Area Forecast Discussion
Issued by NWS Northern Indiana

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109 FXUS63 KIWX 240544 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 144 AM EDT TUE MAY 24 2016 .SYNOPSIS... Issued at 305 PM EDT Mon May 23 2016 Seasonably warm conditions will continue through the remainder of the week with highs expected to reach the lower 80s. A series of upper level disturbance will interact with this warm and increasingly humid air mass to produce periodic chances of showers and thunderstorms from Tuesday night through the weekend. The greatest coverage of showers and storms is expected for Wednesday night. && .SHORT TERM...(This Evening through Tuesday) Issued at 305 PM EDT Mon May 23 2016 A sharp mid/upper level ridge will be very slow to track across the Ohio Valley and southern Great Lakes tonight into Tuesday providing continued dry conditions. Low level winds will veer westerly this evening promoting weak low level warm advection tonight. Weak low level warm advection and eastward departure of low level ridge axis should provide milder conditions tonight in comparison to the past few nights. Coolest mins of around 50 are expected across eastern portions of the forecast area, although upper 40s are possible given closer proximity to departing pocket of slightly cooler air, and persistence of a slightly weaker gradient. Good deal of insolation expected once again for Tuesday, with some increase in high clouds possible later in the afternoon. Slightly warmer low levels and better low level mixing should support highs a few degrees warmer than today, around 80 or in the lower 80s. && .LONG TERM...(Tuesday Night through Monday) Issued at 305 PM EDT Mon May 23 2016 For Tuesday night, an upper level short wave currently across the Plains aiding in shower/thunderstorm coverage will lift northeast and dampen across the Great Lakes. Forcing from this wave should initially outrun higher quality moisture across the Mid Ms River Valley Tuesday night lending to some low confidence on convective coverage. A modest 25 knot southwesterly low level jet should advect increased low level moisture into the area overnight with main question by this time on extent of any lingering mid/upper level forcing. Did maintain low chance thunder PoPs for Tuesday night mainly due to advective forcing and development of some weak elevated instability. Confidence is low for Tuesday night regarding instability magnitude however, as a relatively warm 800-650 mb layer may tend to be a limiting factor. The next mid/upper level perturbation should approach the western Great lakes on Wednesday with persistent broad positive low/mid level thetae advection. Strongest low level flow/moisture transport during this forecast period should occur Wednesday night in advance of this wave and have maintained inherited likely PoPs. Several scenarios still possible for Wednesday night. Prospects of elevated convection should be on the increase given this setup. Could also see a more organized cluster of convection develop across northeast Iowa/northern Illinois in closer proximity to this forcing and eventually propagate southeast. Expected orientation of instability/thickness gradient may tend to favor areas just west and southwest of the local area to be inline for any forward propagating convective system. Remnant outflows/convectively enhanced vortices emanating from upstream convection may also serve a focus for greater shower/storm chances Wednesday night however. Confidence in any severe weather Wednesday/Wednesday night remains on the low side given the above uncertainties and how instability magnitude will play out. However, given some increase in the low level jet, weakening propagation vectors overnight, and warm cloud depths approaching 10k feet, some locally heavy rain is not out of the question. Thursday looks to be a transition day between higher precip chances as aforementioned upper disturbance shifts east, and potential composite outflow settles south of the area, and will just maintain low chance pops during the day. A secondary time of greater shower/storm chances may evolve Friday or Friday night as a more amplified mid level wave ejects across the upper MS Valley. Primary forecast challenge for the Thursday night-weekend period in terms of additional precip chances is resolving the strength of mean mid/upper level ridging across eastern CONUS. Given recent blocky nature to the pattern and preference to maintenance of mean ridging, it is difficult to go more than low to mid chance pops through this period with better forcing and stronger shear displaced to the west. Shear profiles should also diminish post-Friday, which should limit extent of severe potential late week/weekend. In terms of temperatures, not much day to day variability is expected with highs around 80 and lows in the 60s as increasingly moist air mass provides a much more limited diurnal range in temps. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday Night) Issued at 114 AM EDT Tue May 24 2016 An upper level ridge will remain over the area and help limit any chances for storms. Winds should become south to southwest as the surface high moves east. Conditions should remain VFR. && .IWX Watches/Warnings/Advisories... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SYNOPSIS...Marsili SHORT TERM...Marsili LONG TERM...Marsili AVIATION...Skipper Visit us at Follow us on Facebook...Twitter...and YouTube at: is the U.S. government's official web portal to all federal, state and local government web resources and services.