Storm Forecast
Valid: Fri 26 Apr 2019 06:00 to Sat 27 Apr 2019 06:00 UTC
Issued: Thu 25 Apr 2019 19:09
Forecaster: DAFIS

A level 2 was issued for parts of Slovakia, Hungary, Ukraine and Romania mainly for severe wind gusts and large hail.

A level 1 was issued for parts of Slovakia, Croatia, Serbia, Hungary, Ukraine and Romania mainly for severe wind gusts.

Two level-1 areas were issued for Germany, Poland, Czech Republic, Lithuania, Belarus and Ukraine mainly for severe wind gusts, large hail and excessive precipitation.

SYNOPSIS

A deep trough in western Europe is pushed to the east by the Azores High and the strong ridge in eastern Europe is destabilized by short-wave disturbances and the approach of the colder air masses from the west. A smaller trough is also approaching Ireland and the UK on Saturday morning from the Atlantic, associated with a deep low-level cyclone that will produce gale-force wind gusts but non-convective.

The most favourable conditions for deep moist convection can be found in East Europe where warm and moist air masses lie, even though the dry mid-levels and weak wind fields inhibit the development of widespread severe thunderstorm activity. Moreover, France, Benelux and Italy will experience some diurnally driven thunderstorms with a low probability for severe phenomena.

DISCUSSION

.... Slovakia, Hungary, Ukraine and Romania .....

This area lies under the presence of warm and moist air masses and very steep mid-level lapse rates. NWP models are quite aggressive in producing large values of CAPE of about 1.5 - 2 kJ/kg MLCAPE, but the DLS is limited to 5-10 m/s and we only expect isolated thunderstorms in the afternoon. Delta theta-e values from GFS of about 12-15 K suggest that storms will be able to produce severe wind gusts, with a lower probability for microbursts, but they cannot be excluded given the slow storm motions and the uncertainty in numerical model guidance. Moreover, large CAPE values show a high probability for hail producing storms, but hail should not get bigger than 2 cm.

.... E-Germany, W-Poland, Czech Republic ....

The approaching trough brings high PVA over this area and synoptic lift of warm and moist air masses will lead to numerous thunderstorms which can benefit from 1 - 1.5 kJ/kg MLCAPE in the afternoon. Also for this area, DLS is weak and only a few storms will be able to organize in small clusters and produce severe weather. Severe wind gusts will be the main threat, especially in Germany where NWP models show some dry air intrusion from the west. More stable conditions will take over during the night of Friday 26/04.

.... E-Poland, Lithuania, Belarus and N-Ukraine ....

Storms will be more difficult to develop in E Poland, Lithuania and Belarus because of mid-level entrainment, but the strongest updrafts will be able to produce locally severe thunderstorms. Again, only isolated cells are expected which will be able to produce severe convective wind gusts and in Ukraine, possibly excessive precipitation, where PBL moisture is the most pronounced and effective precipitable water is higher than the northern parts of level-1 area.