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Displaying AFOS PIL: AFDGRR Received: 2020-08-14 05:27 UTC
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265 FXUS63 KGRR 140527 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 127 AM EDT Fri Aug 14 2020 LATEST UPDATE... Aviation .SYNOPSIS... Issued at 307 PM EDT Thu Aug 13 2020 - Very warm with a chance of an afternoon shower/storm Friday and Saturday - Best storm chances Saturday night and Sunday morning - Much cooler and mostly dry much of next week && .DISCUSSION...(This evening through next Thursday) Issued at 307 PM EDT Thu Aug 13 2020 -- Very warm with a chance of an afternoon shower/storm Friday and Saturday -- Most areas should stay dry through early Saturday. High cirrus clouds are the main feature over the area this afternoon, with a only a few cumulus developing with ridging holding in control. We expect that a few isolated showers/storms will be possible across the SE portion of the area toward Battle Creek, Lansing, and Jackson later Friday afternoon. That portion of the area will be on the NW periphery of a weak sfc wave trying to lift NNW from OH. This wave will have LI/s of -2 to -3C to work with in popping an afternoon shower or storm. Severe weather is not expected as CAPE profiles are rather thin, and shear is quite limited with a weak flow up through the column. The small chance of a shower or storm will reappear Saturday afternoon for most of the area away from Lake Michigan. The weak surface trough will rotate at little further NW, and combine with the diurnal trough over the land area to produce some convergence to help produce the chance. Instability will be a little better with dew points coming up a bit. Most areas will likely stay dry. -- Best storm chances Saturday night and Sunday morning -- The timing of the best storm chances for the area remains later Saturday night and Sunday morning. This will be when we see the cold front push through the area. Obviously, this is not the optimal time for stronger storms, due to a lack of diurnal heating. Moisture pooling along the front will help to feed some instability, along with a short wave that will be diving in. The models do indicate that we will have a little better forcing around with the short wave diving just a little further south than indicated 24 hours ago. This will help keep a legit chance of storms in for the area. Upper winds with the short wave will help the shear profiles a bit. Lacking better instability seems to be the limiting factor with this system. This does look like it should mostly be clear of the area by 18z Sunday. -- Much cooler and mostly dry much of next week -- We will become under the influence of general trough aloft for much of next week. This results in much cooler temperatures, and a mainly dry forecast. The latest model trends keep the upper jet mainly north and northeast of the area, on the anti-cyclonic side of the jet. A few isolated showers can not be ruled out, especially on Monday with a short wave not far away. However, ridging in the lower levels being produced by the upper ridge to our west should keep most of the area dry most of the time. In addition, moisture will be quite limited once it gets swept out on Sunday. Temperatures will only get into the mid 70s on Monday, and will slowly rebound to the lower 80s by Thursday. && .AVIATION...(For the 06Z TAFS through 06Z Friday night) Issued at 127 AM EDT Fri Aug 14 2020 Some patchy/shallow fog is possible through sunrise, particularly at JXN which is a site more prone to radiation fog. Otherwise VFR conditions generally prevailing overnight and Friday. Widely scattered showers and a few tstms are expected to develop toward 18Z Friday around JXN, spreading west and north from there through early evening before dissipating. If one of these cells passes over a terminal, some brief reductions in vsbys are possible. Sfc winds mainly easterly at 5-10 kts. The risk for thunder is highest at JXN and LAN Friday so included VCTS at these sites and VCSH at the other terminals (except at MKG which should stay dry). That said, instability may be sufficient for a tstm west of JXN/LAN too Friday afternoon so it's something to watch. && .MARINE... Issued at 307 PM EDT Thu Aug 13 2020 We do not anticipate any headlines being needed likely until the late Sunday-Monday time frame. Offshore winds will dominate the next couple of days, with winds becoming onshore for the late afternoon and evening hours due to the development of the lake breeze. Winds will start to come up Saturday night ahead of the incoming cold front. For now, the winds look to stay below headline criteria. The better winds will arrive behind the front, and continue through Monday. Headlines will likely be needed with the lake waters near their annual peak warmth, and with the air mass fairly cool coming in. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ SYNOPSIS...NJJ DISCUSSION...NJJ AVIATION...Meade MARINE...NJJ