pondo1000 Posted December 23, 2017 Share Posted December 23, 2017 9 minutes ago, snowlover2 said: Technically speaking from Dayton south in ILN CWA its the possibility of 3" and they are only saying 2. That being said in the past they would issue a WWA for the first widespread snowfall of the season and being Christmas I thought they would have and they eventually might. Yeah, just a SWS for now out of ILN for this area. 1-2 inches. Link to comment Share on other sites More sharing options...
Hoosier Posted December 23, 2017 Author Share Posted December 23, 2017 Solid discussion by LOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 310 PM CST Sat Dec 23 2017 .SHORT TERM... 308 PM CST Through Sunday... Main forecast concerns/challenges are with the snow expected early Sunday morning into Sunday evening across much of the CWA. Have expanded the winter weather advisory north into parts of the I-88 corridor, and have replaced the advisory for Lake IN and Porter counties with a warning for higher amounts likely owing to additional lake enhancement/effect. In the near term, relatively quiet conditions across the CWA. Cloud cover to the north has reached the northern half of the CWA, providing some partly sunny/partly cloudy skies. This will continue to pass through but likely further scatter with time. Precip not expected this afternoon into the evening. Trends today for most guidance coming in today have been for a more robust system to move across the region on Sunday. A system that will likely provide higher snowfall amounts than previously forecast across much of the CWA. Feeling fairly confident with placement and timing of highest snow amounts/rates, with this confidence also including this trend for higher snowfall amounts. This higher confidence in place also given the fact that this system was sampled by 12z RAOBs today. Large trough expected to swing/dig across the central CONUS tonight into Sunday with a fairly stout vort max likely pushing through the area. Out ahead of it, will see low/mid level flow back to more of a southerly direction, with a period of WAA helping to set the stage for developing snow over IA/MO and western IL after midnight tonight. Initial dry air in the lower levels should not have any trouble saturating, as this strongest forcing continues into the west/southwest CWA around the 3-4 AM CST time frame. Should see this light snow continue to expand and increase in intensity across most locations south of I80 around 6 AM CST, especially with vort max and deepening surface reflection swinging through. Further expansion of this snow into remaining areas in northern Illinois and northwest Indiana then expected through mid morning, with this large scale ascent spreading over the area. With this snow expected within the next 24 hours, able to get a glimpse into the mesoscale features which could be at play. Guidance becoming more focused not only with this system, but with the mesoscale features that are appearing likely to provide periods of higher intense snowfall and amounts. Deep area of frontogenesis expected to push through portions of east central IL and northwest Indiana during Sunday morning. As this occurs, will see low level flow become oriented off the lake with lake enhancement/effect becoming highly probable. This is especially the case by mid/late morning into midday, once again, with frontogenetical forcing increasing. This will likely provide increasing snowfall rates along the Kankakee river valley in the IL and IN up to locations near the lake in northwest Indiana. While this moderate to at times heavy snow occurs along this axis, light to at times moderate snow will occur elsewhere across the remaining CWA. A period of snowfall appearing likely for much of the day Sunday, with a window of more intense snow likely during the 14z-19z time frame. High snow efficiency also appearing probable with a deep dendritic growth zone, forcing likely situated in this zone for a longer period of time, and then with slant wise and upright instability likely in place. Several of the previously mentioned factors have led to growing concerns for higher amounts and possible larger impacts. So have increased snow amounts over much of the CWA with 1-3 inches possible north of I-88, 2-4 between I88 and I80, and with 3-6 south of I80 (especially in the Kankakee river valley in IL and IN). For locations near the lake in northwest Indiana, high delta Ts, High inversion heights, and strong low level convergence will help to offset a lacking longer fetch and produce higher amounts of 5-8 inches. Once again, have replaced the advisory in Lake IN and Porter counties with a warning with the expected higher amounts and with the fact that its quite possible for 1-2 inch hourly snowfall rates to occur at times. This would provide visibilities at or below 1/4 mile at times, and snow covered roads. Will need to continue to monitor this location, as it is definitely possible that I am under forecasting the snow amounts in this location. If more intense snow were to really set up in this location, its possible for isolated amounts of 8-12 inches somewhere in this area. For the Kankakee River Valley locations, have continued the Advisory but did strongly contemplate replacing the advisory with a warning from Livingston- Kankakee- Newton/Jasper counties and areas south. Although the more robust system and highlighted features will bring amounts higher closer to around 6 inches, felt that could keep the advisory going but mentioning these higher amounts and larger impacts. The higher amounts in this location will be due to mesoscale features that could still move slightly or change and with that also in mind, did not change to a warning. That being said, it is still possible for a stronger band to develop in these locations and if this were to occur, could see amounts in the 6-8 inch range. If this scenario were to seem more likely, than a change to a warning would be necessary. Evening/overnight updates will continue to look at this possibility. Did expand the advisory up to along the I-88 corridor, with periods of higher snow intensity also appearing possible in this locations. This along with amounts approaching 2-4 inches will provide some hazardous travel. With this reasoning, felt comfortable issuing an advisory in these locations. Expect snow to exit later in the afternoon, but with lake effect likely continue for locations in northwest Indiana. Will eventually see a weakening trend and more shift to the east of this development by the evening. Rodriguez Link to comment Share on other sites More sharing options...
