Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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347 FXUS63 KGRR 102321 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 721 PM EDT Fri May 10 2024 .KEY MESSAGES... - Cloud forecast for aurora tonight - Showers moving through tonight into Saturday - Back to warm springlike pattern starting Sunday - Rain chances on Monday and Friday && .DISCUSSION... Issued at 457 PM EDT Fri May 10 2024 - Cloud forecast for aurora tonight Chances of an aurora are high tonight given the levels of various indices that are monitored like the planetary kP index. Values have reached 8 this afternoon which is a high confidence event over Lower Michigan. The issue for folks in Southwest Lower Michigan is the amount of clear skies we will have between reaching darkness and before clouds advance into the area. For instance, sunset in Grand Rapids is 853 pm this evening, but we do not get to complete darkness until around 1005 pm. Clouds per the HREF are advancing into Kent County going on midnight. So, the opportunity in the metro area may be a couple of hours. To the northwest towards Ludington, clouds come in even earlier which may spoil the potential show. Best chances may be for an hour or two from near Grand Rapids off to the south and east. Bottom line, once it gets dark its worth a look to see if skies are clear. Given the magnitude of this event, auroras are likely through the weekend. Saturday night will be a better chance at mainly clear skies. We will have to see whether the aurora chances continue into Saturday night. Monitoring the kP index online may be the best way to see if conditions remain favorable. Anything over a 6 is good for Lower Michigan. 7 to 8 values are much better. The auroral oval forecast is another way to monitor trends online. Final point...the band of clouds in Wisconsin advancing our direction for tonight is fairly narrow, so it may be worth trying to be opportunistic overnight to look for breaks in the cloud cover. - Showers moving through tonight into Saturday A compact system will sweep through Southwest Lower Michigan tonight and into Saturday morning. It looks to have increased in speed and we will likely dry out quicker for Saturday afternoon and evening than was expected yesterday. We have high pops overnight when the main band of rain showers moves through. Precipitation amounts look to be on the order of a tenth or two, so fairly light. Any threat for thunder looks to be fairly small given the time the precipitation is moving through away from the diurnal max. An isolated thunderstorm cannot be ruled out tonight however. Saturday night looks to be mainly clear and cool. Patchy frost is possible across Central Lower Michigan into Sunday morning, but at this point holding off on any headline as our current lows are mainly upper 30s. - Back to warm springlike pattern starting Sunday Deep upper troughing over the eastern CONUS will steadily deamplify starting late this weekend and generally continue through next week. This will gradually shift our mean flow away from the chilly northwesterlies we`re in this weekend, and move in favor of a more typical springlike southwesterly flow pattern. This will allow the return of warmer 850 temperatures into Lower Michigan. Normal high temperatures this time of year are in the upper 60s in Grand Rapids, but we`ll spend much of the upcoming week in the lower to mid 70s. - Rain chances on Monday and Friday There are two main chances for rain for next week. Late Sunday night and during the day Monday Lower Michigan will get pinched between a shortwave passing to our north and a stronger 500 mb wave sliding eastward out of Missouri. While we could see a few showers from the northern wave Sunday night and Monday morning, we`re more likely to see areas of rain form as the southern wave moves through later during the day on Monday. This is not looking like a heavy rainmaker at all, it`ll probably be enough to make for a gloomy wet day for many folks on Monday. Much of the middle part of the week will be very pleasant as we come under the influence of some upper ridging moving into our area from the west. For late in the week, we start to bring a more robust upper trough through the Great Lakes. As it encounters the warm and somewhat humid air that will have worked in here during the midweek period, we`ll need to be alert for thunderstorm potential late next week as better dynamics work their way into the area. Overall, this is a typical springlike pattern and it looks like the classic battle between cool and warm air will continue in our area over the next 10 days. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 721 PM EDT Fri May 10 2024 VFR conditions will continue through mid to late evening. A line of showers will move through overnight and some lower MVFR ceilings are expected after midnight especially at the northern terminals. Potential for isolated storms is too low to warrant inclusion in any of the terminal forecasts. Northwest winds will increase and gust to around 20-25 kts Saturday. && .MARINE... Issued at 346 PM EDT Fri May 10 2024 Have opted to not issue a Small Craft Advisory tonight into Saturday, but it will be close. A increase in southwest winds will occur for a couple hours this evening, followed by a cold front sweeping through overnight. Winds may remain elevated on Saturday for a time as well. The issue with this potential event is that winds do not stay up over a longer duration to produce a substantial wave field. The best opportunity may be Saturday morning behind the cold front. The WaveWatch3 produces a couple hours of waves around 4 feet midday on Saturday before they subside once again. Given the borderline wave heights and short duration have held off on the Small Craft Advisory for now. If these levels are maintained we may need to issue a SCA for a time on Saturday. Sunday looks like a better chance at needing a Small Craft Advisory headline as winds ramp up out of the south. The mid lake BUFKIT point even shows a brief period of gales being possible. Given this is a warm air advection event have low confidence in gales. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Duke/AMD AVIATION...Laurens MARINE...Duke