DAY 1 CONVECTIVE OUTLOOK
VALID 13Z TUE 25/03 - 06Z WED 26/03 2003
ISSUED: 25/03 12:27Z
FORECASTER: DAHL

GENERAL THUNDERSTORMS ARE FORECAST ACROSS NORTH FRANCE ... SOUTHERN BENELUX STATES AND SOUTH GERMANY.

GENERAL THUNDERSTORMS ARE FORECAST ACROSS THE WESTERN AND SOUTHERN IBERIAN PENINSULA.

SYNOPSIS

WEAK SHORT-WAVE TROUGH AT THE SOUTHERN FRINGE OF THE NORTHERN UPPER JET IS CLOSING OFF INTO A CUT-OFF LOW OVER CENTRAL EUROPE DURING THE DAY. WEAK THETA-E ADVECTION IS ONGOING AHEAD OF THIS FEATURE AT LOW LEVELS ... PUSHING SLIGHTLY UNSTABLE BOUNDARY-LAYER AIR INTO NORTHERN FRANCE AND SOUTHERN GERMANY. AHEAD OF THE UPPER LOW ATTM WEST OF THE IBERIAN PENINSULA ... LOW-LEVEL WARM ADVECTION IS EXPECTED TO DEVELOP LATE TONIGHT OVER THE SOUTHERN IBERIAN PENINSULA.

DISCUSSION

...IBERIA...
GIBRALTAR 00Z SOUNDING INDICATES DEEP BOUNDARY-LAYER MOISTURE IS IN PLACE ... WHICH IS EXPECTED TO BE ADVECTED INTO WESTERN IBERIA DURING THE DAY. ALTHOUGH EXTENSIVE MID/UPPER CLOUDINESS IS PRESENT ... SFC TEMPERATURES WILL LIKELY CLIMB INTO THE LOW/MID 20 C AGAIN ... WEAK ELEVATED-MIXED LAYER IS ALSO EVIDENT OVER GIBRALTAR BENEATH 650 HPA. GIVEN THAT SUBTLE DCVA WILL BE PRESENT PER LATEST MODEL DATA ... DEVELOPMENT OF SCATTERED THUNDERSTORMS IS ANTICIPATED ESPECIALLY OVER THE WESTERN PARTS OF THE PENINSULA DURING PEAK HEATING HOURS. TSTMS SHOULD DEVELOP LATE IN THE EVENING/NIGHT WITHIN STRENGTHENING LOW-LEVEL THETA-E ADVECTION REGIME SUPPORTED BY WELL-DEFINED VORT MAX EXPECTED TO CROSS PORTUGAL AND THE WESTERN PARTS OF SPAIN LATE IN THE NIGHT. SHEAR PROFILES WILL INCREASE SOME BUT SHEAR MAGNITUDE IN THE BUOYANT LAYER DOES NOT APPEAR TO BECOME SUFFICIENTLY LARGE FOR A SIGNIFICANT ORGANIZED SEVERE-THUNDERSTORM THREAT.

...CENTRAL EUROPE...
SURFACE DEWPOINTS ARE INCREASING OVER N FRANCE ... THE SOUTHERN BENELUX STATES AND SOUTH GERMANY IN ASSOCIATION WITH WEAK LOW-LEVEL THETA-E ADVECTION. INDICATIONS ARE THAT WEAK SBCAPE WILL DEVELOP LATER TODAY WITH DIURNAL HEATING ... SUSTAINED LOW-LEVEL THETA-E ADVECTION AND WEAK MID/UPPER ADIABATIC COOLING AHEAD OF APPROACHING UPPER LOW. WEAK FRONTAL BOUNDARY IS DEVELOPING AT THE NORTHERN FRINGE OF THE THETA-E PLUME REACHING FROM S GREAT BRITAIN EASTWARD INTO EAST-CENTRAL GERMANY. CURRENT RADAR DATA SHOW WEAK /POSSIBLY SLIGHTLY ELEVATED/ CONVECTION MOVING EAST ALONG/NORTH OF THIS BOUNDARY ... WHICH SHOULD BE FOCUS FOR SURFACE-BASED CONVECTIVE INITIATION LATE THIS AFTERNOON. BOUNDARY-LAYER MOISTENING WILL LIKELY BE STRONGEST ACROSS NORTH FRANCE AND WESTERN GERMANY. EXPECT DEVELOPMENT OF SCATTERED SHOWERS AND THUNDERSTORMS ALONG AND SOUTH OF THE FRONTAL BOUNDARY LATER THIS AFTERNOON ... WHICH MAY SPREAD EAST AS FAR AS SE GERMANY LATER TONIGHT. THOUGH UPPER VORT MAX APPEARS TO BE ACCOMPANIED BY MID-LEVEL WINDS OF AROUND 30 KNOTS ... CONVECTION WILL LIKELY BE WEAKLY ORGANIZED AND POSE NO SIGNIFICANT SEVERE THUNDERSTORM THREAT.

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