Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 251036 CCA

Area Forecast Discussion
National Weather Service Northern Indiana
636 AM EDT Sun Sep 25 2016

Issued at 345 AM EDT Sun Sep 25 2016

Dry and mild conditions are expected under an upper level ridge
today. Highs will generally range between the mid 70s and low 80s.
Rain showers will likely accompany a strong cold front tonight
into early Monday morning. An isolated thunderstorm will also be
possible mainly west of Interstate 69 this evening into the early
overnight. Cooler and drier air will settle in on Monday and
Tuesday, with highs in the mid 60s to low 70s Monday and the 60s
on Tuesday. An upper level low will then bring renewed rain
chances Tuesday night into Wednesday.


.SHORT TERM...(Today and Tonight)
Issued at 345 AM EDT Sun Sep 25 2016

Gradual veer to near sfc winds and mostly sunny start under upper
ridge axis will provide a dry and warmer Sunday, save for a slight
chance for a late day shower/storm into areas mainly west of US 31
in Indiana on leading edge of pre-frontal theta-e ridge.

Strong early fall frontal passage becomes the story tonight into
early Monday morning as impressive/deep pv anomaly and round of 200
meter 5H height falls consolidate into the northwest Great
Lakes by later tonight. Favorable large scale upper
divergence/mid lvl dcva overspreading the lower Great lakes will
act to enhance low-mid level frontogenesis along the eastward
progressing front. This deep plume of upward vertical motion and
ample moisture (PWATS > 1.7 inches) should be enough to force a
several hour period of showers into nw IN/sw Lower MI this evening
into the early overnight, and points east overnight into early
Monday. Strong forcing and weak instability may also be enough to
generate some embedded thunder, best chances west of I-69 01-06z.


.LONG TERM...(Monday through Saturday)
Issued at 345 AM EDT Sun Sep 25 2016

Upper-level jetlet dropping south from the Canadian Prairies will
carve out a strong negative height minimum across the
northern/western Great Lakes Monday/Tuesday, with models consistent
in sliding this upper low southeast through the local area later
Tuesday night/Wednesday. Mainly dry/cooler conditions are expected
underneath this system into Monday afternoon/Tuesday as dry airmass
wraps in under Northern Lakes occlusion. Isentropic descent/strong
CAA/steepening low level lapse rates post-frontal will afford a
breezy Monday afternoon, with Tuesday also a little breezy given
deep diurnal mixing and lingering low level height gradient.

Clouds and shower chances increase into Tuesday night and Wednesday
with southeast migrating upper low. The last several ECMWF op
solutions are throwing a wrench into the late week/next weekend
forecast by cutting off the upper low and associated circling
smaller scale vorts across the OH/TN Valleys. The result would be
lingering cloud cover, shower chances, and cooler temps.
For now, given the high level of uncertainty, opted to follow the
dry/warmer consensus forecast/GFS which favors ridging and eastward
exit of this feature.


.AVIATION...(For the 12Z TAFS through 12Z Monday Morning)
Issued at 636 AM EDT Sun Sep 25 2016

Vfr conditions expected to persist through most this period. However
moisture surge ahead of strong cold front advancing eastward out of
the plains this evening will bring a period of mvfr reduction in
shra followed by general stratocu development with fropa overnight.




SHORT TERM...Steinwedel
LONG TERM...Steinwedel

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