Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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819 FXUS63 KIWX 051338 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 938 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. && .UPDATE... Issued at 938 AM EDT Fri Jul 5 2024 Pre-frontal trough is located from roughly central Lk MI to Chicago and east of Bloomington IL. An line of showers has been attempting to slowly expand just ahead of this with very limited electrical activity noted as overall instability is quite paltry and with cloud cover ahead of the line, not overly optimistic on evolution of this area. Several CAMs actually weaken this line over the next couple of hours as denser cloud cover streaming NE ahead of a somewhat more organized cluster of storms over southern IN further impacts potential destablization along/east of I-69. Will monitor trends, but rather unimpressed by the setup this morning and even more concerned that little, if anything will develop this afternoon behind this area as the main cold front swings through. A few CAMs try to develop isolated showers/storms, which would have a fair amount of DCAPE to work with as noted by the overnight forecaster, but a lack of overall shear and lower lapse rates may limit organization. && .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 /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 700 AM EDT Fri Jul 5 2024 Predominantly VFR to MVFR conditions expected at the TAF sites today, with potential for IFR in any heavier showers/storms that develop today. BR and fog around the area this morning will diminish within the next hour or so, including at KFWA which as of 11z reporting 4-6SM. Otherwise, a cold front is on our western doorstep near Lake Michigan, and will progress eastward through the evening. There is a break in the showers/storms along the cold front, with areas between KMDW & KIKK currently dry. It`s questionable whether this area will fill in as the line moves eastward and we gain daytime heating/instability. Carried a VCSH through 17z, then have -SHRA VCTS with a prob30 for storms 20-24z. Similarly at KFWA earlier showers are uncertain, with increasing potential for isolated storms later in the afternoon to impact the terminals. Some of the guidance holds off until after 00z for storms, but I suspect the 19-23z time frame is our best chance. Later tonight potential MVFR deck will impact KSBN (KFWA after 12z). && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None. && $$ UPDATE...Fisher DISCUSSION...Roller AVIATION...MCD