Forecast Update
Valid: Fri 22 Feb 2008 15:00 to Sat 23 Feb 2008 06:00 UTC
Issued: Fri 22 Feb 2008 15:33
Forecaster: TUSCHY

A quite unstable air-sea interface north of Scotland / west of Norway has established during the past 12 hours. Current IR images hint on a mixture of closed and open cell structure and numerous lightning strikes were reported out of this area. This update became necessary for two reasons:

a) The expansion of the general thunderstorm
area over western Norway towards the south.

b) The issuance of a large non-thundery level-1 area. Not much has changed compared to the main outlook but current gust reports over Denmark just ahead of the cold front, which is also quite active regarding convection, increased confidence that a few severe wind gusts along the cold front could become possible over a wide area. Split-flow character of this frontal passage helps to increase lapse rates below about 800hPa , which is good for downward mixing of 30m/s at 850hPa. The main reason for this level-1 is the fact that a few gusts could approach our criterion. Right now the main concern will be over NE Poland and Lithuania, where intense PVA could sustain a forced line of low-topped convection despite very marginal instability release. Winds at 850hPa increase to above 30m/s, which should result in a more concentrated area of severe wind reports.
Another region with an enhanced severe weather risk exists over SW Sweden between 00Z-03Z as cold mid-level air overspreads the highlighted area. 200 J/kg helicity at lowest levels and low-end instability release will be present, which is enough for an isolated funnel / short-lived tornado report.