Storm Forecast

Storm Forecast
Valid: Sat 02 Jan 2016 06:00 to Sun 03 Jan 2016 06:00 UTC
Issued: Fri 01 Jan 2016 17:06
Forecaster: DAFIS

A level 1 was issued for Italy mainly for severe wind gusts, large amounts of small hail and excessive rain.

SYNOPSIS / DISCUSSION

The blocking pattern seems to have been reaching an end after a long time over Europe. A longwave trough with an axis from Ireland towards the Gulf of Biscay is moving eastward and a mid-level cut off low will enter the NW Mediterranean Sea during Saturday, associated with a surface low, formed over the Gulfs of Lion and Genoa. Vigorous depressions in the North Atlantic are still causing problems to Ireland and the UK with the strong westerly flow bringing large amounts of moisture ashore. At the other side of the continent, low geopotentials but high pressure near the surface lead to very low temperatures and foggy conditions, except from the Black Sea and North Turkey, where lake effect snowfall has accumulated large amounts of snow and some thundersnow events take place.

During the first half of Saturday, stratiform rain will be abundant at the west coast of Italy, but during the second half, we expect some thunderstorms over Corsica, Sardinia and west coast of Italy. About -25C at 500 hPa and 5C at 850 hPa will create a quite steep vertical temperature gradient and NWP models forecast the development of more than 400 J/kg of MLCAPE. Furthermore, 20 m/s of DLS will overlap with CAPE, especially after 21:00 UTC and a level 1 is issued for severe wind gusts, large amounts of small hail and excessive rainfall. The area will be under the left exit of a mid-level jet streak and excessive rain is possible due to the presence of about 30mm of PW and the advection of moist air masses which will be orographically lifted in west Italy. Large amounts of small hail is forecast because the DLS will overlap with very low mid and upper-air temperatures and the height of freezing level will be below 1700m, so any storm that will manage to reach the shore will be able to produce some hail on the ground. After 03:00 UTC the aforementioned threats will be found over the Adriatic Sea and during Sunday over the west coast of the Balkans.

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