TICK TOCK, WE'RE ON THE CLOCK

When it comes to snow, it often seems this area is rarely in the sweet spot where I can say with certainty how a storm will perform. Cold air is limited, the track is marginal, it's questionable whether it will be rain or snow, or one model says snow, and the other doesn't, it's always something. One little unchecked box can make the difference between little to no snow or a bunch. It drives me nuts, but I actually kind of like the challenge of solving the puzzle. (My wife says it's a sickness).

Anyway, the first snowflakes of the year are possible this weekend and already the above issues are still apparent, and I find myself in another one of these tough situations facing these critical uncertainties.

• Temperatures will be marginal. Precipitation should start as rain, but as cooling occurs could mix with snow or even transition to all snow Saturday evening.

• Precipitation amounts continue to vacillate up and down from one model run to the other. This is a phasing issue where models are struggling to capture the energy, which leads to minor but important issues defining the strength which alters the track and amounts of precipitation.

• Last, even if we get the transition to snow, the timing will be important to any amounts. If it's sooner, some guidance is showing at least a couple inches of slushy accumulations. If it's later, the switch would be brief and any amounts inconsequential. Then there's the possibility that there's no snow at all, as boundary layer temperatures are a degree or two too warm for anything but rain.

So, as I write this just under 48 hours from the event, even I have uncertainty as to how this plays out. Hopefully, by Friday and my next post there will be better data initialization, and the picture becomes clearer. To begin with, let's start with the amount of liquid precipitation. The current run is on the left, the previous on the right. You can see a propensity for the heaviest axis on the EURO and GFS to shift south. In Dubuque, for example, the EURO went from .40" to .32". On the GFS, it went from .55" to .25". The 3K was fairly consistent. This tells me the system may be tracking further south, perhaps by as much as 50 miles. There is still time to come back north.

The EURO

The GFS

The 3K NAM

The track south of my area will certainly make for a raw day Saturday with northeast winds. Highs should range from 40-45 in the morning hours, the coolest north. In the afternoon, when rain arrives, evaporative cooling will gradually drop temperatures and by 5:00pm readings should range from 35 to 40. It’s about this time, (near or after sunset) that rain could begin to mix with snow from west to east north of I-80, especially closer to HWY 20. From here, the column continues to cool and if there is going to be a transition to wet snow, it would happen in the evening over the north. However, by the time it's cold enough precipitation could be winding down, and it will be a race to get any snow to accumulate on grassy and elevated surfaces.

What is interesting is that by 3:00 in the afternoon when precipitation is maxing out, 850 temperatures (a mile up) are below freezing over my entire area. Traditionally, that is cold enough to get snow down to the surface. Temps of -3 to -4 C north of I-80 is almost always going to get you snow.

In this case, the EURO in particular keeps surface temperatures (the boundary layer) just warm enough to melt the snowflakes before they reach the ground. Most other models see a weaker version of that and at least produce a mix of rain and snow, the 3K NAM much more than that with a full-fledged change to snow. So, despite a good track for snow, it's early in the season and despite what is shown at 850, it might not happen. For sure, it's going to be very close and if evaporative cooling kicks in more than expected, some accumulations would result, but mainly in the north. Anyway, here's what models are currently suggesting for snow. They are not forecasts, just raw model output designed to make forecasts from. In this case, we are looking for trends, but it's apparent we are still not on solid ground.

The EURO, the least snowy...a nothingburger.

The GFS, far more aggressive shows this.

The HRRR, shows a tongue of warm air over my area, with snow west and east. Kind of strange.

The latest 3K is the money ball if you are rooting for snow but mainly in my northwest counties. It is a bit stronger than other models, which apparently enhances evaporative cooling and brings snow down past I-80. Even it shows a drop in totals northeast of the Quad Cities.

This is the National Blend of Models, showing measurable snow north of I-80.

The official NWS forecast.

Fortunately, we have another day to assess new data and pin this down. However, I have my doubts tomorrow's guidance is going to be much better regarding consistency. Anyway, if I was a betting man, I would say the odds are about 70 percent my northern counties see at least a rain snow mix, 30 percent for a full change-over with at least minor slushy accumulations. I don't expect much if any snow in the south.

I still contend that if the Polar low reforms further south at 500mb as the EURO indicates, we will see scattered snow showers Sunday or Sunday night. 2 day previous what's shown, that vortex was in central Illinois near Hudson Bay, sucking up cold air.

At 500mb Sunday night, temperatures over the Quad Cities are shown at -42 C.

That my friends is mighty impressive for November 10th. That has got to generate some instability and snow showers with vorticity wrapping around the west side of the circulation. The EURO is starting to grasp that and while it leaves snow out of the area Saturday, it is beginning to show snow showers that could deposit a dusting Sunday. However, the EURO needs to verify for that to happen, and it's important to note the GFS is weaker and further northeast minimizing that concern, Just one more issue to iron out.

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LET'S ADD SOME COLD TO THE MIX

By that time, any snow showers should have no trouble sticking if you get under one of these streamers, with lows Sunday morning in the low to mid 20s. They will be fast movers but can produce intense short duration snow that briefly limits visibility.

Wind chills with a harsh N/NE wind look like this Sunday morning.

Monday morning lows in the upper teens to low 20s are anticipated, with readings only warming to the low to mid 30s in the afternoon. Wind chills will never get out of the 20s after starting deep in the teens.

Tuesday the upper air vortex grinds east and a building ridge replaces it. Before you know it, we are back in the 50s, and might be close to 60. The EURO meteogram has this for temperatures the next 15 days in the Quad Cities.

I'm still seeing strong signals that the pattern flips to a cold one around Thanksgiving that could carry into December. I'll get into that later when I have a bit more free time on my hands. Happy Friday and roll weather...TS