CONVECTIVE FORECAST - UPDATE
VALID 17Z MON 28/04 - 06Z TUE 29/04 2003
ISSUED: 28/04 17:00Z
FORECASTER: GROENEMEIJER

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN SPAIN, PARTS OF FRANCE, BELGIUM AND THE SOUTHERN BENELUX

GENERAL THUNDERSTORMS ARE FORECAST ACROSS SOUTHERN BRITISH ISLES, NORTHWESTERN IBERIA, FRANCE, BENELUX, WESTERN GERMANY, SOUTHERN DENMARK, EXTREME SOUTHERN SWEDEN.

GENERAL THUNDERSTORMS ARE FORECAST ACROSS POLAND, SOUTHEASTERN BALTIC STATES, WESTERN BELARUS, WESTERN UKRAINE, MOLDOVA, PARTS OF ROMANIA AND BULGARIA.

SYNOPSIS

A LONGWAVE TROUGH IS APPROACHING WESTERN EUROPE FROM THE ATLANTIC.SURFACE CYCLONE OVER ENGLAND WILL MOVE NORTHWARD AND BE SITUATED OVER SCOTLAND AROUND 18Z. A WEAKLY AMPLIFIED UPPER TROUGH IS PROPAGATING EASTWARD OVER EASTERN EUROPE.

DISCUSSION

...SLIGHT RISK AREA...
CONVECTION HAS INITIATED OVER THE BAY OF BISCAY ALONG THE COLD FRONT. VIS IMAGERY SHOWS STORM SPLITTING AND THEREFORE SUGGEST THEY ARE SUPERCELLS. THEY WILL LIKELY CLUSTER OVER THE NEXT FEW HOURS AND MOVE INTO NORTHWESTERN FRANCE. GIVEN STRONG LOW-LEVEL WINDS, THERE IS A THREAT OF DAMAGING GUSTS WITH THESE STORMS. ALSO, SOME LARGE HAIL MAY OCCUR. ELSEWHERE WITHIN THE RISK AREA, STORMS WILL DEVELOP AS WELL DURING THE NEXT HOURS. GIVEN HIGH DEEP-LAYER AND LOW-LEVEL SHEAR, ANY STORM THAT FORMS MAY BECOME SUPERCELLULAR AND POSE A THREAT OF DAMAGING WINDS AND LARGE HAIL. MOST ACTIVITY IS EXPECTED TO CLUSTER ALONG THE COLD FRONT MOVING INTO WESTERN CONTINENTAL EUROPE OVERNIGHT. PREFERRED CONVECTIVE MODE WILL BE LINEAR MCS'S. IF A WELL-DEFINED FRONTAL WAVE FORMS, SURFACE WINDS WILL BACK IN THE WARM AIR-MASS PROVIDING A HELICAL INFLOW WHICH YIELDS SOME CHANCE OF TORNADOGENESIS. IF THIS OCCURS AN UPGRADE TO MODERATE RISK MAY BE NECESSARY.

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