Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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978 FXUS63 KIWX 250441 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 1241 AM EDT Tue Jun 25 2024 .KEY MESSAGES... - A line of thunderstorms is expected to move through late overnight through early Tuesday morning bringing a chance for locally strong/damaging winds. - Confidence remains low on details regarding Tuesday afternoon/evening showers and thunderstorms. If these develop, large hail, damaging winds, and locally heavy rain will be main threats. - Seasonable temperatures and dry conditions expected Thursday and Friday before additional rain chances return Saturday. && .UPDATE... Issued at 809 PM EDT Mon Jun 24 2024 Main focus remains on convective chances and intensity later tonight into Tuesday morning as convection over MN/WI congeals into an upscale growing MCS. The genesis of this is currently underway well upstream over northern MN. Of note through is a separate area of scattered convection north of a warm in srn MN and sw WI as of this writing. The HRRR is starting to pick up on this and hints at this elevated activity surviving east into the area between 7-11z as a corridor of strong low-mid level theta-e advection overspreads the area from west to east. Bumped up PoPs during this time to account for these trends, with this activity to generally hold below severe limits. Attention then turns to the upscale growing MCS and a possible bowing segment turning south into the area between roughly 11-15z Tue AM. This activity does outpace more favorable flow and instability with a trend toward backbuilding and an outflow dominant line this far south, though a wind threat (50-60 mph winds) definitely remains in play across northern portions of the forecast area if a more pronounced bowing segment is realized upstream over WI and Lake MI. && .DISCUSSION... Issued at 250 PM EDT Mon Jun 24 2024 After our extended heat wave last week, we return to a more active, complex weather pattern over the next 24-36 hours. Convection currently in the Dakotas and MN will grow upscale and evolve into a MCS as we head through the evening and overnight hours. Overall agreement is for this complex to maintain intensity through Wisconsin where the greatest instability will reside, along with the stronger shear. A gradual weakening should take place as it works its way southeastward across SE Lake Michigan and Indiana where a rapid dropoff in overnight instability will be located. Nevertheless, mesoscale maintenance of the stronger cells may allow them to produce instances of strong/damaging wind gusts as they push into our forecast area and the updated Day 1 Outlook from SPC now drags a Slight Risk (2 of 5) into North Central Indiana and Southwest Michigan. CAMs have begun to latch onto this better as well, and given the 4mb pressure rises on the HRRR as the MCV moves across the lake, there is some concern for seiche activity along with an increase in wave action and rip current risk leading into Tuesday. Some closer evaluation of this will be needed as we head into the overnight hours... In the wake of the late overnight into early tomorrow morning convective complex, steep low/mid level lapse rates and hot daytime temperatures will contribute to rapid and intense instability across the forecast area. Bulk shear will be limited, ranging from 20-30kt, which will likely prevent a more significant severe episode if anything develops (more below). A corridor of low LCL heights will be favorable for a tornado environment, however, we will need existing surface boundaries to enhance low level helicity as this parameter looks meager. It`s worth noting that confidence in triggers due to the aforementioned earlier convection, and a lack of strong forcing during the day, may keep a lid on afternoon thunderstorms altogether. Therefore, at this time, confidence is very low in Tuesday afternoon/evening severe potential. If anything does develop, the thermodynamic profile will help to create robust updrafts with a hail and damaging wind threat; we`ll just have to see how the AM convection shakes out first. Fortunately, the hottest day of the week will be tomorrow before a frontal passage returns us back into more seasonable temperatures. We will have dry days on Thursday and Friday before another shortwave and surface front brings additional chances for rain and storms. && .AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 1233 AM EDT Tue Jun 25 2024 Medium confidence at best for this TAF cycle as two clusters of thunderstorms bear watching. Generally expect dry condtions thorugh the critical TAF period (especially at KFWA). The exception could be KSBN depending on the evolution of thunderstorms developing over northeast IL in the vicnity of an outflow boundary. Steering flow is from the northwest such that these storms could drift to KSBN, but upper- level support for this is lacking overall. The second area of storms to watch have quickly grown upscale over western WI. These are forecast to congeal and strengthen into an MCS, racing southeast and into Michigan. I`ve adjusted timing the TAFs with the latest guidance. The strength of these stroms will be monitored closely and amendments will be made as needed. Lastly, additional storms are possible late this afternoon, depending on the evolution of the aformentioned MCS. Confidence is low, so a dry late-afternoon TAF is offered for the time being. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...Small Craft Advisory until 2 PM EDT this afternoon for LMZ043- 046. && $$ UPDATE...Steinwedel DISCUSSION...Norman AVIATION...Brown