Absolute Vorticity

Looks good Trev! Most folks should get their first accumulation of the season!

tron777 wrote: ↑Sun Dec 17, 2023 12:29 pm

Trevor wrote: ↑Sun Dec 17, 2023 12:05 pm Lightning tomorrow, anyone? High-res models are picking up on it. Actually is fairly typical to have some of that going on during "peak heating" under a strong ULL.

We should have some steep lapse rates too. The snow squall parameter looked decent especially for folks north of the river.

It's an outside shot Les, but I would love to see Thundersnow happen for you in Burlington!

There you go. Or first Winter Weather Advisory of the season. ILN is calling for up to 2 inches in northern areas. Up to 1 inch in the southern areas of the forecast area.

dce wrote: ↑Sun Dec 17, 2023 2:01 pm There you go. Or first Winter Weather Advisory of the season. ILN is calling for up to 2 inches in northern areas. Up to 1 inch in the southern areas of the forecast area.

Nice! If you remember I suggested that they would issue one in my update yesterday

Trevor wrote: ↑Sun Dec 17, 2023 2:11 pm

dce wrote: ↑Sun Dec 17, 2023 2:01 pm There you go. Or first Winter Weather Advisory of the season. ILN is calling for up to 2 inches in northern areas. Up to 1 inch in the southern areas of the forecast area.

Nice! If you remember I suggested that they would issue one in my update yesterday

You did! Awesome job. The short range models are consistently showing a nice band coming off Lake Michigan. It's just a matter of where that band sets up as to where the heaviest accumulation will occur. Having said that, a couple of nice snow squalls even outside the area that receives that band can do well in accumulation also.

dce wrote: ↑Sun Dec 17, 2023 1:57 pm

tron777 wrote: ↑Sun Dec 17, 2023 12:29 pm

Trevor wrote: ↑Sun Dec 17, 2023 12:05 pm Lightning tomorrow, anyone? High-res models are picking up on it. Actually is fairly typical to have some of that going on during "peak heating" under a strong ULL.

We should have some steep lapse rates too. The snow squall parameter looked decent especially for folks north of the river.

It's an outside shot Les, but I would love to see Thundersnow happen for you in Burlington!

Thanks Doug! I've only seen it once. The drive home tomorrow will be interesting.

dce wrote: ↑Sun Dec 17, 2023 2:56 pm

Trevor wrote: ↑Sun Dec 17, 2023 2:11 pm

dce wrote: ↑Sun Dec 17, 2023 2:01 pm There you go. Or first Winter Weather Advisory of the season. ILN is calling for up to 2 inches in northern areas. Up to 1 inch in the southern areas of the forecast area.

Nice! If you remember I suggested that they would issue one in my update yesterday

You did! Awesome job. The short range models are consistently showing a nice band coming off Lake Michigan. It's just a matter of where that band sets up as to where the heaviest accumulation will occur. Having said that, a couple of nice snow squalls even outside the area that receives that band can do well in accumulation also.

I second this. Great job Trev with the forecasting of this system.

tron777 wrote: ↑Sun Dec 17, 2023 4:14 pm

dce wrote: ↑Sun Dec 17, 2023 1:57 pm

tron777 wrote: ↑Sun Dec 17, 2023 12:29 pm

Trevor wrote: ↑Sun Dec 17, 2023 12:05 pm Lightning tomorrow, anyone? High-res models are picking up on it. Actually is fairly typical to have some of that going on during "peak heating" under a strong ULL.

We should have some steep lapse rates too. The snow squall parameter looked decent especially for folks north of the river.

It's an outside shot Les, but I would love to see Thundersnow happen for you in Burlington!

Thanks Doug! I've only seen it once. The drive home tomorrow will be interesting.

I've seen it several times over the years here in the Dayton area. I've lost count really. Probably 6 or 7 times.

Should be fun driving back from Buffalo tomorrow!

Great job Trev!

Currently 43 here in G'ville and progged for 33 Mon morning, then holding steady at around 34 for the rest of the day.

Anchorage now up to 70" snow for the season. After having the snowiest November on record, we now have a top 10 snowiest December - and the snowiest Nov-Dec combined. Normal snowfall the rest of the season is 49.6".

NWS Anchorage
@NWSAnchorage
As of 9am this morning, NWS Anchorage has officially received 70.0” of snowfall so far this winter, which is nearly 15” more than what we recorded on this exact day last year.This is also the most snow we have received in any winter season through this date (Dec 17th).

Some nice changes showing up on the EPS with the 500mb at the end of the month

Bgoney wrote: ↑Sun Dec 17, 2023 5:46 pm Some nice changes showing up on the EPS with the 500mb at the end of the month




IMG_1047.gif

That looks a lot better…

Great call on the snow Trev. Bgoney the mjo looks to be in phase 8 and then 1 late this month or early January. Once we get deeper into the winter season phase 8 and 1 are fine but once you get into 1 and then 2 its usually better for the east coast. AO and NAO which are positive try and head back to neutral by the end of the month and the pna stays slightly positive. So some good signs later this month and will watch those and also the PV and will it be disturbed enough to really put some cold air down in the lower latitudes or will it continue its pattern so far this season which is more of deep in more narrow arrows.

