Storm Forecast
Valid: Mon 10 Jul 2006 06:00 to Tue 11 Jul 2006 06:00 UTC
Issued: Sun 09 Jul 2006 22:16
Forecaster: GROENEMEIJER

SYNOPSIS

Monday at 06:00 a ridge stretches from Spain over central Europe to northwestern Russia. On its northern flank a strong WSWly jet stream stretches from west of Ireland over central Scnadinavia to northern Finland. Two shortwaves are embedded in the jet, one intitially 700 km west of Ireland and another one over Norway. The latter trough will move quite rapidly eastward reaching eastern Karelia on Tuesday morning.

DISCUSSION

central and southern Finland, parts of northwestern Russia...

Ahead of the approaching trouhg, moist low-level air is expected to accelerate northward into Finland. Within a weakly-capped environment convective initiation is expected over southern Finland during the late morning or early afternoon, where onthe order of 500 J/kg MLCAPE50 or up to 1000 J/kg SBCAPE should become available. Given 15-20 m/s deep-layer bulk shear and storm relative helicity of around 200 m2/s2 and higher, rotating storms / supercells are expected.
Moderate LCL heights of around 1000-1250 m, rather low LFC heights and strong low-level shear of 10-20 m/s in the 0-1 km layer, suggest that a few tornadoes are possible in addition to severe gusts and isolated large hail.

An increasing threat of severe wind gusts will evolve as the storms get organized into linear linear systems. Under influence of well-focused forcing for upward vertical motion ahead of the shortwave trough that crosses Finland during the evening, a bow-echo will likely form and produce quite widespread severe winds. During the evening hours, the system should move into Russian parts of Karelia. Some threat of tornadoes will likely remain present with the system until the boundary layer cools in the late evening.

central and southern Sweden...

Ahead of the approaching trough over Norway SSWly low-level flow over southern Sweden should advect high theta-e air northward. Rising motion is expected to result into the formation of an MCS during the early morning releasing very modest amounts of CAPE. The formation of surface-based convective lines is possible especially during the late morning and early afternoon. These could produce a couple of severe wind gusts and possibly one or two tornadoes within the level 1 area.