Here Comes da Front!

Comedian Flip Wilson famously said, “Here comes da Judge!” I am reminded of that saying as I watch the cold front charging across the landscape tonight.

The cold front reached Memphis tonight between 7 and 8 p.m.  The temperature dropped 18F in just a few minutes and winds gusted to 46 mph.  The temperature fell another 13 degrees to 43 in just 49 more minutes.  Interestingly, the rain and storms arrived behind the front.  That is because this cold front is an anafront, characterized by the fact that the main zone of cloudiness and precipitation develops behind the frontal boundary.  The power of the surging cold air mass is the reason.

This will actually be in our favor as we go through tonight, because it is harder for severe weather to develop behind the front.  But along the surge, damaging winds and isolated tornadoes are certainly possible, and there are two severe thunderstorm warnings and one tornado warning ahead of the line right now over Tennessee and Mississippi.

In addition, thunderstorms are predicted to develop ahead of the front over Louisiana and move into Central Mississippi according to the High Resolution Rapid Refresh mesoscale model.  There storms would more fully tap the unstable airmass ahead of the front where CAPE values are running 1000-2000 joules/kg.  There is also tremendous shear over eastern Louisiana into western Mississippi, where 0-1 km storm relative helicity values are 300-400 m2s2.  Tornadoes will be possible if this convection develops.

The good news for Alabama is that the convection should weaken as the line of storms pushes into our state.

Damaging winds and isolated tornadoes will still be possible when the line of storms moves in later tonight.  The rough timetable appears to be:

Muscle Shoals 12-1 a.m.
Hamilton 1:30 a.m,
Jasper 2:30-3 a.m.
Tuscaloosa 4 a.m.
Birmingham/Gadsden 4:30-5 a.m.
Clanton/Anniston 6:30-7 a.m.

It will turn sharply colder behind the front.  Check out a graphic of surface temperatures over the next 15 hours.

Here are expected temperatures at Birmingham:

69F at 4 a.m.
53F at 5 a.m.
48F at 6 a.m.
45F at 9 a.m.
38F at 1 p.m.

Category: Alabama's Weather