hawkeye_wx

Keep in mind this should be pretty wet stuff with a lousy ratio.

Those of us in Iowa are wondering what happened to our big snow event that appeared as locked in as any storm could be a few days out. Nearly all models are either cutting the precip down, warming us up, or both. Even the HRRR, which nailed the colder, snowier late December storm, has now warmed us up and drops at least a few hours of mix crap here. The 6-9" snow event has been cut in half.

00z Euro - The east trend continues. Central Iowa's snow is fading, but east-central is still good....for now. This run is also a bit south.

While we've been analyzing the thermals, there is a new unfriendly trend for Iowa. Some models are now veering the heavy precip farther east into Illinois and bypassing much of Iowa. The UK has been consistently one of the snowiest models for central to eastern Iowa. Tonight's run cut out a huge chunk of our precip.

So you're saying the precip is not going to change to rain up to Chicago by Sunday morning?

It's going to be a nail biter over here Saturday afternoon. The NAMs have warmed a bit more, which now puts Cedar Rapids on the southern edge with a bit of mix at the start. The HRRR, on the other hand, is colder and changes the precip to snow before reaching Iowa City. I'm hoping it works out like the storm in late December when I received 8.5 inches, with 5.4" in three hours early in the event. That storm also had borderline thermals. Models were wobbling on the fence. It was unclear if Cedar Rapids would get 8" or 3". However, there was a clear model winner (HRRR) and a clear loser (NAMs). The NAMs insisted the warm air aloft would push sleet up through eastern Iowa. The HRRR insisted the snow would hold strong down to Cedar Rapids, at least. The HRRR was absolutely correct. First few hours of the HRRR are in range. This would clearly be much better for Cedar Rapids/Iowa City and also Peoria.

3k NAM

The op Euro's pattern (last couple runs at least) looks interesting at day 10. It has a reloading trough in the west, arctic air pouring into the northern CONUS, and gulf moisture beginning to return.

Down to 50% for 6" here according to the Euro. 6" is the line between moderate and big storm here, so I'd like to get at least that.

Yeah, I'd say Chicagoland is locked in.

GFS still out to lunch. This is the look of a broken model. Barely any snow at all north of the low while all other models have widespread snow.

My area needs the east and north trickle to stop. We're still ok for now, with plenty of support for several inches.

That suggests a lousy ratio (<10:1) along the southern part of the heavy band.

00z Euro - A couple changes. First, the snow doesn't extend into western Iowa like last run. Second, the snow band tracks more eastward compared to the ese track on the 12z run. The snow is really going to be dumping when the precip shield initially blows up. The Euro (and probably other models, too) has 6-8" falling from Iowa into Illinois between 00z and 06z.

Garbage thermals likely mean the GFS can be ignored.

00z NAM

I don't think so. The late December biggie here (8.5") was on top of grass. Throughout January, particularly from central to western Iowa, there has been significant melting in between storms. Des Moines has hit 40+º eight times this month. SW Iowa was in the low 50s, with bare ground, before this last storm. My snow pack had fallen to a couple inches before the recent series of snow systems.

It's rare to get a big snow here on top of an already-existing solid snowpack. This week it may happen twice.

The Euro is very close to the UK over here, but the UK takes the snow band east while the Euro east-southeast.

Euro is farther north with the rain initially over here.

The GFS is certainly focusing the moisture/energy east/southeast of Iowa... different than the UK and Euro.

What does the GFS ensemble avg show for total liquid precip? That would be good to know over here if the GFS is simply too warm.

UK

GFSv16 - Also a bit farther north like the op GFS. Considering the Euro has all snow north of the IA/MO border, I don't see Cedar Rapids/Iowa City getting rain out of this. I've lost count of the number of times the GFS had my area getting rain this winter and we ended up with all snow.

This is looking good for Iowa. The one thing keeping this good storm from being an epic storm is the quick decay of the snow intensity north/northwest of the low following the initial heavy WAA burst.