Saturday Afternoon Forecast Discussion – 12 p.m.

Overall not much has changed in regards to the weather pattern. We remain locked into the cold air pattern with a long wave trough aloft and surface high pressure in place across the Southeast. The high moves to the east today and will only impact our eastern portions of the area Sunday. This means that on a whole most of Central Alabama will be in the upper 30s to even 40s. However patchy to areas of frost will once again be possible in the northeast. Another frost advisory has been issued for the northeast. In West Alabama we’re expecting temperatures to be between 33 and 37 degrees.

Another caveat to the forecast tonight will be the increase in mid level cloud cover across the northwest. This will be in advance of a shortwave trough that should move through Sunday afternoon. A lot depends on what if any development generates in Oklahoma and Arkansas with this shortwave tonight as it will be generally creating its own lift. This little shortwave has been causing havoc with the models for the last couple of days. The GFS along with only short range models and ensembles really dry out the shortwave as it slides through. Meanwhile the Euro at least brings precipitation into the northwest Sunday afternoon. Now that the Euro is finally the outlier on this will trend away from this, especially given the dry conditions already in place.

After the dry shortwave on Sunday…we will continue to modify our temperatures as we see more of a southerly flow at the surface…and zonal flow aloft…ahead of the next substantial cold front Thursday night into Friday. This is more in line with what the Euro has been saying for the last couple of days as the GFS has been progressive then slow. With the models finally beginning to agree with the overall timing we will need to look for any potential of severe weather. At this time the threat for any severe weather should remain to our east as the surface low pressure slides away from the area. Although there is a brief window Friday for at least strong storms as the surface low strengthens as it slides through.

There are some subtle differences between the Euro and the GFS that will need to be monitored over the next few runs to see the exact placement of the upper and surface lows…but there is plenty of time right now to evaluate. Especially with some possible tropical influence coming up from the Caribbean. At this time not expecting any direct impact but the National Hurricane Center does have a 70 percent of development in the next 48 hours so stay tuned. Behind the front look for another shot of cold air for next weekend.

Daniel Sparkman
dsparkman@wvuatv.com
WVUA Weather

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Strong to Severe Storms on Thursday?? Saturday Update 8:45 AM

While we’re several days away from Thursday, I’m interested in this next feature coming our way. We are getting into our fall severe weather season, so we’ll have to watch each storm system very close for the rest of the fall and early winter. Below is the surface chart off the GFS, which is valid for midnight Friday night. A strong low pressure is centered over Kentucky, with a cold front moving through west Alabama at that point. A south flow developing several days before this low moves in will enhance moisture into the area. I’m still iffy on exactly how much moisture return we get. The airmass is very dry not only locally, but well to the south of Tuscaloosa, so it will take some time for deep tropical moisture to advect into the area. This model deepens the low below 1000mb and tracks it from west Tennessee northeast into central Kentucky. This is a favorable track and strength for strong to severe storms, so we need to keep an eye on it for sure.

Below is the 500mb chart off the GFS, valid for the same time. There’s a strong shortwave trough is moving into the south Thursday afternoon and night. That look would certainly be favorable for strong rising air and cyclogenesis.

The jetstream will be very strong for this time of the year, with winds nearing 130mph at 200mb. A strong jetstream would provide rising air and wind shear. This is also off the GFS, valid for midnight Thursday night.

I just wanted to share some thoughts on this system. We have lots of time to watch it before it gets close to Alabama. Model data has changed a bit over the past several days, but we’re starting to get into this consistent look now. Since it is so far out, models will continue to change over the weekend and early next week. We’ll fine tune the forecast as we get closer to it. Again, this is not a major threat at this point. This is just something to keep an eye on. I’ll have much more on this system on Monday’s forecast discussion. Much colder air will arrive on Friday, with a cloudy and breezy day.

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WVUA Chief Meteorologist Richard Scott

rscott@wvuatv.com