Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 232115

Area Forecast Discussion
National Weather Service Indianapolis IN
415 PM EST Fri Feb 23 2018


The Synopsis, Near Term, Short Term, and Hydrology sections have
been updated.


Issued at 400 PM EST Fri Feb 23 2018

A frontal system will continue to linger in the area tonight into
Saturday night, before strong low pressure sweeps through the
upper Great Lakes and drags a cold front through the area late
Saturday night. Widespread rainfall is expected later tonight into
Saturday night, with thunderstorms possible Saturday into Saturday
evening. A few severe storms cannot be ruled out, with damaging
winds the primary threat. Additionally, heavy rain will be a
threat through Saturday night with continued flooding on area
waterways and a threat for areal flooding. A break from the recent
wet weather can be expected for the start of the week, before
another strong low pressure system brings rain back to the
forecast mid to late week.


.NEAR TERM /Tonight/...
Issued at 400 PM EST Fri Feb 23 2018

Should see a quiet start to the evening across most of the
forecast area, with rain chances steadily ramping up later as the
next midlevel impulse approaches the area. Thunder threat appears
minimal tonight and thus will keep only rain showers in the

Consensus temperatures appeared a bit too cool, particularly
across the north and northwest, per model surface wetbulb progs.
With rainfall expected to overspread the area, should see little
problem getting down to the mid 30s northwest tonight. South
should remain in the mid 40s.


.SHORT TERM /Saturday through Monday/...
Issued at 400 PM EST Fri Feb 23 2018

Focus then shifts to widespread rainfall departing the area
Saturday morning and then another more significant slug of rain
associated with the main upper level wave and surface low pressure
system late Saturday and Saturday night.

Strong dynamics will be present with the main system and thus a
thunder threat will be in the grids across the entire area,
particularly Saturday evening. Low level jet may approach 70 knots
in advance of frontal passage, and thus a few severe storms cannot
be ruled out, most likely in the form of a squall line along the
front. Instability will, as is often the case this time of year,
be the limiting factor, but very strong low level dynamics and low
level shear will present a damaging wind and perhaps an embedded
tornado threat, and the push of the slight risk into southern
portions of the forecast area is reasonable.

Hydrologic threat will continue per the flood watch. See the
hydrology section below for details.

Expect rain to end quickly with frontal passage late Saturday
night, and the remainder of the short term will be dry with
clearing skies Sunday into Monday.

Consensus temperatures required some minor tweaks particularly
Saturday into Sunday, as they appeared too warm, first with
widespread rainfall expected Saturday and Saturday night, and then
with cold advection expected to be ongoing Sunday.


.LONG TERM /Monday Night through Friday/...
Issued at 225 PM EST Fri Feb 23 2018

ECMWF suggests a return of the SW Flow pattern of warm air
streaming into the Ohio valley. On Monday night through Tuesday
Night...the ECMWF shows little in the way of upper support.
Meanwhile High pressure remains across Florida...allowing a warm
and moist gulf flow to push into the area. Thus have trended with
above normal temperatures at that point but a dry forecast.

On Wednesday Night through Friday...The ECMWF suggests several
short wave pushing through the SW flow aloft. The coup de gras of
the pattern in this period coming on Thursday night as low
pressure looks to move again through the Great lakes and sweep a
cold front across Indiana. This appears reasonable given the warm
southerly gulf flow in place ahead of the approaching dynamics.
Thus have included several periods of rain showers on Wednesday
and Thursday...with best chances on Thursday as the cold front


.AVIATION /Discussion for the 232100Z IND Taf update/...

MVFR conditions continue. No significant changes to the ongoing

Previous discussion below

/Discussion for the 231800Z Tafs/...

Issued at 1145 AM EST Fri Feb 23 2018

MVFR CIGS are expected to persist this afternoon...before quickly
deteriorating toward IFR and perhaps LIFR this evening and

Tropical plume of moisture across the area will continue to push
through the Ohio Valley this afternoon and tonight.

Forecast soundings and Time height sections show saturated lower
levels persisting this afternoon and observations and GOES16
Imagery suggest MVFR CIGS will persist through the afternoon. heating and mixing is lost this evening...expect CIGS
to become IFR...similar to the previous night before stronger
forcing arrives overnight.

A strong short wave will push through the area tonight and into
Saturday...providing forcing for precipitation development. Time
height sections show strong omega and forecast soundings show a
saturated column starting tonight through Saturday. Again this
will result in IFR conditions.


Issued at 400 PM EST Fri Feb 23 2018

Flooding continues along many area rivers and streams, with
significant flooding ongoing along portions of the Wabash.
Additionally, with another round of rainfall last night, the
ground is saturated across central Indiana.

Tonight into early Saturday`s rainfall will be widespread but
likely less than half an inch, which may cause minor issues.

Rainfall Saturday into Saturday night will be somewhat more
significant, with the potential for 2 plus inches. Precipitable
water values will again approach climatological maximum for the
time of year, especially across the south, tomorrow into tomorrow
night, along with the potential for thunderstorms and attendant
high rainfall rates.

Low lying areas and poor drainage areas may flood rapidly, and
small, flashier watersheds will respond very quickly to any heavy
rainfall, especially given the saturated ground and lack of active

Thus, will continue the flood watch across the southern half,
where the heaviest of the rainfall is likely. WPC excessive
rainfall risk agrees well with this, bringing the moderate risk
into this area for day 2.

River forecasts show significant flooding developing along the
entire rest of the Wabash, along with much of the White, East
Fork White, and a few smaller streams over the next few days.



Flood Watch through Sunday morning for INZ045>049-051>057-



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