Storm Forecast
Valid: Sat 03 Mar 2007 06:00 to Sun 04 Mar 2007 06:00 UTC
Issued: Fri 02 Mar 2007 19:40
Forecaster: TUSCHY

SYNOPSIS

An intense upper-level jet will shift towards the east and will pursue the strong zonal flow regime over central Europe.
This constellation will support warm and dry conditions over S / SE Europe, while a cool and stable environment will prevail for the northern parts of Europe.

An intense depression will form over the N-CNTRL Atlantic Ocean and rapid strengthening is forecast by latest model runs ( pressure fall
of more than 40hPa will be possible ).
There won't be any effects on the forecast area beside increasing WAA from the SW.

DISCUSSION

...NW / W Turkey...

Low-end instability will develop during the morning and early afternoon hours and a few thunderstorms will be able to evolve before positive temperature advection will weaken lapse rates in all levels.
DLS of 20-25m/s will be enough for an isolated storm organisation and an local large hail report can't be excluded.
The threat should finally cease during the late afternoon hours.
No level-1 will be released because of the limited time-frame for stronger storms to develop.

... Most parts of Germany and extreme eastern France ...

A somewhat more complex scenario evolves for parts of Germany.

Strong 135kt jet max will cross southern Germany between 6-18Z and attendant upper-level divergence field in its left exit region will rapidly spread towards the east, crossing central Germany and the Czech Republic from the west.
Models agree in the development of a strong LL depression, although there exist some minor discrepancies regarding the exact track .
The main focus for ongoing / developing storms will be the conjunction point of an eastward shifting cold front and an eastward racing dry slot at mid-levels, which will cross western and central Germany during the daytime hours.
Low-level temperatures cool down somewhat but will continue to contribute to pretty weak LL lapse rates. This inhibiting factor could partially offset by a rapid recover of LL dewpoints in front of the cold front. Temperatures of 7-10°C and dewpoints of up to 8°C will be possible and forcing is forecast to cross those regions during the same time frame from the west.
Expect marginal instability release over western and central Germany in an environment with strong LL shear ( although veering will ease betimes ) and any storm which can manage to root into the boundary layer will be able to produce an isolated tornado and severe wind gusts.
The combination of fine mid-level lapse rates and intense DLS would normally pose a hail risk, but expected shallow nature of thunderstorms should limit this threat....only expect an isolated marginal hail report.

S-Germany was also included into a level-1 because of the combination of forcing at mid-levels under the well defined dry slot. A weak cold front will also support some lift and a few thunderstorms can be expected.
The main threat will be an enhanced severe wind gust threat regarding a strong 25-30m/s 850-hPa flow. Although LL shear is significantly enhanced the directional shear component is pretty weak. Anyway...low LCLs and such a strongly sheared environment will support the chance of an isolated tornado report.

Even without thunder there will exist an enhanced severe wind gust threat along each convective segment.

The general thunderstorm area was extended well towards the east, because a few storms will be possible as far east as E-Austria. Limited thunderstorm coverage and near zero-instability won't justify a level-1 that far towards the east.

...United Kingdom...

Broad area of low-end instability will develop, but missing forcing and weak shear will preclude any significant thunderstorm threat / thunderstorm organisation. Although a few SFLOC reports could occur no special region was highlighted.