Two Severe Weather Threats

| February 22, 2012 @ 6:14 am

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ACTIVE PATTERN: The weather will be very changeable for the rest of the week, with two severe weather threats for Alabama and the Deep South. Let’s take them one at a time…

ROUND ONE: We note this morning a batch of convection is ongoing along the I-40 corridor from Memphis to Nashville as I write this before sunup, and those storms are moving east. The air over far Northwest Alabama is still dry (the dew point is only 30 at Muscle Shoals), but dew points are in the mid 50s now as far north as Birmingham. So, initially the storms to the northwest are elevated, but should become surface based later today.

We will mention a chance of scattered showers and storms this afternoon into the evening hours, and SPC has defined their standard “slight risk” of severe weather for Alabama generally north of a line from Vernon to Birmingham to Roanoke. Temperatures will rise into the low 70s today, with dew points rising into the low 60s, which should provide a pretty decent amount of instability (most models show surface based CAPE values exceeding 1,000 j/kg this afternoon).

At first glance, it seems like the threat will be from hail and strong, gusty winds with the storms that develop, but we note the NAM is showing 0 to 3 SRH (storm relative helicity) values near 310 m2/s2 this evening, which means an isolated tornado can’t be ruled out. We will be watching the radar closely; the main window for severe weather with round one will come from about 3:00 until 8:00 p.m.

ROUND TWO: Before we deal with the second batch of storms, we should note tomorrow looks like a beautiful day. Warm and breezy with a partly sunny sky and a high in the mid 70s. Certainly one of our warmest days so far in 2012.

Showers and storms will move through tomorrow night into early Friday, and SPC has basically all of Alabama in the standard “slight risk” of severe weather for this event. The good news is that SPC has backed down on the higher 30 percent probabilities they had in their outlook yesterday. The upper low over Baja California now is not expected to phase up with the northern branch, which will lessen the overall threat to some degree.

Still, some storms tomorrow night will have potential to produce hail, strong gusty winds, and an isolated tornado. The main window for severe weather seems to be from about 9:00 p.m. tomorrow through 6:00 a.m. Friday. But, we really need to get tonight’s storms out of here, and then we can see the state of the atmosphere tomorrow morning and make a much better call on this second round. Take some time to watch the Weather Xtreme video for all of the graphics and details.

Showers and storms should be over by midday Friday, followed by a clearing sky. The high Friday will drop to near 60 with a cool northwest wind.

OUR WEEKEND: Saturday will feature a bright, sunny sky. We start the day down in the low to mid 30s, but rise into the mid to upper 50s. Sunday looks dry for now with a partly sunny and and a high around 60. We might consider a slight risk of a shower late Sunday afternoon, but for now the chance looks so small we won’t mention it.

NEXT WEEK: The 06Z GFS suggests the first half of the week will be wet, with a chance of rain at times Monday through Wednesday. But, confidence in a specific solution in this active pattern is not all that high. See the Weather Xtreme video for more long range ideas.

STORM ALERT 2012: The show scheduled tomorrow night for Pleasant Valley High School in Calhoun County has been moved to Monday March 5 due to the threat of severe weather.

WEATHER RADIO PROGRAMMING: Need your weather radio programmed? We will be at the Publix on Huntley Parkway in Pelham today from 3:30 until 7:00 p.m. You can also buy a new one at the Publix if needed.

WEATHER BRAINS: Don’t forget you can listen to our weekly 90 minute netcast anytime on the web, or on iTunes. This is the show all about weather featuring many familiar voices, including our meteorologists here at ABC 33/40.

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I will be doing at safety program at UAB this morning… look for the next Weather Xtreme video here by 3:30 or so this afternoon. Enjoy the day!


Category: Alabama's Weather

About the Author ()

James Spann is one of the most recognized and trusted television meteorologists in the industry. He holds the AMS CCM designation and television seals from the AMS and NWA. He is a past winner of the Broadcast Meteorologist of the Year from both professional organizations.

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