Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 280741
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
341 AM EDT Fri Jul 28 2017

.SYNOPSIS...
Issued at 335 AM EDT Fri Jul 28 2017

An upper level disturbance across the Great Lakes will dive
southeast into Ohio today. This disturbance may trigger a few
showers and thunderstorms this afternoon, mainly across far
northeast Indiana, south central Lower Michigan, and northwest
Ohio. However, coverage of the rain showers today is expected to
remain isolated. Drier air will filter in behind this system
tonight, with dry weather then expected from tonight through the
early part of next week. High temperatures today will range from
the upper 70s to around 80, with low temperatures tonight dropping
back into the 50s.

&&

.SHORT TERM...(Today and Tonight)
Issued at 335 AM EDT Fri Jul 28 2017

Shower/isolated thunderstorm chances today will be primary
forecast challenge for the short term.A few showers have been
trying to develop along the northern periphery of old inverted sfc
trough early this morning to the northwest of South Bend. Just
enough pooled moisture is located in vicinity of this inverted sfc
trough to promote 250-500 J/kg of elevated CAPE per latest RAP
analyses. Some weak 925-850 mb frontogenesis could also be
contributing to weak forcing this morning downstream of more
substantial upper level trough approaching the western Great
Lakes. This axis of weak fgen forcing/pooled moisture should
gradually drop south this morning, and did expand iso shower
mention to central locations toward and shortly after daybreak.
Have kept out thunder mention, but could be just enough elevated
instability for an isolated storm through daybreak.

Not much has changed in terms of forecast thinking with
approaching upper trough for today. Subtle low/mid level moisture
axis should develop across northwest Ohio today in response to
large scale flow associated with approaching negative upper height
anomaly. Despite deepening northeast flow on cool side of sfc
boundary today, diurnal warming should promote a pocket of weak
sfc based instability across extreme northeast Indiana/northwest
Ohio this afternoon (500-1000 J/kg). Increasing DPVA/diffluence
aloft with upper trough could allow for isolated-scattered shower
development with perhaps an isolated storm given weak instability
and at least brief window of stronger upper forcing across the
northeast late morning through mid-afternoon. Chances of showers
will diminish post-21Z this afternoon as stronger forcing/weak
instability axis get shunted east of the area. Otherwise for
today, deeper mixing should partially offset low level cold
advection to promote high temperatures from the upper 70s to the
lower 80s.Quiet weather expected tonight as upper trough axis
shifts east of the area, with an influx of much drier low level
air from eastern Canada. Drier air mass will allow for cooler
conditions tonight, although maintenance of weak northeast
gradient will keep lows in mid to upper 50s most locations.

&&

.LONG TERM...(Saturday through Thursday)
Issued at 335 AM EDT Fri Jul 28 2017

Quiet weather shaping for the weekend with some amplification of
upstream western CONUS longwave ridging putting local area in
favored synoptic subsidence region. Broad high pressure will
maintain control across the region for the weekend into the early
parts of next week. Some very gradual moisture recovery to
commence for the early to middle portions of next week as sfc
ridge begins to shift eastward, but quality moisture return will
be difficult to come by in advance of next northwest flow upper
level short wave some time in the middle of next week. However,
given some potential moisture pooling with associated frontal
boundary sagging across southern Great Lakes during this time,
will maintain broadbrush slight to low chance TSRA PoPs Wed-Thu as
this front stalls out across the region. After slightly below
normal temperatures to begin the long term period Saturday, some
moderation in temps expected through early next week but overall
advective pattern through Tuesday looks to be very weak with
prolonged easterly low level flow. Temperatures near seasonal
norms then expected through the end of this forecast period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
Issued at 108 AM EDT Fri Jul 28 2017

VFR/dry through the TAF cycle outside of low chances for MVFR vis
restrictions early this morning at KFWA. Drier low level air makes
better inroads during the day Friday with northeasterly winds
gusting up to 20 knots by this afternoon.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Beach Hazards Statement through late tonight for INZ003.

MI...Beach Hazards Statement through late tonight for MIZ077.

OH...NONE.
LM...Small Craft Advisory until 5 AM EDT Saturday for LMZ043-046.

&&

$$

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


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