An interesting setup is shaping up today across southern Alpine region. A large negative-tilted trough is located over western Europe where its southern part transforms into a cut-off low moving SEwards across the western Alps. At low levels, a developing low surface pressure system is expected over Northern Italy during the day which will be the focus area for today’s convective development.
Ahead of this ejecting trough/cut-off low rather strong QG forcing will be in place, resulting in favorable large scale lifting over Northern Italy.
At lower levels, warm and very moist airmass will continue its advection NEwards and along with diurnal heating, destabilization will occur. Given the practically non-capped environment and steepening lapse rates behind the weak occluded front which passed this region in the night and early morning hours, mostly strong showers and thunderstorms are expected starting towards the midday. Model runs suggest several hundreds of CAPE with max values placed over northern Adriatic an Po valley reaching around 1000 J/kg locally.
Further south, towards the Apennini mountain range and its western side along the Ligurian coast, some severe weather can be expected, as stronger flow and both low and deep-layer shear up to 50kts are located on the southern flank of the ejecting low, however models simulate less MLCAPE in those areas. Given the at least several hundreds of MLCAPE release and favorable wind shear, storms are expected to organize into multicells and possibly also a few discrete supercells with a risk for some large hail and strong winds. A cluster of storms in few small MCSes is not out of the question with the main risk for severe hail and intense rainfalls.
For this reason and favorable environment, ESTOFEX has issued a level 1 threat areas across central Italy where a risk for severe storms development seems reasonable. Visit the Storm forecast for today.
Above morning Udine sounding shows pretty moistened lower levels of the atmosphere and relatively low freezing level height. Given the expected diurnal heating and quite high surface dewpoints over the Po valley (10-12°C), also LL CAPE realease seems reasonably high. Such sounding usually suggest a risk for marginal hail and especially a flash flooding risk with the strongest storms, as weak mid-level winds allow cells to be more persistent over the same areas. According to that, several tenths of mm in couple of hours can be expected locally which might lead into some flash flooding. Also, due to higher CAPE realease and weak winds in the lowest levels, waterspouts/landspouts are possible, especially over the Po valley plains. That is well visible also on the model maps, which show high 0-3km CAPE release and high values of Spout Index. Severe thunderstorms are not expected as wind shear is very low over NE Italy and Slovenia.