CONVECTIVE FORECAST - UPDATE
VALID 12Z SAT 12/04 - 06Z SUN 13/04 2003
ISSUED: 12/04 12:14Z
FORECASTER: GROENEMEIJER

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL ITLAY, THE CENTRAL ADRIATIC AND THE WESTERN BALKANS

GENERAL THUNDERSTORMS ARE FORECAST ACROSS FRANCE, MUCH OF THE CENTRAL MEDITERRANEAN, THE ALPS, THE NORTHERN BALKANS AND THE EXTREME WESTERN IBERIAN PENINSULA

SYNOPSIS

A LONGWAVE RIDGE IS BUILDING QUICKLY OVER WESTERN EUROPE DOWNSTREAM OF AN AMPLYFYING UPPER TROUGH. A VORT MAX OVER SOUTHEASTERN FRANCE IS EXPECTED TO CUT-OFF AND MOVE ESATSOUTHEASTWARD TO THE WESTERN BALKANS. THUNDERSTORMS WILL FORM NEAR AND AHEAD OF THE VORT MAX. STRONG SOUTHERLY WINDS OVER FRANCE WILL ADVECT SLIGHTLY UNSTABLE AIR-MASS NORTHWARD. ESPECIALLY NEAR THE LEADING WARM FRONT SOME THUNDERSTORMS MAY DEVELOP. AT THE END OF THE PERIOD A COLD FRONT WILL BE APPROACHING IBERIA FROM THE WEST. ASSOCIATED STORMS MAY AFFECT THE COASTAL AREA JUST BEFORE THE END OF THE FORECAST PERIOD

DISCUSSION

...ITALY, THE ADRIATIC AND WESTERN BALKANS...
STRONG LINEAR MCS OVER NORTH-CENTRAL ITALY WILL PROGRESS TO THE SOUTHEAST. SOME SEVERE WIND GUSTS AND LARGE HAIL MAY BE ASSOCIATED WITH THIS SYSTEM. MORE CONVECTIVE ACTIVITY WILL LIKELY FORM OVER SOUTHEASTERN ITALY, THE ADRIATIC AND OVER ALBANIA AND SURROUNDINGS. GIVEN DRY MID-LEVELS EVIDENT FROM LIBR 06 SOUNDING THERE IS A POTENTIAL OF SEVERE GUSTS. SURFACE OBSERVATIONS SHOW 5 - 10 KT SOUTHEASTERLY SURFACE WINDS. IN COMBINATION WITH 30 - 40 KT MID-LEVEL WINDS, THIS MAY YIED SIGNIFICANT STORM-RELATIVE HELICITY TO ALLOW FOR FORMATION OF SUPERCELLS. IF THESE OCCUR THESE WILL BE AN ENHANCED THREAT OF LARGE HAIL. NEAR BALKAN WEST COAST MOIST AIR IS PRESENT. 14...17C DEW POINTS ARE MEASUREDIN COMBINATION WITH 17...20C TEMPERATURES, INDICATING THAT LCL HEIGHTS WILL BE LOW. THIS WILL YIELD A THREAT OF TORNADOES/WATERPOUTS IN THIS AREA, ESPECIALLY AS OROGRAPHY MAY LOCALLY ENHANCE LOW-LEVEL HELICITY.

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