Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 140941

Area Forecast Discussion
National Weather Service Northern Indiana
441 AM EST Tue Nov 14 2017

Issued at 418 AM EST Tue Nov 14 2017

Partly to mostly cloudy skies are expected today, with highs in
the 40s. Otherwise, areas of dense fog are expected for many
areas through late this morning. Freezing fog is possible. Be
careful if driving. The combination of fog and temperatures at or
below freezing may create slick spots on the roads. Additionally,
sudden reductions in visibility are expected. Slow down, use your
low beam headlights, and leave plenty of distance ahead of you.


.SHORT TERM...(Today and Tonight)
Issued at 418 AM EST Tue Nov 14 2017

Dense fog advisory remains in effect for mainly our central CWA as
visibilities linger around 1 mile or less for many locations. Some
areas are seeing visibilities of 1/4 mile or less as of 9z. Freezing
fog is also being reported, though with warmer road temps not
sure how much of an impact this will cause to travel. Still, think
its reasonable to mention the potential for slick spots on the
roads this morning due to the combination of fog and temps below
freezing. At this point don`t think I`ll be expanding the dense
fog advisory, but monitor closely for updates. Even outside of the
advisory area, there is potential for some patchy dense
fog/freezing fog, so have handled that with an SPS for now.

Beyond the fog concern, quiet weather is expected today, with a mix
of sun and clouds expected. Highs will rise into the mid-upper 40s
and low 50s if clouds clear out as well as planned. If not, probably
will see highs in the low to mid 40s, especially in the northeastern
portions of the CWA.


.LONG TERM...(Wednesday through Monday)
Issued at 440 AM EST Tue Nov 14 2017

Models have come into agreement with respect to the low pressure
system expected to swing through Wednesday into Thursday. The
deepening surface low and somewhat neutrally tilted upper level
trough is forecast to track across the UP of Michigan Wednesday,
then reach southern Ontario by Thursday morning. The best synoptic
forcing per 850-500mb qvector convergence is well north of us,
especially Wednesday afternoon-but we still have more than enough
support for categorical pops across the CWA. Modest moisture
transport kicks in starting late Tuesday night, bringing PWATS up to
around 1 inch...which is about 150% of normal for this time of year.
This will bring a swath of rain showers through the area, along and
ahead of the cold front, from Wednesday morning into Thursday
morning. Mid level lapse rates of around 6-7C/Km suggest the
continued potential for some thunder, but it looks pretty limited.
Confined to slight chance pops, mainly in the west earlier in the
event per collaboration with neighbors.

High pressure builds in rapidly behind the low, drying out the
forecast for most locations Wednesday night into Thursday night. The
only exception would be some light lake effect rain showers near
Lake Michigan Wednesday night into Thursday morning. After that it
seems drier air takes over and limits any further development. Highs
will be in the 40s Thursday, and lows in the upper 20s and low 30s
Thursday night.

Friday and Friday night we deal with yet another low pressure system
traversing the area. Confidence in any one particular solution at
this point is pretty low given the inconsistencies in the models
over time and between one another. However, the latest runs trend
weaker overall with the front and the associated upper level trough.
Timing is also more disjointed between the models with respect to
timing-particularly the GFS/ECMWF-which lowers confidence even more.
Accordingly, SPC dropped the 15% wind risk associated with the
system. Still have a slight chance of thunder, and kept higher pops
for now on Friday. Hopefully things will come in line soon.

Saturday we`ll see lingering showers across the area associated with
the backside of the low pressure system, and lake enhancement from
Lake Michigan. Morning highs in the 40s will fall to the mid-upper
30s by the afternoon, which will lead to a transitioning from rain
to snow into the evening. Expect temps Saturday night to bottom out
in the mid-upper 20s, and thus precipitation type will be all snow.
With northwest winds and lingering low level moisture with ambient
synoptic support, thinking we`ll have lake effect snow showers
through Sunday. High temperatures Sunday will only reach into the
low to mid 30s, and lows that night will drop into the low to mid


.AVIATION...(For the 06Z TAFS through 06Z Tuesday Night)
Issued at 110 AM EST Tue Nov 14 2017

Fog will be the primary aviation forecast concern through mid
morning. Eastward departure of low cloud deck has been followed
by the development of areas of fog across much of northern Indiana
this evening. Despite lingering mid/high clouds, some patchy
dense fog has also formed. As previous discussion mentioned, just
enough trapped low level moisture beneath inversion has allowed
for some decent radiation fog formation despite rather marginal
looking profiles to support dense fog formation. Hires guidance
depicts corridor across north central to northeast Indiana as most
favored for dense fog development overnight. Of the two
terminals, confidence in longer duration significant vsby
restrictions due to fog is higher at KFWA, with some questions as
to some low level flow increases overnight across northwest
Indiana on periphery of anticyclone that might tend to favor a
combo fog/stratus setup. Continued a fairly conservative IFR
approach at KSBN with these uncertainties, but will monitor
trends and may need to amend to a more pessimistic idea. Other
than IFR/LIFR conditions in fog, remainder of the forecast should
be quiet and VFR from late morning through tonight. Conditions to
become more active again just beyond this forecast valid period as
low level moisture return increases in advance of next system
that will bring rain late Tuesday night into Wednesday.


IN...Dense Fog Advisory until 9 AM EST /8 AM CST/ this morning for

MI...Dense Fog Advisory until 9 AM EST this morning for MIZ078>081.

OH...Dense Fog Advisory until 9 AM EST this morning for OHZ001-004-

LM...Small Craft Advisory from 7 PM this evening to 5 PM EST
     Wednesday for LMZ043-046.




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