Storm Forecast
Valid: Wed 05 Jul 2006 06:00 to Thu 06 Jul 2006 06:00 UTC
Issued: Tue 04 Jul 2006 22:40
Forecaster: GATZEN

SYNOPSIS

Omega flow pattern remains over Europe. Western trough is placed over Bay of Biscay and slowly moves into western France. Ahead of this trough ... warm and unstable airmass spreads from western Mediterranean to France/ western Alpine region and southern North Sea/ British Isles. This airmass is characterized by steep mid-level lapse rates ... while low-level moisture is relatively poor. Locally ridge boundary-layer moisture is present from southern/eastern France to Benelux ... as well as over British Isles ... and highest CAPE is expected from southern France to Benelux and southern Germany.

DISCUSSION

France, western Alps, Benelux, western Germany, British Isles

Ahead of short-wave trough over Bay of Biscay ... frontal boundary stretches from eastern Iberian Peninsula to central France and further to British Isles. A surface low propagates northward along this boundary reaching the Channel region at 12Z. A cold front moves eastward south of this low reaching the Alps/western Germany in the evening hours. North of the surface low ... slowly eastward moving frontal boundary is present over northern France/Benelux and central England. Along and east of the frontal boundary ... warm and unstable airmass is present over western Mediterranean, western Alps and eastern France, western Germany, Benelux, and British Isles. In the morning hours ... MCS should be present over northern or central France. During the period ... MCS should move northward into British Isles ... and new convection is expected to form along old outflow-boundaries in the range of the cold front. Given enhanced vertical wind shear ... about 20 m/s DLS ... multicells and mesocyclones are expected to form ... capable of producing large hail, severe wind gusts and a few tornadoes. During the day ... thunderstorms are forecast to propagate eastward. Although low-level moisture should increase compared to Tuesday ... storms that form should be rather high-based ... and chance for tornadoes should decrease. Highest chance for a few tornadoes is expected over Benelux/England ... where easterly surface winds and rather strong LLS are forecast in the range of the surface low. Large hail and severe wind gusts should be rather likely over western and southern France as well as western Alpine region ... where DLS is enhanced in the range of weakening jet streak present from western Mediterranean to western Alps. Convection should merge into clusters/MCS in the evening hours over eastern France, southwestern Germany, Benelux, and British Isles. Severe potential should gradually weaken due to decreasing vertical shear and CAPE.