Absolute Vorticity

GFS definitely showing the sign for mixing issues up to the river. It also looks like it tries to bring in the dreaded dry slot as well.

Definitely screams high risk vs high reward as per usual with anything that threatens to give us a dumping of snow.

The 12Z NAM is not impressed with the Thurs night and Fri weak little clipper type system, but the 12Z GFS is still looking good for up to an inch for most folks. Nice little way to get the party started in 2025!

Concerning the 5-6th system, it won't be until Friday that the energy starts to get sampled so we are still at least 3 days away from locking this one down. 6Z Euro AI is a major snow storm for most folks with a quicker start time Sunday morning so an earlier exit, Monday morning. 12Z GFS coming in shortly.

tron777 wrote: ↑Tue Dec 31, 2024 10:56 am The 12Z NAM is not impressed with the Thurs night and Fri weak little clipper type system, but the 12Z GFS is still looking good for up to an inch for most folks. Nice little way to get the party started in 2025!

RGEM looked nice, be awesome if that scored.

crazy to see how much that arctic air gets displaced as we get into second week of January. that is an intense arctic hammer dropping in. this will be a bit of shock to our system since we are coming off a warm period right now.

So far, the GFS seems to be weaker, faster, and more south at 108 hours versus the 6Z run which was more north and brought in p-type issues. I also like the spot that 1043 MB high is in too.

Trentonwx06 wrote: ↑Tue Dec 31, 2024 11:04 am

tron777 wrote: ↑Tue Dec 31, 2024 10:56 am The 12Z NAM is not impressed with the Thurs night and Fri weak little clipper type system, but the 12Z GFS is still looking good for up to an inch for most folks. Nice little way to get the party started in 2025!

RGEM looked nice, be awesome if that scored.

Canadian was pretty juicy too. I am keeping it real with up to an inch but I won't mind going 1-2" should more short term models concur in the future.

airwolf76 wrote: ↑Tue Dec 31, 2024 11:04 am crazy to see how much that arctic air gets displaced as we get into second week of January. that is an intense arctic hammer dropping in. this will be a bit of shock to our system since we are coming off a warm period right now.

It's going to be a prolonged period of below freezing air too. If we get a snow pack then it'll only be colder then what guidance is showing as far as intensity goes.

GFS is certainly much slower then the Euro too for the 5-6th. It won't start until Sun afternoon or evening on the GFS. Sun morning it's already snowing on the Euro.

Very suppressed on the 12Z GFS lol. Wow... But this is a risk. I am more concerned about suppression versus a cutter to be honest. It's because of the blocking.

GFS is pretty far south! Darn blocking!

mikeyp wrote: ↑Tue Dec 31, 2024 11:13 am GFS is pretty far south! Darn blocking!

We need the blocking though or this would cut and we'd get a cold rain. We just don't want too much of a good thing.

At Hour 114, the 12Z Canadian looks more Euro like with a further north and stronger low. The incoming high is still up into Canada and has not entered the CONUS yet like on the GFS. So that is a big difference. We need the surface low to be better timed with the arctic high pressing in from the north. Timing, timing, timing as always...

Yesterday 12Z GFS was way north, today way south.
If Euro stays it course then not too worried, we will see what happens.
Everyone needs to remember it can never be easy.

12Z ICON (German model) has the low sliding thru TN so thus a snow storm for us.

Trentonwx06 wrote: ↑Tue Dec 31, 2024 11:18 am Yesterday 12Z GFS was way north, today way south.
If Euro stays it course then not too worried, we will see what happens.
Everyone needs to remember it can never be easy.

Correct. We should still be watching the Ensembles more for trends right now.

tron777 wrote: ↑Tue Dec 31, 2024 11:15 am

mikeyp wrote: ↑Tue Dec 31, 2024 11:13 am GFS is pretty far south! Darn blocking!

We need the blocking though or this would cut and we'd get a cold rain. We just don't want too much of a good thing.

Yep but not that much HAHA! We have days to go! I am by know means worried about missing out on this storm yet. GFS always does this huge shift. See if it adjusts the timing better on more runs and we will see the other model runs. Nice to have something to look at within a week!

tron777 wrote: ↑Tue Dec 31, 2024 11:18 am 12Z ICON (German model) has the low sliding thru TN so thus a snow storm for us.

Which is aligned with overnight Euro.

CMC very Euro like with snow to sleet then back to snow. All snow for I-70 Crew of course. Def a slower start time like Sunday evening so most of Monday is impacted.

Canadian even has a slower transfer to the Coastal Low so we get light snow on the backside into early Tues morning too. Awesome! We have to watch for that idea too. When the transfer occurs and how quick will also determine the strength and track of the primary low for us. Due to the blocking, I would expect a transfer to take place. So far my money is for a CMC, Euro, EPS, Euro AI, ICON type of solution that we are seeing. Snow, sleet, back to snow for us, all snow to the north for precip types. We are seeing this idea on quite a few models now.

Trentonwx06 wrote: ↑Tue Dec 31, 2024 11:18 am Yesterday 12Z GFS was way north, today way south.
If Euro stays it course then not too worried, we will see what happens.
Everyone needs to remember it can never be easy.

I expect the GFS to swing about 3 more times before it makes an actual decision. No other model is swinging 500 miles per run.

If this is correct - https://www.nco.ncep.noaa.gov/idsb/nwpr ... ndex.shtml - Then it looks like the GFS has had data quantity and quality issues over the last 3 runs.

That’s might help explain its odd behavior. Everyone must have skipped work today

12Z UK really wound up and get rain and 34.

There should be reality show called model watchers and how much they age in the winter. I look at them once in the morning after I look at what is actually going on and then try to come up with a forecast. If someone shows a major change during the day I may look at them late afternoon or evening. I try and keep my forecast changes up to 48 hours in advance to once a day and even then I can be stubborn. Having the knowledge of a model bias is nice but also knowing certain models do better in certain situations. These are all factors I try to include as much as possible.My earlier forecast this morning is one that is vague but does have my thoughts on what may happen but no certain outcomes because its just early in the game and yes we are going in with a pattern change which no doubt tends to have models go back and forth. Once you get the pattern established then the models tend to be more reliable. Just to many parts to the equation at first with a pattern change and we are lucky to a certain extent that we have 2 cold fronts before the bigger system late this weekend. So by Friday I would expect models to be rather close with their output and then making a somewhat decent forecast is possible.

Trentonwx06 wrote: ↑Tue Dec 31, 2024 11:53 am 12Z UK really wound up and get rain and 34.

UK two runs ago was weak as hell then last night and now today it's way north. That run you can discount. The GEFS took a bump north of the 6Z run and looks nice for Cincinnati.