Storm Forecast
Valid: Thu 31 Mar 2011 06:00 to Fri 01 Apr 2011 06:00 UTC
Issued: Wed 30 Mar 2011 13:28
Forecaster: GATZEN

SYNOPSIS

A broad trough is present over Europe. To the west of this low geopotential, a short-wave trough ejects from an Atlantic long-wave trough and moves across the British Isles and Germany on Thursday. In the wake of this short-wave trough, a south-westerly flow will evolve over western Europe, building a broad ridge that expands eastward during the period. This situation is associated with warm air advection from the south-west over most of Europe except for the central Mediterranean and the Balkans, where cold air masses remain.

DISCUSSION

Central Mediterranean Sea, Italy, southern Balkans to Romania, Turkey

Within the cold air that covers most of the southern and eastern forecast region, daytime heating leads to steep low-level lapse rates especially in the noon and afternoon hours. Some low-level moisture is also present that allows for some CAPE as indicated by the latest soundings. The best low-level moisture and low-level forcing is forecast along sea breeze convergence lines, and showers and thunderstorms are forecast from the noon to the evening over islands as well as over the coastal regions of Italy, the Balkans, and Turkey.

Over the Mediterranean Sea, latest observations indicate that thunderstorms are not likely to develop given the rather cool sea surface. Some isolated thunderstorms are not ruled out, especially at night along offshore convergence zones.

For Greece and surroundings, some additional lift is expected at the western flank of a warm air advection regime to the south of Turkey. Thunderstorms may cluster in the evening and night hours and may go on until the morning with a local threat of intense precipitation. Severe limits are not expected to be reached.

Latest models also indicate the development of CAPE far away from the sea over Romania, the Balkans, and Turkey. Although low-level moisture will be limited, the strong diurnal heating will likely assist for some CAPE, and weak CIN as well as some forcing near the trough center is expected to assist for isolated thunderstorms that are forecast to decay in the evening hours.

Main threat of these thunderstorms will be local hail and gusty winds that may reach severe limits, but the absence of strong vertical wind shear limits the severe potential of these storms.

Western Poland, Czech Republic, Austria

A weakening short-wave trough will enter this region in the afternoon hours from the west. It will lead to some large-scale lift. At low levels, strong diurnal heating is forecast, and southerly to south-westerly winds will be associated with moisture advection during the day. Latest models indicate the development of weak CAPE that will likely be released given weak CIN and some forcing especially over hilly regions. Isolated showers and thunderstorms are forecast at the afternoon that may pose a threat of local hail that can reach severe limits. The best potential is expected over Austria where the deep layer Bulk shear increases to about 25 m/s. The expected threat seems not to warrant a level 1, though.