Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 201855

Area Forecast Discussion
National Weather Service Northern Indiana
255 PM EDT Tue Jun 20 2017

Issued at 328 AM EDT Tue Jun 20 2017

There is a chance for more showers and storms this evening as an
upper level disturbance moves through the region. High pressure
will then move across our area Wednesday providing fair weather.
The high will move east Thursday evening allowing very warm and
humid weather to return on Thursday along with the chance for more
storms through Friday. Highs Thursday should be well into the 80s
to around 90 with muggy conditions. Cooler temperatures will
return for the weekend and early next week but shower and
thunderstorm chances will continue as well.


.SHORT TERM...(This Evening through Wednesday)
Issued at 255 PM EDT Tue Jun 20 2017

Afternoon water vapor shows healthy shortwave diving into our area
with corresponding area of showers and thunderstorms seen on
regional radar mosaic. Diurnal heating under nearly full sun has led
to a few hundred J/kg of SBCAPE here and upstream, despite dewpoints
near 50F and notable midlevel cap. Initial area of forced ascent is
weakening but starting to see additional development along trailing
convergent boundary and this should expand later this evening. Best
chances for thunder (and rain in general) will be in our SW from
roughly 22-03Z. Hi-res CAM`s generally in line with this idea and
have made some minor adjustments to PoPs, mainly for a slightly
later arrival and peak time. Expect gradual weakening trend through
03-06Z with primarily dry conditions thereafter as shortwave exits
and stability builds. Late-day arrival and lackluster instability to
begin with will greatly limit any strong/severe threat. Deep-layer
shear values are high and steep low level lapse rates/high DCAPE
could support an isolated damaging wind gust if a decent updraft
manages to develop but the chances of that appear low.
Subsidence/AVA and theta-e trough in general NW flow will then bring
dry conditions with seasonable temps tomorrow. Could be a stray
shower in our extreme SE but looks to remain outside of our CWA.
Expect highs around 80F under mostly sunny skies.


.LONG TERM...(Wednesday Night through Tuesday)
Issued at 255 PM EDT Tue Jun 20 2017

SW flow/theta-e advection quickly returns by Wed night. Decent
isentropic ascent and low level moisture convergence could spark an
area of showers and thunderstorms across Michigan early Thursday
morning. Precip chances much more questionable further south given
placement of main LLJ axis. Maintained some low chances PoPs in
south but those could be removed in future forecast cycles. Thursday
will likely be dry during most of the day given zonal flow aloft but
wouldn`t entirely rule out an isolated afternoon shower/storm given
high temps near 90F and surface dewpoints in the mid/upper 60s.

Best chance for rain/storms will be on Friday as moderate amplitude
trough swings through the Great Lakes and sends a decent cold front
through our area. Still some uncertainty regarding exact timing of
frontal passage which will determine what, if any, severe threat
exists. Diurnal timing not looking favorable for any decent
instability right now but will continue to watch it. Does still
appear to be a decent chance of rain late Thur/early Fri though and
maintained likely PoPs.

Rest of the forecast relatively quiet. Cold pool aloft settles
overhead Sat so could be some SCT showers/storms. Otherwise,
currently appears fairly dry heading into early next week with temps
on the cool side of climo.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon)
Issued at 140 PM EDT Tue Jun 20 2017

Shortwave currently approaching the area and expect to see a few
SCT showers/storms along associated convergent boundary later this
afternoon as diurnal destabilization maximizes. Instability is
very limited though and confidence in coverage/impact at the
terminals is not high enough for anything more than a VCTS mention
at this point. Main change was to adjust timing a bit later based
on latest hi-res models. Otherwise, dry VFR conditions with light
winds for the rest of the period as surface high pressure builds
over the area. Slight concern for some BR Wednesday morning given
light winds but confidence in boundary layer moisture is much too
low for inclusion in the TAF at this point.





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