Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 200543

Area Forecast Discussion
National Weather Service Northern Indiana
143 AM EDT Mon Mar 20 2017

Issued at 810 PM EDT Sun Mar 19 2017

It will be a quiet and dry evening as high pressure slides to our
east. There is a chance for showers and a few thunderstorms
overnight with the highest chances over northwest Indiana. Small
hail could occur with any thunderstorm in the northwest. A cold
front will cross the area Monday and widespread showers and
scattered thunderstorms are expected. Small hail will be possible
again with any stronger storms. It will turn colder midweek with
highs on Wednesday only in the middle to upper 30s. A warmup is
expected by Friday with temperatures climbing into the 60s but
rain chances return for late week and the weekend with this


.SHORT TERM...(This Evening through Monday)
Issued at 339 PM EDT Sun Mar 19 2017

As expected clouds have been slow to clear today and finally seeing
some erosion on western fringe. Will take several more hours to
clear in NW Ohio...likely into early or mid evening hours. Focus
then shifts to west with increasing warm air advection and rain
chances late tonight.

Models have been trending toward a more pronounced elevated mixed
layer advecting into far west late tonight. Upstream convection
expected to develop in IL after 06z on nose of modest low level jet
and theta surge. 12z hires CAMs showing this activity spreading east
into western CWA in the 09-12z time frame and across southern areas
mid morning. Mid level lapse rates around 7-8C/km with 0-3km bulk
shear of 30 knots. 4km NAM soundings show over 2K j/kg elevated CAPE
in our far southwest. NAM nearly always overdone with this parameter
but certainly could expect upwards of 1000 j/kg. If upstream storms
can maintain themselves into our west with approaching short wave
there would be a hail threat with any thunderstorm before weakening.
Would expect primarily sub severe size but cannot rule out some
approaching severe limits given bulk shear values...especially if
higher CAPE is realized. Prior grids handled timing rather well
given latest hires guidance and only made some minor adjustments.

Models then showing secondary development Monday afternoon with main
short wave and cold front. Mid level lapse rates still in the 7-7.5
C/km range with 0-3km bulk shear 30-35 knots per hires CAMs. This
will maintain the small hail threat through the afternoon as showers
and storms push southeast. This more conditional on morning storms
and evolution but CAMs seem to be in agreement.


.LONG TERM...(Monday Night through Sunday)
Issued at 339 PM EDT Sun Mar 19 2017

A fast moving short wave now seen in several models on Tuesday which
could bring rain to central and southern areas. Still some
differences on how far north or south this feature will track. High
pressure will be building southward with drier air trying to work
south and this seems to be playing havoc with models and pcpn
placement. For now accepted the blended PoPs which keep low to mid
chance pops in southern two thirds of the area. This high will
establish itself for Wednesday though across the Great Lakes with a
very cold late March day expected despite what appears to be a
mostly sunny day. A cold Tuesday night and Wednesday night expected
with temps well into the 20s.

Return flow still on track later Thursday into Friday with warmup
expected Friday into Saturday. Rain chances do increase as southwest
flow will bring deeper moisture and strong low level jet. Models now
trending a dry slot into the area Friday which will lead to even
warmer temps well into the 60s. Models trending closer on weekend
system drifting east into the Ohio Valley region but differences on
details and timing of rain. Did adjust blended categorical pops down
a touch with model differences but it does look like a wet weekend
with near normal temps at this time.


.AVIATION...(For the 06Z TAFS through 06Z Monday Night)
Issued at 143 AM EDT Mon Mar 20 2017

Focus remains on upstream elevated convection breaking out from wrn
MI swwd into ern IA. Lots of accas noted in GOES-16 through nrn IL
and suspect given unstable elevated mixed layer and increasing low
level theta-e ridging advecting east this line will fill in. CAMS
guidance looks a bit slow compared to radar trends and will opt to
add brief ts mention early.

Otherwise much more significant forcing expected toward early aftn
invof KSBN and mid aftn invof KFWA along/ahead of sfc trough with a
period of vigorous storms likely and fuel alt conditions. Thereafter
post cold advection follows with mvfr or worse cigs.




SHORT TERM...Lashley
LONG TERM...Lashley

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