Storm Forecast
Valid: Sat 12 Apr 2008 06:00 to Sun 13 Apr 2008 06:00 UTC
Issued: Fri 11 Apr 2008 21:42
Forecaster: DAHL

SYNOPSIS

Large and broad quasi-stationary upper long-wave trough is located over the western and central parts of Europe, providing the eastern and southern parts of Europe with a rather intense upper SWLY flow. Low-level flow over S and SE Europe is also SWLY, advecting well-pronounced, deep Saharan EML across the central Mediterranean and the east European countries. Main wavy low-level front associated with the deep long-wave trough is anticipated to extend from the central Mediterranean across the N Balkans into NE Europe on Saturday early afternoon. This boundary should make only weak eastward progress during the period.

DISCUSSION

... N Mediterranean ... N Balkans ...

Though the steep lapse rates of the EML will act to reduce the stability over eastern Europe, limited low-level moisture will likely limit the amount of CAPE. Also, the air mass will be thoroughly capped. However, convection will likely develop along the thermal gradient at the E edge of the warm-sector air mass. It seems that the steep lapse rates will be somewhat displaced from the frontal region towards the south and east, and it is not believed that the thermodynamic profiles will be very conducive to severe weather in the immediate environment of the front. However, ample shear is expected, with 0-6 km bulk magnitudes exceeding 35 m/s. Though this may be inhibitive to long-lived, erect updrafts given the weak thermodynamic support, some cells may develop mid-level mesocyclones, which could pose some threat for marginally severe hail and strong outflow winds, though especially over the N Balkans, the LL wind field suggests that a brief tornado cannot be discounted either.

... France ... British Isles ...

Mainly diurnally driven convection will likely form especially over France and the UK. Deep shear as well as instability should be quite marginal, though the edges of the deeply convecting areas may see 15 m/s DLS. However, in the evening hours there will be a time frame where 10 m/s LLS may occut over western France, and to a lesser extent also over the S UK. Given minimal capping, this may result in a brief spinup of a tornado or two, but activity should remain too isolated to warrant a categorical risk.