Trevor wrote: ↑Sun Dec 17, 2023 5:49 pm

Bgoney wrote: ↑Sun Dec 17, 2023 5:46 pm Some nice changes showing up on the EPS with the 500mb at the end of the month




IMG_1047.gif

That looks a lot better…

Yes it does! Finally we can see the EPO turning more negative along with a positive PNA as we get a typical El Nino pattern with an Aleutian Low. The GEFS has the Aleutian Low but it's too far East so you still have a +EPO / -PNA pattern so that is key... the position of that Aleutian Low. You must have it further West as the EPS shows to get that kind of improvement.

The MJO by a lot of models now is forecast to come out of the COD and get into Phase 1 and then 2 towards the end of this month and early January. If correct, our chances for colder weather and wintry weather will definitely go up. Fingers crossed!

tron777 wrote: ↑Sun Dec 17, 2023 6:32 pm

Trevor wrote: ↑Sun Dec 17, 2023 5:49 pm

Bgoney wrote: ↑Sun Dec 17, 2023 5:46 pm Some nice changes showing up on the EPS with the 500mb at the end of the month




IMG_1047.gif

That looks a lot better…

Yes it does! Finally we can see the EPO turning more negative along with a positive PNA as we get a typical El Nino pattern with an Aleutian Low. The GEFS has the Aleutian Low but it's too far East so you still have a +EPO / -PNA pattern so that is key... the position of that Aleutian Low. You must have it further West as the EPS shows to get that kind of improvement.

The MJO by a lot of models now is forecast to come out of the COD and get into Phase 1 and then 2 towards the end of this month and early January. If correct, our chances for colder weather and wintry weather will definitely go up. Fingers crossed!

Les talked about it earlier this month that we needed the Aleutian Low to be further west and I thought that would happen but just about a week to soon on that call. Hopefully there is a little transition to have some snow in the northern plains and upper mid-west just after Christmas. I will be in Wisconsin that week and hopefully I will get at least some snow during the week.

For tomorrow... check out the simulated radar from the 18Z HRRR. We should see 35 to 45 mph gusts in the strongest snow squalls. Timing wise, around midday with the most widespread action between 3-10pm. The drive home could certainly be impacted by reduced visibilities, falling temps thru the 30s, and slick roads where the heaviest snow showers occur. As others have mentioned, even the HRRR shows some lightning also so thunder snow is also not out of the question. I have not had a lot of time to look over the data for this event, but from what I have briefly seen, you guys are all over it and I agree with everything that is being said on here.

tpweather wrote: ↑Sun Dec 17, 2023 6:35 pm

tron777 wrote: ↑Sun Dec 17, 2023 6:32 pm

Trevor wrote: ↑Sun Dec 17, 2023 5:49 pm

Bgoney wrote: ↑Sun Dec 17, 2023 5:46 pm Some nice changes showing up on the EPS with the 500mb at the end of the month




IMG_1047.gif

That looks a lot better…

Yes it does! Finally we can see the EPO turning more negative along with a positive PNA as we get a typical El Nino pattern with an Aleutian Low. The GEFS has the Aleutian Low but it's too far East so you still have a +EPO / -PNA pattern so that is key... the position of that Aleutian Low. You must have it further West as the EPS shows to get that kind of improvement.

The MJO by a lot of models now is forecast to come out of the COD and get into Phase 1 and then 2 towards the end of this month and early January. If correct, our chances for colder weather and wintry weather will definitely go up. Fingers crossed!

Les talked about it earlier this month that we needed the Aleutian Low to be further west and I thought that would happen but just about a week to soon on that call. Hopefully there is a little transition to have some snow in the northern plains and upper mid-west just after Christmas. I will be in Wisconsin that week and hopefully I will get at least some snow during the week.

You should see some snow while you are there Tim. Just after Christmas, (Day 10) The CMC has a nice track for Wisc but no cold air to work with while the Euro today did have cold air to work with and delivered some snow to the area.

A wonderful AFD from the boys for tomorrow... it's a great read:

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
A dynamic mid/upper level system will dive SE across the
wrn Great Lakes late tonight before pivoting E into the mid and
upper Ohio Valley during the day on Monday. This is an
incredibly sharp/potent mid/upper level S/W disturbance that
will pivot SE into the local area during the daytime Monday.
This rapid uptick in large-scale forcing will coincide with a
cooling and saturation of a greater depth of the LL profile,
allowing for numerous to widespread SHSN to develop by late
morning into early afternoon.

While there are some uncertainties in exact location of where
the greatest banding of SHSN will occur/propagate, there is
enough of a concern for travel impacts to develop (especially
near/after sunset), that have decided to issue a Winter Weather
Advisory to assist with the messaging component of this event.

