CHAMONIX VALLEY AND MONT-BLANC AREA WEATHER FORECAST
ISSUED AT 10:30 THURSDAY JUNE 08 2023
VALID : THURSDAY JUNE 08 -- TUESDAY JUNE 13 2023
Atlantic High Ridge recently refocused N of Scotland (Féroé, Shetland, 1026 hpa) keeps moving very slowly E. • Mediterranean isobaric swamp's pressure field is now weakening slowly from W under distant influence of low "Oscar", 998 off Portugal, and seemingly drifting towards Germany where an altitude cut-off was deepening. Resulting humid W stream on one hand, and weakening pressure field over the Alpine Range [ Chamonix, 1014 - Sion, 1016 - Innsbruck, 1016 ] on the other, should trigger noticeable thundery deterioration on Friday. • Further outlook is very uncertain.
TODAY - THURSDAY JUNE 08 2023
SKY CONDITION : clear or partly cloudy until early afternoon, then threatening cumulus cloud growing above the massifs. Period of sunshine close to 65%.
PRECIPITATION : late afternoon or evening thundery shower risk - rain-snow limit towards 3000-3200 m.
WIND - ground level : calm or variable very light - trend towards SW by early afternoon.
WIND - mid mountain : WSW very light - occasionally light by early afternoon.
WIND - high mountain : NW -> W light to moderate - locally moderate.
TEMPERATURE : low +10°C - high +21°C.
ISOTHERM 0°C : 3200 -> 3400 m.
ISOTHERM -10°C : 4700 -> 4900 m.
SKY CONDITION : high cloud veil, very thin, from W soon after dispelling of cloud inherited from the evening - iso 0°C towards 3500 m.
PRECIPITATION : probably none.
WIND - aloft : W -> WNW light to moderate - occasionally moderate.
TEMPERATURE : low +12°C.
FRIDAY JUNE 09 2023
SKY CONDITION : clear or partly cloudy morning - then cumulus cloud crossings will become widespread - mostly cloudy towards the latter part of the afternoon and in the evening. Period of sunshine close to 40%.
PRECIPITATION : thundery shower towards the latter part of the afternoon, probably fairly heavy in the evening - changeable rain-snow limit between 3000 and 3200 m.
WIND - aloft : WNW -> SW light - occasionally moderate.
TEMPERATURE : low +11 °C - high +21°C.
SATURDAY JUNE 10 2023
SKY CONDITION : clear or partly cloudy in the morning - becoming mostly cloudy with fleeting sunny outbreaks in the afternoon. Period of sunshine close to 25%.
PRECIPITATION : frequent or continuous rain, locally heavy with in the afternoon if triggered by thunderstorm, which remains quite uncertain for now - rain-snow limit rising up towards 3300 m.
WIND - aloft : variable -> NNE very light - possible thunderstorm gust.
TEMPERATURE : steady or rising slightly.
EXTENDED OUTLOOK UNTIL TUESDAY JUNE 13 2023
Sunday : thunderstorm might break out fairly soon - heavy shower in the afternoon - variable light winds high up, W trend towards evening. Monday : noticeable diurnal evolution pattern - persistent thunderstorm risk - light winds, yet with moderate gusts. Tuesday : very unstable - heavy thunderstorm likely - mainly NE quite light high up, yet with possible strong gusts.
Forecast reliability : fairly good until Saturday - poor thereafter.