DAY 1 CONVECTIVE OUTLOOK
VALID 12Z FRI 28/03 - 00Z SAT 29/03 2003
ISSUED: 28/03 12:13Z
FORECASTER: GATZEN

GENERAL THUNDERSTORMS ARE FORECAST ACROSS SOUTHERN GERMANY

GENERAL THUNDERSTORMS ARE FORECAST ACROSS SOUTHWESTERN EUROPE

GENERAL THUNDERSTORMS ARE FORECAST ACROSS EASTERN CENTRAL EUROPE

SYNOPSIS

LONG-WAVE TROUGH OVER WESTERN EUROPE PROPAGATES EASTWARD. OVER CENTRAL EUROPE, FLOW IS QUITE WEAK. CUT-OFF LOW OVER CENTRAL EUROPE MIGRATES EASTWARD.

DISCUSSION

...SOUTHERN GERMANY...
CUT-OFF LOW OVER GERMANY WILL MOVE EASTWARD SUPPORTING THUNDERSTORM DEVELOPMENT. WEST AND NORTH OF THIS UPPER LEVEL LOW, COLD AIR ADVECTION EFFECTS EASTERN AND NORTHERN GERMANY. OVER SOUTHERN GERMANY, RELATIVELY WARM AIRMASS IS FORECAST TO DESTABILIZE DURING THE DAY. STEEP LAPSE RATES JUST WITHIN THE LOWEST KILOMETERS ARE VISIBLE AT 00 UTC-SOUNDINGS. MOISTURE WITHIN THE BOUNDARY LAYER REMAINS QUITE LOW, AND SYNOPTIC SCALE LIFT IS NOT FORECAST ... HOWEVER ... STRONG DAYTIME HEATING AND OROGRAPHIC LIFT SHOULD SUPPORT CONVECTION ... AND THUNDERSTORMS SHOULD FORM DURING THE AFTERNOON. EVEN AS LOW-LEVEL SHEAR IS WEAK, THUNDERSTORMS SHOULD LIKELY PRODUCE SMALL HAIL AND SOME WINDGUSTS. THUNDERSTORM ACTIVITY IS FORECAST TO WEAK DURING THE EVENING.

...SOUTHWESTERN EUROPE...
OCCLUSION OF SURFACE LOW NORTHWEST OF THE IBERIAN PENINSULA IS FORECAST TO REACH THE WESTERN MEDITERRANEAN TONIGHT. WEST OF THE FRONT ... MOIST AIRMASS ORIGINATED FROM THE SUBTROPICAL ATLANTIC ENTERS PORTUGAL AND SPAIN. THIS AIRMASS IS CONVECTIVELY MIXED AND WILL LIKELY DESTABILIZE DURING THE DAY. NEW FORECAST MODELS DON'T SUGGEST STRONG SYNOPTICAL FORCING OVER SPAIN. HOWEVER ... THUNDERSTORMS SHOULD FORM WITHIN THE NEXT HOURS OVER NORTHERN AND CENTRAL IBERIAN PENINSULA, PRODUCING HEAVY RAINFALL AND SOME WINDGUSTS. SEVERE THUNDERSTORMS ARE NOT LIKELY DUE TO WEAK VERTICAL WINDSHEAR. FRIDAY AFTERNOON ... STRONG SHORT-WAVE TROUGH IS PROGGED OVER SOUTHERN PORTUGAL. WEST OF THE ASSOCIATED COLDFRONT ... CONVECTIVELY MIXED AIRMASS SHOULD LEAD TO NEW THUNDERSTORM ACTICITY. STRONG VERTICAL SHEAR WITHIN THE LOWEST 6 KM IS FORECAST OVER SOUTHERN IBERIAN PENINSULA, AND ORGANISED THUNDERSTORMS COULD FORM IN THE EVENING. STRONG WIND GUSTS UP TO 50 KNOTS ARE EXPECTED WHICH DOES NOT WARRANT A SLIGHT RISK.

...EASTERN CENTRAL EUROPE...
CUT-OFF LOW WILL MOVE SLOWLY EASTWARD. DUE TO DAYTIME HEATING, THUNDERSTROMS SHOULD FORM OVER POLAND AND CZECH REPUBLIC. CAPE WILL LIKELY REACH MORE THAN 200 J/KG, AND PROBABLY SOME THUNDERSTORMS WILL PRODUCE SMALL HAIL.

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