VALID 00Z WED 06/11 - 06Z THU 07/11 2002
ISSUED: 06/11 22:51Z
FORECASTER: DAHL

GENERAL THUNDERSTORMS ARE FORECAST ACROSS GREECE...AEGEAN SEA

SYNOPSIS

12Z UPPER AIR ANALYSES SHOW HIGH AMPLITUDE FLOW PATTERN OVER THE N ATLANTIC AND EUROPE... WITH MAIN UPPER LONGWAVE TROUGH EXTENDING FROM THE NRN BALKAN STATES INTO THE S-CNTRL MEDITERRANEAN REGIONS. FAST/INTENSE VORT MAX ATTM OVER FRANCE...WILL CONTINUE DIGGING SOUTHEASTWARDS AT PERIPHERY OF THE MAIN TROUGH... AND IS EXPECTED TO REACH THE NW MEDITERRANEAN SEA BY THE END OF DAY ONE. AT THE SFC... LARGE HIGH PRESSURE AREA OVER EASTERN AND PARTS OF CNTRL EUROPE...IS ADVECTING CONTINENTAL POLAR AIRMASS INTO THE ERN PARTS OF THE FCST AREA. TONGUE OF SUBTROPIC AIRMASS IS STRETCHTING INTO THE S BALKAN STATES AHEAD OF WEAK COLD FRONT ASSOCIATED WITH THE MEDITERRANEAN UPPER TROUGH. OVER WESTERN PARTS OF EUROPE...MERIDIONALLY ALLIGNED OCCLUDED FRONTAL SYSTEM IS PRESENT...WHICH WILL SLOWLY CONTINUE E. DEVELOPMENT OF A FRONTAL WAVE ALONG THAT BOUNDARY IS EXPECTED TOWARDS THURSDAY MORNING OVER THE NW MDITERRANEAN SEA AS VORT MAX DIGS S.

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DISCUSSION

...GREECE...AEGEAN SEA...
SOUNDINGS OF THE PREFRONTAL AIRMASS OVER THE S BALKAN STATES SUGGEST MARGINAL INSTABILITY... ON THE ORDER OF 500 J/KG. LIGHTNING NETWORD AND SAT IMAGERY INDICATE LINE OF TSTMS HAVE FORMED ALONG THE COLD FRONT OVER S GREECE AND THE AEGEAN SEA. DEEP-LAYER SHEAR IS ON THE ORDER OF 40 KNOTS...WHICH SHOULD PROMOTE MULTICELLULAR ORGANIZATION OF SOME OF THE STORMS. LOW-LEVEL SHEAR IS NOT SAMPLED OVER THE COMPLEX TERRAIN OF S GREECE... AND RIBBONS OF HIGH LOCAL 0-1 KM HELICITY MAY BE PRESENT...AND A ROTATING UPDRAFT OR TWO CANNOT BE DISCOUNTED. THAT MAY YIELD AN ISOLATED HAIL AND DAMAGING WIND THREAT ALONG WITH A BRIEF TORNADO. HOWEVER... ALLOVER THREAT FOR SEVERE APPEARS TO BE TOO LOW FOR A SLGT RISK ATTM.

...W BRITISH ISLES...
FIELD OF RATHER SHALLOW CELLULAR CONVECTION ASSOCIATED WITH UPPER VORTICITY CENTER...IS ADVECTED TOWARDS THE BRITISH ISLES. THOUGH THIS ACTIVITY WILL LIKELY NOT PRODUCE MUCH LIGHTNING...GUSTY WINDS...HEAVY DOWNPOURS OF RAIN AND POSSIBLY SMALL HAIL SHOULD BE EXPECTED WITH THE STRONGER CELLS. A GEN THUNDER OUTLOOK IS NOT WARRENTED THOUGH.

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