Mesoscale Discussion
Valid: Fri 17 Jan 2025 10:00 to Fri 17 Jan 2025 13:00 UTC
Issued: Fri 17 Jan 2025 09:32
Forecaster: TUSCHY

This Mesoscale Discussion (MD) was issued to highlight a constantly increasing severe risk within the MD area mainly during the afternoon into the overnight hours. Therefore the validity of this MD does not match the anticipated severe risk.

Latest HVIS loop indicates a long-lived and back-building MCS offshore over the Strait of Sicily. This DMC activity is attached along the tip of the gradually NEward surging IPV maximum/dry slot.

NWP guidance agrees in this MCS to impact Sicily from SW to NE from the noon/early afternoon hours onwards.

A bit hard to assess is the risk of more discrete activity ahead of this MCS as Sicily resides along the edge of most higher resolved models with missing input from downstream, whereas global models have difficulties to resolve the more discrete activity ahead. However, if we combine the messy looking but rather active thunderstorm signals ahead of the ongoing MCS in global models with impressive looking convective parameters in limited area models, signs still support the idea of a potential dangerous event evolving in the MD area during the following hours. In addition, NEward spreading higher IPV in ongoing synoptic-scale lift should also increase CI ahead of the line.

Despite forecast soundings showing a very weak LL cap/neutral lapse rates, we still agree in a rapid modification both due to maximized moisture advection ahead of the MCS and a starting cool-down also als LL. LLCAPE in the 150-300 J/kg range with strongly curved hodographs (supported by latest synop reports with backed surface winds) and lots of effective streamwise vorticity available for any more discrete storm, we still keep the risk for even a strong tornado event in the forecast with the highest risk probably along the E coast of Sicily.

Otherwise the excessive and attendant flash flood risk increases from now on with significant events well possible. In addition, downward mixing of high wind speeds adds a severe wind gust risk with any thunderstorm next to isolated hail.

We expanded the MD more inland over Sicily to account for a further westward adjustment in latest model cycle including the passage of a slow moving MCS event with healthy rainfall amounts.