Area Forecast Discussion
Issued by NWS Northern Indiana

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KIWX 181902

Area Forecast Discussion
National Weather Service Northern Indiana
302 PM EDT Tue Jul 18 2017

Issued at 301 PM EDT Tue Jul 18 2017

High pressure will continue to provide mainly dry and clear
conditions into tonight. A weak front will bring a low chance for
showers and thunderstorms on Wednesday. Lows tonight will drop
into the 60s, with highs on Wednesday well into the 80s. Thursday
through Sunday will feature humid conditions and periodic chances
for showers and thunderstorms.


.SHORT TERM...(This Evening through Wednesday)
Issued at 301 PM EDT Tue Jul 18 2017

A weak low level trough/instability axis may continue to spark a
few isolated showers mainly south of US 24 in nw OH this
afternoon. Dry/warm otherwise late this afternoon into this
evening with stable theta-e minimum still in place from MI sw into
nw IN/ne IL.

An Upper Midwest disturbance will top a building Plains upper ridge
through the Northern Great Lakes tonight. Associated weak height
falls will aid in folding upstream theta-e ridge and convective
outflow boundary into the local area later tonight into Thursday.
Lacking forcing/flow with mid level heights on the rise precludes
anything higher than a slight chance PoP along this boundary even
as boundary layer moisture/instability increases. Increasingly
hot/humid otherwise on Wednesday with highs well into the 80s and
afternoon sfc dewpoints up near 70.


.LONG TERM...(Wednesday Night through Tuesday)
Issued at 301 PM EDT Tue Jul 18 2017

Thursday through Sunday will feature periodic chances for
rain/storms and humid conditions with the area located in a
precarious position on the northeast fringe of a mid-summer
ridge. Several convectively aided/induced waves in quasi-zonal
westerly flow overtop this stout ridge will help focus mesoscale
convective systems ese through the Upper Midwest/Great Lakes near
an oscillating frontal boundary. Moisture/instability parameters
will also become increasingly impressive with time near this
convectively reinforced boundary which could pose a heavy
rain/flooding threat at any time (best chances Thursday night
through Saturday). As expected this time of year shear/flow should
for the most part be on the marginal side for more organized
severe weather. However, if any MCS becomes better established
with a cold pool a severe threat (more than just isolated
wind/hail) could materialize. Confidence in timing/strength of
these low magnitude features, and where frontal boundaries
(modulated by convection) will end up in any one period, remain
low any more than a day in advance. As a result have capped PoPs
in these periods at 40/50 percent. Otherwise...heat indices may
reach 95-100F during each afternoon south of the convective
outflow/cloud debris.

The latest guidance continues to suggest drier and slightly
cooler/less humid wx by early next week as troughing into the Great
Lakes finally forces active boundary and deep moisture south of the


.AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon)
Issued at 105 PM EDT Tue Jul 18 2017

VFR conditions are expected at the TAF sites through Wednesday
afternoon. High pressure over the forecast area will remain anchored
in place for the most part, keeping winds light and variable
overnight. A weakening trough will move in from the west, and could
even kick off a few showers and thunderstorms after 12Z near KSBN.
Given the present weakening trends, left out of the TAF for now.
Expect mainly a wind shift to the west and maybe some SCT/BKN
afternoon cloud cover. KFWA could see some BR between 8Z-13Z, but
it`s likely to be brief and only drop down to MVFR. Winds should be
high enough at KSBN to preclude any BR/FG development tonight.




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

Visit us at

Follow us on Facebook...Twitter...and YouTube at: is the U.S. government's official web portal to all federal, state and local government web resources and services.