Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 260529

Area Forecast Discussion
National Weather Service Northern Indiana
129 AM EDT Sat May 26 2018

Issued at 111 AM EDT Sat May 26 2018

A weak upper level disturbance will bring chances for showers and
isolated thunderstorms into Saturday. Lows will drop into the 60s
tonight, with highs on Saturday in the 80s. High pressure then
builds in for Sunday and Monday with mostly sunny skies and
afternoon highs near 90 degrees each day. Chances for showers and
thunderstorms return by next Wednesday and Thursday.


Issued at 926 PM EDT Fri May 25 2018

No changes of significance will be made to previous forecast.
Disjointed upper level pattern persists this evening with several
smaller scale vortices, a few of which convectively enhanced,
across the mid/upper MS Valley. The vort of interest for local
area will be tracking out of central Illinois during the overnight
hours. Convection across central Illinois has been waning over the
past several hours, although area of rain across east central
Illinois should continue across west central Indiana through
midnight. An outflow boundary has raced ahead of earlier
convection and has reached I-65 corridor as of 01Z. While upper
vort max is weak and tracking across the area during unfavorable
diurnal period for instability, strong low level theta-e gradient
and weak low level LLJ aided advective forcing should be enough
for scattered-numerous rain showers to work across approximately
southern half or southern third of the forecast area overnight.
Some associated increase in elevated instability into the 500-1000
J/kg range also argues for maintaining iso thunder mention.
Confidence a bit lower across the north and have just slightly
sharpened the north-south PoP gradient. Otherwise, previous
forecast left largely as is.


.SHORT TERM...(This Evening through Saturday)
Issued at 210 PM EDT Fri May 25 2018

Upper ridge breaks down allowing a mid level shortwave to progress
east through the Great Lakes region later tonight into Saturday.
Remnant small scale MCV in the base of this trough (over MO as of
18z) roles east-northeast in tandem with associated higher
theta-e/instability fold over may allow a cluster of
showers/elevated thunder to survive into nw IN/sw MI late
evening/overnight...and points east Saturday morning. Bumped up
PoPs considerably given latest CAMs trends, though still some
uncertainty (hence the mid chc pops) given unfavorable diurnal

Surface dewpoints into the low-mid 60s and at least some filtered
insolation should push SBCAPE values to 1000-1500 j/kg Saturday
afternoon. Forcing/deeper moisture associated with the main upper
wave will likely exit east by peak heating, though could see
isolated sfc based convection focus near a leftover sfc trough
southeast of US 24...and possibly near a lake breeze boundary in nw
IN/sw Lower MI (better probabilities southeast of US 24). Lacking
flow/lapse rates should keep any convection pulsy/non-severe with
point chances low given lacking convergence/forcing by peak heating.
Increasing hot/humid otherwise into Saturday with highs generally
mid/upper 80s.


.LONG TERM...(Saturday Night through Friday)
Issued at 210 PM EDT Fri May 25 2018

Height rises/large scale subsidence will result in a mainly
dry/hot Sunday and Monday. Southern fringe of low level
anticyclonic flow will result in more fair wx into Tuesday before
subtropical moisture gets pulled north around late Wed-Thur with
renewed shower/storm chances.


.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
Issued at 111 AM EDT Sat May 26 2018

VFR conditions look to prevail through the period. Weak wave was
moving into NW Indiana with slowly diminishing area of showers
approaching both sites. Will maintain a tempo mention of VFR
showers for a few hours at the start of the period. Quiet
conditions should then prevail the remainder of the forecast with
only very small concern being a popup shower or storm vcnty of
KFWA during peak heating.




SHORT TERM...Steinwedel
LONG TERM...Steinwedel

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