December 2021 Weather Discussion

[Microburst]

Surface CAPE from 18Z ECMWF model.

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Saturday 7 AM EST composite reflectivity.

[MVWxObserver]

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[Microburst]

The 00Z GFS run is showing rainfall totals near 1 inch in most locations by Saturday evening. We'll see winds pick up through the day on Friday with winds gusting to near 30 mph by Friday late evening. Winds overnight into Saturday may gust towards 45-50 mph. Please secure loose items outdoors and exercise caution for high-profile vehicles. Power outages due to the wind alone is also possible.

[Bgoney]

Definitely time to see what the ILN boys have to say when they update this morning. In the meantime severe threat a go . Should see a few isolated showers early evening but the big show, still going with just after midnight for the region as scattered storms should develop and make there way NE throughout the overnight AM , with a crescendo squall line somewhere either side of dawn.

[Bgoney]

Quick note on MJO, mentioned yesterday ,after looking at satellite observations,, the "wheel" was quite generous in it eastward advancement into phase 7 and looks to be correcting that this morning doing the infamous loopty loop ,which basically means it was to fast. So , Slowly but surely I expect it to keep rolling eastward into 7 over the coming 10 days , hopefully, and we should see a response in the 500mb pattern down the road especially in the PAC where it has been stuck for the last 2 months

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[tron777]

Good morning and Happy Friday to you all! Well folks... we've got a lot on our plates here with a wild December coming up! Our first order of business is of course, the severe wx event for tonight into tomorrow morning for the entire area. We will get another severe wx outlook update from the SPC in about an hour or so. We will try and post some soundings from the hi-res and meso scale models today. If work keeps me busy then I am sure others will step in like yesterday (which I again appreciate very much! ) I don't have too much to add for now as I think we've got it covered pretty well. I agree after midnight with the timing with scattered severe storms and some heavy rain / wind/ as well as isolated tornadoes all will be possible. Then a few hours of a break then the squall line with the cold frontal passage in that 5-8am range. Winds will keep on cranking all day long on Saturday with falling temps. You will want to secure all outdoor objects and Christmas decor today.

[tron777]

Overnight discussion from the boys:

Code: Select all

Dynamic mid/upper level system will shift east out of the
Plains and across the Great Lakes region tonight into Saturday.
An associated surface low situated near northwest MO early this
evening will deepen as it lifts northeast into the northern
Great Lakes through Saturday afternoon, with an attendent cold
front sweeping east across the Ohio Valley late tonight into
Saturday morning. This will be accompanied by impressive wind
fields with a 70+ knot 850 low level jet shifting east across
our area later tonight into early Saturday morning.

In continued southerly low level flow ahead of the front,
temperatures and dewpoints will continue to warm through
tonight, with lower 60 dewpoints possibly making it all the way
up into southwest portions of our area after midnight tonight.
This should allow for at least some weaker surface based
instabilities to advect/develop into our area through the
night, possibly up to around 500 J/kg or so across at least
southwest portions of our area. The CAMs continue to show a
fairly wide range of solutions as to how convection may possibly
develop later tonight with the pre frontal trough ahead of the
front and then also with how much convection may develop along
the front as it pushes east across our area Saturday morning.

Given the strength of the low level jet, would expect to see
fairly wide shower and embedded thunderstorm development across
our area after midnight tonight. The storms will likely start
off more elevated, but will then become more surface based as we
start to get into some better surface based instability ahead
of the front late tonight. Damaging winds remain the primary
threat, but given the strength of the low level wind fields, a
tornado or two will also be possible, with the main threat
looking to be in the 3 AM to possibly 10 AM time frame late
tonight into Saturday morning. While locally heavy rainfall will
be possible, especially with any training cells, the system
appears to be progressive enough to limit any widespread
flooding concerns.

As the front moves through, pcpn will taper off quickly from
the west with good CAA developing across the area. This will
allow for windy conditions through Saturday afternoon with
wind gusts in the 30 to 40 mph range likely. Temperatures will
also peak out early in the day with falling temperatures through
the afternoon.

[cloudy72]

6z HRRR certainly looks ominous for us tonight. A one two punch - cells out ahead of the main line in the 11:00 pm to 2:00 am timeframe could be rotators then the squall itself in the 5-8 am timeframe Saturday.

[cloudy72]

…

4F1D1DAE-FD78-4926-A2B5-7BFDD0A4ACB0.jpeg

[tron777]

6Z 3KM NAM does as well. 400-500 SRH 300 J/kg of SB CAPE also.

[cloudy72]

New 12z SPC Day One outlook....

day1otlk_20211210_1300_prt.gif

[Bgoney]

Going with 1-2"+ for at least half the region. With the mostly NE movement of storms they'll be over areas a few minutes longer than if they were just blasting eastward, so for those that get 2 or 3 storms , I think can reach these amounts easily

[tron777]

Looks like the 5% TOR area is for most of the Tri-state area and 2% for I-70 posters. 15% wind for everyone. Dews in the 50s are over Western TN and far SW KY at this time, which will only continue to spread NE as the surface low continues to deepen today.

[tron777]

PWATS in excess of 1" are already over the Western half of KY. I just don't remember a set up quite like this before in December and esp with it being at night. Pretty crazy! We've already got 50 knot bulk shear over us as well. 70 knots are lurking off to the west closer to the surface low. Helicity values are already pushing 300-350 over West KY. Wow...

[cloudy72]

12z HRRR still looking nasty.....gotta watch those cells out ahead of the main line back in Illinois - this is around midnight tonight.

hrrr-conus-indiana-refc-9198800.png

Helicity at this time - yikes!

hrrr-conus-indiana-hlcy_0-3000-9198800.png

[cloudy72]

Updraft helicity tracks.....

hrrr-indiana-upd_hlcy_5000-2000_accum-9220400.png

[tron777]

HRRR probably has been the most aggressive but the NAM isn't too far behind either. A pretty concerning look...

[BookNerdCarp]

Last December tornado was 2016?

[fyrfyter]

12z HRRR still looking nasty.....gotta watch those cells out ahead of the main line back in Illinois - this is around midnight tonight.





Helicity at this time - yikes!

This stuff looks downright rotten! I am thinking If this cellular stuff builds up, it may be the more threatening event of the night, especially with the helicity like that.

We have also seen before where the prefrontal activity steals most of the instability from out atmosphere before the front actually gets here. That seems to be a distinct possibility as well.

[tron777]

Last December tornado was 2016?

Dec of 2015 per Local 12.

DecTOR.jpg

[tron777]

BG StormTalk! https://www.wave3.com/2021/12/10/stormt ... date-1210/

[cloudy72]

Great video from BG! Will definitely have to watch that lid for our hoods as well. As he said, an earlier erosion of the lid the higher potential for supercells and maybe tornadoes.

[Bgoney]

Could get our first watch of the year for many overnight

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[tpweather]

Could get our first watch of the year for many overnight



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That is taking it to the wire.

[Bgoney]

Hmmm, GFS says , "this severe stuff is fun , let's do it again maybe next Thursday/Friday. "