Storm Forecast
Valid: Thu 12 May 2011 06:00 to Fri 13 May 2011 06:00 UTC
Issued: Wed 11 May 2011 13:48
Forecaster: GATZEN

SYNOPSIS

A broad trough centred over Turkey weakens on Thursday. A subtropical high ridges from Algeria into eastern Europe. North-western Europe is dominated by intensifying low geopotential and an associated mid-level jet that spreads into Germany and Poland at the end of the forecast period.

DISCUSSION

Eastern Germany to southern Baltic States

A cold front travels eastwards into Poland. The warm air mass to the east is rather dry and lapse rates above the boundary-layer are quite poor. Ahead of the cold front, a tongue of better low-level moisture currently over Germany is expected to spread north-eastwards into Poland. Along this cold front that will be located over eastern Germany in the morning hours, a weak frontal wave are forecast to develop by latest GFS model output.

With slightly backing winds east of the frontal wave, warm and well-mixed boundary-layer air may spread northward and is forecast to overlap with the low-level moisture along the front. Initiation becomes likely during the day and thunderstorms are expected to develop that may be elevated to the west of the cold front. The storms will likely cluster in the afternoon and evening hours. The weak vertical wind shear is expected to limit the severe weather threat. Locally large hail or excessive precipitation is not ruled out.

Northern Iberia to Czech Republic

The southern part of the cold front will slowly spread southward. Weak winds are forecast and diurnally driven thunderstorms will only profit from the low-level convergence that may assist in a few intense pulse storms, capable of producing large hail and excessive precipitation. Storms will cluster later on whereas the severe weather threat is expected to weaken in the evening and night hours.

Northern Germany

A mid-level short-wave trough will move across northern Germany. At lower levels, cold air advection will likely counteract the DCVA of the trough, and weak low-level convergence is forecast. However, models expect some boundary-layer moisture and diurnal heating is forecast to result in CAPE. Some showers and thunderstorms are forecast to move eastwards in the afternoon hours. Weak vertical wind shear is forecast to limit the severe potential. Storms will likely decay in the evening hours.