Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 191745
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
145 PM EDT Mon Sep 19 2016

.SYNOPSIS...
Issued at 142 PM EDT Mon Sep 19 2016

High pressure over the southern Great Lakes and Ohio Valley
regions will provide mainly tranquil weather through the week with
above normal temperatures. Lows tonight will dip into the upper
50s to lower 60s and highs on Tuesday will reach into the lower
80s.

&&

.SHORT TERM...(Today through Tuesday night)
Issued at 400 AM EDT Mon Sep 19 2016

For the short term, main forecast highlights will be patchy fog
this morning and low chances of showers and thunderstorms far
northwest late tonight into possibly Tuesday.

Despite dry air advection, ideal radiational cooling conditions have
allowed patchy shallow fog to form this morning. Eastern half of the
forecast area appears to be best inline for more significant vsby
reductions this morning. Have opted to hold off on headlines at
present time with low confidence in extent/duration/depth. Shallow
fog should burn off rapidly after daybreak.

Otherwise for today low/mid level warm advection is already underway
with some WAA induced mid/high clouds working across the western
Great Lakes. Mixing heights will be relatively limited in this
pattern but strength of warm advection and mixing up to 925-900 mb
would support highs in the lower to mid 80s (warmest western half).
Water vapor imagery this morning depicts a pronounced upper level
short wave tracking across southern Manitoba which will reach
southeast Ontario tonight. Frontal boundary trailing to the
southwest will have a difficult time making too much progress to
the southeast later today and tonight with robust mid level
ridging in place from the central Plains to the Ohio Valley.
Relatively large low level dew point depressions will linger
across local area through the evening, with narrow axis of pre-
frontal pooled moisture not expected to work across southwest
lower Michigan until well after midnight. Not much change from
previous forecast thinking in that sustaining any upstream
convection along cold front into local area late tonight will be
difficult due to the combination of a possibility of lingering
capping issues with shallow moisture return, bulk of mid/upper
level forcing remaining to the north/northwest, and stronger low
level convergence also to the northwest of the area. Have
maintained slight chance PoPs overnight tonight, with a
continuation of trend from previous forecast in slowing onset of
these PoPs until after 06Z tonight.

Shallow front will sag across the area on Tuesday. Appreciable
surface based instability will likely be tough to come by, but
narrow axis of weak elevated instability may persist somewhere
across central portions of the area. Forcing looks to be on the
meager side, but some uncertainty exists with an outside chance of
a convectively enhanced vort max tracking across the region from
any Monday night mid MS Valley convection. Have opted to keep
Tuesday dry although as this period nears, conceivable some isold
type mention may be needed.

&&

.LONG TERM...(Wednesday through Sunday)
Issued at 400 AM EDT Mon Sep 19 2016

The long term period will begin with continued above normal temps as
broad mid/upper level ridging remains in place. Bulk of convection
Wednesday and Thursday should be confined from the Corn Belt to the
central/northern Great Lakes. Guidance depicts some steep mid level
lapse rates advecting into the region Wednesday-Thursday in
association with an elevated mixed layer. While cannot rule out a low
end chance of a storm across the far north or northwest during this
period, mixed layer aloft will likely act as a cap allowing for
continued dry conditions. Some signal that by Thursday night/Friday,
a more robust south central Canada wave may provide enough
suppression of ridge to allow frontal boundary to drop across
southern Great Lakes by the end of the work week. Thus, have
maintained slight chance PoPs for most of the area for Thursday
night-Friday.

Forecast confidence diminishes by next weekend with medium range
models exhibiting quite a bit of run to run volatility as of late
regarding evolution of larger scale upper trough across western
CONUS and southeast Canadian negative height anomaly. Latest trend
from EC/GFS deterministic solutions suggests a more
stable/amplified wave pattern setting up that could promote longer
residence time of mid/upper level ridging next weekend, and
delayed onset to next precip chances. Given all the run to run
inconsistencies, have opted to accept guidance consensus solution
at this time with gradual ramping up of PoPs late next
weekend/early next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
Issued at 145 PM EDT Mon Sep 19 2016

Surface high pressure to assure vfr conditions through the
forecast period for northern Indiana.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SYNOPSIS...Murphy
SHORT TERM...Marsili
LONG TERM...Marsili
AVIATION...Murphy


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