Masters student in tropical meteorology at FSU. Raised in Alaskan blizzards, but drawn toward tropical cyclones by their superior PGF.
By: Levi32 , 3:11 AM GMT on February 23, 2007
Thunderstorms have increased in coverage, but remain for the most part on the quiet side....for now. The main upper low and surface low haven't made it into the plains yet, and until they do, I think diurnal cooling will tame the storms down to mostly a hail threat with hail diameters not exceeding 1.25 inches. Tomorrow morning things will start to heat up again with the upper trough moving into the picture, and the surface low deepening over Kansas. The strong left front quad of the jet will provide ample upper-level support for the developing storms over the course of the afternoon. Squall lines along the dryline and cold front will advance eastward across Louisiana, Arkansas, and Mississippi throughout the day. Late Saturday and Sunday the low will lose upper-level support and begin to fill near southern Michigan. There is a marginal severe weather threat for northern Florida due to a strong jet streak forecasted to move across the Gulf of Mexico on Sunday. It is still uncertain how favorable conditions will be at this time, but considering the last two storms which have affected the Florida area, it only takes a low-level jet and some moisture to get severe weather going.
We shall see what happens!
Strong t-storms have begun to develop over northern Texas, Oklahoma, and southern Kansas. Severe weather threat will increase as the night goes on from SW Texas to southern Nebraska. Right now diurnal cooling is setting in, but the upper trough to the west will be steadily advancing east throughout the night, cooling upper-level temperatures and therefore increasing atmospheric instability over the entire area. I think the moist inflow from the Gulf of Mexico, the strong dryline, and upper dynamics coming into play will keep a tornado threat going throughout the night, but the main problem will be hail and damaging straight-line winds until tomorrow when the tornado threat will be renewed during afternoon heating. This is only the beginning of the outbreak. The storm system responsible isn't even entirely over the rockies yet. Tomorrow the low will be deepening over Kansas with a strong jet streak in the left front quad of the jet. All these factors will combine to produce more severe storms over parts of Arkansas, Louisiana, and the eastern plains tomorrow.
Update 4pm eastern:
The dryline is beginning to set up in extreme west Texas, and instability will continue to increase as the afternoon goes on. Clouds have limited daytime heating in central/northern Texas into southeast Oklahoma, but all other areas are heating up to near 70 degrees even up into Kansas. Dewpoints are also climbing as the southerly flow starts to grab moisture from the GOM. The first storms are still a few hours away. Be on your guard!
Friday morning update:
There is little change in the models since yesterday. The SPC outlook for today has a moderate risk area focused over Oklahoma, which is where the worst instability will set up late this afternoon. They have also issued a moderate risk area for Louisiana, Arkansas, and Mississippi tomorrow. Severe storms should start developing late this afternoon into tonight over northern Texas, Oklahoma, and Kansas. Some upper-level clouds are drifting northeastward over Texas into Oklahoma, and these could limit daytime heating somewhat, we'll have to see how that goes. The big question will be if the storms break the cap tonight. The main part of this event will be during the night, making it a very dangerous situation for residents.
Thursday evening update:
Some very active weather could be in store for the plains and southeastern states this weekend. An upper trough and associated low pressure system currently moving inland over northern California will move east over the Rockies tonight. By tomorrow morning the low will emerge over western Kansas, and begin to strengthen as the upper-level dynamics intensify. Plenty of low-level moisture is expected to be present due to good inflow from the Gulf of Mexico, with 55 degree dewpoints making it all the way up into northern Kansas tomorrow afternoon. Right now the models are forecasting decent instability down through northern Texas, but exactly how unstable the atmosphere becomes will rest on how much daytime heating will take place. There is a possibility of some clouds moving into the area prior to the arival of the warm front, which could limit daytime heating somewhat. If this is the case then the storms may find it hard to break the inversion cap, but I don't think the cap will be strong enough to hold down the instability that will be developing as the afternoon goes on.
As the low moves east, an impressive dry-line is forecast to develop over western Texas late tomorrow night, and steadily advance eastward through Louisiana and Mississippi. This is a classic setup with plenty of moisture over eastern Texas and Louisiana and very dry air over western Texas and New Mexico. A strong squall line will likely develop along the dry-line Friday night with embedded supercells. Plenty of shear will be present, and tornadoes are definitely a threat. Severe storms will continue on Saturday over Louisiana, Mississippi, Arkansas, and even Tennessee could see some action Saturday night. By Sunday morning the low will be rapidly losing upper-level support, and will begin to fill while moving northeast over southern Michigan. Thunderstorms will continue to affect Alabama, Georgia, and maybe even Florida Sunday afternoon. The storms will gradually diminish in intensity as they move east, and the tornado threat should be minimal by the time they get into Georgia. However things are a little more complicated for northern and central Florida. Depending on how far south the trough digs, thunderstorms could make it down as far south as Orlando, providing some much needed rain for those areas. The forecast challenge is whether or not these storms will become severe. The 18z model runs are now showing a second jet streak forming over the Gulf of Mexico and moving east during Sunday. We still need to see a few more runs to be sure, but if the models are correct, the chances of severe weather in northern and central Florida will be greatly increased.
Right now the SPC has a moderate risk area for the plains tomorrow, and a slight risk area for the gulf coast states on Saturday, which may get upgraded depending on how the storm develops. Bottom line this has the potential to be a significant outbreak, and residents should be ready for a rough ride over the next couple days.
We shall see what happens!
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