CheeselandSkies

I'm just gonna enjoy the nice rain we're having right now.

Video is now live:

Here's hoping Monday is as much of a washout for IA/NW IL as it looks to be on the GFS.

Fair enough.

I have a premiere set up for my 1-year anniversary re-edit/upload of my Keota chase video. Sunday 3/31 at 8:30 AM CDT.

The probabilities on the Day 4 and beyond outlooks don't have a direct correlation to the Day 3 and closer. The 30% zone is for all hazards. For an Enhanced risk, the wind OR hail probability has to be 30% OR the tornado probability of 10%. So it all depends on how things trend and how confident they are. They treat the longer range outlooks a little differently than they used to. Nowadays, they'll introduce a 15% at Day 6 if they're reasonably confident in an at least 15% probability of wind or hail (slight risk) maintaining itself by Day 1. Twenty years ago, if you saw a 25% (then used for a "high-end" slight risk, what would be an Enhanced risk today, the minimum threshold for a slight risk was 15% just like now) contour on the Day 3 outlook, it implied above-average confidence in a widespread/high-ceiling threat and a good chance of a high risk popping up at some point on Day 1.

Ahead of the 1-year anniversary of the 3/31/23 outbreak, NWS Quad Cities has put out a video breaking down the setup for the outbreak in their CWA, including the Keota etc tornado family. One of the frame grabs I sent them is in the graphic at 4 minutes (and on the thumbnail). I was diving a little bit into the archived SPC data earlier this week, and DVN's summary here jives with my impression that this event was surprisingly thermodynamically driven for an early-season Midwest setup. While certainly more than adequate for significant tornadoes given the other conditions in place, the low-level shear (at least in terms of raw SRH values) in this area wasn't jaw-dropping by high-risk, violent tornado outbreak standards. What really put this over the top IMO was the 3CAPE and lapse rates, as well as nearly optimal streamwise vorticity ingestion per the hodograph allowed for maximal use of what spin there was in the atmosphere.

The equinox was only a week ago, lol.

Primary severe threat with early next week system looks to remain southwest of the sub on Monday, with steep positive tilt mitigating things going into Tuesday, but it should bring a considerable amount of rain to a large area.

Oof.

Well, I am a chaser and I do love severe weather, but I advocate for restraint on social media hype unless/until there is actually good model agreement/consistency for a high-ceiling threat.

Every time Weed sees a trough on the models, he drives the social media hype train out of the station at full throttle, derails, crashes, and burns. I remain skeptical of this timeframe due to inconsistency between models/runs. Could it turn into something big? Sure, but IMO it's just as likely at this point to be a relatively modest event with a lot of rain/general thunderstorms and some isolated severe weather.

So when I got to work this morning the thermometer in my car said 27 degrees, and we had a stiff west-northwesterly breeze. 7-day forecasts from my employer and the NWS are rather depressing, with nothing outside of 40s and 50s. When's the flip back to much AA?

DMX with a great AFD write-up on all the potential impacts of the Sunday-Monday system including severe and synoptic winds. DVN/ARX seem purely concerned with snow despite the potential for the narrow instability sweet spot to set up at least partially in one of their CWAs.

SPC's highlight is much further south, but the 12Z NAM (and most antecedent GFS runs up to this point) would certainly support a severe/ threat in a narrow arc across eastern Iowa Monday afternoon. Those hodographs and 3CAPE are something else, if not for the antecedent Gulf drying, I really think we'd be staring down the barrel of another significant late March outbreak. The one thing I will say is that the surface low appears to be weakening with time on Monday; whereas last year March 31 it was deepening or at least holding steady. That might have mitigated the overall threat some in any case, but even so that's a pretty impressive profile despite the paltry on their face T/Td values. You only have to go back one more year (and in the very same state no less) to see what can happen when a setup like that overperforms.

Same.

We don't need no stinking METARs!

Based on what guidance, out of curiosity?

Some moisture issues to sort out, but quite a bit of potential there *if* things trend favorably.

Sounds like that would mean more chances, as well although of course the crucial specifics of any one setup are hard to pin down at this range. GFS has been less enthusiastic about the "open Gulf" idea, as it has been pretty consistently spinning up some sort of southern stream low in the Gulf that runs up the East coast, with its associated cold front plunging south and scouring out the moisture. However it could be completely out to lunch with this. Seen it lock onto a particular idea (such as formation of a TC in the western Caribbean) for something like 120-150 hours worth of runs only for it to not happen. Edit: The feature I talked about is still there in the incoming 00Z run. FH111, 1007mb coming into the Florida Big Bend and then runs up the coast, dewpoints get dropped to the 50s across most of the Gulf (even upper 40s along the Florida Panhandle coast).

Eight years ago today, a localized tornado outbreak occurred across central Illinois. Synoptically the setup was pretty classic with the left exit region of the midlevel jet squarely over the area and a deep surface low. However marginal/"just-in-time" moisture was an expected issue with dewpoints only reaching the mid-50's by go time. However with cold air aloft and the excellent kinematics, it was enough. Although, my chase partner and I thought our tornado chances were done for the day when we pulled into the Casey's gas station on IL-116 at the west edge of Hanna City, ahead of the "tail-end Charlie" cell on the next cluster of storms north of the one that would produce the tornado just west of Springfield around the same time. The storm wasn't looking that impressive on radar and our plan was to gas up, get snacks and drinks, and let the storm roll over us, sheltering his car under the gas station canopy if there was hail and then shoot lightning on the back side on the way home (I never uploaded any of the video from before the tornado encounter until now, I'd forgotten how electrified the storm already was at that point). It was at this point that several things happened in rapid succession. We felt a gust of warm inflow toward the storm still off to our immediate west (when, based on the prior radar presentation, we were expecting cool outflow), which should have been an "Oh s***!" moment but we just kind of shrugged it off "huh, that's interesting." What we didn't know was that the storm had just undergone a constructive cell merger. The radar updated to reveal, while not quite a classic hook on reflectivity, a definite RFD gust front curling back into an inflow notch, with an intense velocity couplet colocated with it, just off to our northwest! Both our cell phones alerted simultaneously with a WEA for a tornado warning, and the town's sirens blared to life! I'll let the video and its accompanying description tell the rest of the story... I'm conflicted about counting this as my first tornado, since we weren't 100% sure of it in real time, and it cannot be confirmed from my imagery alone due to the intervening tree line at the ground. NWS ILX surveyed a 7.1 mile path of up to EF2 damage from northwest of Trivoli to north of Hanna City that matches up with the time and direction of our view. This was one of three EF2 tornadoes to occur with the event; the best-known is probably the earlier one that occurred near Good Hope.

Yup...NAM tease. The lack of prior support from the globals was always a red flag, although one can hope.

Although, this year we've already had multiple events along/north of the IL-WI line starting in frickin' early February. It would be ironic if we started having issues with that now as we finally get into mid-March, on Daylight Time and close to the equinox.

12Z 3K doesn't have the WF getting much north of the IA/MO line, and rakes MO with supercells. Unfortunately that'd be out of range for me for a work-night chase.

Yup. Definitely would rather see the low intensifying with the mass response pulling the warm front northward or at least stationary.