed improvement at KIND and KBMG based on latest trends. Higher
visibility will still work into the area relatively soon.

Previous discussion follows...

IFR and lower over the sites right now with low ceiling from warm
advection lift. Scattered showers/thunderstorms can be expect
around KBMG through the afternoon, but confidence not high that
any will actually hit the airport so will just keep a VCTS going
through the day there. Elsewhere the threat for thunder will
increase this evening after around 0z, and expecting more
widespread development around 1-3z western sites and 3-5z for KIND
and KBMG and have tempo`d this in. After a brief break could see
another line/area of thunderstorms move in later after around 6-8z
west and 7-9z east. Could see significant wind gusts and large
hail with any of the convection this evening and overnight. Also
will see LLWS around 6z, but dropped the mention when including
thunderstorms with wind gusts of 40 kts. Confidence in timing is
moderate at this point, with some model agreement but give or take
a couple hours especially with more than one round expected.

Wind gusts should increase this afternoon and this should help
raise ceilings and visibilities outside of any convection.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch from 7 PM EST this evening through Wednesday
afternoon for INZ067>072.

&&

$$

SYNOPSIS...CP
NEAR TERM...CP
SHORT TERM...CP
LONG TERM....CP
AVIATION...CP/50


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