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Displaying AFOS PIL: AFDGRR Received: 2019-01-11 17:49 UTC
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065 FXUS63 KGRR 111749 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 1249 PM EST Fri Jan 11 2019 LATEST UPDATE... Aviation .SYNOPSIS... Issued at 300 AM EST Fri Jan 11 2019 - A few light snow showers are possible this afternoon and evening mainly along and northwest of a line from Holland to Evart. - While the brunt of snow associated with a weakening low pressure system will stay south of Lower Michigan Saturday, there are hints that light lake effect snow off Lake Huron may make it as far west as central Lower Michigan Saturday evening. - There is an increasing signal that the pattern will become active toward the end of next week. && .DISCUSSION...(Today through next Thursday) Issued at 300 AM EST Fri Jan 11 2019 Quiet weather has returned to Lower Michigan with really no impactful weather expected in the next few days. There may be a few light snow showers this afternoon and evening mainly west of a line from Holland to Evart associated with southwest flow and shallow moisture off Lake Michigan, but minimal accumulations are expected. The low pressure system expected to bring wintry weather to portions of Iowa, Illinois, and Indiana Saturday is still poised to stay well south of Lower Michigan thanks to weakening upper-level support and a dry low-level airmass supplied by a high pressure system to our north. We were happy to see the ECMWF EPS backed off significantly on precipitation potential along I-94, building our confidence that the system will indeed stay to our south. However there'll likely be a tight gradient in snowfall along the northern edge of the system somewhere near the Michigan/Indiana border. Interestingly the 00Z suite of high resolution model guidance has started to hint at the potential for a mesolow or two to develop over southern Lake Huron Saturday morning and drift westward within the broad cyclonic flow of the low to our south. Climatologically speaking, it's pretty rare for lake-effect precipitation off Lake Huron to reach western Lower Michigan, but the lake-induced instability and wind direction will certainly be favorable (not to mention the concavity of Lake Huron), and mesolows tend to be more organized than your average lake effect snow shower. Thus, it's feasible that at the least flurries will make it to Clare, Isabella, Osceola, and Mecosta counties with snow showers not out of question Saturday night. Impacts would still be limited, however, as the mesolows (should they indeed develop) would be weakening as they work their way into our area. Sunday through Tuesday still look quiet and unseasonable warm with highs in the low to mid 30s and ample opportunities to get a peek of the sun. Forecast deterministic and ensemble guidance is in fair agreement that a cold front will sweep through the Great Lakes around the Wednesday timeframe. While sufficient lake-induced instability will be present for the development of snow showers, the wind direction may prove detrimental at least for Lower Michigan with the favored zone setting up in northwestern Indiana (if not on the western side of the lake). The pattern then may become rather interesting toward the end of next week as a reinforcing surge of cold air takes aim at the eastern United States. While differences exist within deterministic and ensemble model guidance on the exact details (maybe a storm system or uptick in LES around the January 20th timeframe?), there is definitely a signal that the upper-level pattern will become decidedly more active if not wintry for the end of January. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) Issued at 1247 PM EST Fri Jan 11 2019 Most of the sites are VFR and will remain that way through 12z. The exception is closer to the lake shore where cigs around 1500 ft were noted. All sites should become VFR by 00z or so. An approaching low will push MVFR cigs north toward I-94 tomorrow and affect AZO/BTL/JXN late morning. Any light snow there should hold off until after 18z. && .MARINE... Issued at 300 AM EST Fri Jan 11 2019 Winds and waves will remain below 21 kts and 4 ft, respectively, through early next week. Conditions may become hazardous for small crafts thereafter. && .HYDROLOGY... Issued at 330 PM EST Wed Jan 9 2019 Water levels are generally above normal for this time of year, but this will be changing this week with the return to winter temperatures. Precipitation will be in the form of snow, thus a trend toward dropping water levels is expected to take hold by the week's end across most of the rivers in West Michigan. Water temperatures are generally in the mid to upper 30s, except on the Muskegon River where lower 30s can be found. These values will fall through the weekend, and ice formation may be possible on rivers by next week. The Maple River at Maple Rapids continues to hover near bankfull, and is expected to remain around this level before a dropping trend starts by this weekend. No flooding is expected. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ SYNOPSIS...Borchardt DISCUSSION...Borchardt AVIATION...04 HYDROLOGY...63 MARINE...Borchardt