Storm Forecast
Valid: Tue 25 Jul 2017 06:00 to Wed 26 Jul 2017 06:00 UTC
Issued: Mon 24 Jul 2017 21:25
Forecaster: DAFIS

A level 2 was issued for parts of Belarus, Ukraine, Moldova, Romania and Bulgaria mainly for large to very large hail, excessice precipitation, severe wind gusts and tornadoes.

A level 1 was issued for a large part of East Europe for large hail, excessice precipitation, severe wind gusts and tornadoes.

A level 1 was issued for Italy and parts of W Balkans mainly for excessive precipitation, large hail and tornadoes.


SYNOPSIS

Three mid-level cut-off lows over Europe destabilize large areas. The main storm activity is expected in East Europe, at the warm sector of a low pressure system with its center over Poland during Tuesday. CAA in Germany, Benelux and France brings stable air masses from the north and some heavy rainfall events are expected but mostly non-convective. Regarding the Mediterranean basin, Italy and W Balkans have a potential for convective activity, where the leading edge of the large-scale wave results in advection of strong PV. By the end of this outlook, another short-wave trough is approaching the British Isles in the early morning of Wednesday while the ridge over Spain and France intensifies.

DISCUSSION

.... Belarus, Ukraine, Moldova, Romania and Bulgaria ....

Ongoing stom activity is expected tonight and in the morning of Tuesday. Latest model outputs show the formation of a long-lived convergence zone inside the large level 2 area shown on the map. The cold front advects moisture from Central Europe as it moves to the east and a strong SE flow from he Black Sea also brings warm and moist air masses under a strongly sheared environment. Moreover, the combination of rich PBL moisture and very steep lapse rates (7.5 - 8 K/km) may lead to more than 2 kJ/kg MLCAPE. DLS will oscillate between 15-20 m/s assisting some storms to become suprecells, producing all king of severe weather. Large to very large hail threat is increased for Bulgaria, Romania and Moldova, where NCAPE is the highest and overlaps with 20 m/s DLS. Almost every storm will also be able to produce excessive precipitation, as PW is calculated to exceed 40 mm, mostly within the center of the depression over Ukraine. The tornado risk increases towards N Ukraine and Belarus with elongated and curved forecast hodographs.

.... Italy and W Balkans....

Unstable air masses over this area will lead to diurnally driven convective activity, but also the PV advection in the mid-levels will assist storms to form over the weakly capped Mediterranean Sea as well. Increasing DLS in the afternoon which will overlap with some hundreds of CAPE, will create a favorable environment for storms to become organized and produce large hail and severe wind gusts. Later, during the night, high-resolution models show the formation of a MCS or a supercell over the Adriatic Sea, reaching the coasts of the W Balkans, able to produce excessive precipitation, severe wind gusts and tornadoes. Finally, waterspouts are expected not only inside level 1 area, but everywhere indicated by a probability of lightning threat.