GENERAL SYNOPSIS- Altitude : Weakening high over France. A little ridge from northern Africa to southern Alps brings a light westerly to south-westerlyflow over the Alps.- Surface : Flat low over France today, with decreasing pressures. A low over Spain this morning will move North and will be centered over Bordeaux in the evening. The associated cloud mass will touch the Southern Alps in the afternoon, giving banck of Cirrus clouds, then layers of Ci , Cc and Ac in the second part of the afternoon, mainly South of Gap/Embrun.That situation, associated with increasing temperatures ( 29 or 30°c in St Auban ) is typical of thunderstorms growing over the highest mountains in the second part of the afternoon, always more probable over the Italian border.

QNH 1015 hPa FL 75 2300m FL 115 3520m FL 195 5960m

AIR MASS / DEVELOPMENT OF CONVECTION - St-Auban sounding :.Drier than yesterday. Very stable below 1600m, the blue thermals will slowly break that layer around 13h or 13h30 Local Time. Then convection will get very quicly 2400m in a favourable layer. Over mountains 1500/2000m, Cumulus will appear, with a base around 2800 or 3000m. As usual they will be rare West of St Auban, and much more numerous Est of Digne.- Aubenasson: very dry and rather stable, allowing blue thermals to reach 2500m, and may be 1/8 Cu 3000m over highest mountains.- St-Crépin sounding : Rather moist below 3400m, allowing 3 or 4 Cu cloud base 3400m, top around 3800m.- Chambery sounding: Moist and cold lowest layers below 1500m, blocking Cu over small mountains.Good convective layer between 1900/3000m, rather moist air allowing 3 or 4/8 Cu to form, with a base around 2600m, top stopped by an inversion around 3200m.
 

ISO 0°C 3900m  ISO -10 °C 5400 m

Favourable elements : - excellent convection, even over the Northern Alps and the Vercors, with higher Cu bases than yesterday.    Unfavourable elements :- Cirrus and Cirrocumulus banks then layers coming from South-West and disturbing the convection.- increasing risk of Cb and isolated thunderstorms in the second part of the afternoon, mainly over the highest mountains of the Italian border and the Vanoise range.
 
Outlook for tomorrow : - weak North-Westerly flow and anticyclonic conditions : probably a great day!;
 
 

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Web page by Denis Flament (from Nogaro aeroclub) consulted times since 13-Jun-97 updated : 13-Jun-97