Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 191850
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
250 PM EDT Wed Apr 19 2017

.SYNOPSIS...
Issued at 250 pM EDT Wed Apr 19 2017

Low pressure developing across Iowa today will promote isolated
to scattered thunderstorms along a frontal boundary draped across
the area into this evening As this system lifts northeast across
the upper Great Lakes Thursday, the accompanying cold front will
move across our area, likely causing thunderstorms. Isolated
severe storms are possible Thursday afternoon. Temperatures will
remain well above normal through Thursday, cooling off to a bit
below normal behind the cold front on Friday.

&&

.SHORT TERM...(This Evening through Thursday)
Issued at 246 PM EDT Wed Apr 19 2017

Water vapor shows MCV from overnight convection working into
northeast IL and southern Lake Michigan this afternoon while surface
frontal boundary has settled into the north. Surface dew points have
reached the lower 60s ahead of this boundary with temps into the
70s. Showers and thunderstorms have increased in coverage with
afternoon heating and modest mixed layer CAPE around 1500 j/kg
despite abundant cloud cover. 0-3km shear has increased
substantially from previous model runs and can be attributed to
approaching MCV and mid level speed max from upstream overnight
convection. Low level convergence near front remains weak but Non
supercell tornado (NST) index does spike near frontal boundary late
afternoon and early evening. This setup should yield scattered TSRA
into the evening with a few strong to isolated severe storms
possible with stronger updrafts. Hail and damaging winds primary
concern but given the weak boundary and NST parameter cannot rule
out a few funnel cloud reports.

Front returns northward tonight with some storms still possible into
Thursday morning near and north of warm front with 40-45kt low level
jet developing. Subsidence from departing MCV may hamper
development initially. Focus then shifts to approaching cold front
mid day. Deep layer shear still around 30-35 knots with 1500 j/kg
mixed layer CAPE. This should support severe weather chances along
front over primarily eastern half of area. Winds and hail primary
hazards on Thursday.

&&

.LONG TERM...(Thursday Night through Wednesday)
Issued at 246 PM EDT Wed Apr 19 2017

Overall quiet long term period currently expected with cool
weekend followed by nice warmup next week. Strong system will
eject out of Rockies for the weekend but 12z medium range models
continue to keep this system in the TN valley with a broad mid
level trough and mid level moisture spreading over our area.
Surface anticyclone looks rather strong and dry over the Great
Lakes with north to northeast low level flow keeping pcpn just
south of the area. Have opted to continue trend of keeping PoPs
AOB 10 percent given little change in latest model runs. Currently
watching low temperatures this weekend as mid to upper 30s
possible over northern third of area as this Canadian high
pressure settles in. This could lead to some frost potential and
will have to monitor. Frost/freeze season/headlines have begun for
our area.

Mid level ridge then folds into the area late in weekend and early
next week with surface high still in control. Models then indicate
another warm front to pass through with substantially warmer temps
by late in the period. For now will keep these periods dry as well
given lack of strong forcing or deep moisture transport at this time.


&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 128 PM EDT Wed Apr 19 2017

A front has stalled just north of Indiana as a low pressure
system approaches the region from the Central Plains.
Thunderstorms and showers are possible along the front especially
this afternoon and evening and separate time tomorrow afternoon
and evening as a cold front pushes through. The lowest levels of
the atmosphere are still fairly dry today, but any thunderstorm
does have the potential to reduce CIGs within heavy rain. At this
point, don`t have enough confidence to reduce CIGs into MVFR so
will keep it above 3kft this afternoon and again tomorrow
afternoon. Additionally, expecting LL shear overnight tonight
especially at SBN and wind gusts 25 to 30 kts Thursday as a low
level jet passes through.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SYNOPSIS...T
SHORT TERM...Lashley
LONG TERM...Lashley
AVIATION...Roller


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