Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 271903

Area Forecast Discussion
National Weather Service Northern Indiana
303 PM EDT Thu Apr 27 2017

Issued at 303 PM EDT Thu Apr 27 2017

Mostly cloudy, cool, and dry conditions are expected into tonight
and Friday morning. Lows tonight will drop into the 40s...with
highs on Friday recovering into the 60s. A frontal boundary will
bring periods of rain and perhaps a few thunderstorms to the
region later Friday through Monday. The heavier, more widespread,
rain is expected to fall later Saturday into early Sunday. Highs
on Saturday will generally range between the mid 50s and mid
60s...with warmer temps into 70s on Sunday. Cooler conditions are
then expected behind this system next week.


.SHORT TERM...(This Evening through Saturday)
Issued at 303 PM EDT Thu Apr 27 2017

Cooler/drier air will continue to funnel in post-frontal late this
afternoon and evening as low pressure lifts north into Ontario. The
only real adjustment to the forecast was to increase sky cover due
to expected slower erosion of low clouds and increase in mid-high
level clouds later tonight into Friday morning as warm advection

Strong Northeast Pacific upper jet will carve out a negative height
anomaly Friday into Saturday across the Four Corners...with
subsequent downstream mid/upper ridging across the Eastern US and a
strengthening low level baroclinic zone materializing across the Mid
MS/OH Valleys. This combined with ample GOM moisture return in
deepening southwest flow will set the stage for periods of ran later
tomorrow into Saturday.

A disjointed lead wave and initial surge of elevated
moisture/isentropic ascent will bring chances for lighter rain later
Friday into Friday evening, though some more moderate rain and
perhaps some embedded thunder will be possible mainly along/south of
US 24 on the nose of the associated weak LLJ. Seasonable temps and
mainly cloudy otherwise tomorrow.

An active low level frontal boundary will then lay/stall out over
the Mid MS/Northern OH Valleys later Friday night into Saturday
morning as high pressure nudges into the Great Lakes and low
pressure organizes over the Southern Plains. The result will be a
trend toward drier/cooler condition northwest of US 24 and continued
higher chances for periods of rain/elevated thunder along/southeast
of US 24 near the frontal slope.


.LONG TERM...(Late Saturday through Thursday)
Issued at 303 PM EDT Thu Apr 27 2017

12z model suite continued to point to the late Saturday through
Sunday morning periods as the best opportunity for more
widespread/heavier rainfall as moisture transport/convergence
maximizes in response to northeast ejection of deepening low into
the Central US. As mentioned in previous discussions it is difficult
to pinpoint where the heaviest swath of rain will occur given
smaller scale elements that cannot be resolved at this forecast
range. With that said will continue to highlight the potential for a
swath of 1-3" and possible low lying/river flooding in the ESF
(Hydrologic Outlook), with favored models hinting at our nw IN/sw
Lower MI counties for heavier totals.

Active frontal boundary likely lifts north into Lower MI/far nw IN
Sunday into Sunday evening in response to deep low eventually
lifting into Iowa. This will allow warmer/more unstable air to
briefly advect back into the local area during this time. Chances
for occasional showers/storms will likely continue during this time
as height falls overspread warm sector and convectively
induced/smaller scale waves lift northeast in strong southwest flow,
especially over nw IN/sw Lower MI near frontal zone. System cold
front/occlusion then swings through sometime Sunday night/early
Monday with additional chances for showers/storms. The main threat
will continue to be locally heavy rain as marginal instability and
late arrival of cold front likely limits the severe threat.

The early week period will feature breezy/cooler conditions and
chances for a few light showers post-frontal as wrap around moisture
rotates through under filling low meandering northeast through the
Upper Midwest/Northern Great Lakes. Drier with temps remaining below
normal into the middle of next week.


.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
Issued at 124 PM EDT Thu Apr 27 2017

A cold front pushed through the area today, but southwest winds
will continue. In addition, the low level jet will be pushing
east so gusts initially up to 35 kts will be reduced as we move
into the early overnight hours. CIGs went into MVFR this morning
with the cooler airmass entering in, but expect a slow rise to
VFR conditions across the area by the first portion of the
overnight as drier air comes in behind the cold front. The area
will be dry overnight with improving CIGs, however southwest winds
usher in another chance at precipitation starting around midday
on Friday.


LM...Small Craft Advisory until 8 PM EDT this evening for LMZ043-046.



SHORT TERM...Steinwedel
LONG TERM...Steinwedel

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