Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 232343
AFDIND

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

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

&&

.SYNOPSIS...
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
forecast.

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
passes.

&&

.AVIATION /Discussion for the 24/00Z TAF Issuance/...

Issued at 626 PM EST Fri Feb 23 2018

Currently, MVFR conditions are prevailing at TAF sites. However,
they will deteriorate to IFR or worse overnight and stay there for
most of the TAF period as waves continue to rotate through a
saturated environment. Periods of heavy rain will result in
reduced visibilities and low ceilings throughout the TAF period.
Meanwhile, winds will generally be northerly, veering to the
southeast tomorrow afternoon. Sustained speeds will range between
5 to 11 kts.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Sunday morning for INZ045>049-051>057-
060>065-067>072.

&&

$$

SYNOPSIS...Nield
NEAR TERM...Nield
SHORT TERM...Nield
LONG TERM...Puma
AVIATION...TDUD



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