Severe Wx. Chance for Saturday Increases

Last night and this morning’s model forecasts show a markedly greater chance for severe weather here on Saturday. This means that a few of us could see fast moving thunderstorms with high winds and possibly a tornado. It’s impossible to say who will see them, but the environment is more conducive, and I’ll explain that after the forecast.

Why the difference from yesterday? Several credible satellite-measured temperature soundings were made in the mid-Pacific that showed a stronger upper air system a bit further south. Until that happened, I was reluctant to jump on the hype train. Expect further refinement tomorrow and Friday as the upper air energy comes ashore and smaller scale models capture it.

Also…this system is different than the last one that caused the busted forecast on Mardi Gras. The low levels should be more warm and moist. First, the forecast…

Here’s just a few details to keep in mind:

1) Note the chance of fog Friday morning. Winds of 5 mph are ideal for fog caused by warm air over cold Lake and Sound water.

2) Much more humid starting tonight.

3) Saturday’s storms could start by mid-morning, but should end by sunset, except possibly in the Biloxi area.

4) Not expecting a lot of rain, maybe a half inch to an inch. The problem will be high winds and possibly a tornado with the chance the greatest in the afternoon hours. Especially dangerous will be individual large and growing storms ahead of any lines. Keep up on the weather through another source.

5) A few cold mornings in low 40s Monday and Tuesday, but warm afternoons. Lovely spring weather after we get through Saturday.

6) News no one is telling you….Expect a dry couple of weeks. Might see a few drops next Thursday, then next chance of rain in about two weeks.

This is the German ICON model for mid-day Saturday showing combined 18, 000 ft upper air (the colored contours) and surface (the black isobars). Here’s the reasons for the severe weather concerns:

1) Note the red arrows parallel to the upper flow move apart over LA and MS. This means air from below is rising fast to replace it. That’s conducive for strong storms, especially considering the thermal structure (But that’s an entirely new level of geeky-ness).

2) Note the small scale low developing over NE Louisiana near Monroe at the blue arrow. This will cause surface winds to turn more to be blowing from the SSE as the air tries to rush into it. This means more shear or rotation between the surface and the upper levels over South LA and South MS.

3) If you squint real close you can see that the surface isobars (black lines) near the Slidell-Biloxi area are showing a wave. Also — not a a good sign because it causes surface winds to come together and rise.

Now….don’t take this model as gospel. It could be off by 80 miles and 4 hours, but it’s the general environment that looks concerning.

Next email will be late tomorrow or Friday.