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Displaying AFOS PIL: AFDIWX Received: 2017-10-18 10:19 UTC

FXUS63 KIWX 181019

Area Forecast Discussion
National Weather Service Northern Indiana
619 AM EDT Wed Oct 18 2017

Issued at 359 AM EDT Wed Oct 18 2017

Another pleasant day is in store as high pressure lingers over 
the area. Mostly sunny skies will give way to high temperatures in
the upper 60's and low 70's. Lows tonight will be primarily in 
the upper 40's. Quiet weather will continue through Saturday, with
temperatures warming to well above normal. Highs through the rest
of the week will range from the upper 60's to the mid-upper 70's.


.SHORT TERM...(Today and Tonight)
Issued at 359 AM EDT Wed Oct 18 2017

As they say, "big bubble no trouble" for the short term. High 
pressure remains at the surface with a building ridge aloft. 850mb 
temps rise to the 10-12C range through Thursday, which keeps our 
high temperatures in the upper 60's and low 70's, and overnight lows 
in the 40's. Low pressure swinging through northern ontario will 
cause a brief increase in the pressure gradient, and thus it will be 
a bit breezy this afternoon-especially near Lake Michigan. A small 
craft advisory is in effect for the nearshore waters as gusts will 
be near 22-25 knots and waves will build to 3 to 4 feet. 


.LONG TERM...(Thursday through Tuesday)
Issued at 359 AM EDT Wed Oct 18 2017

A couple of interesting topics to discuss for the long term 
forecast, with chances for rain starting Saturday night associated 
with a frontal boundary, and perhaps a few Lake effect rain showers 
Tuesday into Wednesday.Thankfully, models are closing in on 
timing for the frontal passage on Saturday night-Sunday. Given the
reasonable output and general agreement during this time frame, 
have allowed the consensus chance to likely pops to remain. 

Kept chance pops through Monday-though they may be slightly overdone 
(especially between 06-12Z). In actuality there may be a break in 
precipitation before the secondary front arrives, but I kept them
given the uncertainty of the timing. If the first front takes
longer to exit, and then the second lags a little slower as the 
GFS suggests we could have some lingering precipitation to deal 
with. Where things begin to differ significantly is Monday 
afternoon- mainly due to the differences with how the models 
handle the secondary trough to our north. The ECMWF is much 
deeper, and brings the trough through Monday afternoon- developing
a closed low over the eastern Upper Peninsula of Michigan. It 
then drags the low across the Great Lakes through Wednesday, 
bringing a touch of colder air in its wake (thus some chances for 
lake effect rain showers Tue-Wed). However, the GFS is slower to 
develop this deeper trough and bring it through-and it differs in 
strength/location from the ECMWF. This would put a larger gap in 
between precipitation batches-keeping things dry all day Monday 
and early Tuesday. 

The one thing that both models have in common, despite the 
variances in location-is that they develop a long north- 
northwesterly fetch across Lake Michigan by Tuesday night and 
Wednesday. Of course, given decent instability on Lake Michigan 
from the falling temperatures, synoptic forcing aloft with the 
upper low, and enough moisture to work with-think that the 
probability of seeing some sort of Lake Effect band (rain) is 
high Tuesday night into Wednesday. Kept the higher probabilities 
where I felt it was most likely based on the current forecasted 
wind direction. Of course with any lake effect it's uncertain 
where any one band would develop, but given the pattern and time 
of year it's a pretty good chance it will play out. We'll see how
it evolves over the next few days.

Otherwise, we'll keep above normal temperatures through Sunday, with 
high temperatures reaching as high as the mid-upper 70's on Friday-
Saturday (especially in the far southwest). Temps for the remainder 
of the weekend and the start of next week are a little trickier-as 
we are not confident on the general timing of that secondary front-
which has substantially colder air behind it. Leaned on the colder 
side for Tuesday/Wednesday per collaboration with surrounding 
offices and earlier shifts, given the pattern is typically one we 
see with the colder, rainier conditions. For now, I have highs in 
the low-mid 50's for both days, with lows in the 40's.


.AVIATION...(For the 12Z TAFS through 12Z Thursday Morning)
Issued at 607 AM EDT Wed Oct 18 2017

Winds will increase later this morning into this evening,
strongest at KSBN. Otherwise VFR conditions are expected. 


LM...Small Craft Advisory from 10 AM this morning to 4 AM EDT 
     Thursday for LMZ043-046.




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