December 2021 Weather Discussion

[Bgoney]

SPC is catching up to the severe threat early Saturday. No changes , DPs, 850 winds, shear, temps, typical OV high shear , low cape event . Friday , scattered afternoon/ evening showers , then the squall lines in the 1-8am range Saturday. A bit earlier range for now , on timing , as sometimes the momentum can speed up. Another couple model runs should narrow that down

[tron777]

Good morning all and I'd like to wish our fearless leader, Trev... a very happy birthday today! Even though you're a damn heat miser, I wish you all the best man!

Okay so on to our severe wx threat... SPC has increased the slight risk area to include SE IN and NKY with a 5% tornado risk and 15% wind. A marginal risk for the rest of AV Country. Enhanced risk for the Western half of KY with a 10% tornado risk down there. We will continue to watch the data today and tomorrow. Best time for severe is Fri night with the cold front coming in so be weather aware as you may get woke up by your weather radio (which is a good thing!)

Overnight discussion from the boys:

The extended period begins Friday night with strengthening surface
low pressure lifting from the lower Missouri River valley to Lake
Michigan by Saturday morning. Strengthening southwesterly flow
ahead of the system will bring Gulf of Mexico-based trajectories up
through the Ohio Valley with 850mb winds in the 60-70 knot range
from the south and southwest. Dewpoints should rise through the 50s
to nearly 60 in this warm air advection regime. Advance checks of
the 3km NAM show areas of highly sheared showers and storms through
the pre-dawn hours. Am hesitant to buy off on the NAM`s depiction of
entirely elevated convection (which is not the case with the GFS);
thus believe that during this first phase, mass convergence from the
LLJ along with modest instability could lead to heavy rain and a few
strong to damaging wind gusts with developing convection. Will need
to keep an eye on forecast soundings as additional high-resolution
models become available later this morning.

The second phase will occur along and immediately ahead of the cold
front Saturday morning. Strong December-like forcing along with
increasingly surface-based CAPE provides concern for a QLCS-type
line of convection -- one with sfc-3km southwesterly shear reaching
around 70 knots. The main hazard will be damaging winds but will
also need to watch spin-up type tornado potential with any bowing
line segments that may develop. In addition, multiple rounds of
heavy rain will raise flash flooding concerns.

Post-frontal CAA will be in full swing for midday Saturday through
the afternoon hours as temperatures fall from early morning highs
near 60 down into the 30s by late in the day. Latest guidance
provides wind gusts in the 30-40 knot range north of Interstate 70,
so will express this potential in the HWO.

[tron777]

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[tpweather]

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Good Morning Les and that is impressive anytime of the year but early-mid December is saying something about this system. Mother Nature really trying to balance out the earth at the moment and that is why we are seeing these rare events. Normally though when we start to see these events a change is a coming and looked at the extended gfs and finally starting to see some cold around Christmas. Look at the mjo and the wave is making progress and if that continues then the colder outlook looks wonderful. How cold is the next issue we have but I have no problem with that issue.

[Trevor]

Thanks Les!! Looks like Mother Nature will provide me with some boomers for a late bday gift. I do like the look of things for tomorrow night regarding potential severe weather. Best threat is south/southwest, but we are very much in the game up this way. Extra emphasis on risk due to it being an overnight event when folks are in bed. Slight risk will more than likely expand a bit north and east in future updates based on model trends.

[tron777]

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Good Morning Les and that is impressive anytime of the year but early-mid December is saying something about this system. Mother Nature really trying to balance out the earth at the moment and that is why we are seeing these rare events. Normally though when we start to see these events a change is a coming and looked at the extended gfs and finally starting to see some cold around Christmas. Look at the mjo and the wave is making progress and if that continues then the colder outlook looks wonderful. How cold is the next issue we have but I have no problem with that issue.

The fantasy 0Z GFS had a 1050 MB high over S Canada dropping some cold into the CONUS. The high was almost 1060 MB on the 6Z run. Fantasy range I know but the colder idea as we approach Christmas and esp beyond is gaining some traction.

[tron777]

Thanks Les!! Looks like Mother Nature will provide me with some boomers for a late bday gift. I do like the look of things for tomorrow night regarding potential severe weather. Best threat is south/southwest, but we are very much in the game up this way. Extra emphasis on risk due to it being an overnight event when folks are in bed. Slight risk will more than likely expand a bit north and east in future updates based on model trends.

Yeah... looking really interesting for sure Fri night. Curious to see what some soundings look like from the hi-res NAM and HRRR come tomorrow. Not really going to worry about checking that today since it's only Thurs. Def looking like the shear and spin will be there, just a question of how much elevated CAPE can we get? If it happens to become surface based (which is very rare for the cold season) then watch out! I'll say one thing... if the model data showing dews getting close to 60 degrees plus by the time the front closes in then that is very concerning to me to add that fuel esp this time of year.

[Trevor]

[flash=][/flash]

Thanks Les!! Looks like Mother Nature will provide me with some boomers for a late bday gift. I do like the look of things for tomorrow night regarding potential severe weather. Best threat is south/southwest, but we are very much in the game up this way. Extra emphasis on risk due to it being an overnight event when folks are in bed. Slight risk will more than likely expand a bit north and east in future updates based on model trends.

