Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 230532

Area Forecast Discussion
National Weather Service Northern Indiana
132 AM EDT Wed Aug 23 2017

Issued at 810 PM EDT Tue Aug 22 2017

Cooler and drier air will continue to filter into the area
tonight behind a cold front. Below normal temperatures, low
humidity, and dry weather are in store through much of the
remainder of the work week as a ridge of high pressure slowly
overspreads the region.


Issued at 810 PM EDT Tue Aug 22 2017

Scattered showers have exited far southeast portions of the
forecast area early this evening along southward advancing cold
frontal boundary. Cooler and less humid conditions will continue
to advect across the area tonight. Sfc wind speeds were augmented
across the north late this afternoon by a secondary sfc trough
marking another wind shift to the north-northwest, but decoupling
should be fairly rapid over the next 1 to 2 hours allowing winds
to settle back into the 5 to 10 mph range after 01Z. Tricky min
temp forecast tonight across the extreme northwest with low
confidence in how far inland lake moderation will penetrate. Will
keep an eye on observational trends over next hour or two, and
may be able to shave a few degrees off lows across the far
northwest. Otherwise, no substantial forecast changes planned at
this time.


.SHORT TERM...(This Evening through Wednesday)
Issued at 211 PM EDT Tue Aug 22 2017

KIWX radar continuing to show weakening trends in precip as it
has now exited the eastern CWA. Cold front moving into NW CWA has
decent mass convergence and combining with lake breeze to generate
a broken line of showers across the northern CWA while pocket of
weak diurnal instability ahead of the front has widely scattered
showers over the north central CWA. Cold front should keep this
activity pushing E/SE and diminishing later in the afternoon with
loss of daytime heating. This will set the stage for a cooler and
drier Canadian airmass to begin building into the region behind
the cold front tonight. Surface analysis has low pressure up in
southern Canada along the Ontario/Quebec border with high pressure
still back to the west centered over the Dakotas. Decent gradient
in between sets up over the area and will generate some gusty
winds through the early evening hours until boundary layer
decouples. Clearing skies can be expected overnight with lows in
the mid 50s. Cooler and less humid conditions on Wednesday with
highs in the mid 70s. Surface high pressure only slides eastward
to the mid MS valley keeping a modest gradient over the area and
have winds gusting to 15-20mph by Wednesday afternoon. Some
residual low level moisture lingering over the area will generate
a decent diurnal cu field...especially in NE CWA.


.LONG TERM...(Wednesday Night through Tuesday)
Issued at 211 PM EDT Tue Aug 22 2017

Surface high pressure builds into the western great lakes region
on Thursday. NW flow aloft will send weak disturbance down into
the area bringing additional cloud cover with it but expect to
maintain a dry forecast. High pressure remains in control through
the weekend and will bring ideal weather to the region with lots
of sunshine...low humidities...and highs in the mid 70s. Clear
skies and calm winds will provide optimal radiational cooling at
night and have lows dropping to near 50...10F below normal...with
some areas dipping into the upper 40s. Meanwhile...a tropical
disturbance associated with the remnants of Harvey is expected to
re-organize as it moves into the gulf of Mexico...eventually
making landfall in SE TX. As expected...models struggling with the
extratropical remains and if/when it will phase into the northern
stream flow. Latest model trends have upper ridge building in the
western US leaving remnants detached from northern stream and
stalled in TX/LA through beginning of next week before finally
lifting northward into the TN valley by midweek. GFS also bringing
northern stream wave sliding down the eastern edge of upper ridge
into the mid MS valley Mon/Tue timeframe with resulting guidance
blend introducing small chance POPs. Given rather weak
signal...will limit values on Mon and keep forecast dry but go
along with blend for chance of showers on Tue. Temperatures remain
pleasant through the entire period with highs in the 70s and lows
in the 50s along with comfortably low humidities for late August.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday Night)
Issued at 114 AM EDT Wed Aug 23 2017

VFR conditions expected through the period. Patchy strato cu at
base of inversion aloft continuing over nrn IN/swrn MI attm and
may persist overnight. Radiational cooling will saturate near sfc
layer early this morning but moisture very shallow, so no vsby
restrictions fcst. Sufficient lingering low level
moisture/instability for sct cu at fwa later today, while areas
near Lake Michigan should be a little more stable resulting in skc
at sbn.


IN...Beach Hazards Statement through this afternoon for INZ003.

MI...Beach Hazards Statement through this afternoon for MIZ077.

LM...Small Craft Advisory until 5 PM EDT this afternoon for LMZ043-



SHORT TERM...Logsdon
LONG TERM...Logsdon

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