Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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258 FXUS63 KIWX 050717 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 317 AM EDT Fri Jul 5 2024 .KEY MESSAGES... - A chance for showers and thunderstorms exist today with the greatest chance occurring during the afternoon. Gusty winds and locally heavy rain are the main threats from storms. - More comfortable humidity levels and leaning dry for this weekend. - Our next chance for showers and thunderstorms occurs between n later Monday afternoon and much of Tuesday. && .DISCUSSION... Issued at 309 AM EDT Fri Jul 5 2024 With a Pacific jet across the mid and northern tier of the CONUS, an upper low and associated strong vort max enter the Great Lakes region today. This increased forcing pushes a cold front through the area. With a subtropical high pressure system in the Gulf States, the cold front is cut off from better moisture and that keeps greater than 70s dew points south of the area today. Even still, the ECMWF has greater than 1000 J/kg of MUCAPE and 30 kts of effective shear for storms to work with. In looking at soundings and hodographs on the NAM3k and HRRR, gusty to near-damaging winds could be possible with DCAPE over 1000 J/kg, along with some small hail likely made smaller as a result of the wetter low levels of the sounding. Shear appears straight likely eliminating the tornado potential. Locally heavy rainfall will also be possible. Look for showers and potentially a few thunderstorms to arrive this morning as an initial area of vorticity comes in from the southwest. But the better storm chance appears to be after 18z between our western border and IN-15, just out in front of the cold front, through around 3z in our east. Still looks like one of the better areas for stronger storms based on ingredients is in the I-69 corridor. The better moisture is gutted behind the cold front for Saturday and that likely keeps the rain chances on the low side to potentially dry despite some delayed areas of vorticity moving through in the flow. A cooler air mass comes in, but models develop showers more in the morning, which is before the better low level lapse rates develop in the afternoon. So this would likely restrict the rain intensity and keep thunderstorms at bay. High temperatures are expected to be in the mid 70s to around 80 degrees, which is slightly below average for this time of year. Surface high pressure begins edging into the area Saturday afternoon and evening and moves east of the area Sunday morning and this provides a time of dry weather through this period. Then, from Sunday afternoon to Monday morning, weak areas of vorticity move southwest to northeast with our Lake MI-adjacent counties potentially on the eastern periphery of their cross-hairs. Will have slight to chance PoPs in this area during this time period, but am not expecting any substantial rain from these opportunities given how weak the forcing is. Finally, better forcing arrives Monday afternoon into Tuesday as a Pacific wave deepens the trough. The best time for instability is Monday evening and Tuesday morning so will allow for thunderstorms during that time frame. The aforementioned trough departs for Wednesday and Thursday, which points to low chances for rain, if at all. Aside from Monday, which has highs slightly above normal, in the upper 80s, highs in the low to mid 80s will be common Tuesday through Thursday, which is right around normal. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 155 AM EDT Fri Jul 5 2024 Quite a pot-pourri of conditions this forecast period, starting with BR/FG troubles for the first half (MVFR to IFR likely, possibly LIFR at KFWA), and then showers/storms this morning and afternoon. Visibilities around the area as of this writing range from 1/4 mile all the way up to 10 miles, likely thanks to firework smoke and low level moisture trapped beneath the inversion. Skies are clear in many locations as well, helping to radiate better with the calm winds. However, a majority of the sites as of the latest observations have 1/4 to 4SM visibility. KSBN and KFWA have fluctuated between around 2 miles and 6 miles, and suspect it will bounce around until sunrise. At KFWA I suspect we have the better potential to drop to around 1 mile or even less towards 12z, so have tempos in for that. Otherwise our first round of possible showers would be this morning as a decaying line of showers and storms moves into the area. All but one of the models suggest the showers will die before reaching KFWA, but most have it reaching KSBN (albeit much weaker). Left thunder out for now as we`ll really be struggling for instability-will monitor lightning trends and adjust as needed. Later in the afternoon showers and storms are possible, but most of the guidance keeps the better potential east of KSBN, but KFWA looks to see showers and storms in the 18-00z window. MVFR to VFR conditions are most likely in thunderstorms, with the occasional drops to 2SM (IFR) possible in heaviest showers/storms. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None. && $$ DISCUSSION...Roller AVIATION...MCD