December 2021 Weather Discussion

[tpweather]

Uhhh OK,.... for next week GFS painting 40-50 degree temp anomalies in the center of the country . Round two lurks


FGI8ADfXEAQKti2.png

That is wild to say the least. Mother Nature will balance things out but very wild to see those possible 80 degree temps. Sure the central plains can get some warm days during the winter season but so widespread is what I notice.

[tron777]

No changes to the 3pm SPC Day 1 Outlook. Carbon copy of the one that came out around lunch time.

[cloudy72]

Another well-written discussion from the boys.....

Code: Select all

At this juncture, we shift our focus to tonight into the day on
Saturday -- a setup that continues to be rather concerning for 
the region. There are several items to break down as we discuss 
the expected evolution as we continue to hone in on particular
impacts locally. 

As has been mentioned for several days now, the overall track of
this system is a climatologically-favorable track that is  
supportive of a severe threat across the OH Vly. A slowly- 
deepening sfc low will track from N MO to Lake Michigan by tonight.
Deep lows on this track have a rather long history of being 
supportive for severe weather events across the OH Vly. And 
although the low will be pulling away/N through MI by the time 
the FROPA actually occurs locally mid/late Saturday morning, it
will continue to deepen as it does so. Both deterministic and 
ensemble solutions seem to have locked in a deeper system, with
the prospect of a sub-985mb low in MI Saturday morning seeming 
very probable. This track and deepening of the sfc low as it 
progresses from MO to MI puts the region squarely in a favorable
zone for robust isallobaric and LL mass field response, aiding 
in enhanced convergence and large-scale ascent for tonight. And
with this track and a very favorable dynamic and kinematic 
environment, traditional thermodynamic evolution, such as 
instby, tends to become slightly less important as the mass 
transport/response can often be sufficient to produce strongly- 
forced vertical ascent amidst an increasingly-frontogenetic 
response. 

Looking more closely at some of the ingredients... the effective
bulk shear of 50+ kts will be /more/ than supportive of storm 
organization likely initially to the W/SW of the ILN FA (more
toward SW IN, W KY) in the form of one or more clusters with 
supercellular structure. Ahead and to the N/E of this activity 
will be LLJ-induced warm-sector storms, which will develop
quickly and overspread the Tri-State/EC IN around/shortly after
02z. This initial activity looks to be primarily elevated in 
nature, with the better LL thermodynamic environment still 
hanging back to the west quite a bit. So even though we will be 
dealing with some heavy rain and some thunder (and perhaps even 
some small hail) between 02z-07z, we do not expect much of a 
severe threat during this time frame. 

By 07z, we will be likely be seeing the remnants of supercellular
structures, which had developed earlier in SW IN and W KY, finally
make their way closer to the ILN FA, riding a more favorable LL
thermodynamic environment that will be supportive of more sfc- 
based activity. Expected to see one or more SW-NE additional linear
convective structures move into SE IN and N KY around/shortly 
after 07z, with the /largely/ unidirectional profile and /very/ 
favorable vertical speed shear still in place (including a H9 
LLJ of 45-50kts and H8 LLJ of 60-65+ kts). It continues to be 
apparent that there will be at least /some/ cross component of 
the LL bulk shear vector to the convective structure 
orientation, helping maintain and enhance LL shear and near-sfc 
SRH, supporting circulations within any convection that moves 
through the ILN FA during the heart of the overnight. Anticipate
that the magnitude of the LL shear (45-50kts) may be sufficient
to overcome the larger angular overlap with the convection 
itself, lending itself to the potential for a few tornadoes 
within the region. And as for the sfc-based instby... despite 
the impressive theta-e advection/LL moisture transport north 
into the area ahead of the front (with sfc DPs in the upper 50s 
and lower 60s and PWATS 250-300% of seasonal norms), will likely
not arrive until after 07z locally. But once this occurs, the 
damaging straight-line wind and tornado threat will begin to 
maximize, perhaps in a 6-hr period from 07-13z before the 
activity quickly moves E toward S-cntrl OH and NE KY after 
daybreak. Synoptic-based and deterministic CAM to depict a 
narrow ribbon of several hundred J/kg SBCAPE nosing north into 
IN and parts of N KY and W OH after 07z. This narrow ribbon of 
slightly more favorable thermodynamics will overlap with an 
impressive kinematic environment, suggesting the SLGHT/ENH risks
placed across the local area are /very/ reasonable and well-
warranted. The UH tracks in the various deterministic and
ensemble CAM guidance suggest we will be contending with several
storm clusters with rotating updrafts beyond 07z, especially
across the Tri-State/northern KY/SE IN and EC IN.

One trend that has been particularly concerning in today's hi-
res guidance has been an increasingly-stronger signal for a
heavy rain and flooding threat. With a very moist and strongly-
forced environment, any training convective activity may yield 
localized flooding, despite the progressive nature of the system
as a whole. With decent overlap between the steering-layer flow
and the orientation of the individual convective elements 
themselves, some training of activity is likely, even with 
individual elements moving quickly within the overall evolution.
Have seen a signal toward this training convection/heavy
rain/flood threat become the strongest across the Tri-State area
and especially northern KY, especially with the elevated
convection priming the soils in the 02z-07z time period before
the more significant storm activity arrives a bit later in the
overnight. While confidence is not quite there yet to issue a 
Flood Watch, this trend will be monitored closely and we have 
added mention in the HWO/official wx briefing for now. An uptick
in messaging may be required later this evening should trends 
become more concerning. 

