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Never a dull moment in the weather office this time of the year….
TONIGHT AND TOMORROW: Our weather should stay relatively quiet, while a major severe weather outbreak threatens areas to the west. For the rest of today and tonight, the greatest risk of severe storms will be over Oklahoma and Texas; then, the risk shifts eastward to Louisiana, Arkansas, Missouri, and the western part of Tennessee and Kentucky. A few violent, long track tornadoes are possible in these areas, and the first PDS watch of the event is up now for parts of Central and West Texas (PDS=Particularly Dangerous Situation).
We might see an isolated shower tomorrow afternoon during the peak of the daytime heating, but most Alabama communities will remain dry.
TOMORROW NIGHT AND FRIDAY: The leading edge of the storms could reach Northwest Alabama late tomorrow night, especially after midnight. We think those storms will gradually weaken toward daybreak Friday, but they have a great chance of laying down an outflow boundary, which will serve as a focus for new convective development during the afternoon Friday. That boundary will also help the low level helicity, meaning the possibility of a few tornadoes. Of course, with this kind of system in April we will also have the chance of large hail and damaging winds.
Here are some convective values from the NAM Friday afternoon:
Surface based CAPE: 940 j/kg
2m agl Dewpt(F): 66
0 to 3 km helicity: 187 m2/s2
We do note the GFS is much more aggressive with severe weather parameters. As always, the details of the severe weather will be on the mesocale, and we won’t be able to determine that setup until early Friday morning. But, the synoptic scale features sure suggest some chance of severe storms in Alabama Friday.
The models are a little slower; I think we can now define the primary severe weather threat from about 12:00 noon Friday until 8:00 p.m. Friday. Rain amounts of one inch are likely, with isolated totals to 1.5″.
LATE SEASON COLD SNAP: A deep upper trough sets up over the eastern part of the U.S. over the weekend. For Saturday, I think we need to maintain a chance of light rain during the morning hours with a high in the 60s. Then, you will really feel the difference on Sunday. Areas north of Birmingham night not get out of the 40s with a very chilly north wind, and clouds will be around much of the day along with some scattered light rain. A few snow flakes are likely Sunday night over Tennessee, possibly down into the northeast corner of Alabama.
HOW COLD? The latest GFS MOS is printing 33 for Birmingham Monday morning, but with clouds and wind, frost does not seem likely. I still believe the coldest morning will be Tuesday, when radiational cooling will be in full force. Lows early Tuesday will most likely range from 28 in the coldest valleys to 40 on the ridge tops, and widespread frost looks likely. Growers will need to watch this forecast closely in coming days.
We will warm-up during the middle part of next week, and the next frost for Alabama should come sometime in the fall.
VOODOO LAND: The GFS continues the idea of shifting the primary storm track northward over North America during the latter half of April, which means the severe weather threats here won’t be coming as fast and furious as they have been during the last 8 weeks.
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