Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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184 FXUS63 KIWX 060034 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 834 PM EDT Sun May 5 2024 .KEY MESSAGES... - Primarily dry conditions will persist through Monday night but there is a low chance of rain south of US-30 late Monday. - Several rounds of thunderstorms are possible Tuesday through Wednesday night. Some of these storms may be capable of producing large hail and damaging winds. However, confidence in timing, placement, and strength remains low. - Cooler weather returns to end the week with periodic additional chances for light rain. && .UPDATE... Issued at 830 PM EDT Sun May 5 2024 Low clouds have largely eroded across the area, all but the far northeast. Low clouds have been replaced by high clouds with more extensive high cloudiness lifting into the area overnight. Near term guidance low level RH progs do suggest some potential of some stratus redevelopment downstream of the eastern Great Lakes with good deal of lingering low level moisture beneath subsidence inversion. Previous forecast has these trends in hand and no major changes to near term will be made this evening. && .DISCUSSION... Issued at 250 PM EDT Sun May 5 2024 Dry/tranquil weather will persist through Mon morning. Weak/diffuse cold front has largely cleared our area with stubborn postfrontal stratus deck holding in our northern counties. Can`t entirely rule out a sprinkle in our far E/SE but best chances remain outside of our area. Overnight cloud forecast is tricky with most guidance suggesting clearing by sunset. However, models have struggled with this cloud cover over the past 12 hours and confidence is not high. Will therefore hold with partly cloudy skies and lows generally around 50F. Cooler temps possible if clouds scatter entirely. Broad midlevel shortwave will lift into the Ohio Valley tomorrow but sharp midlevel ridging/AVA will maintain strong subsidence over the Great Lakes. Still some uncertainty exactly how far north showers survive tomorrow. General trend has been to keep precip just to our south given weak 850mb theta-e advection in our area. There are a few outliers though that suggest light showers sneaking to about the US-30 corridor. Have therefore stayed very close to inherited low PoP`s confined to our south. No impacts expected either way as profiles appear too stable to support thunder and any rain will be very light. Primary focus continues to be on Tue-Wed for potential severe weather and heavy rain concerns as deep western CONUS upper low lifts NE toward the Great Lakes. This will actually occur in piecemeal fashion as another strong Pacific jet/trough comes onshore Monday and forces the development of a very large upper low over the Northern Plains/Rockies that will also eject eastward in a piecemeal fashion later this week. Unsurprisingly models are struggling with exact details in this complicated pattern and confidence remains on the low side. Still expect the initial wave and associated warm front to lift through the area late morning-early afternoon Tue. Models have slowed this initial wave a bit which complicates the severe weather forecast. A later arrival could result in that being the primary "show" (which could itself feature large hail and damaging winds given steep midlevel lapse rates, moderate instability of 2000 J/kg SBCAPE, and a strongly sheared environment). Early arrival could limit the instability but if the slower trends continue that will increase the risk with round 1. If that is the case that will in turn limit our potential for a second round during the evening hours though with primary focus for severe storms well to our south. After a break Tue night into early Wed we will watch the potential for another round of storms Wed evening-overnight as the primary upper low finally releases east. All ingredients for severe weather and flooding remain favorable given ample moisture advection on strong LLJ, high instability, and very strong shear. The question for Wed will be where exactly these ingredients come together with track of surface low dependent on exact evolution of upper low and likely some mesoscale influences from the day before. It is possible the surface low and associated highest severe risks remain to our south as suggested by the 12Z deterministic GFS and reflected in the SWODY4. However several models suggest a further north track that would impact our CWA. Bottomline...the ingredients are in place for potentially several rounds of strong/severe storms but details regarding exact timing, placement, and strength remain low. Continue to monitor the forecast closely as we narrow down these details in the coming days. Negative height anomalies persist over eastern Canada for much of the Thu-Sat period. This will result in cooler temps with periodic chances for light rain. Better moisture and associated instability is shunted out of our region though. Chances for generic thunderstorms (let alone strong storms) appear very low. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 830 PM EDT Sun May 5 2024 Earlier higher coverage stratus has been replaced by mainly high level clouds this evening. The last of more substantial stratus deck is confined to extreme NW Ohio as of 00Z. Some small signal still remains in guidance of some southwest expansion of stratus possible across northeast Indiana with flow trajectories off eastern Great Lakes, but confidence still remains quite low. Have maintained continuity from previous forecast with mention of some cigs in the 2- 3k ft range at KFWA early Monday morning. Otherwise, mainly high clouds overspread the area overnight into early Monday. An upper level trough shifting east-northeast from the southern Plains will have an accompanying precip shield that will remain south across the Ohio River valley. Some cigs in the 4-6k ft range are possible at KFWA on Monday on the northern periphery of a slowly northward advecting low level theta-e boundary, but expecting primarily VFR conditions Monday. Fairly stout gradient between Great Lakes anticyclone and sfc low across the Ohio Valley may produce a few easterly gusts into the 15 to 20 knot range Monday afternoon. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None. && $$ UPDATE...Marsili DISCUSSION...AGD AVIATION...Marsili