11/28 – Brittany’s “Pleasant” Monday Evening Forecast
Pleasant weather with seasonable temperatures have been observed throughout the day today on the backside of a shortwave trough lifting into mid-atlantic CONUS as height rises and stable air keep things quiet today. This will change, however, beginning overnight tonight in preparation for a more prolific, deep trough that will dig into the central plains. A lee cyclone is developing over eastern Colorado in the exit region of this trough and will track eastward across Kansas tonight which will tighten the surface pressure gradient across the Southern Plains and Gulf Coast leading to advection of seasonably rich moisture from the Gulf of Mexico into the Lower MS River Valley. This will lead to development of low stratus and advection fog across the area Tuesday morning as this moisture streams northward leading to a dreary morning for those commuting.
By mid-morning, the warm front will have rapidly advanced northward leaving a wide open warm sector across much of southern Louisiana and southwest Mississippi. Thermodynamic profiles will begin to become favorable for more robust updrafts to develop in the warm sector.
A second round of convective activity more closely associated with the frontal boundary is expected later Tuesday night into the morning on Wednesday which could also still carry a severe weather threat, though much more limited in nature. Thermodynamic profiles appear to wane as diurnal forcing weakens and the trough lifts out of the area and wind profiles become more unidirectional leading to more linear convective modes. This will make this round of storms primarily a damaging wind threat as they move through overnight. The caveat with this round being the uncertainty of how the warm sector convection earlier in the day modifies the environment these storms will pass through. Excessive rainfall will also be possible Tuesday afternoon through Wednesday morning as these storms track across the area given the rich moisture and anomalously high PWAT values between 1.8 to 2″. The threat for locally heavy rainfall will be highest in southern MS and the Florida Parishes where storms producing rainfall rates of 1- 3″/hr could move over the same areas, especially given the potential for rainfall with the second round of storms overnight. The front will then move through on Wednesday morning clearing out rain chances with gusty winds upwards of 20-25 mph from the north on the backside of the boundary.