GRR’s official H/L yesterday was 35/28 there was 0.16” of precipitation that fell as 2.7” of snowfall. There was 2” on the ground at 7AM. The highest wind was 33MPH out of the W. There was no sunshine. For today the average H/L is 32/21 the record high of 59 was in 2004 the coldest high of 8 was in 1920 the record low of -2 was in 2001 the warmest low of 52 was in 1897. The most rainfall of 1.35”fell in 1897. The most snowfall of 6.4” was in 1999 the most on the ground was 12” in 2001.

FZRA with this is becoming more likely - at least with the EURO - for C/S MO. Latest 06 Euro-

EAX this morning with a extremely detailed and well written write up. Bottom line up front, increasing confidence in Winter Storm impacts expected, mainly Sunday into Monday, could see issues start as early as Saturday late evening. South of Interstate 70, there are concerns about freezing rain leading to ice accumulation. Then Sunday, heavy snow amounts from Interstate 70 to just north of Hwy. 36. Amongst ensemble guidance, solutions depicting dry conditions across the forecast area are very few, therefore, the increased confidence in the occurrence of wintry precipitation and substantial accumulations. Also, you may have noticed the Winter Storm Watch issued by neighboring offices to the west. We conducted a collaboration call with WPC and our neighboring offices this morning to coordinate this. We have held off issuing a Winter Storm Watch on this shift, to ensure there is no confusion on the small event Thursday afternoon. In addition, our neighboring offices are expecting impacts earlier than our forecast area will, thus warranting the watch headline for areas west of us. By Saturday evening, deep mid-level trough axis is progged to be crossing the Front Range, with strong dCVA into the High Plains and Panhandle Region. This results in strong surface cyclone, and overall appears to be a typical panhandle hook cyclone. After preceding cold temperatures, low-level flow turns southerly, providing weak WAA, along with notable isentropic ascent. Through late Saturday, this will result in a warm-nose around +2.0C above a freezing surface. Therefore, there will be a melting layer for any dendrites that develop and fall. The greatest upglide with the isentropic ascent is mainly south of Interstate 70, though could make it northward a bit. When it comes to the lowest portion of the boundary layer, and the actual temperatures of surface itself, there is still a wide range of temperature solutions. Some model soundings are showing a shallow layer that is below freezing, with below freezing surface temperatures, but the layer is not cold enough to generate sleet, therefore, allowing liquid water to make contact with a frozen surface. This could result in several hundredths of an inch of ice accumulation from freezing rain Saturday evening into the overnight hours of Sunday morning. Some higher end solutions suggest over one-tenth of an inch of ice for our southern counties. However, there are also some model soundings showing a rapid drop- off in temperature just above the surface between -8.0C to -10.0C with a frozen surface. This kind of sounding would result in more sleet. For right now, will remain concerned with icing potential, especially south of Interstate 70 but difficult to confidently discuss amounts. Regardless, this could make for difficult travel. The Kansas City metro is also going to be right on the gradient of this. Heading into Sunday morning, mid-level height falls continue, along with a rapid drop in surface pressure. While the H5 wave is progged to be closed in most deterministic model solutions, there is still some vertical tilt to the system as a whole, which will allow the system to continue to deepen. Even coarser synoptic scale models are showing stronger FGEN bands starting to develop in the deformation zone northwest of the cyclone center, and structure appears to be favorable for a textbook TROWAL, with the warm- conveyor belt providing a lot of Gulf Moisture into the warmer sector of this storm and wrapping around to the backside of it. Synoptically speaking, this would be the reason for increased confidence in winter storm impacts. Most ensemble suites seem to be hinting on accumulating heavier snow from just south of Interstate 70 to just north of Hwy. 36, with lower end accumulations but still impactful along the Iowa border. (There is still a lot of potential for this axis of heavier snow to shift north or south, between 50-75 miles if not more). Before discussing snow totals and their associated probabilities, a few notes on what will make snowfall accumulations difficult. For Interstate 70 and southward, including the KC metro, will be the timing of transition from potential freezing rain and sleet to snow. Overall QPF amounts are very high for this event, but, if the CAA lags and an extra hour of wintry mix precip that is not dominantly snow, this would largely eat into the snow totals. If the boundary layer fails to saturate quickly, or isentropic ascent is not as robust ahead of the cyclone as currently progged, more of the QPF could go into snow, providing higher totals. This could also result in a sharp-cutoff between very high snow accumulations, and lower but still impactful snow accumulations. Areas between Interstate 70 and Hwy. 36 seems to be the most favorable for snow accumulations, because the probabilities for mixed precipitation well north of Interstate 70 are lower. However, if the system has a subtle shift, this could change. For far northern Missouri and northwestern Missouri, accumulating precipitation/snow is still expected, but, the stronger moisture transport may not be able to reach that far. However, we may still reach winter storm criteria that far north. The second factor, is if a robust dry slot or sting jet with drier air comes in. At the current moment, there are not really any solutions that do this. And given the access this system will have to Gulf Moisture, even if it shifts northward, does not seem overly favorable and has very low probabilities amongst ensemble guidance, just need to respect this highly dynamic system that could try this. But at this time, not seeing robust dry slot potential. Now to snowfall amounts. Deterministic GFS and and ECMWF are still coming in with the double digit amounts. Can this system achieve it? Sure, if this TROWAL develops and we get the right FGEN band or some other form of CSI release, it could. However, always skeptical of double digit snow events given climatology of stronger winter time mid-latitude cyclones for this region. In addition, also thinking that snow ratios will be a bit lower given the higher moisture transport, generally around 8:1, therefore your 10:1 assumed snowfall maps from deterministic model guidance would be over producing snow. Ensemble suites continue to show more consistency from run to run, especially for areas just north of Interstate 70 to just north of Hwy. 36. Ensemble means are generally in the 5 to 8 inch range, with pockets of the 7 to 9 inches. In this area, probabilities for exceeding 6 inches of snow are starting to climb above 60 percent. The probabilities south of Interstate 70 are a bit lower, in the region where mixed precipitation is more likely at the onset of this event, and the lower northward toward the Iowa border. Probabilities for at least 12 inches of snow have increased, hanging around 30 percent for areas east of Interstate 35 in Central Missouri (this misses the KC metro). Again, climatologically speaking it is very difficult to get a single event that produces over 10 inches, and with expected snow-ratios closer to 8:1, having a hard to buying into those 12 inch exceedance probabilities. So, for south of Interstate 70, thinking 3-5 inches of snowfall, but keep in mind the ice accumulation potential before that. For the KC Metro, between 4 and 7 inches. The KC Metro remains uncertain due to the aforementioned mixed precipitation. Central Missouri east of Interstate 35, 5-8 inches with pockets of 8-9 inches. Again, depends on the exact snow ratios. Lots of QPF though with this, For north-central Missouri and northwest Missouri, at least 3 to 6 inches, but could see potential for 4 to 8 inches. This will largely depend on how much moisture gets transported northward, and if there is any shift in the cyclone or if the mid-level trough starts to lift. Travel will is expected to be an issue south of Interstate 70 late Saturday Night, and then travel across the rest of the area will be difficult most of Sunday and likely into Monday morning. The system finally exits by late Monday morning, and very strong CAA will bring in a Polar and Arctic airmass providing very cold temperatures next week.

Day 10 (4-run trend)

Night Shift 6z GEFS Day 7 (4-run trend)