088 FXUS63 KGRR 080723 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 323 AM EDT Fri Oct 8 2021 LATEST UPDATE... Synopsis/Discussion/Marine .SYNOPSIS... Issued at 323 AM EDT Fri Oct 8 2021 - Warmer than normal into next weekend - Showers and isolated thunderstorms into tonight - Dry most of Saturday and Sunday but storms still possible - Fall storm Monday night into Tuesday - Stronger fall storm Thursday then a little cooler && .DISCUSSION...(Today through next Thursday) Issued at 323 AM EDT Fri Oct 8 2021 - Warmer than normal into next weekend Our warmer than normal weather pattern will continue through this week into the following week. I have to admit through, from Friday on, it will be significantly closer to normal, but it will still be warmer than normal even so. These conditions will continue into the third week of October. What is causing this is persistent strongly negative mid level height anomalies from northern Russia (near the Arctic Ocean), across Alaska into the Gulf of Alaska to near the California Coast. That results in above normal heights over most of central and eastern North America. Both the GFS, the ECMWF and numerous ensemble runs of those models continue to show this pattern persisting. This pattern also creates a storm track just west of us during this time frame. - Showers and isolated thunderstorms into tonight In the shorter term, we have an ejecting closed upper low that will slowly open up as it's center crossed northern lower Michigan early tonight. The upper trough associated with this system is east of our CWA by mid morning Saturday. This puts our area in the prime area for convection today as the upper level jet axis crosses our area from southwest to northeast. The low level jet axis stays over eastern lower Michigan into Lake Huron during the day but core of the highest winds lifts northward with time. Given the cold air aloft and very moist air over us (precipitable water around 1.5 inches) plus MU capes near 1500 j/kg this all says showers and thunderstorms with locally heavy rainfall. Since the low level jet is really near and east of I-75 today, it makes sense there would be an axis of convection from say Jackson to Lansing to Clare. With some lake breeze wind convergence we would get a second band of convection between US-31 and US-131 too. I do not see severe storms all that likely given the deep layer shear is under 20 knots today. Mostly we will see slow moving storms dump locally heavy rainfall. That heavy rain will be very limited in area, most locations will get less than a 1/4 inch of rain today into this evening. Tonight the upper trough axis will force the convection to move to the eastern sections of the CWA, and with sunset, there will be less instability so convection will be limited. - Dry most of Saturday and Sunday but storms still possible The current system moves out of our area Saturday and upper level ridging moves in. That would normal bring us surface high pressure. However in this case we have another ejecting shortwave from the Southwest CONUS. That will mean we largely stay in warm and moist air even so. Still the clouds should break up some. As the next system quickly lifts north and east of us Sunday a sort of warm front could cause showers and thunderstorms north of I-96 Saturday night into early Sunday. Otherwise most of Saturday and Sunday will be dry for most of our CWA. With a good surge of warm air ahead of that next system Sunday could be quite warm, highs may be near 80 near and south of I-96. Record highs are in the mid 80s then so it does not seem we would get quite that warm. - Fall storm Monday night into Tuesday Now, there is a strong height fall center over the Bering Sea, this is the currently the strongest such thing in the entire Northern Hemisphere actually. That center dives quickly into the western CONUS by Tuesday. That in turn ejects the system that is currently there into the southern plains were it quickly becomes a negative tilt upper wave that then quickly closes off another deep, closed upper low. That system moves through the western Great Lake Monday night into Tuesday. I could see some decent thunderstorms and a lot of wind with this system as it moves through. Given all the wind with it, and deep, warm moist flow from the Gulf, strong storms would be possible depending on the timing of the front. I would expect gales on Lake Michigan from this storm. - Stronger fall storm Thursday then a little cooler Of course, we must remember that, that system is not the main show, it is the system behind that one that is the stronger storm. That one will come out into the Plains on Wednesday as an even more impressive fall storm and significantly more surface wind. This will be another one for gales on Lake Michigan and possibly strong to severe storms for our area. This storm though will have something the other storms has not had for us, COLD AIR! So even through as I said in the first paragraph, that the upper trough will remain west of us through the third week of October, this storm will bring in some 850 temperature that are negative. This could bring our air temperatures cold enough for highs in the 50s and lows in the 30s for a few days (which by then would be close to normal actually) but that cold push will be brief as there are more western storms heading toward us to put us back in the warm air again. Point being we may see get near freezing over northern sections Saturday morning, once we are deeper in the cold air (if only for a day or so). && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 118 AM EDT Fri Oct 8 2021 Widespread LIFR stratus clouds are in place, with some light MVFR fog across the area. There are a few isolated breaks, but the fog satellite imagery shows the extensive cloud cover pretty well. This will continue through sunrise, before the conditions will slowly improve late this morning and this afternoon. We expect a few scattered showers will start to develop around the terminals toward and after about 09z this morning. Can not rule out a rumble of thunder, but the instability will be fairly limited early. Showers and storms will develop with the heating of the day and the wave moving overhead. The best chance of lightning/thunder will be after 18z and prior to 00z. Rain showers will likely gradually come to an end later this evening. We do not expect fog and stratus to be an issue tonight with the area being behind the low and drier air trying to move in. && .MARINE... Issued at 323 AM EDT Fri Oct 8 2021 This will be an active storm week for us. We have the system missing us to the west on Sunday, but it will be close enough even so to bring winds strong enough for a small craft advisory if not a low end gale warning Sunday. Then there is that system Monday night into Tuesday, the winds will be strong with the Monday night into Tuesday system than the Sunday system. I would expect gales with at one. The storm behind that for the Thursday time frame will be stronger yet, so I would expect more gales again. This may be a good week not to do much boating in the near shore waters! && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ SYNOPSIS...WDM DISCUSSION...WDM AVIATION...NJJ MARINE...WDM