DATE : Monday, July 7th 1997 sunset 21 h 18 min
 

GENERAL SYNOPSIS- Altitude : Strong Northerly flow on the Eastern side of a strong ridge over Atlantic ocean. A little trough, actually over the swiss Alps, will pass over French Southern Alps around midday, then will move away over Mediterranean sea. Consequently, the wind will turn a little bit more North-Easterly and the speed will slow down. - Surface : Strong anticyclone 1030hPa over the Atlantic ocean and Western Europe, bring a moderate North then North-Easterly flow in the Alps.A old warm front is dying over Northern Alps, giving some banks of Altocumulus and some Stratocumulus.In the Southern Alps, the sky will remain without significant  clouds, just a few lenticular altocumulus.

QNH 1018 hPa FL 75 2330m FL 115 3550m FL 195 5990m

AIR MASS / DEVELOPMENT OF CONVECTION SOUTHERN ALPS- St-Auban sounding :. Thermals will reach 1600m when a first inversion will be destroyed, around 13h30pm, with a temperature of 24°C.Then, in a layer rather favourable for convection, blue thermals will slowly reach 2800m over valleys, and 3400m over mountains 2000m high.. Over mountains East of Digne, Cumulus will appear and will become congestus in the second part of the afternoon.- Aubenasson sounding : dry and rather stable air mass, with a first inversion around 1900m, a second one around 2400m, and a last one around 3400m, as in ST Auban sounding.Evolution : Blue thermals with top 1900m over valleys, 2400m over the major part of mountains, and perhaps 1/8 cumulus around 3400m over the highest mountains.- St-Crépin sounding : very dry air mass, with an inversion around 3200m; Mainly blue thermals or 1/8 Cu stopped around 3200/3500m.
 

ISO 0°C 3000/3700m North to South  ISO -10 °C 5000/5300 m

Favourable elements : - north lee waves and northerly slope updrafts in the very beginning of the afternoon, only West of Durance valley. - good convection South and East of St Auban.    Unfavourable elements :- diappearing lee waves in the afternoon ( decreasing and turning NE wind ).- risk of Cu congestus close to the Italian border.
 
Outlook for tomorrow : - weak North-Westerly flow and anticyclonic conditions : probably a great day!;
 

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