Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 182313

Area Forecast Discussion
National Weather Service Northern Indiana
713 PM EDT Sat Aug 18 2018

Issued at 125 PM EDT Sat Aug 18 2018

While isolated showers this evening are possible, most places
will remain dry. Some areas of fog are again possible towards
daybreak Sunday. Overnight lows will be in the lower to middle
60s. Under partly to mostly sunny skies, temperatures will rebound
into the lower to middle 80s on Sunday. A strong low pressure
system approaches and will bring widespread rain to the region,
especially late Monday into early Tuesday. Look for dry and cooler
weather by the middle of next week.


.SHORT TERM...(This Evening through Sunday)
Issued at 351 PM EDT Sat Aug 18 2018

Weakly sheared environment coupled with poor mid level lapse rates
lending to small towers with only a couple/extremely isolated light
showers past hour. Surface based CAPE peak near 1500 j/kg in a few
hours and some minor pops through evening with northeast CWA favored
amid lake boundary intersections and presence of subtle
secondary/trailing shortwave lagging primary downstream trof. Decay
of diurnally driven cu field and weak high pressure sprawled across
Great Lakes present similar to last night with potential strong
radiational cooling to 3 to 6 degrees below crossover temperatures.
Have added areas of fog mention from 09-12 UTC Mon and defer
stronger wording to later analysis.


.LONG TERM...(Sunday Night through Saturday)
Issued at 351 PM EDT Sat Aug 18 2018

Focus continues on early next week system. Strong mid level vortex
over southeast Montana to drive into Mid-Mississippi Valley on
Monday. Leading height rises and upstream deep layer cyclogenesis to
provide rich/rapid onslaught moisture flux convergence with focused
lift within large warm advection leaf. Any leading discrete storms
could pose a low risk, however given deep warm layer depth,
precipitable water to 2 inches, heavy rainfall rates/totals appear
to be primary risk. Ramped pops higher than blend in collaborative
effort with surrounding offices from Monday afternoon through Monday
night. Cooler mid week in wake of strong frontal system pulling
northeast into eastern Canada/Lower Great Lakes. Large surface ridge
over central CONUS spreads into the southern Lower Great Lakes by
Friday, supportive of blends extended dry period with gradual
thermal moderation.


.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 704 PM EDT Sat Aug 18 2018

Isolated showers will be near the KFWA terminal for the first
couple hours of this TAF issuance, but KSBN looks to remain dry.
Clearing skies and light winds will likely result in another round
of fog between 8 and 12Z Sunday morning. Have retained MVFR visby
for both terminal, but did go ahead and put a tempo IFR for KFWA
given the greater supply of surface moisture. There is a
possibility that visby could be lower for KFWA, but as of now,
confidence is too low to decrease further. Each terminal should
mix out quickly to return to VFR by 14Z. Light winds prevail
throughout this TAF cycle while slowly rounding the dial out of a
southeast direction by tomorrow midday.




LONG TERM...Murphy

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