Tuesday, October 16, 2012

Wild Weather Wednesday


In the previous blog post, I wrote about the secondary severe weather season we are now in and it appears more and more likely a round of strong to even severe thunderstorms will sweep across the state Wednesday afternoon and evening. 

What makes this potentially wild as well will be the temperatures and winds both ahead and behind the frontal boundary.  I expect strong southerly winds Wednesday and this will draw in Gulf of Mexico moisture.  At times, wind speeds could easily exceed 20 mph and maybe go up to 30 mph.  Temperatures will likely reach the low to mid 80s and as a result of the increased levels of heat and humidity, instability levels will reach more than 2000 j/kg.  This is called CAPE (Convective Available Potential Energy.) 2000 is considered very strong.

The front will quickly move through the state and as the evening progresses, those instability levels will come down.  There will only be a narrow window of a few hours when severe weather will be likely.  Winds will become west-northwest behind the front at speeds greater than 20 mph with falling temperatures and falling moisture levels.  It will be a wild day for sure.  Models show highs Thursday in the low to mid 70s, but watch out, that could be too warm.

As far as the tornado threat, you know my saying, "never say never to Arkansas weather."  The threat is LOW however, it can't be completely ruled out.  If any cell can develop by itself and away from the squall line, it could happen, but it's a low threat.  IF there is any tornado threat, it will be early in the event, then this should organize into a line and sweep off to the east.  The main threat for Arkansans will be hail and wind. 

Check out the maps below.

This is the NAM hi res simulated radar at 4PM Wednesday.  It's warm and humid across the SE 1/2 of the state with showers and storms developing near the front to the northwest.
Hires simulated radar data shows the line quickly forming from NE to SW across the state by 7PM.  The main threat will be wind and hail.
By 10 PM, it's east of Arkansas.  Notice how short of a window the severe potential is at your location!
The NAM shows a large build up of instability across western AR by 4PM.  There's an area of up to 2500 j/kg forecast in the middle of that yellow blob.
As the front moves through and daytime heating decreases.  The instability levels gradually decrease over time and it shifts to the east.  This is at 10 PM.
The SPC has much of AR under a slight risk for severe weather Wednesday.


Anonymous said...

I'm dying for some jailbreak arctic air here!!! Snowbirdbob keeps on lying about another cold front 2 weeks from his tweet and it never pans out!

SnowbirdBob said...

To: Anonymous...I did not lie about a Cold front..I made a Tweet on Sept. 28th..That was nearly 2 1/2 Weeks ago about a Cold front in the Oct.14th-18th Time-Frame..My forecast has panned out to perfection..Big time Cold front moving in on the 18th..With High's in the 60's & Low's in the 30's for parts of the State..So,to you anonymous, Get the facts straight.So, To Me " Great Call from almost 3 weeks Out" By the way watch out for the Coldest Air of the Season so far in the Oct.27th to the 31st Time-Frame..We Shall See.;)

Bob Read AKA SnowBirdBob

NOAA Winter Guidance