All model guidance seems to be in agreement that the severe threat for south Mississippi will remain on the “low end” of things on Tuesday. A combination of good timing and a lack of low-level return flow in the area means the potential for severe weather will remain low and isolated to individual storms that just happen to develop at the right place at the right time – and forecasting that is outside the scope of meteorological ability.
Quick synopsis of setup
As the next area of low pressure moves through the area, there will be a lack of overall organization of the necessary parameters for severe weather. Often with storm systems moving into the area, when an area of low pressure at the surface develops, and it is in teh same general area as an area of low pressure aloft, the atmosphere does a “good job” at putting the rest of the pieces together to promote the development for severe weather.
While still possible, it just isn’t as likely this time.
I mentioned the other day that it was odd that the models were showing such a disorganized system and that it didn’t make much “meteorological sense” given the time of year and general potential for storms built like this one. But here we are. With an area of low pressure moving through that is reasonably disorganized.
The only asterisk
The Karrie Meter is still holding onto a chance for severe weather.
While a 2.65 does estimate a risk level between a Marginal Risk and a Slight Risk from the SPC, the “3.64” at the bottom is a new little number I’ve been working on for the last few years. The number itself is meaningless. But it is the ratio of that number vs the Karrie Meter number. When it is higher, there is an increased potential – with all other things being equal – for a tornado to develop.
In this case, because the risk is so marginal, any tornado that would develop would likely be very short-lived and pretty weak, but it does suggest it is possible. So keep an eye to the sky late tonight and through Tuesday morning.
The Karrie Meter map shows much higher numbers north of the warm front, but thankfully those are also meaningless numbers. Once you go north of the warm front, the overall threat for severe weather diminishes because all of the “stuff” to make severe weather is stuck up in the clouds.
From the SPC
Speaking of the SPC….
Day 1:
Convection will become more widespread along and north of the warm front through the period, as strengthening large-scale ascent (warm advection area-wide and DCVA in western parts late) overspread the region, with destabilization aloft. The most intense cores north of the front could yield isolated marginal to sub-severe hail, while the gust potential will reside mainly in the near-surface frontal zone southward over the adjoining warm sector. Given the intensifying flow aloft, and related increase in deep shear, supercells are possible, along with multicell convection, including organized clusters and bowing segments. As such, a tornado cannot be ruled out, especially along and just south of the front, though potentially messy mode and weak lapse rates will limit buoyancy substantially. Even in the warm sector, MLCAPE should be only around 500 J/kg east of the Sabine River.
The severe threat is expected to be constrained:
1. With northward extent by increasingly stable, less-buoyant air north of the frontal zone, and
2. With southward extent by weaker lift/convergence in the warm sector, and the somewhat related issue of gradual storm maturation as cells get closer to the frontal convergence max.
3. Somewhat on the west side, as low-level streamline forecasts and corresponding UVV progs suggest a zone of enhanced low-level convergence will form in the warm sector over east TX and act as a preferential convective genesis zone, in addition to the front itself. The maximized outlook probabilities reflect these limits, with the eastern extent representing a probable range of surface-based strong-severe convective potential around the end of the period.
Day 2:
Scattered showers and thunderstorms will likely be ongoing with in a zone of warm air advection, aided in part by a 55-kt southwesterly LLJ over MS. The strengthening southerly, low-level flow will advect richer moisture northward during the day, coincident with the diurnal heating cycle. Despite modest mid-level lapse rates, 250-1000 J/kg MLCAPE is likely across the coastal plain of AL into southern GA by midday. Forecast soundings show veering low levels beneath strengthening westerly flow with height, supportive of organized updrafts, including supercells. In addition to damaging gusts with the stronger storms, a tornado risk could develop as early as midday over AL and spread east into southern GA during the afternoon. This activity will likely weaken by early evening as the surface low moves east of the Atlantic coast and veering boundary-layer flow/nocturnal stabilization contribute to a diminished severe risk.
Even the CIPS is pulling back…
While there is still a chance for severe weather, the CIPS Analogs is also showing a overall lower potential. Originally, a few days ago, it was highlighting parts of Georgia and Alabama with a pretty decent shot for seeing severe weather. Now, not as much.
Bottom Line & Timeline
It looks like there will be a low-end chance for seeing some severe weather. That means most people will just get rain and thunder. A few people will see a stronger storm. And even fewer will see a severe storm.
The main concern within any severe storm will be heavy rain, lightning, gusty wind, small hail and the potential for a brief and weak tornado.
The timeline shows between about 2am and 10am on Tuesday morning.
