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Displaying AFOS PIL: AFDGRR Received: 2019-03-15 14:53 UTC
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367 FXUS63 KGRR 151453 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 1053 AM EDT Fri Mar 15 2019 LATEST UPDATE... Update .SYNOPSIS... Issued at 330 AM EDT Fri Mar 15 2019 - Rain showers becoming mixed with snow today, changing to all snow by tonight - Light snow accumulations of an inch or so possible, mainly near and west of Highway 131 - Slick roads possible late tonight and early Saturday morning as temperatures dip below freezing - Lengthy period of benign weather with seasonal temperatures next week && .UPDATE... Issued at 1053 AM EDT Fri Mar 15 2019 No major updates with the forecast this morning, other than bumping the pcpn chances up to account for the latest radar trends. Drizzle from earlier this morning, is transitioning to more solid rain showers as the DGZ becomes saturated this morning. The DGZ is both becoming saturated with deeper moisture coming in ahead of the next short wave, and due to temperatures aloft dropping in the saturated layer. We are now also starting to see pcpn changing over to some snow across the west with the temperatures aloft dropping. We will see more snow mix in this afternoon. We do not expect to see much accumulation this afternoon outside of a heavier burst with temps above freezing, and ground temps above freezing also. The best chance for some light accumulations will come this evening once we lose daylight, and before the short wave passes by. Some slick spots will become possible overnight as temps drop below freezing later. We do not expect this to cause significant impacts, especially with tomorrow morning being a weekend. && .DISCUSSION...(Today through next Thursday) Issued at 330 AM EDT Fri Mar 15 2019 Strong low level cold advection and cyclonic flow on the back side of the departing sfc low, paired with sharp mid level troughing and deep moisture, will lead to widespread showers today. Precipitation type is somewhat complicated however since sfc temperatures holding in the upper 30s supports mostly rain whereas H8 temps falling to around -7C this afternoon suggest a changeover to snow or a least a mixture developing. Typically in this type of late season lake effect/lake enhanced set-up, the higher elevations north of Big Rapids are favored for more in the way of snow. However snow could also be more favored at any location today during times of heavier precipitation rates. A vorticity maxima which tracks across far srn Lwr MI may very well support some more intense showers, particularly near and south of I-96. Either way, getting snow to stick on the roads and cause travel impacts today will be challenging given the recent warmth and rain. However a coating to one inch on the grass is certainly possible this afternoon. Tonight we should see a transition to more of a pure lake effect scenario, with cooler temperatures and nighttime promoting a changeover to all snow. Some light accumulations, generally under one inch, are possible near and west of Hwy 131. Some slick spots may develop overnight into Saturday morning, before sfc temps climb above freezing again Saturday afternoon. Chilly pattern persists all weekend as upper trough remains over the Great Lakes Rgn. A clipper low passing just south of the state late Saturday night and Sunday morning could produce a dusting of snow along and south of the I-94 corridor. Surface ridging and cool air mass looks to dominate through the middle part of next week, although a weak cold frontal passage on Tuesday night/Wednesday could produce some light precipitation. Temps appear to moderate toward the end of next week - with no impact weather expected at this time. && .AVIATION...(For the 12Z TAFS through 12Z Saturday morning) Issued at 752 AM EDT Fri Mar 15 2019 Widespread IFR to LIFR expected this morning as rain or a mix of rain and snow impacts the area. Conditions improving to MVFR after 18Z from west to east as main/widespread area of precip moves out. However scattered lake effect snow or mixed rain and snow showers will linger into tonight, so still some brief vsby reductions to IFR possible this afternoon and tonight. West winds of 15 to 25 kts today, dropping to 10 to 20 kts tonight. && .HYDROLOGY... Issued at 330 AM EDT Fri Mar 15 2019 The combination of 36-hour rainfall totals from one half inch to nearly two inches with the rapid melting of the snowpack over frozen ground has led to considerable run off and flooding mainly along and north of I-96 where emergency management officials report road closures due to high water. Area rivers have also experienced significant rises over the past 12 hours, with the Chippewa River at Mt. Pleasant, Maple River at Maple Rapids, Pine River at Alma already in minor flood stage. The Rogue River at Rockford and Grand River at Comstock Park and Robinson Township are expected to reach minor flood stage by this evening, with the Muskegon River at Bridgeton and Newaygo expected to reach minor flood stage Saturday. With these considerations in mind, an areal flood warning remains in effect for areas mainly north of I-96, river flood warnings where minor flooding is already occuring or likely to start within the next 24 hours, and a river flood watch remaining for the Muskegon River at Bridgeton and Newaygo. Most area rivers are expected to crest this weekend with a gradual decrease in water levels into early next week. Moderate flood stage is not expected to be met at any forecast point after the recent snowmelt/rainfall event. While low temperatures through this weekend and into early next week will at times fall into the upper teens to lower twenties, no significant ice build-up is currently forecasted. However, the recent mild temperatures and rainfall likely broke up the majority of ice in area rivers leading to a low but nonetheless still present threat for ice jams, especially on the White and Muskegon Chippewa basins. People with interests along rivers in Central Michigan should continue to be alert for rapid changes in river levels. && .GRR WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...NJJ SYNOPSIS...Meade DISCUSSION...Meade AVIATION...Meade HYDROLOGY...Borchardt