Area Forecast Discussion
Issued by NWS Northern Indiana

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617
FXUS63 KIWX 290549
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
149 AM EDT Sat Apr 29 2017

.SYNOPSIS...
Issued at 149 AM EDT Sat Apr 29 2017

A warm front near the Ohio River will work north today bringing
showers and thunderstorms to the region for the weekend. Locally
heavy rainfall will pose the greatest threat, but isolated strong
storms are possible. The low will move slowly northeast across
the Great Lakes early next week resulting in windy and cool
conditions across our area with a chance of showers.

&&

.SHORT TERM...(This Evening through Sunday Night)
Issued at 339 PM EDT Fri Apr 28 2017

Periods of rain/embedded thunder and possible flooding this
weekend...

Initial shot of elevated theta-e adv/isentropic ascent with
lead/sheared shortwave will bring a period of rain to portions of
our IN/OH counties late this afternoon and evening. The rainfall
will be light in most locations, though a period of more moderate
rain and perhaps some thunder possible for areas southeast of US 24
closer to developing low level frontal boundary/instability axis
near a developing low level jet.

Some drier air filters into at least our nw IN/lower MI zones later
tonight into early Saturday morning as sfc high pressure nudges east
into the northern/western Great Lakes. May even see a lull in the
shower/iso storm coverage southeast of US 24 during this time with
the surface portion (convective outflow) of the aforementioned front
settling toward the Ohio River.

Rain chances/intensity will quickly ratchet back up from south to
north during the day on Saturday as strengthening low level
southerly flow transports deep Gulf Of Mexico moisture into a
northward returning warm front. This warm front will get a slow kick
nnw into our area as low pressure organizes across the Southern
Plains/Missouri Valley. The more organized rain/thunder activity
then likely pivots into our nw IN/sw Lower MI counties by later
Saturday night-Sunday morning as deepening low lifts north and
convergent/deep moisture channel sets up more sw to ne on leading
edge of stronger height falls. Expected convective elements combined
with 850 mb dewpoints of 12-14C (precipitable water values in excess
of 1.50 inches) could allow for some impressive rainfall
totals/rates...especially Saturday afternoon south of US 30, across
the entire area Saturday evening, and then shifting mainly into nw
IN/sw Lower MI late Saturday night into Sunday morning. Per
collaboration did pull the trigger on a Flash Flood Watch across
far nw IN/sw Lower MI where pivot point of front affords longer
duration of heavier rainfall. Lower confidence elsewhere for
anything more than an inch or two, so held with EST/HWO mention
here.

System warm sector will likely build in for a time on Sunday/Sunday
evening as frontal zone stalls north near the Lake MI
shoreline/Lower MI. The result will be warmer temps and chances for
scattered showers/storms as environment becomes at least weakly
unstable with convectively induced/smaller scale perturbations
lifting through in strong southwest flow. A more organized line of
rain/embedded thunder then rolls through the area Sunday night/early
Monday along cold front/occlusion. The main threat will continue to
be locally heavy rain as marginal instability and late arrival of
cold front likely limits the severe threat.

&&

.LONG TERM...(Monday through Friday)
Issued at 339 PM EDT Fri Apr 28 2017

Monday into Tuesday will feature a trend toward cooler/windy
conditions under filling/deep low tracking ene through the Upper
Midwest/Northern Great Lakes. Cyclonic flow/wrap around moisture and
secondary front may generate a few light rain showers each day.
Dry/cool then for the middle of the week as weak ridging briefly
moves in.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
Issued at 139 AM EDT Sat Apr 29 2017

Although extensive showers and storms were ongoing along the Ohio
River, lighter rain and drizzle has allowed for pockets of
increased saturation and subsequent lowering of cigs into IFR
range (actually KMZZ sitting at 400 ft). No clear signals that
this trend will take over as weak returns over the area have been
on the wane and may signal the temporary lull in activity. A small
cluster of storms has formed N of KIND but will remain south of
KFWA. Still expecting slowly deteriorating at KFWA as warm front
works north during the day with rain/storm chances increasing.
Similar trends, albeit slower, will take place at KSBN with an
extended period of rain/embedded storms across the area through
the remainder of the TAF period.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Flash Flood Watch from this afternoon through Monday morning for
     INZ003-004-012.

MI...Flash Flood Watch from this afternoon through Monday morning for
     MIZ077-078.

OH...NONE.
LM...Small Craft Advisory from 1 PM this afternoon to 5 AM EDT Sunday
     for LMZ043-046.

&&

$$

SYNOPSIS...Roller/Fisher
SHORT TERM...Steinwedel
LONG TERM...Steinwedel
AVIATION...Fisher


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