Storm Forecast
Valid: Fri 13 Jun 2008 06:00 to Sat 14 Jun 2008 06:00 UTC
Issued: Thu 12 Jun 2008 15:29
Forecaster: TUSCHY

SYNOPSIS

An extensive upper trough is present over NW Europe with quite cold air spreading southwards over the North Sea. At upper - levels this is the most dominant feature over the entire forecast area. At lower levels a strong baroclinic zone splits the forecast area in half with warm and humid conditions on its eastside and much cooler conditions to its west. Weak pressure gradients continue to favor a mainly diurnal driven thunderstorm day.

DISCUSSION

... S - Belarus and N Ukraine ...

All models indicate a weak and ill defined depression which evolves over the area during the day. Exact placement of this feature is difficult and no real path of this depression can be seen as this surface low pressure system will wobble around during the day with an overall slow northward movement. A well mixed and humid boundary layer, reasonable steepened mid - level lapse rates and strong insolation should lead to 500 - 1000 J/kg MLCAPE which is enough for strong updrafts. Shear, especially DLS, is quite weak with 10 - 15 m/s, but the LL shear should increase betimes as the LL depression evolves. Backed winds in its NE and N quadrant will help to enlarge lower parts of the hodographes. As the LCL comes down during the afternoon and evening hours, the risk of an isolated tornado should increase. Despite the lack of very steep lapse rates at mid - levels we can 't exclude an isolated large hail report during the mature phase of an intense pulsating / multicell storm. Weak DLS should support rapid clustering with an attendant heavy rain risk and a cluster of thunderstorms should affect SE Belarus during the overnight hours.

We issued a broad level - 1 area as strong instability release could result in a few large hail reports as far south as NW Moldova.

... Parts of Sweden / Norway, and Germany ...

Just like the past few days, atmosphere features quite steep LL / mid - level lapse rates with low - end to moderate instability release. Shear at all levels is weak but strong instability release at the lowest 3 km could result in a few funnel / short lived tornado reports. This risk depends on too many smaller scale / local facts so uncertainties are too high for issuing any level area. Small hail could also accompany stronger storms as the WBZ level will be quite low.

... N - Italy and parts of Croatia ...

Multiple rounds of scattered to widespread thunderstorms are anticipated as upper - levels cool down, especially over NW and N - central Italy. DLS is somewhat stronger with 15 - 20 m/s and a few pulsating thunderstorms could cash in on better shear with an attendant large hail / strong to severe wind gust risk.


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