Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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489 FXUS63 KGRR 060732 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 331 AM EDT Mon May 6 2024 .KEY MESSAGES... - Strong to possibly severe storms possible on Tuesday - Rain on Thursday and Saturday && .DISCUSSION... Issued at 331 AM EDT Mon May 6 2024 - Strong to possibly severe storms possible on Tuesday We are looking at a quiet period for the first 24-30 hours of the forecast for the area. High pressure at the surface is nearly overhead this morning, and the supporting upper ridge is west of the area. We are seeing a veil of high clouds lifting north over the area from a system that is centered south of the area near the Ohio River Valley. Dry air at the lower levels will keep our dry forecast going for today. The flow becoming a little more SE by later today along with the building heights will warm temperatures a few degrees over yesterday. The warmest temps will be found near the Lake Michigan shoreline with the offshore flow. Monday night and most of Tuesday morning will remain dry before rain chances increase quickly Tuesday afternoon from the SW. A piece of energy from the Severe weather outbreak expected over the Central Plains this afternoon and evening will be lifting toward the area. This part of the scenario looks rather benign as the wave and low level jet accompanying it will be weakening. It will hold together enough to bring a weakening band of showers and embedded thunder through the area centered around the early to mid-afternoon time frame. No severe weather is expected with this. What does bear watching though is potentially a second round of storms with a trend of increasingly favorable instability and shear for late Tuesday and maybe evening into early Tuesday night. In the wake of the initial showers and storms, we see a secondary short wave approach the area from the WSW around the parent low complex. Even though we see rain early that will temper sfc temperatures, instability builds to over 1,000 J/kg. This is the result of the short wave and associated colder mid level temps moving over the moist low levels with dew points in the 60s. Mid level winds will be increasing also, with 500 mb winds increasing to around 60 knots or so. Given the aforementioned instability, forcing arriving with the short wave, and deep layer shear increasing to over 50 knots, we could be looking at some strong to severe storms developing. Large hail looks to be the biggest threat with mid level lapse rates around 7.0C/km, and some of the storms likely to be rotating in the mid levels with the strong shear, and microbursts will be possible too. An isolated tornado can not be ruled out either at the leading edge of these storms with some backed wind flow, and some initially decent low level shear with the low level jet just starting to move away. - Rain on Thursday and Saturday A couple shortwave troughs will result in chances for showers peaking Thursday and Saturday. Confidence is above average with good model agreement and ensemble support. An area of mid-level frontogenesis north of a low pressure center tracking across the Ohio Valley will result in rain moving in late Wednesday night and continuing through Thursday afternoon. Northerly flow on the back side of the low will advect in a cool Canadian airmass. We will have to watch for frost potential if skies clear out Thursday night. Shortwave ridging should continue the fair weather for Friday into Friday night but clouds will be moving in after midnight as the next shortwave trough approaches, with rain moving back in for Saturday. There could be some diurnal enhancement of the showers Saturday along with some thunder given steep lapse rates as the upper trough axis moves through. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 128 AM EDT Mon May 6 2024 VFR conditions will prevail through tonight. The exception will be an area of MVFR conditions in thin layer of stratus clouds at JXN early this morning but those should break up by 12Z. Winds will be light and variable tonight and east or southeast around 10 knots on Monday. && .MARINE... Issued at 331 AM EDT Mon May 6 2024 && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Ostuno/NJJ AVIATION...Ostuno MARINE...NJJ