CHAMONIX VALLEY AND MONT-BLANC AREA WEATHER FORECAST
ISSUED AT 08:35 FRIDAY DECEMBER 6
VALID FROM : FRIDAY DECEMBER 6 ‑‑ UNTIL : WEDNESDAY DECEMBER 11 2019
On my brush tip
A water drop
High 1031 hpa, Azores. High 1030 hpa, Black Sea. Slightly lower high pressure ridge stretching in‑between, still protecting the Alps this Friday morning. Very light flow high up, between north and west. • Barely deepened altitude low however, northeast of Canary Islands to Gulf of Genoa : while merging with polar air thalweg from Norwegian Sea, it could give some activity to resulting cold front which is expected to crossing over our Region southeast bound overnight. • This means ending of current fair weather spell, therefore. • Condition expected to getting noticeably worse by Monday afternoon, upon crossing of an occluded front (linked to < 950 hpa low north of Scotland) which might trigger fairly heavy snowfall, blown by severe gale force winds high up during the following night.
TODAY - FRIDAY DECEMBER 6
SKY CONDITION : clear until the latter part of the afternoon ‑ thin high cloud from northwest in the evening. Period of sunshine close to 95%.
PRECIPITATION : none.
WIND - ground level : calm ‑> SW very light.
WIND - mid mountain : WSW very light ‑> light to moderate in the evening.
WIND - high mountain : NW very light ‑> WNW moderate in the evening.
TEMPERATURE : low ‑5°C - high +6°C - temperature inversion toward 1600 m early in the morning.
ISOTHERM 0°C : 2400 ‑> 2100 m.
ISOTHERM -10°C : 4100 ‑> 3900 m.
SKY CONDITION : high cloud thickening soon after nightfall, then continue to grow while getting broken towards the latter part of the night.
PRECIPITATION : shower risk towards the latter part of the night ‑ rain‑snow limit towards 1700 m.
WIND - aloft : WNW moderate ‑> NW strong.
TEMPERATURE : low +1°C.
SATURDAY DECEMBER 7
SKY CONDITION : mostly cloudy ‑ frequent patches crossing over ‑ becoming cloudy with sunny spells in the afternoon. Period of sunshine close to 45%.
PRECIPITATION : shower risk in the morning‑ rain‑snow limit towards 1700 m, rising trend.
WIND - aloft : NW strong ‑> moderate.
TEMPERATURE : low +2 °C - high +5°C.
SUNDAY DECEMBER 8
SKY CONDITION : cloudy with sunny spells ‑ mostly cloudy at times. Period of sunshine close to 40%.
PRECIPITATION : showers in the course of the afternoon, light to moderate on the whole ‑ rain‑snow limit towards 1700 m, dropping towards 1200 m ‑ expected snowfall towards 1800 m : ± 5 cm.
WIND - aloft : NW light to moderate ‑> > moderate to strong.
TEMPERATURE : slightly dropping lows ‑ rising highs.
EXTENDED OUTLOOK UNTIL WEDNESDAY DECEMBER 11 2019
Monday : very unsettled ‑ continuous precipitation, becoming moderate to heavy later ‑ rain‑snow limit towards 1000‑1100 m ‑ northwest to north reaching severe gale force high up in the evening. Tuesday : mainly cloudy ‑ snow shower (800 m) slight risk ‑ morning north gale high up, backing and decreasing later. Wednesday : strong westerlies keep blowing moderate snowfall high up.
Forecast reliability : fairly good until Saturday ‑ poor thereafter.