WAA morning convection influence

[Andrew Clope]

It seems that this last weekends system was influenced by what I saw termed as WAA thunderstorms and MCS's the morning of. I was just wondering if there's a way to forecast this, and determine ahead of time how this will play out before picking target areas? I would imagine that the SPC would take this into account when making their outlooks?

Also, I noticed that there was not much inhibition this weekend, a lack of an EML. Was this the reason that the storms were able to fire early in the morning? Or were they elevated mostly above the EML?

Is it something that can be forecast with great accuracy or is it something that you guys just use the 4k nam for?

 

[Greg Blumberg]

Currently there are big issues with knowing how much nocturnal thunderstorms will affect the morning of a severe weather setup. This comes primarily from not understanding entirely what controls the evolution and development of night time convection, which will be the topic of a big field project this summer called PECAN (Plains Elevated Convection At Night). Nighttime convection is a giant wall in front of how well we can convection the following day. One of the easiest synoptic setups (there are many) you can have to deduce whether or not convection will affect the area is a.) looking for if there is a surface boundary (front, outflow boundary, etc.) nearby and b.) instability (most likely elevated...see my other post), and c.) looking to see if low-level flow will force parcels upwards as it ascends along the aforementioned boundary. SPC does take this into account, and this was many of the reasons why many of their outlooks over the last week or so have mentioned (from Saturday's 6 UTC Day 1):

ANOTHER MESSY/COMPLEX FORECAST AS EXTENSIVE CONVECTIVE OVERTURNING
OCCURRED ON FRI AND MORNING CONVECTION IS EXPECTED TO BE ONGOING.

For them, it's just as much of a difficulty as it will be for anyone else. I can't tell you much other than to look for the sources of lift, instability, moisture, and shear for nighttime convection and do your best. Daytime convection and nighttime convection happen through the same ingredients, they're just going to come together via different ways.