Posted: Apr 29, 2014 8:24 AM by Meteorologist Josh Eachus
Updated: Apr 29, 2014 8:24 AM
We'll need to pay close attention to the forecast once again before a cold front clears the region and the threat for severe storms subsides.
The setup: The storm system that has been making headlines for the last several days with large, long-lived and deadly tornadoes will finally clear the local area today.
An upper-level low pressure system is parked over the Great Plains, while a surface cold front is positioned ahead of this system and is slowly sagging southeastward. Like Monday, the atmosphere is juiced with instability and any storms that develop could quickly become strong. However, the upper level waves of energy that enhance storm development will remain to our northeast and mid-level winds and forcing will be more favorable in those locations as well. But, a key ingredient that was missing on Monday, a lifting mechanism, will be present today as a surface cold front arrives in the area. Precipitation chances are in the 40-50% range meaning that there is about a 1 in 2 chance that any given point in the viewing area experiences measurable precipitation.
The morning weather balloon once again shows a significant amount of instability aloft, however the atmosphere is capped and will require a warmer layer in the lower levels to cool and erode. This did occur yesterday but surface thermometers missed the temperature needed to release warm, moist air into the atmosphere by a degree or two and as was noted, no external lifting mechanism was present. Severe weather parameters also remain high today. One change in the vertical profile is that shear has lessened somewhat which should diminish the tornado threat locally.
Simulated radar runs show scattered showers and storms developing during the afternoon and congealing into a weak line near the 6pm hour. This is also a change from yesterday when models correctly projected little to no precipitation. Activity seems to diminish from west to east by midnight.
The cold front will clear the area overnight dragging rain chances and humidity away with it. On Wednesday, high pressure in the Mountain West will begin to impact our weather promoting a several day stretch of dry conditions and slightly below average temperatures.
The forecast: One more day featuring unseasonable warmth, humidity and possibly strong storms is expected. Leftover morning showers and thunderstorms will remain east of Southern Louisiana. A bit of sun may break out and once more return thermometers into the upper 80s, while dew points remain sultry near 70°. Alas, a cold front that will put an end to the summer-like feel for a few days will arrive during the afternoon hours. The front may generate enough uplift (there was none Monday) to trigger a round of isolated to scattered showers and storms. With so much surface instability, once more, any storms that do form could become strong with heavy rains and gusty winds. Tonight the showers and storms will pass from west to east and wrap up before sunrise Wednesday. Lows will start to drop off, with many bottoming out below 60°.