431 FXUS63 KGRR 100552 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 152 AM EDT Wed Oct 10 2018 LATEST UPDATE... Aviation .SYNOPSIS... Issued at 310 PM EDT Tue Oct 9 2018 Isolated showers will continue this evening then rain will arrive on Wednesday afternoon, with heavy downpours possible Wednesday evening as a strong cold front comes through. Cold air is in place for the end of the week with frost and freezing temperatures possible Friday night. && .DISCUSSION...(This evening through next Tuesday) Issued at 310 PM EDT Tue Oct 9 2018 Similar to Monday evening, we will have some isolated showers with brief heavy downpours this evening before loss of instability after sunset. Then we wait for widespread rain on Wednesday afternoon as prefrontal trough moves east. Severe threat is limited by lack of instability based on extensive clouds and showers preceding narrow line of convection just ahead of the cold front. There is still a high wind threat with this feature if it gets organized along with heavy rains that could cause localized flooding. Lake effect rainshowers were added on Thursday and Thursday night as cyclonic flow and steep lapse rates combine to produce instability showers that should reach well inland on strong northwest flow. Frost and freeze headlines may be needed Friday night as sfc high is centered south of Lower Michigan. The airmass is cold enough that clearing would allow winds to decouple and frost to form. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 151 AM EDT Wed Oct 10 2018 An active next 24 hours is expected as a cold front will approach and push through the region. The TAF period is starting out with VFR conditions at all TAF sites but that will change today as showers spread in from the south midday. Around 15-16z, we expect showers to break out across the area becoming numerous in the afternoon. Ceilings will deteriorate fairly rapidly this afternoon as well, going from VFR at midday to IFR by evening. The low ceilings will sweep in from west to east. At this point have only included rain showers as the threat for thunder at any one TAF site is somewhat low. Thunder is certainly possible although confidence at this point in time is low. The rain will sweep east during the evening with ceilings steadily rising later tonight. Southerly winds of 10 to 20 knots today will shift to the southwest tonight after the cold front moves east. && .MARINE... Issued at 310 PM EDT Tue Oct 9 2018 A Small Craft Advisory will begin Wednesday morning north of Grand Haven then expand across the southern zones for late Wednesday night as strong southerly flow shifts to the west behind the cold front. && .HYDROLOGY... Issued at 1254 PM EDT Tue Oct 9 2018 The Kalamazoo and Grand Rivers continue to slowly drop as rainfall from last weekend works its way through the river system. Most small and medium-sized tributary streams are seeing falling water levels as well. The mainstem of the Muskegon river is rising slowly as the 1.0 to 1.5 inches of rain that fell yesterday morning drains into the river. A few showers and thunderstorms are possible across West Michigan this afternoon and evening, but are not expected to result in any flooding. The next chance for heavy area-wide rainfall arrives on Wednesday afternoon and evening as a strong cold front is set to move through our area. At this time it looks like many areas may see rainfall totals around 1 inch. This would cause the larger rivers to rise, but is not expected to cause any flooding on the mainstem rivers. Despite a few days break in the heavy rain, soils remain saturated and the smaller streams may see a quicker water level rise than normal. Sycamore Creek near Holt may rise to near bankfull by Thursday morning in response to Wednesday evening rainfall, but is not expected to reach flood stage. What will also need to be monitored is the potential for urban areas to be overwhelmed by heavy rainfall if the storms linger over the same areas repeatedly. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...Small Craft Advisory from 8 AM this morning to 8 PM EDT Thursday for LMZ847>849. && $$ SYNOPSIS...Ostuno DISCUSSION...Ostuno AVIATION...Duke HYDROLOGY...AMD MARINE...Ostuno