Storm Forecast
Valid: Wed 27 Apr 2011 06:00 to Thu 28 Apr 2011 06:00 UTC
Issued: Tue 26 Apr 2011 21:02
Forecaster: PUCIK

No threat levels have been issued.

SYNOPSIS

A rather inconspicuous synoptic situation is prevailing over Europe with a pool of seasonally low geopotentials / temperatures covering most of the continent at mid-levels of troposphere. A broad and shallow cut-off low is forecast over the Central Mediterranean and Central Europe, centered over southern Germany. To the west, a ridge is simulated over the Atlantic. All of the features will be embedded in a weak flow with no jet-stream structures. Stronger, zonal flow will be observed only over extreme north Scandinavia.

Closer to the surface, large high pressure system will dominate northern and eastern half of Europe with shallow low over the Mediterranean. No significant frontal boundary should exist during the forecast period.

An abundance of diurnally driven showers and thunderstorm is forecast over many areas of Europe, driven mostly by the local circulations and mesoscale features. Instability will build up due to the cool mid-levels, which result in high temperature gradient below this level and subsequent day-time heating should lead to the marginal to moderate CAPE. MLCAPE values should be in the order of hundreds of J/kg and due to the weak mid and upper level flow, wind shear values will stay weak. Due to the weak wind shear and rather marginal instability, organised severe thunderstorm threat will be almost non-existent.


DISCUSSION

...Germany and Western Russia...

Due to the cool vertical temperature profiles with low freezing levels, stronger cells will likely be capable of producing hail. Albeit most of the hail should be under 2 cm in diameter due to the limited thermodynamic setup, it seems plausible that a very isolated event with severe hail is possible. In case of Germany a proximity of cut-off center will slightly enhance flow, contributing to the stronger wind shear than over the other areas. The highest threat of hail will come from the stronger multicellular storms. In case of Western Russia, both higher MLCAPE and ICAPE values suggest stronger updrafts in this area with chance of pulse convection producing very isolated marginally severe hail. The overall threat seems to be too low to warrant Level 1 for any of those regions.