Storm Forecast
Valid: Wed 07 Jan 2009 06:00 to Thu 08 Jan 2009 06:00 UTC
Issued: Tue 06 Jan 2009 21:48
Forecaster: PUCIK

SYNOPSIS

An outbreak of very cold and stable airmass is underway across most of Europe. A deep trough at midlevels will stretch from Eastern Russia to Spain. A weak impulse on its forward side above the western Mediterranean has led to the surface cyclogenesis, resulting in a weak surface low, which will stall over Sardinia and Corsica region. On its front side, slight warm advection will occur.

DISCUSSION

...Western coast of Italy...

Only weak instability signals are shown by GFS, with MLCAPE values well below 500 J/kg. Nevertheless, at least slight mid-level support
and a convergence especially by the coastal areas should help in the initiation of deep moist convection. Electrification is questionable, due to the low moisture content and overall very weak instability. However, EL temperatures should be lower than -20°C and few ltg strikes are anticipated.

... Southern coastal areas of Sicily....

This area will experience only slightly better thermodynamic conditions than the one mentioned above. GFS is simulating a belt of strong mid-level winds, surrounding the base of the trough, which will increase DLS values to more than 20 m/s. As the shear in the lowest 3 km should stay only around 10 m/s and storms will probably stay low-topped, the degree of organisation allowed by such configuration should be only limited. Slightly higher SREH values are expected, locally over 100 J/kg, so multicells or weak supercells might form. Mostly sub-severe hail might occur as well as few waterspouts, due to the concentration of instability in the lower levels. The overall threat however does not seem to warrant an issuance of Level 1 at the moment.