Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 200004

Area Forecast Discussion
National Weather Service Northern Indiana
804 PM EDT Sat Aug 19 2017

Issued at 250 PM EDT Sat Aug 19 2017

High pressure will provide fair weather into tonight and Sunday,
with lows near 60 degrees tonight and highs in the 80s tomorrow.
More humid conditions are expected on Monday with low chances for
afternoon thunderstorms west of Interstate 69. A cold front will
swing through later Monday night into Tuesday with chances for
several rounds of showers and thunderstorms. Cooler and drier air
then filters in behind this system Wednesday through next weekend.


Issued at 753 PM EDT Sat Aug 19 2017

No major concerns for the evening update, with previous forecast
appearing to be on track. Only item that may need watching is
patchy fog potential late tonight/early morning. Crossover temps
are highest for areas roughly along and south of US Route 30, but
would expect that any patchy fog should be shallow in nature and
confidence in extent continues to preclude ZFP mention at this


.SHORT TERM...(This Evening through Monday)
Issued at 250 PM EDT Sat Aug 19 2017

Subsident west-northwest flow will allow surface ridging to drift
through the region late this afternoon into tonight ensuring
dry/mostly clear conditions. Sunday into Monday will feature a brief
transition to high latitude/quasi-zonal flow. Low level flow will
veer more southwesterly during this time promoting gradual
moistening/warming, especially by Monday when airmass becomes
moderately unstable. Will have to watch the slow eastward
progression of upstream convection on Monday as low
amplitude/convectively aided shortwave energy emerges on southern
fringe of westerlies. Outflow from this feature could generate some
convection into nw IN/sw Lower MI mainly into Monday afternoon,
though kept PoPs low as main frontal zone develops into the Upper
Midwest/Western Great Lakes.


.LONG TERM...(Monday Night through Saturday)
Issued at 250 PM EDT Sat Aug 19 2017

Chances for rain/storms increase Monday night into Tuesday/Tuesday
evening as another seasonably strong upper trough digs southeast
into the Great Lakes. Ample moisture transport near the associated
cold front and/or pre-frontal trough/outflow, combined with the
potential for lead convectively induced waves to translate through
in strengthening wsw flow, support going mid chance to likely PoPs
(several rounds of rain/thunder). There remains some potential for
strong/severe convection Tuesday afternoon given increasing
flow/forcing aloft over moist/unstable surface conditions, though
where/when convection is more active (near possible composite
outflow or along main front?) remains uncertain at this fcst range.
Expansive high pressure then builds in post-frontal mid week through
next weekend on the subsident southwest periphery of an Eastern NOAM
longwave trough.


.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 753 PM EDT Sat Aug 19 2017

VFR conditions expected to prevail this period with possible only
exception late tonight into early Sunday morning when some patchy
shallow fog may form. Confidence in patchy fog formation is low at
this time, and best chance appears as though it would be generally
along and south of Route 30 where crossover temps are slightly
higher. Did include a tempo MVFR vsby restriction at KFWA in the
08Z-12Z period. Otherwise, sfc high pressure will provide light to
calm winds tonight, eventually favoring south 5 to 10 knots on
Sunday as the ridge of high pressure pushes off to the east.




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

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