Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 141146
AFDIWX

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

.SYNOPSIS...
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.

&&

.UPDATE...
Issued at 611 AM EST Tue Nov 14 2017

Conditions along the southern portions of our forecast area are
gradually improving already, with visibilities of 4-7 miles. Do
not expect dense fog to redevelop in these areas, so have dropped
the dense fog advisory there (Blackford, Jay, and Grant Counties,
IN). However, dense freezing fog has developed in Fulton County
OH and northwest Henry County, OH. I expect these conditions to
linger due to winds remaining calm through the remainder of the
morning, so opted to expand the dense fog advisory into these
areas.

La Porte County, IN I was on the fence about, as visibilities have
been 1/4 mile or less for a couple hours, however latest satellite
and observational trends suggest conditions may gradually improve
fairly soon. Will leave out of the advisory for now, as it also
appears to be localized to the observation site (KPPO). Michigan
city is up to 4 miles, and even Starke county is up to 2 miles in
the northern portion of the county. Additionally, winds are
forecast to increase slightly through the morning, which will only
serve to further improve conditions.

&&

.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
20s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday Morning)
Issued at 642 AM EST Tue Nov 14 2017

Surface observations/satellite continue to depict dense fog
across much of northern Indiana, especially along and north of
Route 30. The more widespread coverage of dense fog at 11Z appears
to extend from around KGSH to KFWA, with dense fog more patchy in
nature at KSBN. Distinct improvement in vsbys has also been noted
south of KFWA over the past few hours. Challenging forecast this
morning in terms of fog trends, but confidence in dense fog
remains lower at KSBN where low level flow is expected to remain
a bit stronger. KFWA also may remain on the edge of the more
widespread dense fog through 14Z, but with low cloud deck now
having pushed east of KFWA, would suspect LIFR conditions will
remain for a bit longer. The potential of LIFR conditions should
persist at both terminals through about 13Z or 14Z with
improvement to MVFR expected after this time, followed by VFR
conditions after 15Z or 16Z timeframe. Outside of dense fog
potential early this morning, VFR conditions expected the
remainder of the forecast period with subsidence in wake of short
wave tracking across the Great Lakes. The next Pacific wave will
race east across the Northern Plains tonight bringing a good
chance of showers to northwest Indiana toward the end and just
beyond this forecast valid period as axis of stronger moisture
advection works in from the west.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Dense Fog Advisory until 9 AM EST /8 AM CST/ this morning for
     INZ004>009-012>018-020-022>027.

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

OH...Dense Fog Advisory until 9 AM EST this morning for OHZ001-002-
     004-005-015-024.

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

&&

$$

UPDATE...MCD
SYNOPSIS...MCD
SHORT TERM...MCD
LONG TERM...MCD
AVIATION...Marsili


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