BLOG: Severe Weather Threat Today; Quick Long-Range Peek

Good morning everyone,

Hope you enjoyed the warm weekend. Today will be the last balmy day for a while. The transition from the May Preview to more of a late-March pattern will be marked by some showers and thunderstorms today into tonight. Will the ingredients come together for some big storms and perhaps even severe weather?

The setup: 

A cold front is marching east this morning and can easily be picked out on the surface map:


Ahead of the front, it is warm but not super humid. Dewpoints are in the 50s in most places.


As the front pushes east and some sunshine heats the air mass up, the atmosphere over the region will grow moderately unstable. Have a look at the CAPE, (Convective Available Potential Energy) which is a measure of how unstable the air mass is, at 2pm:


A few/several hundred J/KG of CAPE is certainly enough for thunder and some “strong” storms but it’s hard to get “severe” weather with CAPE values that low.

Another thing we look at is something called “helicity”, which measures the atmosphere’s ability to produce rotating storms. It is not very high locally so the threat for a tornado is very very small.


That said, there is a fair amount of wind energy above our heads and any stronger shower or storm could bring some of that down to the ground. Winds at 5,000 feet will be around 40-50 mph early this afternoon:


So we are looking at some showers and thunderstorms getting going during the midday and early afternoon. The 2pm simulated radar off our highest-resolution model shows this:


If we are going to get some heavy storms today it looks like 1-4pm is our best window. By 5pm, the threat has shifted east, and the threat for severe weather is certainly higher in that direction.


The Storm Prediction Center odds of large hail are low but not zero around the Valley today. Higher odds east.


Threat for damaging winds is on the low end of the scale as well but overall is probably the more likely threat from any heavy storms today.


As always, we will keep you updated on TV and online as we navigate the day today. A quick reminder of the difference between watches/warnings/etc:


OK, once we are done with today, it’s not a very late-April like forecast for a while. Why? Well an area of low pressure in the upper levels is going to get bogged down for a while around the northern Great Lakes and SE Canada. This will prevent any sort of warmth from gaining a foothold and will steer chilly Canadian air south.



We may start to emerge from that pattern by the middle of next week as the atmosphere gets “unclogged”. jetweds

Long-range modeling shows a better pattern emerging by early May. The pattern may not produce temperatures as warm as we have seen recently, but it should be milder than the next 7-8 will be.


Thanks for reading!