Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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203 FXUS63 KGRR 140150 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 950 PM EDT Thu Jun 13 2024 .KEY MESSAGES... - Low/Medium Confidence on Severe Storms this evening - Near Record Heat and Bouts of Heavy Rain possible next week && .UPDATE... Issued at 941 PM EDT Thu Jun 13 2024 The cold front wast dropping southward into northern parts of the CWA near KRQB and KMOP. South of it the atmosphere remains unstable so we could see an isolated storm or two develop. High res models support most locations remaining dry though so we will trend the forecast towards slightly lower POPs. Current satellite trends support less cloud cover as well. Patchy fog may develop as well as the recent rain has level southern parts of the CWA with elevated surface dewpoints at this time. With less cloud cover around we will see additional radiational cooling which could also enhance the fog risk. && .DISCUSSION... Issued at 257 PM EDT Thu Jun 13 2024 - Low/Medium Confidence on Severe Storms this evening Current radar trends show a line of strong to severe storms across the Michigan U.P. along the cold front, while convection is just starting to initiate across northern Illinois into western Lower Michigan in an area of low level convergence combined with mid- upper level ascent in the pre-frontal trough. We expect that storms will initiate and begin to fill in across central and southern Lower Michigan in the area of agitated cu from Ottawa County to Gratiot County and then slowly drift southeast ahead of the cold front, clearing the southeast forecast area by 9 pm. Downdraft potential energy and deep layer shear is sufficient for a threat of at least isolated damaging winds, which could become more widespread along an organized line of storms this evening as the convection moves into a more unstable airmass that has not been modified by Lake Michigan. That "lake shadow" effect could inhibit stronger convection across the central forecast area, decreasing the extent of severe storms there. The cold front comes through later tonight with fair and cooler weather for Friday and Friday night. - Near Record Heat and Bouts of Heavy Rain possible next week An upper level ridge will be building over the Great Lake region through the weekend and through mid next week. The biggest concern through this timeframe will be the building heat. Temperatures may approach record high temperatures. The hottest day should be Monday the 17th. Lansing, Kalamazoo and Battle Creek are currently forecasted to be at or close to records. Grand Rapids current max temp for Monday the 17th is within two degrees. Current record for Grand Rapids is 95 (1994). The last time Grand Rapids airport reached 95 or greater was June 21st, 2022. This is expected to be the first period of 90 degrees or more for this year. One of the concerns is the duration of the heat. There are potentially three to five days in the 90s from Sunday through Thursday. Lows through this period stay around 70 degrees so maximum low temperature records are at risk as well from being broken. There is the potential through this period, Sunday through Tuesday, that several Mesoscale Convective Systems (MCS) move through the Great Lakes. The latest EC/GFS along with ensemble means are trending toward a dome of High pressure setting up over the southeast which will force moisture to stream over this high through the region which could bring a steady stream of moisture along with the warm air. So while periods of showers will be possible the heat and humidity could create heat indices near 100. This could allow for an extended period of Heat Advisory Criteria. As far as precipitation goes there is enough spatiotemporal variability to not have large pops in any one period. However, latest ensembles show a multi day period of +1 to +2 anomalous PWATS over Michigan with PWATS upwards of 1.5 inches through this timeframe. So there could be periods of showers/storms possible late Sunday and late Monday. Given the hot/humid air mass, and given the previously mentioned PWATS, heavy rain is a consideration. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 743 PM EDT Thu Jun 13 2024 VFR conditions are ongoing at all terminals this evening. Showers and thunderstorms from earlier this afternoon have exited to the south. VFR is expected to continue for MKG, LAN, and GRR for the entire TAF window. Heavy rain from this afternoon at AZO and BTL will likely lead to a period of MVFR fog and ceilings early Friday morning dissipating after sunrise. At JXN, confidence is low in fog or low stratus potential so did not include visibility or ceiling restrictions with this package. Locally IFR ceilings or fog cannot be ruled out at these three sites, but confidence is too low to justify inclusion of IFR. SCT or lower cirrus will be the main source of cloud cover Friday. West to southwest winds will become northerly Friday, remaining below 10 knots during the TAF window. && .MARINE... Issued at 257 PM EDT Thu Jun 13 2024 Strong thunderstorms this afternoon and evening could bring locally strong winds to 50 knots, hail and higher waves. Otherwise, southwest winds to 20 knots this afternoon will decrease overnight. Then winds will go north behind a cold front on Friday to 20 knots and some choppy waves around Big and Little Sable Points. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ UPDATE...MJS DISCUSSION...Ostuno/Ceru AVIATION...Thomas MARINE...Ostuno