813 
FXUS63 KIWX 130532
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
132 AM EDT Mon Sep 13 2021

.SYNOPSIS...
Issued at 303 PM EDT Sun Sep 12 2021

A weak cool front will drop in late tonight. There is a slight 
chance of showers and thunderstorms Monday afternoon and night, 
though only for southern Lower Michigan. Remaining warm for most, 
but a bit cooler in southern Lower Michigan. A stronger system 
will bring showers and thunderstorms beginning Tuesday evening.

&&

.SHORT TERM...(This Evening through Monday)
Issued at 303 PM EDT Sun Sep 12 2021

Primary frontal wave/stronger pressure fall/rise couplet associated 
with north central Iowa shortwave.  Common consensus of 12 UTC CAMS 
have shunted low chance convection Monday/Monday night farther 
north, just clipping far northern/northeast CWA. Continued weak 
pressure rises with more stout upstream shortwave and associated 
fall/rise couplet should aid in maintaining convective focus farther 
north. Furthermore, strong mixed layer inhibition, on order of 500 
J/kg, afforded by capping inversion/8-9C/km mid level lapse rates 
should remain sufficient in suppressing southern extent of 
precipitation overnight into Monday morning. Just a slight chance 
far northern CWA Monday afternoon owing to proximity of backdoor 
frontal incursion. Otherwise, unseasonably warm forecast for Monday 
most of CWA, though closer to normal far northern CWA with incursion 
of shallow colder air north associated with tight low level thermal 
gradient. 

&&

.LONG TERM...(Monday Night through Sunday)
Issued at 303 PM EDT Sun Sep 12 2021

Strong shortwave energy over far southwest Alberta into Pacific 
Northwest to drive strong cyclogenesis from central Plains into 
Upper Midwest Monday afternoon/night. Reestablishment of warm sector 
with surface dewpoints pooled to near 70F to provide sufficient 
instability/shear combination with CWA on southern periphery of mid 
level jet streak. Jet streak however could be sufficiently lagged of 
frontal boundary so severe potential remains quite conditional. 30-
50M/12 hour 5H height falls along with frontal forcing brings high 
likely/categorical convective chances Tuesday evening/night. Minor 
chances linger into Wednesday, especially southeast as frontal 
boundary slows. Once again have carved out a dry period Thu with 
signals indifferent. Some disparity yet on Friday with ECMWF hinting 
a front approaching/passing through with GFS held far upstream, will 
acquiesce to low chance pops Friday afternoon.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday Night)
Issued at 132 AM EDT Mon Sep 13 2021

A boundary was observed to be slowly sinking south from the lake 
into the forecast area this evening. Behind the boundary, IFR CIGs 
were observed at KMCG. This lends some credence to the previous 
forecaster's note of a possibility of affected flight conditions at 
SBN that the aviation guidance is keying into. With cooling low 
levels and some moisture to work with allowing for an inversion 
depicted in BUFKIT soundings at SBN, will continue the idea for this 
forecast issuance with MVFR conditions most likely, but IFR 
conditions are not out of the question, especially as we get towards 
10-12z this morning. 

Otherwise, expect VFR conditions the rest of the period at SBN and 
for FWA. The pressure gradient has relaxed and so has the low level 
jet meaning gusts won't be as strong today as they were this weekend.

&&

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

$$

SYNOPSIS...Murphy/Brown
SHORT TERM...Murphy
LONG TERM...Murphy
AVIATION...Roller


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