Area Forecast Discussion
Issued by NWS Northern Indiana

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997
FXUS63 KIWX 220535
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
135 AM EDT FRI JUL 22 2016

.SYNOPSIS...
Issued at 805 PM EDT Thu Jul 21 2016

Hot and humid conditions will persist through this upcoming
weekend. With this heat and humidity will come chances for
thunderstorms each day as a frontal boundary stalls over the
region. Lows through the weekend will generally range between the
upper 60s and mid 70s...with highs in the upper 80s to mid 90s.
Afternoon heat indices on Friday are forecast to range between 100
and 107 degrees...with near 100 degree heat indices likely
Saturday and Sunday.

&&

.SHORT TERM...(This Evening through Sunday Night)
Issued at 315 PM EDT Thu Jul 21 2016

Hot/humid wx will remain the main story through the weekend on the
northeast fringe of an expansive Central US mid-upper level ridge.
High PWAT/dewpoint air within theta-e ridge will no doubt provide
the moisture/instability for at least low shower/storm chances
through most of the forecast as several low amplitude/convectively
enhanced perturbations ride ridge into the Great Lakes laying out
convective outflows. These difficult to fcst convective complexes of
varying organization will modulate the positioning of said composite
outflow(s), temps, and where convection possibly develops, which
beyond the first period or two is unforecastable.

The main focus for the remainder of the afternoon will be on
timing of line of convection through the area. Established cold
pool with MCS remnants and strong heating/instability downstream
of this line now pushing through our nw IN/sc Lower MI zones as of
19z should help sustain line into ne IN/nw OH mid-late afternoon
despite lacking background flow (20 kts of deep shear).
Lightning/heavy rain/isolated wind damage (gusts 40-60 mph) appear
to be the primary threats with this activity as it settles
through.

Leftover boundary from this afternoon`s activity and primary
backdoor front edging closer into the lower Great Lakes in response
to series of larger scale shortwaves tracking ese through Ontario
will keep low chances for storms in the forecast into tonight and
Friday. A somewhat consistent theme in guidance has been to
develop another MCS near synoptic boundary/nose of LLJ over WI/MI
which could survive south into the region later tonight-Friday
morning...with possible iso/sct re-development on outflow Friday
afternoon/evening. Again, lacking flow/forcing and varying
solutions held with a conservation 20-30 type PoP tonight into
Friday. Any storms would provide some relief from dangerous
heat/humidity but could pose an iso wind/heavy rain threat.

A similar story then into this weekend with max heat indices/temps
dependent on convection/cloud debris. Some drier air may briefly
work into our northeastern zones (far ne IN/sc lower MI/nw OH) on
Saturday as primary composite outflow and pooled 70 plus dewpoints
possibly settles into southern portions of the forecast under
slight height rises aloft. Retained slightly higher PoPs later
Saturday Night through Sunday Night as next series of convectively
modified/small scale shortwaves result in a renewed theta-e surge.

&&

.LONG TERM...(Monday through Thursday)
Issued at 315 PM EDT Thu Jul 21 2016

Upper ridge will retrograde westward allowing weak mid level
trough to work southeast through the Great lakes by around Monday.
This process should finally force active frontal boundary and
extreme heat/humidity south by Monday Night-Tuesday. Unfortunately
guidance over the last several days has trended a little slower
with the main frontal passage resulting in a muggier/warmer Monday
and better chances for mainly aftn convection across IN/OH. Dry
otherwise into the middle of next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
Issued at 129 AM EDT Fri Jul 22 2016

Low confidence tafs for the upcoming period as models have
absolutely no consenus on what may unfold through tonight.

Initial focus on outflow boundary moving southeast already clear
of ksbn and likely to make an attempt to reach kfwa. Despite a
weakening stratiform rain field in its wake...enough elevated
instability existsto allow for sporadic development of showers and
storms along this boundary. Will hold onto a period of showers and
introduce vcts at kfwa to handle the threat. Locally gusty winds
have been occuring in the wake of the convective system over lk
michigan and near the shoreline with gusts of 30 to 35 kts. These
could work in land and affect ksbn but for now will leave out of
tafs.

Focus then shifts to convective potential this afternoon with
what should be rather unstable conditions in place for a frontal
boundary (assuming skies clear out today) to interact with as it
drops south into the area. At this point...confidence low enough
to just maintain vcts after 18z with any threat ending around 00z
as loss of heating diminshes any convection.

&&

.IWX Watches/Warnings/Advisories...
IN...Heat Advisory until 8 PM EDT /7 PM CDT/ Saturday for INZ003>009-
     012>018-020-022>027-032>034.

MI...Heat Advisory until 8 PM EDT this evening for MIZ077>081.

OH...Heat Advisory until 8 PM EDT Saturday for OHZ001-002-004-005-015-
     016-024-025.

LM...NONE.
&&

$$

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


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