Area Forecast Discussion
Issued by NWS Northern Indiana

Home | Current Version | Previous Version | Graphics & Text | 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 202321

Area Forecast Discussion
National Weather Service Northern Indiana
721 PM EDT Wed Jun 20 2018

Issued at 325 PM EDT Wed Jun 20 2018

Scattered showers and isolated thunderstorms especially along and
south of Route 24 should diminish early this evening. Rain chances
will increase across northwest Indiana once again late this
evening into the overnight hours. Widespread rain showers with
some scattered thunderstorms are then expected to affect much of
southwest Lower Michigan and northern Indiana on Thursday as a
storm system slowly approaches the Mid Mississippi Valley. Some
locally heavy rainfall is possible across these locations on
Thursday. The unsettled weather pattern will continue Thursday
night through Friday night with continued chances of showers and
thunderstorms. Low temperatures tonight will range from the upper
50s to mid 60s. High temperatures on Thursday will be in the 70s.


.SHORT TERM...(This Evening through Thursday)
Issued at 325 PM EDT Wed Jun 20 2018

After a brief lull this evening into the early overnight, active
period of rain and scattered thunderstorms will continue through
the remainder of the work week.

An upper level short wave across northeast Illinois will continue
to drift across northern Indiana this afternoon. Best chances of
showers and thunderstorms this afternoon into early this evening
will be following this upper forcing and associated southward
migration of near sfc trough axis. Instability is limited and
thunder should be more isolated in nature across the far
southeast. Could have a few downdrafts capable of some non-severe
gusts across the extreme southeast through around 00Z. Lull in
precip chances should set up this evening, but additional
showers/isolated storms may develop mid evening through the
overnight hours across southwest portions of the area in advance
of lead vort max lifting out of southern Illinois. Near term
guidance does suggest secondary low level theta-e ridge trying to
nose into west central Indiana toward daybreak Thursday as well.

Overall guidance has trended a bit faster with upper level low
digging across the Mid MS Valley on Thursday, and faster timing
with lead vort max in diffluent flow regime across the southern
Great Lakes Ohio Valley. As a result, bulk of deterministic
guidance has trended upward with rainfall potential on Thursday.
Much of the heavier rain should be tied to fairly strong low level
moisture flux convergence associated with warm frontal type
feature. This front will not make significant northward progress
during the day given digging nature to upper forcing. Based on
these recent trends, did increase PoPs for the day on Thursday,
with heaviest amounts of rain expected for areas roughly southwest
of a Benton Harbor MI to Fort Wayne IN to Lima OH line. Low level
convergence/deep warm cloud depths/relatively high PWATs suggest
potential for some widespread rain amounts of an inch or more
across these locations Thursday/Thursday night. Not much in the
way of severe weather threat given weak mid level lapse rates and
widespread clouds/precip, and did maintain highest chance of
thunder across the far southwest. Forecast confidence with temps
on the low side given clouds/precip, but did try and indicate
coolest mins in the lower 70s across the southwest where earlier
rain onset is expected.


.LONG TERM...(Thursday Night through Wednesday)
Issued at 325 PM EDT Wed Jun 20 2018

Unsettled period will continue Thursday night through Friday night
as occluded system drifts south of the area. Track of the primary
upper low will result in extended period of wrap around moisture
residing across the area with several vorts wrapping cyclonically
from parent low to the south. Best convective chance still appears
to be across the southeast Friday afternoon/evening as sfc
reflection slowly migrates northeastward. While a few strong
storms are possible, greatest concern over the next few days will
be on localized heavier rain amounts/flooding as several rounds of
rain are possible. Chance of thunder should linger into Saturday,
particularly across the east where coolish mid/upper level
profiles will persist with departing upper PV anomaly. A break in
the greater rain coverage should develop later Saturday into
Saturday night, but medium range models have been consistent in
bringing next short wave across the area on Sunday with another
chance of showers and thunderstorms. Passage of this short wave
will put local area downstream of upper level ridging that should
provide a dry start to next work week.

ECMWF/GFS are in fairly good agreement in next eastern Pacific
wave impacting the region for midweek with another chance of
showers/storms. An overall slightly cooler than normal period
shaping up through through Saturday with temps moderating back
into mid 80s by Wednesday. Some indications of heat dome building
once again for late next work into next weekend, just beyond this
forecast valid period.


.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 701 PM EDT Wed Jun 20 2018

Southern edge of persistent IFR deck continues to plague KSBN so
will at least need to cover with a tempo group to start. Clouds
expected to stay locked in for both sites through the
period...mainly MVFR with some breaks to VFR. Should be rain-
free for most of this TAF cycle...approaching upper low and
surface boundary will bring precip shield close to both terminals
late afternoon Thursday. Light easterly flow will increase to
around 10kts by midday Thursday.




SHORT TERM...Marsili
LONG TERM...Marsili

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.