cyclone77 Posted December 23, 2017 Share Posted December 23, 2017 Models are averaging about 0.1-0.13" for precip for the QCA and here. With the expected ratios that should get us somewhere in the 1.5-2.0" range for snowfall. I'll take it. Link to comment Share on other sites More sharing options...
Hoosier Posted December 23, 2017 Author Share Posted December 23, 2017 The HRRR Kuchera map has ratios even >20:1. That would be nice. With the DGZ, lift, moisture profiles and relatively light winds, 15:1-20:1 should be a good bet in many areas. The area that gets under the enhanced frontogenetic banding may have the best shot at something higher, at least in a transient sense. Link to comment Share on other sites More sharing options...
cyclone77 Posted December 23, 2017 Share Posted December 23, 2017 18z RGEM came in a little juicier. It has been slowly getting juicier with each run. Link to comment Share on other sites More sharing options...
Stebo Posted December 23, 2017 Share Posted December 23, 2017 Thinking 3-5 for metro Detroit especially the eastern and southern counties. Looks like a solid event. Link to comment Share on other sites More sharing options...
Hoosier Posted December 23, 2017 Author Share Posted December 23, 2017 HRRR picking up on the lake enhancement at the end of the run Link to comment Share on other sites More sharing options...
Kaner88 Posted December 23, 2017 Share Posted December 23, 2017 Looking forward to some mood flakes here by ORD. Staying home for the day so luckily won't have to mess with travel, but safe travels to those venturing out. Link to comment Share on other sites More sharing options...
RCNYILWX Posted December 23, 2017 Share Posted December 23, 2017 Yeah there are some that do the split. I'm not sure if they could just do it or if it would have to go through some sort of approval process. Maybe Ricky could provide some info.We would have to go through an approval process. Cook County would be ideal to split into separate zones because of its shape and it's something I'd like the office to do. I also think LaSalle County would be a candidate for a north half and south half zone because of its size. Sent from my SM-G935V using Tapatalk Link to comment Share on other sites More sharing options...
Radtechwxman Posted December 24, 2017 Share Posted December 24, 2017 Hrrr showing some banding features. Has me at 4.9in by 17z and still snowing. A few areas may hit minimal winter storm warning criteria but a high end advisory looking more likely now. This precip really gets a nice trowal/deformation zone look to it Link to comment Share on other sites More sharing options...
snowlover2 Posted December 24, 2017 Share Posted December 24, 2017 0z NAM snowfall. I do like that lollipop 3" area over me. Link to comment Share on other sites More sharing options...
homedis Posted December 24, 2017 Share Posted December 24, 2017 0z NAM snowfall. I do like that lollipop 3" area over me.That’s also 10:1 ratio Link to comment Share on other sites More sharing options...
Hoosier Posted December 24, 2017 Author Share Posted December 24, 2017 Link to comment Share on other sites More sharing options...
IWXwx Posted December 24, 2017 Share Posted December 24, 2017 It's been looking like a LAF special for a couple of days now. Doesn't look like that's changed much. Link to comment Share on other sites More sharing options...
Hoosier Posted December 24, 2017 Author Share Posted December 24, 2017 Lake is the obvious wildcard but I don't have confidence in anything more than 4-5" here. The lake enhanced band does look like it could be fairly intense so if it were to set up overhead for even a couple hours, then better chance to reach 6". Link to comment Share on other sites More sharing options...
Hoosier Posted December 24, 2017 Author Share Posted December 24, 2017 1 minute ago, IWXwx said: It's been looking like a LAF special for a couple of days now. Doesn't look like that's changed much. It's so an Earl Park special. Link to comment Share on other sites More sharing options...
Hoosier Posted December 24, 2017 Author Share Posted December 24, 2017 Nice banding in Nebraska right now. Link to comment Share on other sites More sharing options...
Radtechwxman Posted December 24, 2017 Share Posted December 24, 2017 Is it just me or did 0z nam seem to shift the heaviest band south? Link to comment Share on other sites More sharing options...
