CHAMONIX VALLEY AND MONT-BLANC AREA WEATHER FORECAST
ISSUED AT 10:45 WEDNESDAY OCTOBER 20 2021
VALID FROM : WEDNESDAY 20 -- MONDAY OCTOBER 25 2021
Evening let it glow
Red my mountain
In a radiant window
ALTITUDE STORM WINDS SETTING UP • Fair high ridge, Azores to the Mediterranean, mostly above 1025 hpa, and reinforced high up by sub-tropical air income reaching Central Europe and Balkans – aiguille du Midi temperatures already noticeably above 0°C. • Which high pressure spread begins collapsing from Northwest this morning, upon thalweg income linked to the powerful 963 hpa low system which is expected to reaching Norwegian Sea oil fields fairly close to the coast toward the end of the night to Thursday. • Anticyclonic influence will thererfore diminish up to completely in the Alpine Range, allowing for an active cold front (15-20 mm) to crossing over the Alps SSE bound, by then and possibly generating severe strom winds high up. • Second disturbance will probably follow during the night to Friday, though causing nothing more than cloudy deterioration by daybreak.
TODAY - WEDNESDAY OCTOBER 20
SKY CONDITION : partly cloudy on the whole - high cloud crossing over - some thicker patches at times in the evening - oragraphic patches taking shape on highest summits. Period of sunshine close to 75%.
PRECIPITATION : none.
WIND - ground level : SW very light -> moderate - locally strong foehn puffs in the valley during the afternoon.
WIND - mid mountain : WSW moderate -> SW moderate to strong.
WIND - high mountain : WSW moderate to strong -> gale.
TEMPERATURE : low +7°C - high +21°C.
ISOTHERM 0°C : 4200 -> 3500 m.
ISOTHERM -10°C : 5600 -> 5800 m.
SKY CONDITION : thickening high cloud veil in the high altitude range during the first part of the night - becoming fairly high overcast thereafter - iso 0°C dropping steeply towards 2700 m by dawn.
PRECIPITATION : starting up between 03:00 and 05:00 - locally heavy shower towards dawn - rain-snow limit dropping steeply towards 2000 m - expected snowfall towards 2500 : 20-40 cm, windblowN.
WIND - aloft : WSW gale -> W severe storm towards the latter part of the night.
TEMPERATURE : low +8°C.
THURSDAY OCTOBER 21
SKY CONDITION : mostly cloudy in the morning - sunny spell spreading swiftly towards the middle of the day. Period of sunshine close to 45%.
PRECIPITATION : shower becoming light and scattered, then ending by noon - rain-snow limit towards 2300 m - almost nothing left on the ground.
WIND - aloft : W severe storm -> WNW strong.
TEMPERATURE : low +8 °C - high +13°C.
FRIDAY OCTOBER 22
SKY CONDITION : cloudy with sunny spells - skies clearing towards the evening. Period of sunshine close to 60%.
PRECIPITATION : none.
WIND - aloft : NNW moderate.
TEMPERATURE : dropping noticeably.
EXTENDED OUTLOOK UNTIL MONDAY OCTOBER 25 2021
Saturday : mainly sunny, yet unseasonably cold. Sunday : mainly sunny - getting considerably milder in the afternoon. Monday : sunny - unseasonably mild.
Forecast reliability : uncertain.