THE CUTTING EDGE...

The winter storm that's on its way to the Midwest Sunday continues to look impressive. Aside from being a day closer to the event, not much has changed from my thinking yesterday. My area appears to be on the cutting edge of the storm, where little if any snow is found in the north to potentially heavy snow in the "extreme" south. The system will be hitting the richer data grids off the west coast soon, and that should remove what little doubt there is regarding the ultimate track.

For the majority of my area to get nailed by a heavy snow producing storm, the golden track is considered to be from near St. Louis to just south of Chicago. That keeps us solidly in the cold sector and what is known as the deformation band. It gets us in on the warm advection snows as well as the trowel that forms in the NW quadrant. That's the way you put up big snow numbers. In this event, the storm is expected to pass over far southern Missouri and instead of curling northeast, blocking sends it due east and actually obstructs further intensification. The likely result is the northern edge of the heavy snow band barely clips extreme southern Iowa and WC Illinois as it proceeds east. We missed out on the golden track.

What you are looking at below are plots of the surface low by the individual members of the EURO ensembles. There is good clustering among the various members, indicating the surface low Sunday evening is in the boot heel of Missouri or extreme SW Kentucky.

24 hours earlier on Tuesday, about a third of the members had the low as far north as St. Louis, some west of Columbia, Missouri (not far from the golden track). It's very apparent that there was much greater spread in solutions, raising concern heavier snow could swipe my counties south of I-80. Now confidence is growing, the track will end up being well south of St Louis, somewhere close to the Missouri boot heel. See the difference between Tuesdays clustering and what is showing up Wednesday.

What I'm trying to convey is that the latest trends are converging on a solution that is well south of the golden track. This strongly implies the best opportunity for any significant snow is over my far southern counties, especially south of HWY 34. Small shifts in track going forward could even take the far south out of the game, or move the heavier totals further north closer to I-80. If there is a shift, I think it's further south and even less snowy than what's shown in my southern counties. Thursday's new data should tighten up the clustering even more. For now, here's some raw model snow guidance for later Sunday and Sunday night. It's too early for any of this to be considered hard numbers or a solid forecast, but we are getting there. Soon these trends that will at some point be stout enough to be used as forecasts!

The EURO has some healthy snow south of HWY 34 in SE Iowa and WC Illinois. North of there, amounts taper off in a hurry.

The latest GFS is further north and heavier, with a hefty snow depicted just south of I-80. Those numbers in Missouri and central Illinois are eye-popping. I expect those to lower in future runs by 6–12 inches, more like what the EURO is showing. A good snow is likely across my counties south of HWY 34, but it is unlikely to be as heavy as the GFS indicates.

Another factor to note is that extremely dry air is feeding into the northern edge of the snow band. It will act like a wall and create a very sharp edge to the northern periphery of the snow shield. My counties north of I-80 are likely to see little if any snow. We will have much more to discuss in my next post as we get closer to the event and into higher resolution data. In theory, that should evoke even higher confidence as to where the hefty snows occur. Northern Missouri currently is looking to be the epicenter of this storm, with just a glancing blow for my southernmost counties.

SNOW ISSUES FOR MY CENTRAL COUNTIES TODAY

If the major weekend storm is not enough, a clipper will whiten things up Thursday in my central counties near I-80. The digging energy riding a thermal gradient is expected to produce frontogenesis from central into eastern Iowa. This and a narrowband of steep lapse rates near the dendritic growth zone should promote the development of at least a brief period of moderate snow. It begins shortly after sunrise in EC, Iowa and shifts E/SE as the morning evolves. The NWS has issued a Winter Weather Advisory for parts of EC Iowa where snow intensity and duration should last the longest. Here, 2–3 inches of snow is expected. Some isolated 4-inch totals are on the table in an area extending from Cedar Rapids to Iowa City. The advisory lasts from 8am to 5pm and travel will be impacted. The far north and far south should see little if any snow.

Here's what models are suggesting for snow totals Thursday.

The EURO

The GFS

The 3k NAM

The HRRR

The 10K GEM

By the time the Sunday's storm moves out, colder air is surging in behind it. Arctic air will make itself felt for much of the period January 6th-13th. However, (and this is a positive), the mean trough is further east and less amplified, which keeps the extreme cold further northeast. That said, it will be plenty frosty. Here's the 6-10 day outlook from the Climate Prediction Center through January 11th. Head west, young man (or woman)!

That's the nuts and bolts of it for the post. Those of you that see the snow today and later this weekend, please enjoy it for me. It looks like I'm on the outside looking in. Snow avoids me like the plague. Roll weather...TS

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