Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 190738

Area Forecast Discussion
National Weather Service Northern Indiana
338 AM EDT Tue Sep 19 2017

Issued at 331 AM EDT Tue Sep 19 2017

A warm front and upper air disturbance will move across our area
today causing showers and scattered thunderstorms. An upper level
ridge will build over the region Wednesday and then remain
stationary into early next week, resulting in generally dry
conditions, with unseasonably warm temperatures.


.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 06Z TAFS through 06Z Tuesday Night)
Issued at 138 AM EDT Tue Sep 19 2017

Regional radars showing an area of showers and embedded storms
over northeastern IL working ENE. Flight conditions will
deteriorate to MVFR and likely at least a period of IFR overnight
into least Tuesday morning as hi res models all suggest this will
shift east with a upper level system and possibly expand in
coverage. Have introduced VCTS to KSBN TAFs given slow increase in
lightning to the west, but held off for now at KFWA. Also moved up
timing of precip.

There should be a lull in any precip moving in from west to east
late morning into the early afternoon. With an unstable
environment in place, can`t rule out widely scattered showers or
storms, especially at KFWA. No mention for the time being.

While outside current forecast, some signals of potential for fog
(possibly dense) at both sites after 6Z Weds given moist boundary
layer and possibility of at least partial clearing. May need to
address in 12Z TAFs.





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