Yeah... looking really interesting for sure Fri night. Curious to see what some soundings look like from the hi-res NAM and HRRR come tomorrow. Not really going to worry about checking that today since it's only Thurs. Def looking like the shear and spin will be there, just a question of how much elevated CAPE can we get? If it happens to become surface based (which is very rare for the cold season) then watch out! I'll say one thing... if the model data showing dews getting close to 60 degrees plus by the time the front closes in then that is very concerning to me to add that fuel esp this time of year.

Correct. CAPE levels are what are keeping things from going crazy up this way. Still a notable risk regardless. But like you said if we can manage to get a couple to few hundred CAPE, tornado risk will surely increase.

[tpweather]

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Good Morning Les and that is impressive anytime of the year but early-mid December is saying something about this system. Mother Nature really trying to balance out the earth at the moment and that is why we are seeing these rare events. Normally though when we start to see these events a change is a coming and looked at the extended gfs and finally starting to see some cold around Christmas. Look at the mjo and the wave is making progress and if that continues then the colder outlook looks wonderful. How cold is the next issue we have but I have no problem with that issue.

The fantasy 0Z GFS had a 1050 MB high over S Canada dropping some cold into the CONUS. The high was almost 1060 MB on the 6Z run. Fantasy range I know but the colder idea as we approach Christmas and esp beyond is gaining some traction.

Les no doubt I was a couple weeks ahead of the change and Bgoney caught this first but in November the mjo was not moving at all for such a long time. This was delaying the true pattern change and we are still trying to get there but with these stronger systems we are working towards the colder pattern. Last week when the big storm hit Alaska this was imo the start of the change and though the low went a little further northwest than I thought it did bring in a milder period for them. Saying that we have another decent storm heading into Alaska but much further to the southeast and yes more snow for some areas but it will keep them colder than normal for about another 5 days. Though we are very mild cold air continues to build in the northern 1/4 of the globe and heading into mid-late Dec that cold may get a little stale but withe total darkness in many areas that cold will be good for quite awhile.

[cloudy72]

Happy Birthday Trevor!

[tpweather]

Happy Birthday Trev!!! Hope you have a wonderful day and I know you are loving the warm weather.

[cloudy72]

It certainly is amazing to think with current temps in the 25-30 degree range that we will see potential 60+ dewpoints in here in just over 40 hours!

[cloudy72]

Slight risk by SPC certainly matches the overnight 3km NAM STP parameter of 2+ pretty well. This is for 4am Saturday.

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[cloudy72]

So since most on this board are cold weather lovers, check out this tweet regarding record cold in Russia:

-61.1°C in Delyankir (#Siberia )! - this is -78 Fahrenheit!!

First -60°C in #Russia in December since 2008 (-60.0°C Oymyakon, Dec. 20).

Coldest temperature in Russia in Dec. since 1984 (-62.8°C Oymyakon, Dec. 15).

One of the coldest temperatures ever recorded in Russia in early December.

[tron777]

Great posts guys... keep 'em coming! If temps can be in the 60s Fri night which by the looks of things is doable as well as dews at 60 plus then the concern for strong winds and a few tornadoes is there. Once we get past this system, we drop to seasonal temps briefly before torching next week, esp by Wed and Thurs. Then another front moves in by late next week then we'll see how things look beyond that once we get closer heading into Christmas.

[tpweather]

So since most on this board are cold weather lovers, check out this tweet regarding record cold in Russia:

-61.1°C in Delyankir (#Siberia )! - this is -78 Fahrenheit!!

First -60°C in #Russia in December since 2008 (-60.0°C Oymyakon, Dec. 20).

Coldest temperature in Russia in Dec. since 1984 (-62.8°C Oymyakon, Dec. 15).

One of the coldest temperatures ever recorded in Russia in early December.

Looks like we have been playing cold around the world that past 40 days or so. Started in northeast Asia, then we hit Alaska,Canada, Scandinavia and finally Russia. Over the past several days Russia has gotten really cold but that of course has warmed up much of Canada. Hopefully this is a sign to get some of the really cold air into some of the lower Latitudes over the next month or so.

[cloudy72]

Yikes! Significant tornado parameter from SPC SREF model valid 9z Saturday (4am)

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[tron777]

Wow Mike... very impressive for December!

[tron777]

What the heck... 6Z Hi Res NAM sounding near CVG valid at 9Z Sat morning just before the pre frontal trough comes thru.

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6Z HRRR valid at 6Z Sat (end of the model run so fantasy range but....)

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[tron777]

StormTalk! https://www.wave3.com/2021/12/09/stormt ... pdate-129/

[Bgoney]

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Good Morning Les and that is impressive anytime of the year but early-mid December is saying something about this system. Mother Nature really trying to balance out the earth at the moment and that is why we are seeing these rare events. Normally though when we start to see these events a change is a coming and looked at the extended gfs and finally starting to see some cold around Christmas. Look at the mjo and the wave is making progress and if that continues then the colder outlook looks wonderful. How cold is the next issue we have but I have no problem with that issue.

Looking at satellite pics over the MJO region this morning, imo, the MJO wheel is very generous in its eastward position phase 7. I see Very little convection near/east of the dateline , which is where 7 lies

[cloudy72]

60 degree dewpoints now currently surging north into NE Texas and even some 70 dewpoints along the Texas Gulf Coast.

[cloudy72]

Looks like La Niña will be winding down and heading into neutral for the spring and summer 2022.

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[cloudy72]

12z 3km NAM coming in and actually looking more ominous to folks SW of us. Take a look at Paducah sounding for 6z Saturday......wow!

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[cloudy72]

Here is CVG at 8z Saturday - helicity over 400!

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