Storm Forecast
Valid: Sat 09 Sep 2006 06:00 to Sun 10 Sep 2006 06:00 UTC
Issued: Fri 08 Sep 2006 18:36
Forecaster: TUSCHY

SYNOPSIS

Upper-level trough, placed over Finland, Belarus and the Ukraine will start to lift out towards the ENE and no decrease in amplitude is expected.....Despite this prominent synoptic feature, most parts of western, southern and central Europe will see rising pressure due to a strengthening high pressure area , running from the North Sea towards Hungary... A cool and stable airmass should suppress convection over a broad area of NW Europe....SW Europe will see an increase in convective activity due to the advection of a warmer and more humid airmass from the E-CNTRL Atlantic, but a weak wind field should prevent any storm organisation for this time.

DISCUSSION

...Portugal, Spain and S - CNTRL France ...

Somewhat cooler low-levels but still cool mid-levels continue to create a broad area of steep mid-level lapse rates over SW Europe.... A weak SW-erly flow will persist during the forecast period and should support the advection of a warm and humid airmass towards Spain.....Latest WV loop indicates a new region of higher moisture content north of the Canaries, which should affect Spain and Portugal during the daytime hours ( although GFS weakens it during its northward shift ).... Insolation should be strong enough for temperatures around / above 30°C over most parts of Spain / Portugal... models do not indicate a significant increase in moisture, but yesterday's convection should locally support marginal higher dewpoints...However, expect the boundary layer to be well mixed like the days before....Scattered TSTM development ( mainly over mountainous areas ) looks reasonable and also development along the E / SE coast of Spain , where diurnal increase of dewpoints should be favorable for a few TSTMs.
The prior storm mode should be pulsating due to lack of shear, but steep lapse rates could locally yield enough instability for a stronger updraft to form, producing marginal large hail and mostly sub-severe wind gusts.

The same procedure for S / SE France, where a slight increase of boundary layer humidty should be enough for low - end instability release ( ~500 J/kg ).... Weak shear and also diminishing lapse rates should support storms, which stay mostly sub-severe.

.. Estonia, Lativa and extreme western Russia...

Broad area of low-end instability release, low LCLs and moderate helicity values should be favorable for an isolated tornado report, but expected TSTM coverage will be too low for warranting higher probabilities.