Absolute Vorticity

This is our new storm thread for the early next week system. How can we get screwed again out of a snow storm? This time, models are losing the northern stream shortwave so it's purely STJ energy now. We'll have to see how strong that low gets and its track to see what precip types we get. I am thinking we may start out as rain, but that will depend on timing for precip onset, which we can nail down later. Temps are going to be marginal for this event and nighttime will be key to accumulations.

Right now, I am expecting a range of Sun night thru Tues morning for precip window. We can narrow that as time goes on. Storm track and low strength are also key. 12Z EPS has a wonderful track right up the spine of the Apps thru KY and WV. If we had cold air in place, we'd be dancing in the streets! But we don't, so we need a track like that and a strong enough low to get a heavier stripe of snow in the deformation zone. The deform zone will be small so not everyone in AV Land will see snow from this system.

18Z GFS looking good too... nice deform band on the model Mon night into Tues morning. Rain to snow...

CVG

Soil/surface temps will be at the very least low to mid 40s at start of event

Bgoney wrote: ↑Thu Feb 08, 2024 5:59 pm Soil/surface temps will be at the very least low to mid 40s at start of event

Yes! It will be all about the precip rates as is usually the case in these marginal events. If you can get a 1-2" hour deform band for a few hours, that kind of thing, is about the only way you can get accumulations. I hope it's a nighttime or early morning event. That will help.

5:1 Snow Ratios too won't help. Flake size will be huge though so we have that going for us. There are a lot of negatives going against significant accumulations but we do seem to find ways to fail in a good pattern so let's see if we can fail again amidst a warm pattern.

Good Evening and I agree a nighttime period of snow would be our best bet. Hopefully this slows down more and again gain strength as this can help in the system developing more cold air. The system itself looks rather nice and yes some decent precip but timing is so key with system as we are just getting back into colder air but not quite arctic air we see later this month.

The boys had this to say earlier this afternoon:

The cold front will move southeast across the region Saturday
morning with any lingering rain showers tapering off. The front
will stall out to our southeast Saturday night into Sunday as a
weak wave slides east along it. This could lead to a few
additional showers along and south of the Ohio River Saturday
night. Cooler air will begin to move in behind the front through
the day on Saturday with highs ranging from the lower 50s
northwest to the lower 60s in the southeast and highs on Sunday
ranging from the lower 40s northwest to the lower 50s southeast.


A mid level short wave will eject out of the Southern Plains on
Monday to the Mid Atlantic through the day on Tuesday. This
will lead to a developing surface low that will lift northeast
across the Tennessee Valley region to the central Appalachians
Monday into Monday night, but there remain a fair amount of
model differences with the timing, strength and placement of
this system. Nonetheless, fairly widespread pcpn should
overspread our area later Sunday night and into the day on
Monday before tapering off Monday night. We will remain on the
northern side of this system and with some cooler air in place,
highs on Monday will range from the upper 30s northwest to the
mid 40s southeast with lows Monday night dropping into the upper
20s to lower 30s. Ptype will likely be an issue with this
system and will obviously depend on the exact track of the low.
Will continue with mainly snow across our northwest on Monday,
with mainly rain in the southeast and a rain/snow mix in
between. The best chance for any snow accumulations look to be
across our northwest, but amounts and placement will again be
determined by the eventual low track.

High pressure and a drier airmass will build into the region
Tuesday through Wednesday. A chance for pcpn will return on
Thursday as another short wave approaches from the west.
Temperatures will be a few degrees above normal with highs
mostly in the 40s through the end of the long term period.

Right now this reminds me of the snowstorm here the end of March 2018. Think we actually had a winter storm warning but not much on the roads.

NAM and RGEM will start becoming more useful tomorrow. 0Z GFS has the nice Cincy thump still. CMC grazes us only with a cold light rain and the Euro is like the GFS showing the Cincy thump. EPS is further south then the OP with the low over TN. GEFS is even further south then that... too far south to be honest. Models are still trying to nail the track down which of course is of importance to us.

6Z GFS still shows the deform band snows over the Cincy Tri-state late Mon night into early Tues morning. I am narrowing the goal posts as far as event duration goes. Monday evening light rain moves in and gets heavier as the night goes on. It changes to snow and ends sometime after rush Hour Tues morning. That is my current thinking. Snowfall amounts obviously TBD. 6Z GEFS Mean is still SE of the OP with the best snows SE of I-71. However the 6Z GEFS run was a good bump NW of the OP and stronger with the surface low too.