The other item, and it is not an insignificant one, will 
be the robust synoptic-based winds, especially during the day 
on Saturday. With the trend of a stronger system, a Wind 
Advisory has been issued for locations near/N of I-70, with
additional expansions possible as we get closer to the event. 
In the WAA advection tonight ahead of the FROPA, could very 
well see sustained winds of 20-25kts, especially near/N of I-70,
which in-and-of itself would be close to advisory-level 
criteria. However, behind the front during the day/afternoon on
Saturday, within the increasingly- well mixed BL environment, 
we will see gusts 40+ kts at times for locations further north
where the advisory will be in place. Will see gusts 30-35kts
further south (between I-70 and OH Rvr), with gusts to 30kts 
expected south of OH Rvr.

[cloudy72]

Also to note: Wind Advisory has been issued north of I-70 for later tonight/tomorrow.

URGENT - WEATHER MESSAGE
National Weather Service Wilmington OH
159 PM EST Fri Dec 10 2021

OHZ026-034-035-042>046-051-052-056-110300-
/O.NEW.KILN.WI.Y.0004.211211T0900Z-211212T0000Z/
Hardin-Mercer-Auglaize-Darke-Shelby-Logan-Union OH-Delaware-Miami-
Champaign-Licking-
Including the cities of Kenton, Ada, Celina, Coldwater,
Wapakoneta, St. Marys, Greenville, Sidney, Bellefontaine,
Marysville, Delaware, Troy, Piqua, Tipp City, Urbana, and Newark
159 PM EST Fri Dec 10 2021

...WIND ADVISORY IN EFFECT FROM 4 AM TO 7 PM EST SATURDAY...

* WHAT...West-southwest winds 20 to 30 mph with gusts up to 50
mph expected.

* WHERE...Portions of Central and West Central Ohio.

* WHEN...From 4 AM to 7 PM EST Saturday.

* IMPACTS...Gusty winds could blow around unsecured objects.
Tree limbs could be blown down and a few power outages may
result.

[Bgoney]

DPs

Screenshot_20211210-154315_Chrome.jpg

[Bgoney]

Also to note: Wind Advisory has been issued north of I-70 for later tonight/tomorrow.

URGENT - WEATHER MESSAGE
National Weather Service Wilmington OH
159 PM EST Fri Dec 10

Free end of the season gutter cleaning for everyone

[tron777]

ADMIN NOTE

Folks,

We are trying something new. Please continue the severe wx talk with this next system in the dedicated thread Trev had made. Direct link below.

https://www.absolutevorticity.com/viewt ... p?f=9&t=93

Please continue to use the monthly December thread for normal model analysis and long range discussion as we've always done. What we are experimenting with is that when we get a big ticket item, severe wx, snow storm, etc, we are going to try to create a new thread for said event. We are trying this to try and get more people to join our awesome forum and get more folks involved in the discussion.

If anyone has any questions, comments, or issues, please IM an Admin directly. Me, Trev, or Aaron Thanks!

[Trevor]

Trying something new: future posts about the developing severe weather threat should be posted in the new thread. All other general wx discussion can go on as usual in here!

[Trevor]

Les ya beat me to it haha! Thank you sir

[tron777]

Les ya beat me to it haha! Thank you sir

Somebody has to clean up your mess!

[tron777]

Long range EPS Days 9-14.... this would be nice to see if it holds around Christmas. Temp anomalies below.

EPSCold.png

[Bgoney]

It would be nice to have something close to average instead of our current situation. The 500mb players are trying

1897730934_12zEPSfullrun.thumb.gif.85ee32f61a01ace402259b0ca64ad1e0.gif

[tron777]

Good morning! We will spike up into the 60s again next week, probably by Wed. Best chance for rain looks to be with our next front around Thurs and Fri. Thankfully, we should not see a severe wx event like what we just had, but we will be watching to see if t-storms do develop once we get closer.

What's interesting about this is that the front stalls nearby and we will have several waves of low pressure riding along it. GFS is wanting to show a nice baroclinic boundary and if we can get some cold air involved, perhaps some wintry weather finally entering the picture by next weekend and as we kick off Christmas Week for portions of our forum area. We will also need to keep an eye on this set up as next week progresses. GEFS is also on board. Euro showing all rain because the front is by us well to the East by the time the cold air does come where the GFS still has the front much closer to us.

[cloudy72]

Indy down to 39 now

[cloudy72]

Storm total up to 1.17” now that the line went through. High was 65 around 5:00 am - 57 and plunging now!

[tron777]

The line is just moving into my hood now... Still 62 but it won't last much longer of course.

[tron777]

Wow... blinding rains and winds gusting to 50 here. This line is no joke!

[cloudy72]

Must have been a pre frontal wave as it’s back up to 59 now. Front is not too far behind so we should start plunging into the 40s in next couple of hours

[tron777]

Front has now passed and temps beginning to drop. 57 now... Rainfall total for this event imby is 0.56". Pretty wicked visible sat. image where you can clearly pick out the front.

1kmv.gif

[Bgoney]

65 here

[MVWxObserver]

My gauge picked up 1.40"

Currently 45 here in G'ville with a gust of 41 mph.

Last night while in bed the rain at times hitting against the windows sounded like paper crumpling.

[young pup]

It has reached me. Thinking I should have moved that truck. Sheets of rain blowing through.

[Bgoney]

1.1" total here

[cloudy72]

Temp down to 40 here with wind chills in the upper 20s!

[MVWxObserver]

Will have to keep a firm grip on the mail today, unless of course you have a door slot one. The only door slot one I can recall from my past was one when my sister were Pre-K and K during our years in North College Hill.

Currently 36 with a 54 mph gust here in G'ville.