Mt d'Arbois - 21/01/21

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Mt Blanc Valley Weather - 3 Day Forecast

Extended Mediterranean high marginally shielding the Alpine Range this Wednesday, strengthened by an altitude African originated spur. Thewhole system is drifting east. Storm low Christoph, 980hpa Southern Scotland, expected 948 over northern North Sea by Thursday evening, making foehn gradient tighter along northwestern Alps over the hours. Thus, strong winds expected overnight, with possible gale force gusts in the valley. Foehn expected to decreasing by Thursday; first showers likely to breaking out in the evening. Fairly long lasting unsettled period thereafter, one week or more as of Thursday evening. Snow accumulation likely to becoming overabundant in the median altitude range by theend of the month.
Fairly sunny morning ‑ more cloud withfoehninthe afternoon ‑ windy highup
SKY CONDITION : partly cloudy this morning, some high cloud crossings ‑ becoming cloudy in the afternoon while altitude cloud patches will gradually thicker. Period of sunshine close to 65%.
WIND - ground level : calm or variable light ‑ fhn getting up and increasing in the afternoon.
WIND - mid mountain : SW moderate ‑> moderate to strong.
WIND - high mountain : WSW ‑> SW moderate to strong.
TEMPERATURE : low ‑10C - high +4C - temperature inversion toward 1600 m early in the morning.
ISOTHERM 0C : 2100 m.
ISOTHERM -10C : 3900 m.
ROAD CONDITION : dry and mild with foehn - snow patches drifted by the wind (Thursday,05:50).more
Strong foehn gusts ‑ clear outbreaks leeward ofborderinghigh massifs
SKY CONDITION : cloud keep crossing over from southwest ‑ clear outbreaks on the lee side of the bordering high massifs ‑ thickening cloud running over from Italy towards the end of the night iso0C rising up slightly towards 2100m.
WIND - aloft : SW moderate to strong ‑ sustained foehn in the valley ‑ possible gale force gusts.
Fhn will decrease in the afternoon‑ thensomeshowers ‑ windy highup
SKY CONDITION : cloudy with fleeting sunny spells in the morning ‑ becoming mostly cloudy to overcast. Period of sunshine close to 20%.
PRECIPITATION : some showers towards the latter part of the afternoon with rain‑snow limit dropping towards 1500m.
WIND - aloft : SW ‑> WSW moderate to strong ‑ occasionally strong ‑ decreasing foehn in the valley ‑ strong gusts still possible at first.
TEMPERATURE : low 0 C - high +6C.
Disturbance crossing over in the afternoon‑ light precipitation ‑ strong wind high up
SKY CONDITION : mostly cloudy on the whole ‑ fleeting sunny outbreaks likely towards the middle of the day. Period of sunshine close to 10%.
PRECIPITATION : light in the morning ‑ occasionally moderate in the afternoon ‑ changeable rain‑snow limit between 1200 and 900m ‑ 10‑15cm snowfall likely towards 1500m.
WIND - aloft : WSW ‑> SSW strong.
TEMPERATURE : slightly dropping highs.

Saturday: sunny spells in the morning, possibly caused by the few hours of foehn left ‑ wintry precipitation in the afternoon upon approach of westerly disturbance, rain‑snow limit likely to rising up towards 1000m at times ‑ whole gale high up. Sunday: uncertain, probably improving ‑ some sunny spells from noon or so, ahead of active disturbance expected during the following night. Monday: uncertain, in the tail of preceding nights cold front, fleeting sunny spells and snow showers even at lowest altitude.

Forecast reliability : fairly good until Thursday ‑ poor thereafter.