Area Forecast Discussion
Issued by NWS Northern Indiana

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000 FXUS63 KIWX 161909 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 309 PM EDT Wed Aug 16 2017 .SYNOPSIS... Issued at 308 PM EDT Wed Aug 16 2017 Chances for showers and thunderstorms will arrive tonight into Thursday as a strong frontal system moves through. There is a low chance for isolated strong to severe thunderstorms Thursday afternoon into Thursday evening. Lows tonight will only drop to near 70 degrees...with highs on Thursday in the upper 70s to mid 80s. Cooler and drier air will filter in behind this system Thursday night into Friday. This will followed by low rain chances on Saturday as an upper level disturbance tracks through. && .SHORT TERM...(This Evening through Thursday) Issued at 308 PM EDT Wed Aug 16 2017 A well defined shortwave and attendant sfc reflection will track ene into the Upper Midwest tonight and the Northern/Western Great Lakes by tomorrow. Associated height falls will elicit a decent LLJ response downstream (30-40 kt), which will force a tight theta-e gradient/warm front northeast through the Lower Great Lakes this evening into early Thursday morning. Scattered showers/storms are expected with this elevated WAA, best chances north of US 24 in an area of more pronounced moisture convergence and upper divergence. Brief heavy downpours will be possible as PWATS approach 2 inches. A somewhat narrow corridor of forcing/deep moisture then follows along a pre-frontal trough later Thursday morning through nw iN/sw Lower MI and points east late morning through mid afternoon...with the actual/main cold front to follow late Thursday into Thursday evening. The result will be additional chances for a couple of rounds of showers/storms...though timing/coverage remains in question as better upper level forcing bypasses north. SPC upgraded areas east of US 31 into a slight risk for severe storms Thursday afternoon into Thursday evening as breaks in cloud cover could push MLCAPE values to 1500-2000 j/kg in pockets. 40-50 kt mid level westerly flow over top this moist (sfc dewpoints low- mid 70s) could allow for some multicell organization...with 20-30 kts of 850 mb flow and low LCL`s also hinting at an isolated tornado threat. However, extensive cloud cover and poor lapse rates...with several CAMS firing renewed afternoon/sfc based convection east of the area (near pre-frontal trough) with little activity along the actual cold front...suggest chance PoPs and low/conditional severe threat the way to go at this fcst range. && .LONG TERM...(Thursday Night through Wednesday) Issued at 308 PM EDT Wed Aug 16 2017 Drier/cooler air will filter in post-frontal Thursday night into Friday as the above mentioned upper trough weakens northeast into eastern/southeast Ontario. The next shortwave will dig southeast under this feature bringing renewed chances for showers/iso storms later Friday night into Saturday. Forcing per 5-3H Q-Vector looks good later Friday night into Saturday morning with this wave, though moisture quality will really be lacking this time around resulting in nothing more than 20-30% type PoPs. Flow pattern flattens out leaving dry/warming conditions Sunday into Monday...followed by another chance for showers/storms later Monday night through Tuesday night as another larger scale upper trough amplifies into the Great Lakes forcing a cold front through. && .AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon) Issued at 1231 PM EDT Wed Aug 16 2017 This afternoon will continue to feature dry/VFR conditions...with gradual moistening near 5 kft allowing a scattered to broken stratocumulus deck (VFR) to fill in with time. A weak disturbance and elevated theta-e gradient over the Mid MS Valley will lift north into the region later this evening into the early overnight bringing chances for scattered showers/embedded thunder. Better chances for rain/thunder and restrictions arrive later tonight into Thursday morning as deeper moisture/forcing (near a pre- frontal trough) swing east into northern Indiana. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SYNOPSIS...Steinwedel SHORT TERM...Steinwedel LONG TERM...Steinwedel AVIATION...Steinwedel Visit us at www.weather.gov/iwx Follow us on Facebook...Twitter...and YouTube at: www.facebook.com/NWSNorthernIndiana www.twitter.com/nwsiwx www.youtube.com/NWSNorthernIndiana

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