ConvectiveIA Posted December 24, 2017 Share Posted December 24, 2017 11 minutes ago, StormChaser4Life said: Is it just me or did 0z nam seem to shift the heaviest band south? Slightly. But the 01, 02 etc HRRR and RAP are juicing up big time north and heavy. Im not quite expecting their outcomes but on the other hand, the 0z NAM is a southerly outlier in comparison to those and the GFS. Radar trends seem promisingly early with flurries for us here now before the main event. Some signs the current radar echos are beginning to lift north a little on their northern reach across eastern NE Link to comment Share on other sites More sharing options...
cyclone77 Posted December 24, 2017 Share Posted December 24, 2017 Gonna be interested to see how the LSRs turn out. Further north in the snow band where we are the DGZ is pretty respectable; at about 200mb of depth. However, soundings show the best lift is mostly above that layer. There is still some decent lift at the top of the DGZ though, so not really sure how things will play out. I think a conservative 15:1 may do it, but wouldn't be surprised if it turned out closer to 20:1. With all that being said, the 00z model consensus for us is around 0.11-0.14", with the RAP coming in the highest with around 0.17". I think I'm gonna bump my call up for here to around 2". Link to comment Share on other sites More sharing options...
Powerball Posted December 24, 2017 Share Posted December 24, 2017 00z NAM's also showing a couple nice WNW flow convergence bands in MI on Christmas day. Link to comment Share on other sites More sharing options...
Radtechwxman Posted December 24, 2017 Share Posted December 24, 2017 50 minutes ago, ConvectiveIA said: Slightly. But the 01, 02 etc HRRR and RAP are juicing up big time north and heavy. Im not quite expecting their outcomes but on the other hand, the 0z NAM is a southerly outlier in comparison to those and the GFS. Radar trends seem promisingly early with flurries for us here now before the main event. Some signs the current radar echos are beginning to lift north a little on their northern reach across eastern NE Just seems like actual radar is a bit further south than simulated radar and the movement is more se than models showing. But that one band arcing ahead is showing some signs of lifting more north and as that wave deepens and approaches the snow should really blossom Link to comment Share on other sites More sharing options...
Hoosier Posted December 24, 2017 Author Share Posted December 24, 2017 The recent HRRR runs are trying to swipe the Illinois shore with that lake enhanced band for a while. Something to watch if we have anybody on here from near the lake from Chicago southward. Link to comment Share on other sites More sharing options...
homedis Posted December 24, 2017 Share Posted December 24, 2017 The recent HRRR runs are trying to swipe the Illinois shore with that lake enhanced band for a while. Something to watch if we have anybody on here from near the lake from Chicago southward.Too bad im north of Chicago Link to comment Share on other sites More sharing options...
CoalCityWxMan Posted December 24, 2017 Share Posted December 24, 2017 Hoping to squeeze 3-5" out of this one. Have only had 0.05" of measurable precip this month here along with a trace of snow. Link to comment Share on other sites More sharing options...
Kaner88 Posted December 24, 2017 Share Posted December 24, 2017 1 hour ago, Hoosier said: The recent HRRR runs are trying to swipe the Illinois shore with that lake enhanced band for a while. Something to watch if we have anybody on here from near the lake from Chicago southward. Nice look at a little tail of that in the latest HRRR, in the midst of its attempt to drag the 4" line north to ORD and beyond. Link to comment Share on other sites More sharing options...
Hoosier Posted December 24, 2017 Author Share Posted December 24, 2017 52 minutes ago, CoalCityWxMan said: Hoping to squeeze 3-5" out of this one. Have only had 0.05" of measurable precip this month here along with a trace of snow. Yeah it's been brutally dry. Link to comment Share on other sites More sharing options...
Hoosier Posted December 24, 2017 Author Share Posted December 24, 2017 Trends are looking a bit better for cyclone's area. Might get a few inches out there. Link to comment Share on other sites More sharing options...
Hoosier Posted December 24, 2017 Author Share Posted December 24, 2017 1 minute ago, Kaner88 said: Nice look at a little tail of that in the latest HRRR, in the midst of its attempt to drag the 4" line north to ORD and beyond. Mentioned it before but for some reason there is a noticeable difference between the Kuchera map at COD compared to the one at Pivotal. The COD one seems a bit inflated to me but may need to observe them over a period of time to be sure. Link to comment Share on other sites More sharing options...
Kaner88 Posted December 24, 2017 Share Posted December 24, 2017 2 minutes ago, Hoosier said: Mentioned it before but for some reason there is a noticeable difference between the Kuchera map at COD compared to the one at Pivotal. The COD one seems a bit inflated to me but may need to observe them over a period of time to be sure. Good eye, looks like you're right. Would be interested to know why that is- maybe different Kuchera calculations? Link to comment Share on other sites More sharing options...
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