Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 142054

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

Issued at 345 PM EST Sat Jan 14 2017

Clouds will diminish from north to south tonight, but will
increase again Sunday afternoon in Sunday evening. Dry conditions
are expected through Sunday afternoon with next chance of
precipitation Sunday night into Monday when a light wintry mix is
expected. Light icing is possible Monday morning before
precipitation changes over to rain Monday afternoon and continues
through early Tuesday. Rainfall Monday night into early Tuesday
may lead to some renewed rises on some area rivers. Above normal
temperatures can be expected for much of the upcoming week, with
just a brief shot of colder air for mid week. Lows tonight will
range from the upper teens north to the lower to mid 20s. Highs on
Sunday will reach the mid 30s.


.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 18Z TAFS through 18Z Sunday Afternoon)
Issued at 1217 PM EST Sat Jan 14 2017

The combination of a weak upper level disturbance progressing
through the region and a weak inverted surface trough lingering
across northeast Indiana has allowed for some deterioration in
cigs over past hour or two at KFWA. Not expecting IFR conditions
to be of very long duration as eventual eastward progression of
sfc trough through 20Z will allow drier air to begin to advect
southeastward. Any precip in the form of freezing drizzle would be
very light and limited to the 18Z-20Z timeframe, and still
expecting the bulk of freezing rain/freezing drizzle to remain
south of KFWA. Otherwise for the remainder of the day winds will
be generally light and variable, but beginning to favor light
northwest later this afternoon/early evening. Surface high
pressure will build into the region today which could allow for
some patchy fog formation at KFWA, in closer proximity to slightly
better near sfc moisture trapped beneath the inversion.




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

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