Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 272338

Area Forecast Discussion
National Weather Service Northern Indiana
738 PM EDT Tue Jun 27 2017

Issued at 716 PM EDT Tue Jun 27 2017

High pressure over the Ohio Valley will move east tonight, with
southerly winds behind it resulting in breezy and warmer
conditions across our area tomorrow. The strong south winds will
cause high waves and dangerous swimming conditions along western
Michigan beaches Wednesday. A cold front will drop slowly
southeast across the Midwest late this week, likely causing
showers and thunderstorms in our area, with heavy rainfall and
severe storms possible.


.SHORT TERM...(This Evening through Wednesday)
Issued at 413 PM EDT Tue Jun 27 2017

An upper level ridge remains entrenched over the region through the
rest of today into tonight, with surface high pressure below. The
pressure gradient tightens as we creep into Wednesday, as sfc low
pressure over the Dakotas drifts eastward into Minnesota/Wisconsin
with a shortwave aloft. This feature will be our next weather maker.

For tonight, expect gradually increasing cloud cover as the system
nears from the west. Lows will drop into the upper 40`s and 50`s.
Due to the tightening pressure gradient ahead of the low, we`ll see
winds become southerly and increase to roughly 15-25 mph on
Wednesday, with gusts up to 30 mph not out of the question Wednesday
afternoon. This will lead to choppy wave conditions on Lake
Michigan, where a small craft advisory will be in place, along with
a hazardous swimming conditions at area beaches.

The question then turns to whether or not we`ll see any
precipitation Wednesday. Most of the higher resolution models this
afternoon are pointing towards a dry afternoon, though the GFS and
consensus blends suggest chances in our far west as the system
nears. I am skeptical of our chances earlier in the day-given that
the upper level ridge remains strongly entrenched over our area.
As the negatively tilted trough arrives and begins to erode the
western edges of the ridge late Wednesday afternoon/evening-we
could see some precipitation-though per 850-500 mb the best
forcing is further north and west of our CWA. Additionally, better
moisture transport/Instability of around 500 J/kg doesn`t arrive
until after 21z-with best moisture after 3Z. Thus have likely
showers/storms mainly after the 3Z time frame.


.LONG TERM...(Wednesday Night through Tuesday)
Issued at 413 PM EDT Tue Jun 27 2017

Wednesday night into Thursday we`ll have the frontal boundary swing
through and stall out across the northwestern CWA, providing a
source of lift through Friday when a second low swings a stronger
cold front through. This will bring us chances for strong to severe
storms, particularly Thursday night into Friday. Heavy rain will
also be a concern, with warm cloud layers as deep as 13kft, and
PWATS up to 150 to 175 percent of normal. Instability ranges from
around 500 J/kg (SFC CAPE) to 1500 J/Kg during the Thursday
afternoon and Friday time frame, with steeper mid-level lapse rates
on Friday afternoon of around 7C/Km. 0-6 km shear looks to be around
30-40 knots in the northwestern part of our forecast area, but in
the east probably only around 20-30 knots. SPC has our forecast area
in a slight risk for Thursday night into Friday. Given the above, I
kept the likely pops from the previous forecast. It will be
interesting to see how the ingredients come together for severe
potential, with confidence still not the greatest given diverging
model solutions/it being further out still. Temperature wise,
we`ll back to warm and humid, with highs in the upper 70`s and
80`s. There are a few chances for showers/storms into next
weekend, but confidence is lower at this time.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 716 PM EDT Tue Jun 27 2017

VFR conditions should cont across the area through this taf
period. Cu along lake shadow convergence zone through FWA
expected to dissipate with loss of heating this eve. Upr level
ridge will cross nrn IN overnight and Wed with associated
subsidence limiting cloudiness. A shrtwv lifting ne from the
central Plains to the upr Midwest will cause convection to our
w-nw, with some debris cloudiness prbly spreading across nrn IN
during the day Wed. Strong southerly flow to the se of this system
will combine with diurnal heating to cause winds to gust to
around 25kt at the terminals Wed.


MI...Beach Hazards Statement from Wednesday afternoon through
     Thursday afternoon for MIZ077.

LM...Small Craft Advisory from 8 AM Wednesday to 2 PM EDT Thursday
     for LMZ043-046.




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