Sunday Night Look At The Upcoming Chance of Severe Weather on Monday Afternoon

We will have no issues throughout the remainder of tonight and through the overnight and early morning hours in Central Alabama, as the showers moving across the northern parts of the area are light to moderate in nature. The latest HRRR simulated radar run is showing a batch of showers and maybe a few claps of thunder rolling across the northern parts of the area from around midnight through 3:00 AM Monday morning. Neither of the NWS offices in Birmingham or in Huntsville is expecting any severe storms with this batch. At this time, this batch is over the Memphis area and the extreme northwestern tip of Mississippi. Latest radar trend is showing that this back is moving in a general direction that will keep it north of the Tennessee River, but it could spread a little southward since our atmosphere has been untapped today in the northern parts of the area and up into North Alabama.

For the morning and early afternoon hours on Monday, much of the area should be dry and we may have a decent supply of sunshine at times. We will have a cap in place for much of that time that may allow the temperatures to climb well up into the 70s and may get close to 80 degrees north of I-20 and I-20/59. The latest HRRR goes through noon on Monday and it keeps all of Central Alabama dry through that time. According to the HRRR, temperatures will be just at or above 70 degrees for nearly everyone in the area. The latest NAM run is showing activity starting to fire up after the 3:00 PM hour with cellular formation in highly unstable air.

Latest NAM Surface-based Instability values at 5:00 PM.

Surface-based instability values will be in the 2500-3000 J/kg range and possibly higher in some locations.

Helicity values in the 0-1 km levels will be well more than high enough to support rotating updrafts, in the 160-400 m2/s2 range. Anything over 100m2/s2 does suggest an increased threat of tornadoes with supercells, especially with larger values, but there is no clear thresholds between a tornadic or non-tornadic supercells.

Latest Significant Tornado Parameter values valid at Monday 8PM.

Significant Tornado Parameter values will be well above 1.0 at 4:00 PM (according to the NAM), topping out at 5.3, and will max out during the 8:00 PM hour with values topping out in the 7.9 range.

Bulk Shear values will be in the 55-75 kt range throughout the area, meaning that thunderstorms will be more organized and will stay organized longer when shear values are greater than 35-40 kts.

Lapse Rates will be in the 6.3-7.3ºC range, meaning that deep convection is more probable leading to stronger updrafts and larger hail development.

The main window for severe storms will come from roughly 3:00 PM until 10:00 PM. The cap may break a little earlier along the Alabama/Mississippi state line, and strong storms could linger a little longer through midnight. All modes of severe weather will be possible for all of Central Alabama… large damaging hail possibly up to 2 inches in diameter, damaging straight line thunderstorm wind gusts of 60 MPH and possibly higher, and a few tornadoes (some of which could be strong).

The good news with this system is that flooding should not be an issue, as most places will see amounts 1/2 inch or less.

According to how the rain affects the atmosphere during the overnight hours could weaken our severe storm chances tomorrow, but then again it may not. We will not know that until tomorrow. We’ll be watching for any small scale boundaries that are backed with southeast surface winds… these could bring a localized higher tornado threat.

Tonight is a good time to review your tornado plan.

Be sure you can hear warnings if needed. NEVER rely on an outdoor warning siren; if that is your main way of hearing warnings, you have little hope of hearing them indoors. Have a NOAA Weather Radio in your home or business, and a good app designed for warnings on your smart phone like WeatherRadio by WDT.

Know the safe place in your home. Small room, lowest floor, away from windows, and near the center of the house. If you live in a mobile home, you have to leave and go to a shelter or site built structure.

In your safe place, be sure you have a helmet for everyone to wear (not just children)… it is also good for everyone to have a portable air horn (to get the attention of first responders if you need help), and be sure and wear hard sole shoes (you don’t want to walk over a tornado debris field with tennis shoes, or bare feet).

Stay tuned to the blog throughout the day on Monday for updates!!

Tags: ANC, exp08

Category: Alabama's Weather, ALL POSTS