Refined threat dates. Has some serious potential IMO.

First of all, I do apologize that the model pic in the last post is outdated. I did not know that even after uploading an image to Blogspot, the image is still active and auto-updating.

A note on the last system -- 1 person was killed in New Orleans, LA as a result of a nocturnal tornado. I pretty much busted on the last system as I didn't anticipate that nocturnal event, which was probably a result of localized enhanced low level shear from the warm front.

OK, onto next week.

As the polar vortex in the northeast begins to retreat, the flow over the CONUS begins to turn more zonal. One thing to keep note is that the ridge over the western CONUS has not been a true block, so to speak, so it is undercut quite nicely (this is unlike Jan. 2003, when the ridge was an Omega block that persisted for entire January, preventing any sort of severe wx). SST's and the ENSO support mild Pacific air beginning to infiltrate the CONUS next week as the Pacific jet stream is allowed to impact the CONUS unobstructed. Thus, the flow begins to turn zonal.

(Note that several significant outbreaks have occurred after this scenario occurred. Several I can think off the top of my head:
4/3/1974
3/13/1990
1/21/1999
3/12/2006
11/10/2002

I suspect that the remains of the cool air allowed for steeper lapse rates than what would be expected, and also, the atmosphere is in a constant state of balance, something I explained when I started the thread on Eastern two weeks before the 11/14-16 tornado outbreak in 2006.

There are other times where it did not occur, but I have explained that in my previous paragraph before the parentheses using Jan 2003 as an example.)

Disturbances will ride along the jet stream. A slight ridge will still remain, which the initial disturbance will cut through. This disturbance could spark the first of possibly two severe wx events. Timeframe: Feb. 20-22. Threat should not be too significant although a localized outbreak is possible. This was the system that I harped on a week ago. However, this is not the big tamale, so to speak.

The first disturbance will leave a perturbation in the flow as the weak ridge retrogrades to the Aleutians. This leads to a trough downstream. All the ingredients come together for a vort lobe or a shortwave to accelerate down the eastern side of the ridge, carving out another trough over the Intermountain west. This is the second system. Timeframe: Feb. 23-26. This could be significant. Since the image I posted, each GFS operational and ensembles run have showed 1) trough digging in the intermountain west and tugging eastward, and 2) a sub-1000 low. Incredible model consistency, and stuff that really deserves watching. How fast the first system goes away will be critical in determining how much return flow will be available for this system. If sufficient, this really has a LOT of potential to be a significant severe wx outbreak from the Plains to the foot of the Appalachians, and from the Gulf Coast all the way up to the Great Lakes.

Basically, after that, I believe there are two options:
1) If the Feb. 23-26 system turns out to be large amplitude and wide, it could merge with the remnants of the Polar Vortex over Canada and draw another shot of cold air over the eastern CONUS, ending the severe wx threat.
2) If the AO (Arctic Oscillation) does not remain negative, zonal flow should begin to dominate; there will be no sufficient Polar Vortex over Canada.
3) The Pacifc could reload, resulting in another outbreak.

In reality, I believe the first option is the most likely at this time to start out March. Looking out REALLY long range, another high-impact event is possible in mid-late March if Scenario 1 verifies. If Scenario 2 or 3 verifies, any additional severe wx events should be relatively localized and small until later in spring (possibly waiting until late April or May).

Anyhow, some other pros' comments:

DVD on EasternUSWx:

And now, on to the next one.....give it 7-14 days and I think the severe weather crew will be very busy. Just a sneak preview there of what I'm preliminarily beginning to think.

Hoosier4caster on EasternUSWx:

I reappear just to be the bearer of bad news...All sign's pointing to the end of winter for much if not all of the E Conus after the period of 19th to 22nd. Indices have been hinting at this for days...with model representation of the upcoming pattern change. So start gearing up for Svr weather season...its right around the corner! There maybe a brief shot of colder air...but nothing like what we have seen the last few weeks. And no I don't think we are heading for 60s either, just normal to slightly above...as the pattern change is at hand.

Now, the following are images from the Op GFS since the Feb.12, 12Z run, to prove its consistency. You'll have to trust me on the Ensembles, they have been agreeing well.

12Z Feb 12 run:



0Z Feb. 13 run:



12Z Feb. 13 run:




0Z Feb. 14 run:



I hope you get the point. This does not even include today's runs which continue to show this.
After 5 or 6 primary runs that have good support from the Euro and the Ensembles, I think it's a good betting hand.