Storm Forecast
Valid: Sat 10 Jan 2009 06:00 to Sun 11 Jan 2009 06:00 UTC
Issued: Fri 09 Jan 2009 16:16
Forecaster: TUSCHY

SYNOPSIS and DISCUSSION

A strong high pressure area dominates most of the European weather map with a cold and dry airmass present, so no thunderstorms are forecast over the continental areas. Yesterday's upper low over extreme SW Europe continued to move to the south as an intense mid-/upper jet evolved along its western quadrant due to an increase of the geopotential height gradient. The airmass and the atmosphere above the western and central Mediterranean remains marginal supportive for a few thunderstorms, but there should be an overall weakening trend during the evening and night hours as somewhat drier air filters in from the north. Weak shear and marginal CAPE favor weak/short-lived storms. After 21Z, thunderstorms also evolve south of Spain and the shear-especially directional shear- is strong enough for a very isolated large hail event.

An intense, zonal flow has established over far N/NW Europe during the past few days and numerous depressions, embedded in those westerlies, move ENE/NE-wards during the day. Depression number one crosses Iceland and approaches NW-Norway during the night hours and despite some weak instability release, thunderstorm probabilities seem to be too low to highlight the coastal areas of NW-Norway. However, the environment is supportive for severe wind gusts as a strong low/mid-level speed max overspreads the region. Depression number two approaches an area NW of Ireland during the night hours and linking to a subtropical airmass is excellent with poor mid-level lapse rates. We do not expect that airmass to affect our forecast area until 06Z so no thunderstorm zone was introduced although the severe wind gusts risk (not associated with deep and electrified convection) should start to increase during the morning hours (11th), as winds at all levels gain strength.