Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 142354

Area Forecast Discussion
National Weather Service Northern Indiana
654 PM EST Sat Jan 14 2017

Issued at 625 PM EST Sat Jan 14 2017

High pressure continues to work toward the region tonight allowing
clouds to break up as well as a chance for areas of radiational
fog in the morning, Sunday. Sunday will be a dry day with only
high clouds working into the region for the afternoon. Next, low
pressure will be approaching the region from the south allowing
for precipitation to fall across the region Sunday night into
Tuesday. Within the onset wintry mix, light icing is possible
Monday morning, but then precipitation will be able to change to
rain later Monday and continue into Tuesday. Rivers, already
feeling the effects of the recent rainfall, will continue to rise
with this new dose of rainfall. Temperatures will be able to fall
to around 20 degrees overnight tonight, but will then be able to
rise to the mid 30s on Sunday. High temperatures this coming week
will be well above normal and will have a few opportunities to be
near 50 degrees.


.SHORT TERM...(This Evening through Sunday)
Issued at 345 PM EST Sat Jan 14 2017

A period of quiet weather can be expected for the rest of the
weekend, with the next potential impacts and freezing rain chances
of note for the late Sunday night/Monday period which will be
discussed in the long term section.

Sheared vort max and associated area of enhanced freezing rain/sleet
mix has about shifted out of the forecast area late this afternoon.
An hour or two of patchy freezing drizzle will remain possible
across the extreme southeast but low level dry air advection
associated with inverted sfc trough passage will result in a
continued improvement through the afternoon. Low level dry air
advection in wake of this trough will also begin to erode low clouds
from north to south late afternoon/evening although mid level clouds
should increase late night across southwest half as weak induced mid
level ridging/mid level WAA axis shifts into the area from the mid
MS valley. Some patchy fog is possible across the south tonight in
proximity to slightly more pronounced near sfc moisture profiles
trapped beneath the inversion. Did add patchy fog mention across
approximately southern half to cover this potential, which may
someone depend on extent of mid cloud coverage overnight.

For Sunday, mainly just mid/high clouds across the area which should
allow for some moderation in temperatures into the mid 30s. By late
in the day, renewed isentropic lift could result in low end
rain/snow chance across the far southwest but areas to the
southwest of forecast area appear more favorable at this time.


.LONG TERM...(Sunday Night through Saturday)
Issued at 345 PM EST Sat Jan 14 2017

By Sunday night, cut-off PV anomaly across southwest CONUS will
begin to track across the Southern Plains with induced downstream
mid/upper level ridge axis shifting across the southern Great
Lakes/Ohio Valley. This ridge axis will be accompanied by the
leading edge of a strong low/mid level thetae gradient and
stronger advective forcing during the late Sunday night/early
Monday timeframe. Magnitude of low level flow across this gradient
will be somewhat limited, and outside of advective forcing, not
much signal in terms of substantial mid/upper level synoptic
forcing. Still feel a band of precip in the form of a light wintry
mix is possible late Sunday night/early Monday morning as this
thetae gradient advances northeast, but given above limiting
factors precip amounts should be quite light. Nevertheless, will
need to watch this period for potential light icing given brief
favorable thermo profiles for freezing rain once again.

Precip coverage to ramp up by late Monday afternoon and especially
Monday night as primary deeper moisture axis begins to surge north-
northeastward. Stout east-southeast flow could keep mixed precip
concern in place until early Monday evening across the extreme
northeast where drier/cooler low level profiles could yield a
slightly longer duration mixed precip threat. Widespread rain is
then anticipated for Monday night/early Tuesday with a small
probability for an isolated thunderstorm. The combination of fairly
strong upper dynamics and a moisture rich 1+ inch PWAT axis could
yield some respectable rainfall amounts Monday night-early Tuesday
that may aggravate ongoing minor flooding concerns across some area
rivers. Utilized a non-diurnal temp curve for Monday night during
period of strongest advection, with temps beginning to fall behind
cold front later Tuesday afternoon/evening.

Cool, but still above normal temperatures in store for the mid
week period behind the early week system with relatively low
predictability for late week precip chances due to differences in
evolution of phasing departing upper short wave trough Tuesday
with another Canadian upper trough. Of greater confidence however,
is transition back to above or much above normal temp pattern
Thursday and beyond as longwave pattern should be characterized by
western troughing/eastern ridging.


.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 625 PM EST Sat Jan 14 2017

High pressure continues to move towards the region from the Northern
Plains with plenty of dry air. Clearing is now evident in NW IL and
S MI and will be moving into the region on the northerly flow
tonight. FWA and SBN have already gone to VFR. With the clouds
breaking up, expecting fog to be able to form overnight in FWA.
Then, high clouds will be able to come back in especially during the
afternoon on Sunday as theta-e advection works into the region.




SHORT TERM...Marsili
LONG TERM...Marsili

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