429 FXUS63 KABR 091800 AAB AFDABR Area Forecast Discussion...UPDATED National Weather Service Aberdeen SD 100 PM CDT Tue Oct 9 2018 .UPDATE... Issued at 1244 PM CDT Tue Oct 9 2018 See the updated aviation discussion below for the 18Z TAFs. UPDATE Issued at 1155 AM CDT Tue Oct 9 2018 Significant upper level low pressure trough shown on satellite this morning lifting north towards our region. Strong lift in advance of it shown by an expansive area of rain across Nebraska and Kansas. This will expand across our cwa through the afternoon and evening. Looking at the model thermal profiles, this should change over to snow by midnight west of the James Valley and after midnight into early Wednesday morning for the James Valley and east. The issue will be the dry slot in the far east tonight into Wednesday morning holding off the snow. With the higher elevations being cooler along with the strong lift and precipitation cooling, think it will change over to snow with several inches of accumulation expected. Therefore, have expanded the Winter Weather Advisory to the east through Wednesday afternoon. && .SHORT TERM...(Today and Tonight) Issued at 349 AM CDT Tue Oct 9 2018 Areas of light rain are exiting to the north and west this morning, but drizzle is expected to persist through much of the day. Kept low slight chance pops in there as a result even though hi-res models are calling for completely dry periods. Radar is indicating enough drizzle coverage to merit some light accumulations. The real forecast challenge begins tonight. Sfc low pressure begins to trek northeast from Oklahoma through the Plains. At this time that low looks like it will be too far east to really affect this region, but it will help to wrap moisture back in on northeast to north flow. The precipitation chances are hinging on where the 700 mb low sets up. Models are notorious for having difficulty with placement and intensity of lows at this level. But, forcing relies on this low and 500 mb shortwaves. As such, it appears that there will be a band or two of snow that sets up in this forecast area. Exact locations and amounts are still uncertain. Latest guidance suggests the heaviest snowfall potential will be west of the James Valley tonight where 1-3 inches is possible before sunrise Wednesday. Blended WPC and CONSAll QPF and lowered "all snow" temps to 33 degrees to get a slightly lower accumulation throughout the event. With temperatures hovering at or slightly above freezing, there is some uncertainty about how much of this snow will stick, especially as we progress into the daytime hours on Wednesday. That said, this event will likely result in the first significant snow of the season and snow advisory headlines, at a minimum, are probable beginning tonight. .LONG TERM...(Wednesday through Monday) Issued at 349 AM CDT Tue Oct 9 2018 Storm system will be right over the region at the start of Wednesday, with plenty of precip spread across the area. 500 mb low is overhead with plenty of synoptic scale lift. Main surface low tracks well east of the area, allowing for cold air to drain southward across the northern plains. Thermal profiles do go cold enough for all snow by Wednesday morning from the Glacial Lakes area westward into central SD. As the day progresses, profiles get cold enough for snow over the eastern CWA as cold air advection continues. Models continue to trend upward in snow potential, with perhaps a couple inches possible from central through northeast SD. What will be very tricky with this system is just how much accumulates on roadways. We'll be dealing with surface temps at or a couple degrees above freezing through this event, so expect the bulk of accumulations on grassy areas. Just how much accumulates on roads is tough to determine. As this system departs, surface high pressure will be building into the western Dakotas by 12Z Thursday. This high moves across the area Thursday through Thursday night, and have dropped lows a couple degrees from inherited grids. Not much in the way of changes for latter portions of the forecast period vs what was inherited. Overall, temps look to stay on the chilly side as weak disturbances cross the region. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon) Issued at 1244 PM CDT Tue Oct 9 2018 Complex weather scenario shaping up in this forecast period as an early season winter storm moves into the region. Anticipate cigs will remain IFR through the period at all TAF sites. A more steady type rain begins to move in late this afternoon and early evening. Colder air drawn in overnight will change the rain to snow at KMBG and provide for a mixture at KPIR and KABR. A more brief period of all snow could be possible at KPIR and KABR early Wednesday morning. Eventually the mix works into KATY Wednesday morning. Visibilities will mostly be IFR but in heavier precip, LIFR vsbys will be possible...especially at KMBG and KABR. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...Winter Weather Advisory from midnight CDT /11 PM MDT/ tonight to 1 PM CDT /noon MDT/ Wednesday for SDZ003>005-009-010- 015>017-033>037-045-048-051. Winter Weather Advisory from midnight tonight to 7 PM CDT Wednesday for SDZ006>008-011-018-021. MN...None. && $$ UPDATE...Vipond SHORT TERM...Wise LONG TERM...TMT AVIATION...Vipond