Area Forecast Discussion
Issued by NWS Northern Indiana

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297
FXUS63 KIWX 272342
AFDIWX

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

.SYNOPSIS...
Issued at 740 PM EDT Thu Apr 27 2017

Mostly cloudy, cool, and dry conditions are expected overnight
and Friday. Lows tonight will drop into the lower to middle
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 late 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 to mid 60s...with temperatures warming 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
commences.

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 rain
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 conditions 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 persist into Sunday 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 00Z TAFS through 00Z Friday Evening)
Issued at 733 PM EDT Thu Apr 27 2017

Primarily VFR conditions to persist through the forecast period.
Some brief excursions to MVFR due to cigs through this
evening...however do not anticipate any cigs blo 2kft for impact.
Otherwise attention on backing surface flow and a more elevated
ceiling into Friday. While rain chances non-zero, they do not
appear sufficient for inclusion at this time as a more significant
chance with impact potential holding off until just beyond current
forecast period.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...Small Craft Advisory until 8 PM EDT this evening for LMZ043-046.

&&

$$

SYNOPSIS...Murphy
SHORT TERM...Steinwedel
LONG TERM...Steinwedel
AVIATION...Murphy


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