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Area forecast discussion
National Weather Service northern Indiana
200 PM EDT Mon Aug 21 2017

issued at 200 PM EDT Mon Aug 21 2017

Rain chances will ramp up overnight ahead of a strong cold front
progressing out of the plains. Best chances will exist late tonight
northwest and early Tue morning southeast. Otherwise much drier and
cooler air will overspread the are in behind this system midweek
through next weekend.


Short term...(tonight and tuesday)
issued at 200 PM EDT Mon Aug 21 2017

Challenging fcst this period owing to messy mesoscale. Decaying MCS
over cntrl Illinois attm with remnant mesoscale convective vortex over NW Illinois. Expect this feature
will continue downstream and initiate new convection this evening
invof well established lake breezy boundary over SW Michigan. Secondary
additional development likely within elevated low level warm
advection zone through cntrl Illinois which would then carry newd through
wrn zones into late evening.

Otherwise large scale cold front in association with potent SW
trough digging out of cntrl mb will continue sewd overnight. Ewd
passage of prefrontal trough expected late tonight with cold front
to follow Tue morning for most. Far se zones lag with perhaps some
isolated development possible Tue aftn pending degree of convective
overturning that occurs in the morning. Regardless 12z guidance
across the board quite tepid with pops. Best coverage/most
appreciable qpf expected through NW zones within zone of maximized
low level mass flux along nose of low level jet late. But given
timing and relative stable near sfc layer severe weather threat
looks minimal if at all.


Long term...(wednesday through monday)
issued at 200 PM EDT Mon Aug 21 2017

Little of note this period as broad sfc ridging becomes established
through the wrn lakes with an extended period of delightful late
Summer weather. Some semblance of return flow seen toward Mon where
some token low chc pops were retained yet sys aloft/return flow
both look pretty weak.


Aviation...(for the 18z tafs through 18z Tuesday afternoon)
issued at 1258 PM EDT Mon Aug 21 2017

VFR/dry with SSW winds generally 6-12 knots expected this afternoon
as any convection likely fires south of the terminals near a
leftover outflow boundary. A shortwave over Iowa should migrate east
into the area this evening into the early overnight with chances for
scattered showers/storms. Better chances for rain/embedded thunder
and restrictions arrive later tonight into Tuesday morning as
monsoonal moisture overspreads in advance of a strong cold front.


Iwx watches/warnings/advisories...


short term...T
long term...T

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