Storm Forecast
Valid: Fri 20 Apr 2007 06:00 to Sat 21 Apr 2007 06:00 UTC
Issued: Thu 19 Apr 2007 18:32
Forecaster: TUSCHY

SYNOPSIS

Disturbed weather pattern continues over Europe with a strong low pressure area over Sweden and Finland, feeding cold air well towards the SE.
Showers / Isolated thunderstorm activity will likely perk up somewhere over E-Belarus , where thermodynamic profilers indicate a limited time-frame for some low-end instability release in a weakly sheared environment.
A weak upper-level low will reach Morocco during the end of the forecast period and will bring unsettled weather conditions to SW Europe.
Otherwise, weak geopotential differences will affect southern / western Europe, where diurnal driven convective activity can be expected.


DISCUSSION

....Portugal and parts of Spain...

+++Correction in line 7+++

The main feature of interest will be an ill-defined upper-level low, drifting southeastwards towards the Strait of Gibraltar / NW Morocco.
Yesterday's sounding of Lisbon (12Z) already had up to 1100 J/Kg SBCAPE and convective activity was characterized by scattered, pulsating thunderstorms.
Right now, there are no reasons to expect any serious modification of the atmospheric stratification over Portugal.
A fact, which can't be ignored will be somewhat lower mixing rations over extreme SW Spain / S-Portugal, where mid-levels also should warm up slightly. Isolated storm evolution should be still possible given the stronger environmental forcing.
Anyway, in response of the approaching depression the wind field at mid-levels will undergo a marginal strengthening trend combined with some backing more towards southeasterly directions. This will help to boost SRH-3km values up to 100-200 J/kg.
Main concern will be an isolated large hail threat mainly over Portugal, where steep lapse rates, moderate instability values and enhanced shear will overlap ( mainly central Portugal ).

A level-1 was not issued because of the displacement of the best shear / thermodynamic parameters and the over-all marginal looking set-up.