Storm Forecast
Valid: Thu 24 May 2007 06:00 to Fri 25 May 2007 06:00 UTC
Issued: Wed 23 May 2007 21:41
Forecaster: GATZEN

SYNOPSIS

To the south of intense upper long-wave trough over northern Europe, a ridge axis is present from northern France to Ukraine. Two cut-off lows are centered over southern Portugal and Greece. At lower levels, a frontal boundary separating a stable and unstable air mass is present from northern France to central Germany, Slovakia, and farther to northern Ukraine.

DISCUSSION

Eastern Iberian Peninsula, southern France

Indications are that best shear profiles will be present over north-eastern Iberian Peninsula during the period. Moderate southerly jet is expected to spread across eastern Iberian Peninsula. At the same time, low-level winds are backed north of a weak surface low-pressure system that moves into north-eastern Iberian Peninsula in the late evening hours. Low-level helicity (around 100 J/kg SRH) and shear values (10 m/s LLS) will be favorable for mesocyclones. However, rather weak forcing and quite cold/dry boundary-layer will be a strong negative. Expect that only isolated storms will develop, chance for isolated large hail/severe wind gusts is quite poor. Thunderstorms are expected to dissolve in the night hours.

Most of central Europe

A broad region with unstable air mass characterized by a deep moist layer in the lower levels as well as steep mid-level lapse rates remains along/south of the frontal boundary. Capping inversion is rather weak, and diurnal heating coupled with upslope flow in mountainous regions and/or old outflow boundaries will be strong enough for initiation. Given weak vertical wind shear, single cells are expected to develop. Although isolated large hail cannot be ruled out especially as high CAPE may realize, most convection is forecast to be non-severe. High precip and flash flooding due to slow propagating cells will be possible, though. Storms will rapidly decay in the night hours.