Two of the most fascinating things in weather to me is a heat burst and the chinook wind. We may discuss the heat burst some other day, but this morning I want to discuss some unbelievable temperature changes due to either a dying chinook wind or, more likely, a stalled front in the Black Hills of South Dakota.

The extreme temperature changes in such a short period of time are unbelievable. This is not an old husband’s tale. This incident is documented in files of the National Weather Service in Rapid City.

On January 22, 1943 in Spearfish, South Dakota at 7:32 a.m. the temperature jumped from 4 below zero to 45 above—a rise of 49 degrees in just two minutes! That still stands as a world record. But it did not last long. At 9:00 a.m. it was 54 degrees, but 27 minutes later it was back down to 4 below zero.

The sudden change in temperatures cause some strange things to happen. Thick frost appeared almost instantly on windshields as people drove from the warm air into the cold air. Glass window panes broke. The contrast in temperature was even noticeable on different sides of buildings. You could escape winter by walking from the east side of the building around the corner to balmy spring-like conditions on the south side.

In Spearfish, every plate glass window in town broke because of the quick changes. At one time, the temperature was -2 on one side of the town of Spearfish at the same time it was 54 across town. Spearfish is about the size of Oneonta.

The changes were caused by a very shallow arctic air mass along the north and eastern slopes of the Black Hills with the lighter and warmer air aloft. As the boundary between the two air masses shifted slightly, like rocking a bowl of water, the temperature changed dramatically.

I remember being on duty one day at the NWS in Birmingham watching satellite photographs come off the printer every 15 minutes. I witnessed an 18-inch snow cover in NE Colorado disappear in 8 hours due to the warm downslope chinook winds.

All of this fascinates my little brain no end!

The Thursday afternoon video update is on the server:

http://beta.abc3340.com/weather/video.hrb

NOTE: Due to our travel schedule, there will be only one video update tomorrow from Brian Peters. We will be making plenty of posts on this blog, however, from the Southeast Severe Storm Symposium at Mississippi State University.

Check out that huge mass of rain over Florida.. that is the storm the GFS identified nicely over a week ago. It passed just too far south to impact us.

Coming attractions:

Pleasant, dry weather is ahead through Sunday with temperatures recovering into the 60s. The clipper system north of us will drag a cold front through here Saturday evening, but most of the precipitation should stay north of us and we will just see a few clouds with the passage. Temperatures will drop about 5 to 8 degrees on Sunday, but the sky will be mostly sunny.

The 12Z model runs continue the trend of no phasing next week, which means a cold front coming through here Monday night with some rain, but no heavy rain or severe thunderstorms. And, the cooldown Tuesday of next week will be only a moderate one. We will go ahead and buy into this solution.

Another northern stream wave is expected to sharpen the trough later next week, which could drive colder air down here by Thursday and Friday, and I expect temperatures to dip into the 20s again on one of those mornings.

Beyond that everything still looks muddy, the GFS has no clue as to how to handle the upper low in the far southwest U.S. this weekend, it just drifts the thing down to Mexico and loses it. Makes for a low confidence outlook in the longer ranges.

A special thanks to J.B. Elliott for working extra forecast shifts for me during the Storm Alert 2005 tour... guess I will have to buy his BBQ Saturday night at the Little Dooey in Starkville...

The Thursday morning web video update is online now:

http://beta.abc3340.com/weather/video.hrb

Thanks to everyone who came out to our Storm Alert 2005 tour during the last five weeks... we saw over 3,000 people along the way and had a blast as usual. We are already thinking about Storm Alert 2006!

The Southeast Severe Storm Symposium begins tomorrow at Mississippi State; we would love to see you there. If you want to learn more about weather, it is a wonderful opportunity. I will be speaking tomorrow, Bill Murray is up on Saturday. Read more here:

http://www.msstate.edu/org/nwa/symposium.htm

What a good looking storm this morning in the Gulf of Mexico. But, the big rain mass will stay over south Alabama while we mostly stay dry up here. Quite frankly, there is a good chance we stay dry through Sunday. The clipper system Saturday has very little moisture to work with, so other than a few sprinkles over north Alabama we really don't exepct any rain. Temperatures will continue to moderate, with 60s tomorrow and into the weekend. Finally back to normal levels for March. For the time being.

NEXT WEEK

The models are all bamboozled over the system early next week. After showing a major, phased storm yesterday, now the models are trending toward a non-phased look, with the northern branch and southern branch systems keeping away from each other.

If the non-phased look is correct, we will have a band of showers Monday night, and cooler weather on Tuesday. If the phased solution is the right one, we will have heavy rain and strong storms late Monday into Tuesday morning, and a major blast of cold air at the middle of next week.

Quite frankly I really am not leaning strongly either way at this point... we will just have to say the confidence in forecast details beyond five days is low, and we will watch the new runs arrive today.

The afternoon video will be on time today, but the schedule will be a bit disrupted tomorrow due to the Mississippi State conference. I am going to see if Brian Peters can knock out a video update tomorrow, but I will be making posts to the blog from the conference. In fact, I will try to post a running commentary on the vast knowledge offered by the speakers. Never covered a weather conference as a blogger before....

Unfortunately we must prepare for Alabama’s prime severe weather season, which is March, April and May. In the last four or five years, our secondary severe weather season (November and early December) have been the most active. I sure don’t think there is going to be a permanent switch. Over the long haul we will see more tornadoes in the spring, but still the autumn season cannot be taken lightly.

Our spring season is mostly March, April and the first half of May. That is why I have always been puzzled why May 27 seems to stand out like a sore thumb for severe weather.

On May 27, 1917, a powerful F4 tornado devastated areas along the Jefferson-Walker County line. Other tornadoes in that outbreak struck in Tuscaloosa, Bibb and Blount Counties. The worst of those heavily damaged areas around Sayre, Bradford and Village Springs. Bradford was almost wiped off the map with 17 persons killed. Nine died in Sayre.

Then on May 27, 1973, a very powerful F4 tornado touched down NE of Demopolis and cut a long, long path finally breaking up on the SW slopes of Mt. Cheaha. Seven persons died and 199 were injured. That tornado seemed to like Alabama Highway 25. It cut across the SE part of Greensboro and followed Route 25 to Brent where it almost destroyed the town. Then it continued passing near Montevallo, Wilsonville and breaking up on Mt. Cheaha. The main street of Brent was some of the hardest hit area. Five persons were killed and 26 injured. The tornado destroyed 216 buildings and 97 mobile homes. Unfortunately, a few miles before getting to Brent, it knocked out the NWS WSR-57 radar system that we all depended on so much.

Other major tornadoes have struck on May 27 in St. Louis and in 1997 in Jarrell, Texas. That was a powerful F5 that destroyed most of Jarrell. I called it a scorched earth tornado, because it literally swept the earth clean, even ripping up miles of pavement.

-- J. B. Elliott