Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 280001
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
801 PM EDT Tue Sep 27 2016

.SYNOPSIS...
Issued at 759 PM EDT Tue Sep 27 2016

Clouds will increase overnight as a large upper level disturbance
across Lake Superior drops southward. Rain will become likely
overnight across southwest lower Michigan and portions of far
northwest and north central Indiana, with scattered to numerous
showers across the entire region for Wednesday. Unsettled weather
will continue through Saturday as the upper level disturbance
moves very little. Low temperatures tonight will drop into the
upper 40s to around 50. High temperatures on Wednesday are
expected to be limited to the lower to mid 60s.

&&

.SHORT TERM...(This Evening through Wednesday)
Issued at 335 PM EDT Tue Sep 27 2016

Quiet weather early this evening will give way to unsettled
conditions late tonight into Wednesday, with unsettled weather
continuing through the first half of the long term period.

An upper level low across the northern Great Lakes will dig
southward tonight into Wednesday as a 100 knot upper jet streak digs
into mid MS River Valley tonight. Air mass to south of this upper
low is quite dry, evident by 12Z RAOB from KDVN this morning (0.25
PWATS). A more substantial vort lobe rounding this upper negative
height anomaly is evident on water vapor imagery this afternoon
across west central Minnesota. This feature should eventually slide
across the southern Great Lakes late tonight into early Wednesday
morning. Still expecting associated low level cyclonic circulation
to slide southward along eastern Lake Michigan shoreline and sharpen
late tonight/early Wednesday as thermally induced sfc troughing
becomes more defined. Only tweak to previous forecast was to
slightly slow PoPs tonight, and to add low PoPs far southeast as
low level fgen response looks a bit more impressive in latest
runs.

Some indications that by early Wednesday some low/mid level fgen
response could allow for continued shower development across
southeast portion of the area. Low level baroclinic should pivot
back to the west in the afternoon with better scattered afternoon
shower potential possibly setting up across central portions of
the forecast area. Will keep low cat/high likely PoPs in the far
northwest closer to stronger low level moisture moisture
convergence fields, with gradually waning PoPs Wednesday night.
Much cooler day in store for Wednesday due to low level thermal
troughing and impacts from clouds/precip.

&&

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 335 PM EDT Tue Sep 27 2016

Unsettled weather to continue through at least the first part
of the weekend as upper low will be very slow to exit the region.
A series of vorts will also rotate around the upper PV anomaly
resulting in some retrogression of key features for the end of the
work week. Increased low/mid level moisture will also be drawn
northward around parent circulation for the Thursday night/Friday
period. With little overall movement in mid/upper level cold pool,
will maintain chance PoPs through Saturday with likely PoPs for
Friday in response to stronger vort lobe tracking around the upper
low and aforementioned moisture wrapping back into deformation
zone. Trends still support eventual ingest of this PV anomaly by
southeast Canadian wave late weekend/early next week. It still
appears as though temps will moderate early next week as mid/upper
level ridging builds. Another fropa looks like it may impact the
area just outside of this forecast valid period as wave of eastern
Pacific origin tracks across central CONUS.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 800 PM EDT Tue Sep 27 2016

Primarily VFR conditions expected through the forecast period.
However transition to long duration unsettled period through
remainder of the week replete with scattered shra and eventually
lowered ceilings. Have trended KSBN down below fueling/alternate
criteria late in forecast period as nocturnal cooling and
secondary moisture surge to lend lowered ceilings.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...Small Craft Advisory until 11 PM EDT Wednesday for LMZ043-046.

&&

$$

SYNOPSIS...Marsili
SHORT TERM...Marsili
LONG TERM...Marsili
AVIATION...Murphy


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