SEVERE WEATHER THREAT

Fort Smith 6Z Tuesday (Midnight of Monday)

Fort Smith 12Z Tuesday (6 AM)

We're under a slight risk for severe weather over the next few days. A sharp trough will be transitioning eastward over the next 36 hours and air out ahead of the parent cold front has really been heating up. We were only a few degrees off of records today and by tomorrow we'll be within a few degrees of records. Plenty of moisture has worked its way into our area too. In fact, you may have just felt a tiny bit humid today! Dewpoints have surged into the 50s and Poteau earlier today had a dewpoint of 61 F! So, plenty of moisture is in place.

Check out the Midnight sounding of Fort Smith. The atmosphere is weakly capped, though there is some low level moisture with a surface dewpoint over 60 F. Some upper level moisture is present too, though mid-levels are very dry. This type of sounding presents a threat of gusty winds. The dry layer allows falling precipitation in collapsing / decaying thunderstorms to really cool the air fast as evaporation takes place in the dry layer. This cold air can fall like a ton of bricks! Although some wind shear is present (turning with height of winds) the vertical profile is predominantly out of the SW. Again, this is conducive to and indicative of straight line winds. Lapse rates are moderately unstable with nearly 500 J/kg. of CAPE (Convective Available Potential Energy).

Lastly, the cold front, which is running through SE OK and NW AR in the surface map above will likely kick off a line of concentrated thunderstorms. This will be the primary lift. Earlier in the event though, some elevated storms, which are lifted from above the cap, may be isolated. These will have to be watched closely and may pose the greatest tornado threat. Precipitable water values are very high through the event too, approaching nearly 4". Some areas may see some localized flooding by Tuesday afternoon. We're monitoring developments closely.

Keep it tuned to 40/29... we'll keep you advised on air and on the web!

Posted by Ted Zarras at 8:24 PM