Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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446 FXUS63 KIWX 220952 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 552 AM EDT Wed May 22 2024 .KEY MESSAGES... - An isolated thunderstorm possible south of US Route 24 across far northeast Indiana and northwest Ohio this afternoon into this evening. Severe weather is not expected but an isolated strong storm is possible. - Less humid conditions overspread the area later today into tonight. - Periodic chances of showers and thunderstorms for much of the long term period, especially Friday and Sunday. && .DISCUSSION... Issued at 350 AM EDT Wed May 22 2024 Focus for today`s forecast will be additional chances of storms with a few showers and storms this morning, and a potential of an isolated storm later this afternoon into this evening across the far southeast. Small pockets of showers and isolated thunderstorms are ongoing this morning from southeast Illinois into south central Indiana. These showers and storms appear to have formed in left exit region of a 90 knot upper jet streak approaching from the southwest. Would expect these showers to track across southeast third of the area this morning, with a few stronger sub-severe gusts possible. A secondary area to possibly watch for isolated development is along cool front working its way across northeast Illinois. Some pooled low level moisture could be just enough to overcome stubborn weak cap for an isolated shower or thunderstorm as it works across the area later this morning into early afternoon. It does appear a lull in these rain chances will develop this afternoon as better pooled moisture shifts east of the area, and weak capping lingers. Some uncertainty this afternoon whether isolated convection may focus along the cold frontal boundary, or possibly immediately downstream near weak pre-frontal trough feature that could have slightly better low level moisture to overcome a weak cap. If the pre-frontal area is favored, any isolated convection would likely focus just east-southeast of the local area this afternoon. A decent westerly flow regime will persist today, and while better shear profiles are post- frontal, the cold front/pre-frontal zones should have 35-40 knots of deep layer shear and moderate instability to work with. However, with secondary upper trough still upstream and shearing out across NW IL/E IA, confidence in developing this isolated convection across the far southeast is on the low side given what should be fairly weak frontal/pre-frontal convergence fields. If convection is able to develop this afternoon, cannot rule out an isolated stronger storm across the far southeast. Good low level mixing will result in breezy conditions today, with strongest gusts across the far southeast where warmest sfc temps into the low to mid 80s are expected. High closer to the lakeshore may only reach around 70 behind the cool front. For tonight, it is possible some low coverage showers and storms develop south of US 24 with perhaps some response to the weak mid/upper level forcing with the wave shearing out across the southern Great Lakes. However, waning instability by this time should preclude a severe threat. Dry weather is expected overnight with noticeably cooler and less humid conditions. For Thursday, low level theta-e gradient will stall out across far southern portions of the forecast area. A low level anticyclone will begin to depart the area setting up a weak southerly return flow regime. This could interact with this moisture gradient for a low end chance of an isolated shower, but confidence in measurable precip continues to diminish Thursday and have confined slight chance mention to far south/southeast. The next upper level short wave of note for local area should be the negative upper height anomaly working across the Pacific Northwest this morning. Guidance is in reasonable agreement in favored track of this wave bypassing the area across the Upper Midwest, with the disturbance eventually reaching southern Manitoba late Friday. It does appear the Great Lakes upper ridge will be a bit stubborn once again to break down which would delay next fropa until Friday evening with the best chance of showers and storms. Portions of local area have been placed in Day 3 Marginal Risk of severe storms. Limiting factors to isolated severe weather appear to be possible later timing of best chances of storms and shear limitations given potential of Great Lakes mid/upper level ridging to be stubborn to break down. The first half of the weekend should feature primarily dry conditions in wake of Friday`s system, but pattern looks to remain active for latter parts of the holiday weekend as a fast moving eastern Pacific wave cuts across central CONUS into the Mid MS Rvr Valley by early Sunday. This could be a period to watch for stronger storms, but a good deal of uncertainty exists with how far north sfc reflection will make it. It is possible a decent instability gradient could be sprawled across the Ohio River Valley on Sunday. There does appear to at least be a good signal for precip for Sunday/Sunday night however. A modest shot of cooler air should filter back in for Monday/Tuesday with some scattered showers possibly lingering with indications of broad cyclonic flow across the Great Lakes. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 549 AM EDT Wed May 22 2024 On satellite, a band of stratocumulus clouds can be seen entering Indiana as of 10Z. Ceilings may drop as low as 3500 ft this morning, but should remain VFR. Southerly winds will be gusty this morning and afternoon with gusts 25 to 30 kts possible. Winds become westerly after sunset tonight and diminish to 5 to 10 kts. Dry conditions and VFR ceilings prevail throughout much of today. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...Small Craft Advisory until 8 AM EDT this morning for LMZ043- 046. && $$ DISCUSSION...Marsili AVIATION...Johnson