Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 281945

Area Forecast Discussion
National Weather Service Northern Indiana
345 PM EDT Fri Apr 28 2017

Issued at 124 PM EDT Fri Apr 28 2017

A warm front over the southern U.S. continues to lift north into
the Ohio Valley this afternoon, causing showers and a few
thunderstorms to move into our area late this afternoon and
evening. The warm front will move slowly north across our area
over the weekend as a strong low pressure system moves slowly
northeast from the southern plains resulting in showers and
scattered thunderstorms with locally heavy rainfall across our
area. 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

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

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 18Z TAFS through 18Z Saturday Afternoon)
Issued at 124 PM EDT Fri Apr 28 2017

Moisture will be lifting north during the afternoon and will
moisten the atmospheric column, however low levels will take a
while to become saturated. As such, MVFR CIGs/VISBY will take
their time to get here and may take until Friday night to reach
FWA and after midnight at SBN. Will hold off on bringing CIGs back
into IFR range with a low confidence in time of occurrence at this
time. Rain will get started around early evening at FWA and later
at SBN. A low level jet will be moving through the area, but not
enough mixing and not enough strength in the jet itself will only
allow for sporadic gusts up to 20 kts this afternoon so have left
those out.


IN...Flash Flood Watch from Saturday afternoon through Monday morning
     for INZ003-004-012.

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



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

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