Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 191716

Area Forecast Discussion
National Weather Service Northern Indiana
115 PM EDT Tue Sep 19 2017

Issued at 115 PM EDT Tue Sep 19 2017

Scattered showers north of highway 30 will diminish this evening. A
rumble of thunder is possible along and east of interstate 69 this
afternoon. Otherwise skies will partially clear overnight with dense
fog likely west of state route 5 late. Lows 60 to 65.

Dry and warmer weather follows for Wednesday with highs in the low
to mid 80s.


.SHORT TERM...(Today and Tonight)
Issued at 331 AM EDT Tue Sep 19 2017

Stalled frontal boundary over central IN/IL will lift northward this
morning in response to shrtwv movg ene from IL. Convergence at
nose of 20-25kt LLJ associated with this system should combine
with a very moist airmass along and south of the boundary with
pwats >1.5" and wk instability to cause widespread showers and
scattered thunderstorms to move across our area this morning. Wk
shrtwv movg across the area this aftn may provide forcing for sct
convection to re-develop as diurnal destabilization occurs. Given
the light wind fields and deep warm cloud layer in place, locally
heavy rainfall is psbl today. Clouds/rain should limit temp
rises, but prbly still sufficient sunshine for some diurnal
recovery. Lowered going temps a few degrees, with highs expected
to range from the lwr 70s ne to the upr 70s sw.

Shrtwv will cont to move slowly east and weaken this eve, psbly
allowing for some lingering convection over ern portions of the
area. Diminishing cloud cover behind this system combined with light
winds and moist airmass should allow patchy fog to form with dense
fog psbl, especially wrn portions of the cwa.


.LONG TERM...(Wednesday through Monday)
Issued at 331 AM EDT Tue Sep 19 2017

Models cont to indicate highly amplified upr level flow over the
conus by late week with a deep wrn long wave trof and upstream ern
ridge. This should result in a mainly dry period in our cwa with
well above normal temperatures. Shrtwv lifting ne across the upr
Midwest and into Ontario Wed ngt may result in some dying convection
reaching our area. GFS lingers the sfc reflection boundary from
this system over our area Thu-Fri and generates some qpf as
airmass goes through diurnal destabilization. Prefer dry ECMWF or
at worst isolated aftn convection suggested by GEM in this
timeframe, but for now maintained a dry fcst.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday Morning)
Issued at 115 PM EDT Tue Sep 19 2017

Tricky short term period owing to pesky stalled upper low over
northwest IN. Near term increase in shra activity expected and esp
invof KFWA terminal where some marginal sfc based instability had
developed yet will diminish quickly by evening as upper sys slowly
lifts out.

Thereafter at least partial clearing expected to follow overnight
with dense fog development likely esp wwd including the KSBN
terminal. Will hold with prior LIFR mentions at both sites late





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