CONVECTIVE FORECAST
VALID 06Z SAT 03/05 - 06Z SUN 04/05 2003
ISSUED: 02/05 19:18Z
FORECASTER: DAHL/LOWINSKI

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN EUROPE.

GENERAL THUNDERSTORMS ARE FORECAST ACROSS THE IBERIAN PENINSULA AND EASTERN EUROPE.

SYNOPSIS

ZONAL UPPER FLOW PATTERN PRESENT ACROSS EUROPE ... WITH RATHER STRONG EMBEDDED SHORT-WAVE TROUGH ATTM REACHING E FRANCE/W GERMANY ... IS QUICKLY SHIFTING EAST AND WILL BECOME NEGATIVELY TILTED DURING SATURDAY ... STRETCHING FROM THE EASTERN BALTIC SEA INTO N ROMANIA BY SUNDAY 06Z.

DISCUSSION

...EASTERN AND CENTRAL EUROPE...
PRIMARY FEATURE WILL BE THE COLD FRONT ASSOCIATED WITH THE EASTWARD-MOVING SHORT-WAVE TROUGH. SLY FLOW ACROSS SE EUROPE WILL CONTINUE TO ADVECT CONDITIONALLY UNSTABLE AIRMASS INTO BELARUS WITH MLCAPES ON THE ORDER OF 500 TO 1000 J/KG ESSENTIALLY CHARACTERIZED BY INVERTED-V TYPE PROFILES. TSTMS SHOULD RE-DEVELOP DURING THE DAY OVER E POLAND AND HUNGARY ALONG THE SFC COLD FRONT IN MARGINALLY UNSTABLE RELATIVELY COOL AIRMASS W OF THE SLY RETURN FLOW. TSTM ACTIVITY SHOULD SIGNIFICANTLY INCREASE AS THE UPPER TROUGH ENCOUNTERS THE WARM AIRMASS OVER ROMANIA AND W UKRAINE/W BELARUS. SHEAR PROFILES WILL BE QUITE STRONG ... WITH DEEP SHEAR AROUND 60 KNOTS. PRIND THAT HODOGRAPHS WILL BE RATHER STRAIGHT-LINE E OF THE COLD FRONT IN THE FIRST HOURS AFTER INITIATION ... AND WILL BECOME MORE FAVORABLE FOR SUPERCELLS LATE IN THE DAY ... AFTER THE UVV'S AHEAD OF THE TROUGH HAVE ENCOUNTERED RATHER DRY/UNSTABLE LOW-LEVEL AIRMASS. MAIN THREAT WILL BE STRONG/DAMAGING WIND GUSTS WITH RATHER LOW POTENTIAL FOR TORNADOES GIVEN WEAK LOW-LEVEL VEERING. HOWEVER ... ANY STORM THAT ENCOUNTERS SMALL-SCALE REGIONS OF HIGH LOW-LEVEL HELICITY IN THE FIRST FEW HOURS OF INITIATION ... WHEN LCL HEIGHTS ALONG THE COLD FRONT ARE EXPECTED TO BE RATHER LOW ... WOULD POSE THE THREAT OF PRODUCING AN ISOLATED TORNADO. LATER IN THE DAY ... AS HIGH LCL'S/INVERTED V-PROFILES ARE INTERCEPTED ... THREAT WILL SHIFT TOWARDS DAMAGING WINDS AND LARGE HAIL WITH ANY HIGH-BASED SUPERCELL.

BENEATH UPPER THERMAL TROUGH IN THE POSTFRONTAL ENVIRONMENT... DIURNALLY DRIVEN SHOWERS AND TSTMS SHOULD FORM ... WHICH ARE APT TO PRODUCE GUSTY WINDS AND ISOLATED SMALL HAIL.

...IBERIA...
OVER THE IBERIAN PENINSULA ... MARGINAL INSTABILITY SHOULD DEVELOP DURING THE AFTERNOON AS STEEP LAPSE RATES ATTM COVERING THE SW MEDITERRANEAN SEA ARE ADVECTED NORTHWESTWARDS. PROBLEM MAY BE WEAK UPPER FORCING AND A RATHER STRONG CAP. HOWEVER ... ISOLATED OROGRAPHICALLY FORCED BRIEF TSTMS MAY FORM IN THE AFTERNOON ... AND POSE A THREAT OF STRONG DOWNDRAFTS AND SMALL HAIL GIVEN QUITE DRY ENVIRONMENT. ADDITIONALLY ... ELEVATED TSTMS MAY FORM LATE IN THE EVENING/NIGHT WITHIN LOW-LEVEL THETA-E ADVECTION REGIME OVER THE NW MEDITERRANEAN.

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