Extended Forecast
Valid: Tue 12 Feb 2008 06:00 to Wed 13 Feb 2008 06:00 UTC
Issued: Sun 10 Feb 2008 23:14
Forecaster: TUSCHY

SYNOPSIS

Major split-flow regime continues during the forecast period with attendant intense high pressure area placed over the North Sea. Eastern part of this feature erodes somewhat but will still be in place for the next 24 hours to support stable conditions for most parts of Europe.


DISCUSSION

... An area SW of Portugal ...

A SSE-ward moving upper-level low encounters warmer SSTs ( at or above 20°C ) and in combination with cooler mid-levels widespread instability release will be the result. As surface depression establishes ties with a very moist subtropical airmass to its south a nice theta-e ridge downstream of this feature develops and in combination with aforementioned environmental conditions, instability could reach 1000 J/kg during the latter part of the forecast period but mainly just out of the area of responsibility. Shear could be adequate for an isolated organized thunderstorm risk, especially when the depression moves further to the east than currently anticipated.

... Central Mediterranean ...

Consistent signals of isolated to scattered thunderstorms exist over parts of the central Mediterranean somewhere west of Sicily and south of Sardinia. SSTs around 15°C and a slowly mixing boundary layer should help to release some low-end instability. Degree of mixture and LL instability dictates the risk for waterspouts.

... Belarus...

A cold-core upper-level low migrates erratically to the south. Boundary layer moisture is too meager for any enhanced thunderstorm risk, but cold profiles and a low wet-bulb zero level could support marginal hail in any stronger updraft.As this is a mainly daytime driven event risk should stay confined to Belarus. Threat area could shift significantly as global models have difficulties handling those features.

... N-Norway / N-Sweden and N-Finland....

An intense cold front approaches those regions during the end of the forecast period. Timing and meager moisture should suppress any thunderstorm activity over N-Norway. In addition incoming flow supports subsidence in the lee of the Norway mountain range.
The main attention turns to the 00Z-06Z time-frame over northern Finland as cold front pushes southward.GFS constantly showed a tongue of higher dewpoints along the cold front in this area and as atmosphere cools down a broad area of up to 200 J/kg CAPE is forecast in an environment with high helicity and shear values, supportive for storm rotation. This area has to be monitored during the upcoming model runs.