Storm Forecast
Valid: Tue 13 Apr 2010 06:00 to Wed 14 Apr 2010 06:00 UTC
Issued: Mon 12 Apr 2010 22:24
Forecaster: KOROSEC

A level 1 was issued across N Algeria and N Tunisia mainly for severe wind gusts and large hail.

A level 1 was issued for extreme SW Iberian Peninsula mainly for marginally large hail and excessive convective rainfall.

SYNOPSIS

A blocking pattern with a large-scale upper low dominating over much of central Europe persists through Tuesday as well. Another upper low slowly approaches Iberian peninsula.

DISCUSSION

... N Algeria and N Tunisia ...

Another active convective day is expected over this region, though a less active than yesterday. A developing weak surface depression over west-central Algeria should enhance LL shear/SREH and organized storms will again be possible. Moderate to strong DLS will be supportive for organized multicells and a few supercells posing a threat for isolated large hail and strong winds. Activity should diminish after sunset.

... extreme SW Iberian Peninsula ...

Another upper low with a deepening surface depression approaches the SW Iberia. During the day, a warm front advects across Spain and improves LL moisture across the SSW Iberian Peninsula. Moderate forcing ahead of the upper low will support scattered convection. With an entering cold frontal boundary and better forcing/shear towards the evening hours, severe potential with threat for large hail and excessive convective rainfall increases. For this reason, a level 1 was introduced for parts SW Iberian Peninsula. Despite the diminishing instability in the evening hours, enhanced forcing suggests that storms might continue well into the nighttime hours while slowly moving more inland onto Iberia.

... western Balkans and southern Italy ...

On the southern side of the large upper low, marginal warm advection will maintain decent LL moisture across central Mediterranean and western Balkans. Diurnal heating will force convective activity which could gain some organization in near 10-15m/s of deep layer shear. However, weak instability signals do not suggest more organized cells, but only low chances for sub-severe hail threat storms.

... northern Poland ...

Placed beneath the PVA maximum, the northern Poland will see a diurnal driven showers and thunderstorms. DCVA forced ascent will support scattered convective initiation under the near -30°C at 500hPa levels. Marginal instability in weakly sheared environment could lead into strong storms with small hail/strong wind event locally.