Storm Forecast
Valid: Mon 20 Jun 2011 06:00 to Tue 21 Jun 2011 06:00 UTC
Issued: Mon 20 Jun 2011 02:13
Forecaster: DAHL

A level one threat has been issued across N Spain mainly for large hail and severe wind gusts.

A level one threat has been issued across NE France mainly for large hail, damaging winds, and tornadoes.

A level one threat has been issued across the eastern Ukraine and western Russia mainly for excessive convective rainfall and to a lesser extent for large hail and damaging winds.

SYNOPSIS

Progressive upper pattern continues ... with an upper trough over eastern Europe and another one over the Atlantic, approaching W Europe. The latter feature is accompanied by a SFC low, which allows moist/warm air to return to central Europe. Quiescent synoptic conditions persist across the southern portions of Europe.

DISCUSSION

... NE France ...

A focus for potentially severe convection seems to exist over NE France where some 1000 J/KG CAPE and about 20 m/s DLS will exist. Some WAA should persist through the day, which should provide large-scale ascent to aid in convection initiation. However, storm coverage is uncertain and is not coherently simulated by the different models. Expect isolated thunderstorms, the most intense of which may produce large hail and damaging wind gusts. LLS will increase towards the NE, being maximized outside the region where instability exists. Still, storms over the NE parts of the LVL1 area may pose an additional threat for a brief tornado or two.

... N Spain ...

Scattered high-based storms should form over N Spain during peak-heating hours. Deep-layer shear and CAPE will be marginal, but an isolated/marginally severe hail/wind event cannot be discounted, marginally justifying a LVL1 area.

... W Ukraine ... E Poland ... W Belarus ... S Baltic States ...

A rather broad area of essentially uncapped, weakly unstable modified polar air should allow for widespread showers and thunderstorms. GFS simulates a region of 10 m/s LLS across the W Ukraine, E Poland, W Belarus into the S Baltic States, which could support at least briefly rotating updrafts. As a consequence, the threat for a brief tornado and perhaps some hail is slightly enhanced, but the overall severe threat should remain below LVL1 limits.

... E Ukraine ... W Russia ...

Some instability should persist in a narrow tongue ahead of the cold front attendant to the E-European upper trough. DLS increases rapidly towards the west (cold side of the front), leaving most of the unstable air in rather weak shear. DLS directly along the front may be on the order of 10 m/s, which is sufficient for weakly-organized multicells. Expect very isolated large hail and severe wind gusts with this activity. The primary threat should be locally excessiv rain, however. Overall, a marginal LVL1 threat is warranted.