The potential for severe weather will return to the state on Thursday, March 29th. While no large scale system will be driving the storms, a well defined short wave trough will be pushing into the central Plains by late afternoon. The southern end of this wave will graze northwest Oklahoma.
Seasonably cool mid-level temperatures combined with our above normal surface temperatures and increased moisture will create a very unstable atmosphere in the warm sector. This high instability will be found along and east of a nearly stationary surface boundary which will extend from southeast Nebraska to southwest Texas.
The strongest forcing is likely to remain north of the state, but sustained convergence along the surface boundary – afternoon heating – and weak lifting from the passing short wave should be sufficient to allow the development of storms in far western Oklahoma by late afternoon. Given the degree of instability, the storms will likely become severe with the potential of producing very large hail. Overall, the tornado threat would be considered minor, but non-zero.
Some model indications suggest that a complex of storms will advance as far east as central Oklahoma during the overnight hours early Friday morning. Also, any storms that form in southwest or west central Oklahoma may be far enough away from the strongest mid-level flow to allow for very slow storm motions at times. This may result in localized areas of flash flooding.
After a couple of weeks avoiding the record books, the warm air has finally started making a dent. On March 13th, the high temperature of 83 degrees broke the old record of 82 degrees set in 1996 and 2008. On the 14th, the high low temperature record was set at 61 degrees. The previous record was 55 degrees set in 2007. And, on the 15th, the high low temperature record was set at 62 degrees. This breaks the old record of 49 degrees set in 1995 and 2000. These temperatures are only coming within a couple of degrees of breaking all time March records.
Through the first 15 days of March, the average temperature has been 56.5 degrees. If this were to hold, it would be the second warmest March of record. Only two days have seen temperatures below normal, and both of them have only been one degree below. In a typical year, there would still be about an 88 percent chance of a freeze following March 16th. By the end of the month, the chance at another freeze is still around 71 percent. However, this has been a far from typical winter and with no freezing weather seen on the latest medium range models, we are ready to kick the gardening into full gear. The green light has been given to plant just about anything starting this weekend and hopefully we can get in one of the longest growing seasons we have seen around here in quite some time.
Now that we have the climo part of the discussion out of the way, let’s look at the potential for an active and wet weather pattern setting up which will likely include some of the first significant severe weather events for the year in Oklahoma.
For today (Friday, March 16) – a long extending dryline will be in position from South Dakota to western Texas. The atmosphere east of the dryline will become quite unstable with afternoon heating, however it will remain quite capped during most of the afternoon. There is a weak upper system which will be moving out of New Mexico that may provide enough lift for isolated thunderstorms to form – first in southwest Texas and then later into western Oklahoma. The wind profiles are supportive of organized updrafts and given the degree of instability – some of the storms would be severe. Large hail and damaging winds would be the primary threat in Oklahoma.
After a lull in the action on Saturday – Sunday looks to be setting up for a significant round of severe weather along the dryline. The dryline will be far enough west to keep the most dangerous storms in western Oklahoma. By late afternoon on Sunday, a very strong upper storm system will be moving through the southwest U.S. Stronger mid level winds will be spreading over the high Plains creating an environment very favorable for organized severe storms – including supercells with the potential of producing all facets of severe weather. The dryline will not change position much during the afternoon and extend from southeast South Dakota to western Kansas to southwest Texas. Storms will move to the north and northeast and make it into western Oklahoma near or just before sunset.
While the severe weather threat will start to lessen after dark, a complex of storms producing very heavy rain will continue to work toward central Oklahoma. The morning rush hour could be a soggy one in Oklahoma City. After the heavy rain works through, another round of severe thunderstorms will be possible in parts of central and eastern Oklahoma. This threat is conditional on getting enough surface heating after the early storms to develop pockets of higher instability. The first half of the upcoming week stands to be showery as moisture wraps around the strong upper low which will become nearly stationary over Oklahoma. The heaviest rain by Tuesday/Wednesday will have pushed into far eastern Oklahoma and Arkansas.
A very strong early season storm system will be moving out of the Plains and into the eastern U.S. over the next 24 hours. This has most all general ingredients necessary for producing widespread severe weather – including the possibility of several dangerous tornadoes.
A very strong upper level jet will overspread a large moist warm sector. Combined with a strong low level jet and deep surface cyclone – a near classic setup for a tornado outbreak will evolve this afternoon.
While severe weather in some form is possible all the way from Texas to the mid-Atlantic coast, and northward to Michigan – the most dangerous weather is likely to be found in the Ohio Valley, Tennessee Valley and part of the lower Mississippi Valley.
It has already been a deadly start to the 2012 storm season and there is not much reason to believe that trend won’t continue today and into tonight.