Good Morning Les and very nice posts this morning. This system like many are about timing and strength. Probably more so since we almost need the perfect track,strength and timing to get a thumping of snow. The good thing is the trends for the most part is to slow this system down and at the same time have it getting stronger and a decent path southeast of us.

Like you mentioned the other day not everyone will get the thumping and you may see a 50-100 mile wide area at best. I am not making any predictions for snow since we are at least 84 hours away before any snow would be flying. Hopefully on Saturday we can start looking at the shorter term models as the whole system will be in the computer banks.

I agree Tim.... we should be able to hone in more on this thing over the weekend. I also agree with you that the snow band will be narrow. It may come down to a nowcast with regards to being able to figure that out. The where and how much? Temps and precip rate as well as how much precip do we have to work with will all need to be looked at when trying to come up with a good forecast. Attm, the timing looks favorable for snow since this looks to be a nighttime to early Tues morning event so we have that going for us.

Overnight thinking from the boys:

Cold front that moved through our region will begin to stall
across the southeastern CONUS. A weak wave of low pressure will
move along this boundary, which could initiate some light rain
across our northern KY counties primarily. Coverage in rain will
be determined by the placement of the frontal boundary, with
chances persisting into the early part of Sunday before the
precip axis shifts further southeast.

Cooler air settles in on Sunday, but we still remain ~5-10
degrees above seasonal normals. Only a brief lull in precip
expected across our CWA before chances begin to increase again
late Sunday night into Monday. This is in response to a
developing low pressure system that originates from the Gulf.
This low will strengthen into a mature cyclone and translate
northeastward. Models currently take the low pressure through
the Tennessee Valley. This track leads to more favorable chances
for snowfall across our northern counties as we progress late
into Monday and Monday night. Track of the low still varies
quite a bit in long range models, but there has been a
consistent signal in accumulating snowfall across our CWA from
this system given its southern track. I-71 corridor still acting
as a marker for the transition zone in the grids, with
locations along/NW of I-71 having better chances for
accumulating snow, with locations SE observing primarily rain.
Snow will mix in across our southern counties late Monday night
as colder air builds in, but accumulations expected to be more
limited further south.

12Z NAM shows a weak system so the deform band on the NW side is also weak.

12Z GFS continues to show that nice thumping of snow Mon night into early Tues morning. If everything comes together just right, I could see a couple to a few slushy inches accumulating on the grass / car tops / higher elevations. The quicker the low deepens, the better in this situation. We need it to really get going over SE KY and WV to deliver us the goods.

12Z CMC is weak / SE so just some light rain and that's it.

tron777 wrote: ↑Fri Feb 09, 2024 11:19 am 12Z CMC is weak / SE so just some light rain and that's it.

The CMC though moved quite a bit further west and that is a good sign

90% of the GEFS members now have the deform band of snow showing up as the GFS is definitely locked in! We shall see what happens as we get closer.

latest GFS run snowmap

airwolf76 wrote: ↑Fri Feb 09, 2024 11:35 am sn10_acc-imp.us_ne.png.1a054491d2cc4a2d66e36b02f355634f.pnglatest GFS run snowmap

Not saying those totals are correct but this storm is gaining strength as it moves into the mid-Atlantic area so snow is likely but a little early on amounts.

tpweather wrote: ↑Fri Feb 09, 2024 11:49 am

airwolf76 wrote: ↑Fri Feb 09, 2024 11:35 am sn10_acc-imp.us_ne.png.1a054491d2cc4a2d66e36b02f355634f.pnglatest GFS run snowmap

Not saying those totals are correct but this storm is gaining strength as it moves into the mid-Atlantic area so snow is likely but a little early on amounts.

Not sure about your hood Charles, but ratios won't even be 10:1 for us. 5:1 or 7:1 is more likely. Whatever snow falls will be on the cement variety.

12Z Euro isn't looking too bad. Around 0.55" of QPF for CVG and I'd say around 0.30" of that falls in the form of snow.

12Z Euro

I think confidence is increasing for a 1-3" cement snowfall for parts of the tri-state. Is that over Cincinnati or areas close by remains to be seen, but the GFS has been very consistent and the 12z Euro now shows an almost identical outcome. Not really optimistic about higher amounts attm but that is something we may see in runs as we get closer. But a good, early 1-3" call seems reasonable.

A higher ceiling can be achieved if we see a similar mesoscale setup as that event last January I think it was? NWS has a SPS then a WWA then a WSW. Not saying that will happen again, but these type of systems can be tricky and feature a narrow band that goes crazy.

I like the prelim 1-3" call Trev. Makes sense and it is very reasonable. Do you like my thread title?