Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 271928

Area Forecast Discussion
National Weather Service Northern Indiana
328 PM EDT Sat May 27 2017

Issued at 313 PM EDT Sat May 27 2017

High pressure will keep the region mostly dry into the overnight
hours tonight but there is a small chance for thunderstorms toward
daybreak. Lows will drop into the upper 50s to lower 60s. A low
pressure system and trailing cold front will move through the area
on Sunday with showers and thunderstorms likely, especially in
the afternoon. Highs will be in the 70s. Memorial Day will begin
mostly sunny but a weak system will increase clouds in the
afternoon and bring a small chance for a shower or thunderstorm in
the mid to late afternoon hours. Highs will be in the low to mid
70s. The rest of the week will primarily be dry but there are some
small chances for light showers during the period.


.SHORT TERM...(This Evening through Sunday)
Issued at 312 PM EDT Sat May 27 2017

Short term concerns center around convection potential overnight and
Sunday. Impressive MCV over central Iowa this afternoon tracking
northeast while warm frontal boundary and instability axis over the
MO and OH valley leading to convective development there. Afternoon
surface analysis shows high pressure over northern IL ahead of MCV
with northeast surface flow off of Lake Michigan aiding in low level
stabilization of boundary layer. CAMs seem to pick up on this with
weakening convection associated with MCV as it lifts northeast this
evening. CAMs also indicate deeper convection with boundary to our
south will primarily stay south overnight. A few models do spin off
some shra/tsra northward toward daybreak and have maintained a low
PoP for this possibility.

Primary synoptic scale short wave expected to move through the
region Sunday. Surface low will lift northeast across our area in
the afternoon as associated warm front lifts north late morning into
early afternoon followed by cold front passage. CAMs not overly
aggressive with convection along warm front but with modest mixed
layer CAPE of 1000-1500 j/kg developing should see some scattered
convection lift north mid to late morning. Main activity looks to be
with cold front and have adjusted likely PoPs to afternoon and early
evening along and ahead of this boundary. A lot of uncertainty with
respect to cloud cover and evolution of tonight`s MCS to our south
which will dictate development in our area on Sunday. Isolated severe
still possible with mixed layer CAPE as high as 1500-2000 J/kg if we
can get some sunshine and destabilize ahead of front. 0-6km bulk
shear on order of 30-40 knots so isolated wind damage and hail will
be possible.


.LONG TERM...(Sunday Night through Saturday)
Issued at 312 PM EDT Sat May 27 2017

Overall trend toward a drier pattern is on tap for this long term
period but we will see some small chances for mainly light
showers through the period. Upper level low over Manitoba this
weekend will drift and wobble across Ontario and eventually into
western Quebec by end of the period. Several small scale
perturbations will rotate around this low through the week and
each will bring a small chance for light showers to mainly
northern areas. First such wave will arrive on Memorial Day during
afternoon and evening. Moisture will be limited but timing of
wave with afternoon heating will lead to some instability and
small pcpn chances.

Timing of short waves remainder of the week to likely change given
the location of upper low and how far south waves will make it. Most
of the week does look dry for most with a chance to dry out and
allow rivers and streams to recede. Next decent chance for rainfall
may arrive next weekend but models remain in flux and confidence low
so only small chances per inherited Superblend.


.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 135 PM EDT Sat May 27 2017

A boundary pushed south and ridging, coupled with weak low level
winds, moved into the area early Saturday morning. Early morning
MVFR/IFR CIGs diminished during the day setting up an afternoon
with VFR conditions, which will continue into the overnight. For
the overnight, expect VFR conditions as the convection from the
Plains dies out before it gets here. Then, expect a low pressure
system and trailing cold front to approach the area from the
Central Plains Sunday with a chance at showers and storms along
with a renewed chance at MVFR conditions in the morning.




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

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