CHAMONIX VALLEY AND MONT-BLANC AREA WEATHER FORECAST
ISSUED AT 08:10 WEDNESDAY MAY 25
VALID FROM : WEDNESDAY MAY 25 ‑‑ UNTIL : MONDAY MAY 30 2016
Altitude Mediterranean High tends towards driving warm african air over Central Europe high up. Extended high area linked to surface polar air income over the British Isles. Moderate to strong westerly to southwesterly stream in‑between, driven by a 1000 hpa low, currently whirling far northwest of Portugal. • All this will result in pleasant weather, yet showing some diurnal instability which will gradually increase with the air mass warming : afternoon thundery shower risk should therefore increase as well on Friday and Saturday. More organized disturbance then expected to affecting the area on Sunday and Monday, going along with a noticeable temperature drop.
TODAY - WEDNESDAY MAY 25
SKY CONDITION : clear or partly cloudy in the morning ‑ becoming cloudy in the afternoon ‑ cumulus cloud growth while fairly thick high cloud will be running over from the southwest. Period of sunshine close to 70%.
PRECIPITATION : probably none.
WIND - ground level : variable ‑> SW light ‑ light afternoon thermal breeze.
WIND - mid mountain : SW light ‑ light to moderate at times in the afternoon.
WIND - high mountain : WSW moderate ‑ moderate to strong at times.
TEMPERATURE : low +1°C - high +19°C - temperature inversion toward 1300 m early in the morning.
ISOTHERM 0°C : 3000 ‑> 3200 m.
ISOTHERM -10°C : 4700 m.
SKY CONDITION : clear or partly cloudy after evening cumulus cloud dispelling ‑ some high cloud passings.
PRECIPITATION : none.
WIND - aloft : WSW moderate ‑ moderate to strong at times.
TEMPERATURE : low +6°C.
THURSDAY MAY 26
SKY CONDITION : partly cloudy in the morning ‑ high cloud crossing over ‑ cumulus cloud growth in the afternoon, locally shadowing sunshine. Period of sunshine close to 70%.
PRECIPITATION : later afternoon shower slight risk.
WIND - aloft : WSW moderate ‑> moderate to strong.
TEMPERATURE : low +6 °C - high +23°C.
FRIDAY MAY 27
SKY CONDITION : partly cloudy to cloudy ‑ high cloud crossing over ‑ afternoon cumulus cloud growth, locally considerable. Period of sunshine close to 60%.
PRECIPITATION : late afternoon shower risk ‑ rain‑snow limit towards 3400 m.
WIND - aloft : WSW moderate to strong.
TEMPERATURE : rising highs.
EXTENDED OUTLOOK UNTIL MONDAY MAY 30 2016
Saturday : high diurnal instability ‑ sunny morning ‑ afternoon thundery shower. Sunday : disturbance crossing over ‑ heavy precipitation in the afternoon ‑ getting colder. Monday : cool and unsettled tail ‑ mainly cloudy ‑ moderate showers.
Forecast reliability : fairly good until Thursday ‑ poor thereafter.