Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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384 FXUS63 KIWX 210004 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 804 PM EDT Thu Jun 20 2024 .KEY MESSAGES... * Hot and humid conditions will persist through Saturday. Peak afternoon heat indices will approach 100 degrees in many locations, hazardous to sensitive and vulnerable groups. * Isolated to scattered thunderstorms (20-40%) are possible during the afternoon and early evening hours today and Friday, mainly north of US 30. Locally heavy rainfall, lightning and wind gusts in excess of 40 mph are the primary threats. * Better shower and thunderstorm chances (40-70%) arrive Saturday night into early Sunday along a cold front. && .DISCUSSION... Issued at 220 PM EDT Thu Jun 20 2024 A shallow/weak sfc trough the focus for diurnally driven convection this afternoon into early this evening, mainly north of US 30. A slightly drier boundary layer and lacking forcing/flow to once again limit coverage (isolated to scattered), and the threat for severe storms, though stronger water loaded pulse cells will carry the potential for wind gusts in excess of 40 mph in the collapse phase. 700 mb temps warming to +10C plus should should keep a lid on convection across southern portions of the area. Gradual suppression of the OH/TN Valley upper ridge is expected into Friday and Saturday in advance of an upper trough ejecting from the Rockies into the Upper Midwest. The associated active/elevated frontal zone will remain north of the area with mainly dry/hot conditions anticipated, though still cannot rule out isolated convection again Friday afternoon-evening near any lingering outflow boundaries in the north. Continued to carry a dry forecast during the day on Saturday with the area capped in deeper pre-frontal southwest flow. Long duration heat wave remains the primary wx story otherwise through Saturday on the northern fringes of the 595-598 dm 500 mb upper ridge. Round of height falls through the Great Lakes does bring a well needed cold front through Saturday night into Sunday morning with chances for showers/storms, followed by a break from headline worthy heat into early next week. Poor diurnal timing of the frontal forcing and resulting limited buoyancy suggests a weakening trend and lesser coverage (40-70%) of convection later Saturday night into Sunday morning. Theta-e ridge axis builds in advance of the next approaching Upper Midwest upper trough Tuesday into Wednesday with chances for a convective complex to bring needed rain/storms. Confidence at this range is low however given a notable ensemble and deterministic model solution spread. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 804 PM EDT Thu Jun 20 2024 Isolated convection will likely stay NE of the terminals through the rest of the evening and slowly dissipate with the loss of daytime heating. Additional convection is possible again Friday given hot/humid conditions but coverage will remain isolated given lack of forcing and instability limited by a modest cap. KSBN will have the best chances again but will hold dry for now. BR is possible again tonight given light winds and near-surface moisture but based on last night it is not likely to impact the terminals. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...Heat Advisory until 8 PM EDT /7 PM CDT/ Saturday for INZ005>008-012>015-020-022-023-103-104-116-203-204-216. Excessive Heat Warning until 8 PM EDT Saturday for INZ009-017- 018-024>027-032>034. Air Quality Alert until midnight EDT /11 PM CDT/ Friday night for INZ020-103-203. OH...Excessive Heat Warning until 8 PM EDT Saturday for OHZ001-002- 004-005-015-016-024-025. MI...Heat Advisory until 8 PM EDT Saturday for MIZ078>081-177-277. MARINE...None. && $$ DISCUSSION...Steinwedel AVIATION...AGD