WHO'S THAT KNOCKING AT THE DOOR

RARE SNOW EVENT KNOCKING ON THE DOOR...

For over a week now, I've had my eye on what's about to be one of the larger snowstorms in some time. In fact, the NWS in their discussion indicated an event of this magnitude only occurs once every 10–12 years. By the time the final flake falls, some local areas could see tallies around 15 inches....rare indeed! Overall, most of the region should end up in the 8-12 inch category.

Since I last checked in, some new data has arrived which I will pass along as snow begins to show up on the radar in my southern counties. Let's begin with the official NWS forecast, which has gone up from the previous issuance. It's been quite a few moons since I saw I've seen a chart such as this. Do note: there is a 4-5 inch range in most spots, so it remains to be seen if we can come close to reaching those max totals.

Just for kicks, the NWS high end amount is shown at 19 inches in Iowa City. However, the odds are only 10 percent that or any of the higher totals shown below will be reached.

The numbers below are the low end of the spectrum. Right now, odds are 90 percent they will be reached, at least according to the NWS algorithms.

One thing I have noticed is the new deterministic runs of the GFS and EURO have actually shifted a bit southeast and trimmed the amount of QPF. That has pushed the maximum snow band southeast and lowered totals an inch or two. It's difficult to say if that's a hard trend or a wobble in the 18z run. Whatever, the axis from Ft. Madison and Burlington, to Geneseo and Sterling, is where the max accumulations are now showing on the EURO and GFS.

The EURO

The GFS

The HRRR just in, which had been much further NW has also noted and taken on the shift southeast. It looks to me like the official NWS forecast might need to be altered southeast by at least 50 miles. Take 2-3 inches off what they are showing in the NW and add 2-3 more over the southeast. Here is the latest HRRR which might be pretty close in the end.

The SREF short range ensembles are not bad either.

Again, mesoscale details will be important in the process going forward. New data will be forthcoming in a couple of hours. Snow has begun to fall across the southern half of my area. I hear it knocking on my door. Roll weather...TS