CHAMONIX VALLEY AND MONT-BLANC AREA WEATHER FORECAST


Natsume Sôseki
Evening let it glow
Red my mountain
In a radiant window
ISSUED AT 09:10 THURSDAY SEPTEMBER 23 2021
VALID FROM : THURSDAY 23 -- UNTIL : TUESDAY SEPTEMBER 28 2021

GENERAL SYNOPSIS
High 1033 hpa northeast of Azores, going along with very mild maritime air coming in high up, extending a 1024 ridge or so up to eastern-most part of the Alpine Range (Vienna-Slovenia), weakening very slowly. • Fairly high pressure (1020), Mediterranean area, weakening in it's western part, then merging with some high pressure link, Lybia to southern foothills of the Alps, by Friday evening. • Fair post-summer sequence until Saturday morning as that high area will persist, Central Mediterranean to Northern Italy, thereafter turning into low pressure northwest of the Alpine Range, upon approach of an Atlantic thalweg; thus, possible fœhn gradient, which might delay Atlantic disturbance income until the night to Sunday.
TODAY - THURSDAY SEPTEMBER 23
Fair weather - cool in the valley at first - unseasonably warm in the afternoon
SKY CONDITION : clear on the whole - tiny cumulus above the massifs in the afternoon - very thin high altitude cirrus cloud in the afternoon. Period of sunshine close to 85%.
PRECIPITATION : none.
WIND - ground level : calm -> SW very light - occasional thermal reinforcement early afternoon.
WIND - mid mountain : NE -> NW very light.
WIND - high mountain : ENE <-> ESE very light -> calm towards evening.
TEMPERATURE : low +6°C - high +22°C.
ISOTHERM 0°C : 4200 -> 4100 m.
ISOTHERM -10°C : 5500 -> 5600 m.
OVERNIGHT
Fair weather - rather cool in the valley by dawn - with temperature inversion
SKY CONDITION : clear on the whole, after some evening cloud dispelling - very thin cirrus cloud crossing over from northeast - iso 0°C steady towards 410 m - yet snow surface re-freezing will be good.
PRECIPITATION : none.
WIND - aloft : calme -> NW -> W very light.
TEMPERATURE : low +7°C - temperature inversion toward 1500 m.
FRIDAY SEPTEMBER 24
Fair weather - hot in the afternoon - extended visibility high up
SKY CONDITION : partly cloudy, then clear - some very thin cirrus patches in the morning - probably cloudless in the afternoon. Period of sunshine close to 95%.
PRECIPITATION : none.
WIND - aloft : W very light -> WSW light - light to moderate in the evening.
TEMPERATURE : low +6 °C - high +23°C - temperature inversion toward 1300 m early in the morning.
SATURDAY SEPTEMBER 25
Fairly sunny until the first part of the afternoon and becoming hot with foehn by then
SKY CONDITION : partly cloudy in the morning, high cloud running over from SW - partly cloudy to cloudy in the afternoon, some thick cloud running over from Italy with foehn effect. Period of sunshine close to 65%.
PRECIPITATION : none.
WIND - aloft : SW moderate -> moderate to strong • in the valley : moderate to strong foehn likely, late morning -> mid-night to Sunday.
TEMPERATURE : rising.
EXTENDED OUTLOOK UNTIL TUESDAY SEPTEMBER 28 2021

Sunday : disturbance crossing over the Alps, northeast bound - some sunny spells in the morning - extended cloud patches crossing over in the afternoon, triggering locally heavy shower (5-10 mm) - getting relatively cooler, though with temperatures remaining above seasonable. Monday : uncertain - improving slightly, more frequent sunny outbreaks than previously, slight shower risk and somewhat milder atmosphere. Tuesday : uncertain - improving no more, gloomy keeps ruling.

Forecast reliability : good until Friday - poor thereafter.

ReportsAs a reminder, today in Chamonix, the sun rises at 07:22:48 and goes down at 19:25:48.
Chamonix - ville
45.55 N 6.51 E - Altitude 1020 m
September 23 08:00
Temperature +6.6°C
Relative humidity 92%
Wind 0 km/h
Sea level pressure 1023 hpa - rising slowly
Pressure at 1042 m 904 mb
Precipitation last 6h 0.0 mm
Skies clear
Visibility 100000 m
Altitude 3845 m
September 23 07:00
Temperature +0.5°C
Wind N 10-21 km/h
Altitude 2250 m
September 23 07:00
Snow depth -- cm
Wind SW 10 km/h
Gusts 18 km/h
Temperature +9.7°C