Storm Forecast
Valid: Sat 12 Mar 2016 06:00 to Sun 13 Mar 2016 06:00 UTC
Issued: Sat 12 Mar 2016 01:58
Forecaster: TASZAREK

A level 1 was issued for parts of S Italy mainly for the excessive precipitation.

A level 1 was issued for S Greece and part of Aegean Sea mainly for the large hail and in lesser extent for the tornado.

SYNOPSIS and DISCUSSION

A mid-level large ridge extending from Azores High and low level high over N and CNTRL Europe prevents from any deep convective activity. Low values of mid and upper temperature (500 hPa ~ -25C) and geopotential levels covers E, CNTRL and S Europe. A cut-off placed over CNTRL Mediterranean moves eastwardly and on its right flank provides an advection of moist air in low-levels. Within this overlap a thermodynamic instability will develop, and deep moist convection will be likely.

The complex of thunderstorms is expected to move eastwardly ahead of trough and reach S Greece and Aegean Sea in the late forecast hours. Due to an increased mid and low level flow it is likely that thunderstorm will organize linearly and pose a threat for the severe wind gusts, especially along the SW coast of Greece in the afternoon hours. The overlap of boundary layer's mixing ratio up to 10 g/kg and a steepening lapse rates on the SE flank of the trough will result in a CAPE locally up to 800-1000 J/kg. In the late afternoon hours, this area will receive a PVA signal (that along with orographic lifting may trigger new cells) and will overlap with 25-30 m/s DLS and 150-250 m2/s2 0-3km SRH, thus creating threat for the supercell thunderstorms capable of producing large hail (~ up to 2-3 cm) and severe wind gusts. Since the low-level shear and SRH will be also favorable, a mesocyclonic tornado in the SE edge of Greece cannot be ruled out. In the late evening hours thunderstorm should move over Aegean Sea. Limiting factor that prevents from issuing a level 2 is a small coverage of favorable CAPE/shear combination and a rather low thermodynamic instability.

Another level 1 is issued for S part of Italy where a superimposing large-scale precipitation with an almost stationary low CAPE / low shear thunderstorms may produce locally up to 50-100mm rainfall. Thus, local flash flooding cannot be ruled out. The threat falls mostly on the morning hours.