Storm Forecast
Valid: Fri 23 Jun 2006 06:00 to Sat 24 Jun 2006 06:00 UTC
Issued: Thu 22 Jun 2006 19:53
Forecaster: TUSCHY

SYNOPSIS

An upper-level trough will be placed nearly stationary over northern Europe during the next 24 hours.... Downstream of this feature, an area with weak pressure differences will be present and this, combined with the influx of a warm and humid airmass, should help to disequilibrate most areas of eastern and southeastern Europe.
Another trough // in a developing stage // will also start to affect parts of SW Europe during the latter part of the foreast period.
The Mediterranean will stay dry and hot!

DISCUSSION

....Northern Portugal, northern Spain and extreme southwestern France ...

Downstream of an approaching trough,strong insolation and intense diabatic heating should take place ( up to ~35°C ).
A well-mixed boundary layer and slightly cooler mid-levels should help to initate isolated storms over the mountainous regions (NE Spain ) as early as the soon afternoon hours... A constantly lowering of the geopotential heights and cool-down of the mid-levels ( although not significantly) will help for scattered TSTM initation over the area of interest... Exact amount of instability release depends on how fine dewpoints can recover, but current indications are, that no significant change will occur, so only low-end to moderate instability release can be expected... DLS of 10-20 m/s will be present and there should be a marginal severe wind gust threat ( enhanced downburst potential, mainly further inland ) but expected coverage and all-over conditions won't be enough for issuing higher probabilities ATM.

....Eastern and southeastern Europe...

A slowly eastward moving frontal boundary separates slightly cooler and drier airmass (postfrontal) by a warm and humid airmass, which covers most areas of eastern Europe...
Steep mid-level lapse rates and up to 1500 J/kg should help for widespread TSTM development, mainly in the level 1 area...
Wind shear will be on the lower-end side and therefore, main risk will be an isolated hail threat with each stronger storm.
Like the past few days, high instability and locally modified wind field ( by the topography and the front ) could be enough for a few supercells to develop, but the coverage will be too low for an higher threat level.

...Parts of extreme southeastern Finland and eastward...

Praefrontal low level jet continues to advect a warm and humid airmass northward... Despite the marginal instability release, strengthening background flow and forcing ( due to the approaching front ) will be a favorable environment for a few organized storms to develop...Low level shear will be enhanced along the slowly eastward shifting front and fine LCL- levels should be enough for mentioning the possibility of an isolated tornado report ...otherwise, a few severe wind gust/large hail reports can be expected.

...Sweden...

Pool of cold mid-levels will slowly cross Sweden from the SW and should help to release widespread low-end instability... Weak wind shear over most parts of Sweden will preclude any significant storm organisation.