There were many factors that went into the fcst/headline
decisions this afternoon, knowing full-well that the traditional
accumulation advisory criteria (2" in the S and 3" in the N)
is very unlikely to occur. The overall signal for SHSN/squall
activity is fairly robust from a broad-scale pattern /and/
ingredients-based perspective. The PV anomaly is impressive and
the gusty winds/deep vertical mixing will certainly be there.
Good saturation within the DGZ will develop overlapping narrow,
but respectable, LL instby (owing to the incredibly steep/deep
LL lapse rates). Some hi-res ensemble guidance supports the
development of >100J/kg SBCAPE to coincide
(temporally/spatially) with the most aggressive large-scale
forcing (especially near/N of the OH Rvr), suggesting that
convective snow rates could briefly be high enough (even during
the daytime with warm(er) air temps and sfc road temps still
well above freezing) to quickly coat the ground and cause brief
slick conditions to develop (before it melts as soon as snow
rates subside). Adding to this concern will be the wind gusts
~40 MPH at times, greatly reducing visibility and causing
potential travel impacts, even with relatively minimal
accumulation of the snow itself. There is good consensus that
both road and air temps will be above freezing through the first
part of the afternoon, but that may be no match for extremely
heavy rates on a very small temporal scale (~5-10 minutes). As
we progress later in the day, with the sun angle decreasing and
continued sfc CAA (allowing for air temps themselves to go below
freezing), the concern for slick conditions to develop
increases markedly, especially for nrn metro areas of Dayton and
Columbus by the evening rush. Although the greatest coverage of
SHSN/squall activity should be gradually waning toward/beyond
sunset, it will continue in pockets well into the evening. And
with data indicating that sfc road temps will fall below
freezing toward 6 PM and beyond (especially near/W of I-75), the
prospect of having residual moisture (or renewed moisture via
melting snowflakes or sudden snow accumulations), come into play
for the potential for slick conditions for the latter half of
the evening commute Monday.

All of this being said, there are still a few factors that may
inhibit impacts beyond more than just a few ISO instances. The
first, and perhaps most influential, is the fact that antecedent
air/ground temps are going to be fairly warm. Dry sfc road
temps should be in the 40s by early afternoon Monday and there
really isn`t /that/ impressive of a LL thermal gradient that is
going to be charging in from the W or NW. Yes, LL CAA will be
ongoing, but it isn`t going to be a quick (1-2 hour) drop of
15-20 degrees. It is going to be much more gradual in nature,
suggesting that the lack of a "sudden" temp drop/arctic
intrusion could allow for surfaces to quickly dry before
potential refreezing occurs.

So while the accumulations themselves will be relatively
minimal, do feel that there will be some travel-related impacts,
potentially numerous in nature, due to the SHSN/squall
activity. Again, these travel impacts may not subside until well
after the activity dwindles in coverage, so decided to have the
advisory go to 06z to account for the potential for lingering
slick spots late in the evening.

Yes I believe the roads will still be warm but if you can get a heavier snow shower to occur especially once we get to the very late afternoon and early evening it can cause some slick spots and visibility issue's. Hey it beats nothing at all.

tpweather wrote: ↑Sun Dec 17, 2023 6:50 pm Yes I believe the roads will still be warm but if you can get a heavier snow shower to occur especially once we get to the very late afternoon and early evening it can cause some slick spots and visibility issue's. Hey it beats nothing at all.

Exactly Tim... the rate at which the snow falls is what is going to be key to get any slippery road conditions. If it comes down hard enough, it will trump the warmer ground conditions.

tron777 wrote: ↑Sun Dec 17, 2023 6:57 pm

tpweather wrote: ↑Sun Dec 17, 2023 6:50 pm Yes I believe the roads will still be warm but if you can get a heavier snow shower to occur especially once we get to the very late afternoon and early evening it can cause some slick spots and visibility issue's. Hey it beats nothing at all.

Exactly Tim... the rate at which the snow falls is what is going to be key to get any slippery road conditions. If it comes down hard enough, it will trump the warmer ground conditions.

If we get accumulating snow on Monday it looks like Bgoney wins the contest. Not sure what the prize is this year.

tpweather wrote: ↑Sun Dec 17, 2023 6:59 pm

tron777 wrote: ↑Sun Dec 17, 2023 6:57 pm

tpweather wrote: ↑Sun Dec 17, 2023 6:50 pm Yes I believe the roads will still be warm but if you can get a heavier snow shower to occur especially once we get to the very late afternoon and early evening it can cause some slick spots and visibility issue's. Hey it beats nothing at all.

Exactly Tim... the rate at which the snow falls is what is going to be key to get any slippery road conditions. If it comes down hard enough, it will trump the warmer ground conditions.

If we get accumulating snow on Monday it looks like Bgoney wins the contest. Not sure what the prize is this year.

Bragging rights I guess!

CVG / DAY both had 53 and CMH 52 on Sun.