Storm Forecast
Valid: Sat 25 Apr 2009 06:00 to Sun 26 Apr 2009 06:00 UTC
Issued: Fri 24 Apr 2009 22:36
Forecaster: DAHL

SYNOPSIS

An omega-type upper flow pattern exists over Europe, with the high-pressure ridge over the Baltic-Sea region, and the upper lows/troughs being located over W and E Europe, respectively. The western upper trough is expected to make some eastward progress and should be the main contributor to the convective scenario this period. At low levels, warm-air advection is underway ahead of this feature, with SFC cyclogenesis anticipated over Iberia. A sturdy SFC high-pressure area persists over the eastern portions of the forecast area.

DISCUSSION

... France ...

The convective threat is somewhat uncertain given that instability is expected to remain very weak amidst the war air mass advecting northwards ahead of the large-scale upper trough. Still, scattered thunderstorms should occur. Over France, these may tend to be elevated given that seem to be forced mainly by low-level WAA. Minimal instability as well as quite marginal deep shear, should limit the severe threat, though fairly decent 0-1 km shear (12 m/s) and 250 J/kg SRH3 are simulated. If storms managed to root into the boundary layer, they would at least briefly pose a threat of becoming supercellular and producing tornadoes. However, this scenario is rather conditional, and a threat area is not warranted at the moment.

... N Spain ...

Farther south over Iberia, deep shear should be in the 20 to 25 m/s range. In addition, indications are that a rather dry/deep CBL will develop during the day so that very gusty winds and possibly some hail may accompany the strongest cells.