740 FXUS63 KGRR 120658 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 258 AM EDT Mon Oct 12 2026 .KEY MESSAGES... - A round of showers and non-severe storms tonight - Additional chances of rain into Friday - Cooling down Thursday and beyond && .DISCUSSION... Issued at 258 AM EDT Mon Oct 12 2026 - A round of showers and non-severe storms tonight We will see another very nice autumn day with temperatures actually quite warm by mid-October standards. The low clouds on the periphery of the remnants of "Isaias" from yesterday have moved out, allowing for much more sunshine, although it will become filtered with high clouds streaming in. 850 mb temps will warm from around 13C on Sunday, to almost 18C which will support highs near 80. The cold front currently north of the area will drop down into the area this evening and overnight as a short wave over the northern portion of the state pushes it overhead. Also ahead of the short wave and sfc low will be a 40 knot low level jet nose aimed right at the area. This moves in between 00z and 06z tonight. We would expect a good area of showers with embedded scattered storms. The storms are not expected to be severe as they will be elevated in nature (limiting wind and tornado potential) and mid level lapse rates neutral around 6.0 C/km and updraft strength will be limited with MU CAPEs a few hundred J/kg. - Additional chances of rain into Friday The showers and storms will move out before daybreak Tuesday as the short wave moves by, and the cold front sinks south of the area. The front will stall out as it becomes parallel to the upper flow with the cutoff low out west pumping up the ridge over the area. Much of Tuesday should remain dry with no organized short waves expected to move through. We do see the next short wave ejecting from the western low Tuesday night along the front, which will be by that time just north of the Ohio River valley. This sets up the best chance of rain across the south, closer to the front. We will be on the cool side of the front by then, so thunder chances will diminish a bit. The same thing happens around Thursday with the front even a tad further south. A better low is forecast to develop and move along the front, which will help bring a bit better rain chances into more of the area. Fast on the heels of the Thursday southern stream system, a strong northern stream wave will drop in by Friday and usher in much cooler air on fairly strong winds. This will bring another chance of rain with the front, and could produce some brief lake effect rain showers while the upper jet core briefly drops below our area. The upper trough then moves out quickly Friday, helping to bring high pressure to the area. This will clear things out for the weekend. - Cooling down Thursday and beyond We will see cooler air first arrive on Wednesday as the cold front sinks far enough south. Much cooler air will move in Thursday and Friday with more clouds and showers with the upper cold pool overhead. Highs may struggle to get out of the 50s. Temperatures will recover a bit then starting Sunday as return flow sets up on the backside of the ridge. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 132 AM EDT Mon Oct 12 2026 We are seeing some fog developing early this morning, especially further SE where clouds lingered much of the day and low level moisture lingers. We will see an increasing gradient from NW to SE that will help keep fog likely from becoming too dense. We do expect that KJXN will see IFR to LIFR. All of this will quickly burn off toward and after sunset. High clouds will rule much of the daylight then with no restrictions to visibilities allowing for VFR. Winds will gust a little bit up to about 20-24 knots. We will see clouds increase late in the day in the mid levels around 8-10k ft. These will give way to some shower development after dark from west to east. There is sufficient instability present from 02-06z, so added prob30 thunder to all sites for now. && .MARINE... Issued at 258 AM EDT Mon Oct 12 2026 We are expanding the Small Craft Advisory further north through our last marine zone. We are also extending the headline to start earlier this morning, and last a little longer this evening. High pressure is moving away from the area, and the next frontal system will be approaching to ramp up the southerly winds. The winds will be warm winds, so we will not see the full potential with a lot of the wind remaining elevated. There will be a short break then this evening and early tonight as the front leans in. The winds will increase again with a sfc low coming through and a good gradient on its periphery. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory from 9 AM this morning to 11 PM EDT this evening for LMZ847>849. && $$ DISCUSSION...NJJ AVIATION...NJJ MARINE...NJJ

NWS GRR Office Area Forecast Discussion