Storm Forecast
Valid: Sat 20 Jun 2015 06:00 to Sun 21 Jun 2015 06:00 UTC
Issued: Sat 20 Jun 2015 05:06
Forecaster: DAFIS

A level 2 was issued for SW Russia and NE Ukraine mainly for large hail and excessive rain.

A level 1 surrounds the level 2 area mainly for a similar risk but with less confidence in extreme events.

A level 1 was issued for parts of Italy and Austria, Slovenia and Croatia for excessive rain and marginal large hail.

SYNOPSIS

From a synoptic scale we see that several disturbances in central and east Europe but in central Europe, overall risk of severe storms is low due to weak CAPE. The most interesting boundary will be a wavy quasi-stationary baroclinic zone, which runs from NW Russia to the NE Ukraine.
A low pressure system is approaching the UK and another one is affecting south Scandinavia where some weak storms are forecast. The longwave trough in central Europe moves slowly eastwards but still affects large parts of the continent. Thunderstorms should weaken in the late evening hours but not in Adriatic Sea.

DISCUSSION

....SW Russia and NE Ukraine....

We expect isolated to scattered thunderstorms to evolve over the E Ukraine, which grow upscale rapidly into some organized clusters. Models produce large amounts of MLCAPE during the evening in a large area with maximum values just out of our forecast domain, but in NE and SW Russia the values should reach 2500J/kg. On the other hand, DLS is rather weak, reaching 10m/s, maybe 15m/s, so the thunderstorms are forecast to be quasi-stationary, producing excessive precipitation and large to very large hail. Large hail is expected due to large amounts of CAPE, steep lapse rates (>7.5K/km) and very moist BL (mixing ratio >12g/kg). A few tornado events are possible with SRH-1 in excess of 200m^2/s^2, low LCL's and the aforementioned CAPE, although LLS is absent.

....Austria, Italy, Slovenia, Croatia....

Marginal MLCAPE of 400-800J/kg in N Italy and Austria is juxtaposed to quiet strong DLS of 20-25m/s and if storms eventually form they will be able to produce marginal large hail due to very moist BL (mixing ratio >10g/kg) and steep lapse (>7K/km) rates by the diurnal heat. According to high resolution models, MLCAPE values should be higher in central and south Italy with values exceeding 1000J/kg in the evening. Furthermore, very moist and unstable BL overlaps with DLS of 20m/s and the clusters of storms are forecast to be long-lived, able to produce excessive rain and large hail. In Croatia, LL convergence zones at the mountains near the coast will enhance the lift and the CI will not have troubles during the evening.


....other areas....

Models produce some large amounts of precipitation in Hungary and Romania but weak DLS and CAPE result in pulsating storms during the late evening. In south Adriatic Sea some clusters of storms are forecast to move east, to Albania during the night and finally in North Greece, GFS produces PW of 40mm in Macedonia area with MLCAPE of 500J/kg but there is uncertainty of the CI as CIN exceeds 50J/kg. Early morning storms are forecast in N Aegean Sea, on Sunday.