Area Forecast Discussion
Issued by NWS Northern Indiana

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491
FXUS63 KIWX 162048
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
348 PM EST Mon Jan 16 2017

.SYNOPSIS...
Issued at 335 PM EST Mon Jan 16 2017

Rain will become more widespread this evening as an upper level
disturbance approaches from the Plains. An isolated thunderstorm
is also possible tonight. Ahead of this disturbance, widespread
fog with areas of dense fog can be expected to continue this
evening. Temperatures will rise tonight as a low pressure area
tracks across the southern Great Lakes, reaching into the lower
50s across portions of northeast Indiana and northwest Ohio. Rain
will taper in coverage on Tuesday as this system pulls off to the
east. A warming trend will develop from Thursday to the weekend
with highs expected to reach the upper 40s to mid 50s by Saturday.
Periodic chances of rain will accompany the mild weather however.

&&

.SHORT TERM...(This Evening through Tuesday)
Issued at 335 PM EST Mon Jan 16 2017

Fog and precip concerns to dominate the short term period, with
warming temperatures this evening.

Water vapor imagery this afternoon depicts a strong upper vort max
across eastern Kansas that will eventually make its way across
the southern Great Lakes late tonight into Tuesday. Another
secondary vort topping southwest Canadian ridge will dig in behind
this initial vort max for Tuesday/Tuesday night. Favored zone of
low level warm advection/isentropic upglide has slowly pushed
across southern lower Michigan this afternoon with rain gradually
filling back in across northeast Illinois as stronger low level
flow begins to impinge on this baroclinic zone. With a break in
the rain across many locations, and continued moist advection,
widespread fog has developed and has been dense in spots,
particularly north central/northwest Indiana extending into
portions of northeast Indiana. Did issue a dense fog advisory
earlier this afternoon which extends through 06Z. Low level
jet/theta-e advection will ramp up more aggressively after 00Z as
another 1+ inch PWAT axis advects across the area tonight, along
with increasing upper diffluence (particularly northwest half of
the area) downstream of upstream short wave. Rain will overspread
the area late afternoon into this evening coincident with this
stronger advective forcing. Visibilities may actually show
improvement as rain becomes more widespread this evening, which
may not necessitate maintaining advisory through its 06Z
expiration time. However before rain moves in, dense fog may
expand north and east of current advisory across northern Indiana,
and trends will be monitored for possible expansion over next few
hours.

Along with the anomalous moisture advecting into the region this
evening, some uptick in elevated instability could yield an isolated
thunderstorm tonight, with already some isolated/scattered storms
developing across eastern Missouri. Rain amounts will likely be
somewhat variable across the area tonight with local convective
contributions providing the greatest amounts. Generally expecting
one quarter to three quarters of an inch of storm total rain with
at least a potential of slightly higher amounts across the
northwest half.

Patchy light rain or patchy drizzle may continue into Tuesday
afternoon with temporary loss of deeper moisture and lull in
stronger upper forcing. By late afternoon/evening, the secondary
upper trough should dig across the southern Great Lakes which may
provide brief enhancement to scattered light rain Tuesday evening
before diminishing.

In terms of temps, warm front lifting across the region this evening
will provide yet another night of temperature rises, into the lower
50s far southeast, and into the upper 30s to mid 40s far north-
northwest. Tuesday will feature temps slowly falling through the
afternoon with cold advection becoming established during the
morning.

&&

.LONG TERM...(Tuesday Night through Monday)
Issued at 335 PM EST Mon Jan 16 2017

After the brief shot of cooler air mid week (although still
above normal), the long term period will be characterized by much
above normal temperatures with periodic chances of rain as an
active pattern of short wave passages ensues.

Secondary upper trough will exit Tuesday night with some lingering
light rain or patchy drizzle gradually coming to an end during the
overnight hours. This should be followed by a period of dry weather
for Wednesday and Thursday, with temps moderating back into the mid
40s by Thursday as low level thermal troughing departs.

The long term period still looks to be characterized by longwave
trough (western CONUS) - longwave ridge (eastern CONUS) pattern
through next weekend with a series of waves expected to amplify
across Southern Plains/lower MS Valley and lift northeast across the
Ohio Valley bringing periodic higher rain chances. Medium range
models have come into better agreement with a complex wave
evolution during this period. Broad southerly flow in this
pattern to create broad eastern CONUS thermal ridging with highs
well above normal into the upper 40s to mid 50s next weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
Issued at 1212 PM EST Mon Jan 16 2017

Cigs/vsbys continue to deteriorate early this afternoon, with
prospects of appreciable improvement minimal through the
afternoon. Corridor of warm advection forced rain and pockets of
freezing rain have lifted north of the terminals as of midday with
no additional freezing rain threat anticipated. Widespread fog
will continue this afternoon into this evening with LIFR/IFR
conditions. Vsbys may drop to one quarter of a mile late this
afternoon into tonight, with greatest threat of vsbys to this
extent at KSBN. Rain will become more widespread this evening as
an upper level short wave continues to eject northeast out of the
Southern Plains, which may at least provide some minimal vsby
improvement this evening. Periods of rain will persist overnight
before diminishing in coverage early Tuesday morning as deeper
moisture axis and short wave forcing begin to depart. Will also
have to watch LLWS potential tonight, with a period from 06Z-12Z
looking to be the greatest threat as a low level jet in advance
of this short wave impinges on northern Indiana.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Dense Fog Advisory until 1 AM EST /midnight CST/ Tuesday for
     INZ003>009-012>018-020-022>026-032.

MI...NONE.
OH...NONE.
LM...Dense Fog Advisory until 10 AM EST Tuesday for LMZ043-046.

&&

$$

SYNOPSIS...Marsili
SHORT TERM...Marsili
LONG TERM...Marsili
AVIATION...Marsili


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