CHAMONIX VALLEY AND MONT-BLANC AREA WEATHER FORECAST
Eugène Delacroix, La Liberté guidant le peuple
ISSUED AT 19:30 ON FRIDAY APRIL 29, 2016
VALID FROM : FRIDAY APRIL 29 2016 -- UNTIL : THURSDAY MAY 05 2016

GENERAL SYNOPSIS
Weak Azores high ridge sheltering the Alps until Saturday morning on the southern edge of a complex low system over North Sea, fed by maritime polar air, yet filling slowly almost stationary. • Clear night, thus fairly cold in the valley, until the income of high cloud from the southwest shortly before dawn. • Low's cold air invading France from the northwest on Saturday morning will be isolating as an altitude cold drop which will probably be gliding west close to the Alps by Saturday evening, while heading towards the Genoa Gulf. • Light rain will therefore begin Saturday towards the latter part of the afternoon, then become moderate during the night and at last change to light snowfall by Sunday morning. Atmosphere should then remain gloomy on Sunday afternoon under a fairly strong northeasterly wind. • Anticyclonic evolution likely from Monday.
FRIDAY EVENING APRIL 29 - AND OVERNIGHT
Clearing skies, then becoming slightly hazy later - cold in the valley
SKY CONDITION : cumulus cloud dispelling - becoming clear or partly cloudy - thin high cloud running over the High Massifs from the southwest.
PRECIPITATION : none.
WIND - ground level : variable light -> calm.
WIND - mid mountain : SW -> variable light.
WIND - high mountain : W -> SW moderate.
TEMPERATURE : low -1°C.
ISOTHERM 0°C : 2000 -> 2100 -> 1900 m.
ISOTHERM -10°C : 3700 -> 3500 m.
Same weather in the bordering Valais. Becoming quickly cloudy in the Upper Aosta Valley.
TOMORROW - SATURDAY APRIL 30
Hazy sunshine in the morning - becoming mostly cloudy, then somewhat rainy
SKY CONDITION : partly cloudy early in the morning - thin high cloud - increasing cloud from the southwest - becoming overcast in the evening. Period of sunshine close to 40%.
PRECIPITATION : starting up towards the latter part of the afternoon - mostly light before nightfall - rain-snow limit towards 1400 m, dropping - expected snowfall towards 1800 m : ± 5 cm.
WIND - ground level : calm -> variable light - fœhn wind puffs towards the middle of the day, light to moderate.
WIND - mid mountain : variable light -> SW light to moderate.
WIND - high mountain : SW moderate -> SSE moderate to strong.
TEMPERATURE : low 0°C - high +12°C.
ISOTHERM 0°C : 1900 -> 1500 m.
ISOTHERM -10°C : 3500 -> 3000 m.
Same weather in the bordering Valais. Becoming quickly cloudy in the Upper Aosta Valley.
SATURDAY TO SUNDAY NIGHT - MAY 30 TO 01
Cold front crossing over - moderate rain changing to snow shower
SKY CONDITION  : overcast or mostly cloudy.
PRECIPITATION : light rain, becoming moderate in the first part of the night - changing to scattered snow showers thereafer - rain-snow limit towards 1100 m, dropping towards 800 m for a short while - expected snowfall towards 1800 m : 10-20 cm.
WIND - aloft : variable cyclonic moderate to strong -> SE moderate.
TEMPERATURE : low 0°C.
Uncertain.
SUNDAY MAY 01
Winter-like - light snow in the morning ‑ probably dry with cold wind high up later
SKY CONDITION : skies should remain mostly cloudy due to the barrier effect against the northern slope - fleeting sunny spells likely in the afternoon - improving in the evening. Period of sunshine close to 15%.
PRECIPITATION : remaining showers in the morning, light and scattered - rain-snow limit towards 1000 m - dry in the afternoon.
WIND - aloft : SE moderate -> NE moderate to strong.
TEMPERATURE : low 0 °C - high +3°C.
Incertain.
MONDAY MAY 02
Fairly sunny ‑ cold at first, getting milder - decreasing wind high up
SKY CONDITION : partly cloudy in the morning - cloudy with sunny spells in the afternoon due to cumulus cloud growth. Period of sunshine close to 60%.
PRECIPITATION : none.
WIND - aloft : NE moderate -> N light to moderate.
TEMPERATURE : low +3°C - high +13°C.
Uncertain.
EXTENDED OUTLOOK UNTIL THURSDAY MAY 05

Tuesday : uncertain ‑ high toping over Brittany, yet driving cold unsettled air towards the Alps along it's eastern flank ‑ increasing cloud with shower risk in the afternoon. Wednesday and Thursday : fair weather ‑ morning cool in the valley ‑ mild in the afternoon.

Forecast reliability : fairly good until Saturday ‑ poor thereafter.

ReportsAs a reminder, today in Chamonix, the sun rises at 06:19:34 and goes down at 20:39:42.
45.55 N 6.51 E - Altitude 1040 m
30 April 07:00
Temperature 0°C
Relative humidity 83%
Wind 0 km/h
Sea level pressure 1016 hpa - steady
Pressure at 1042 m 895 mb
Precipitation last 6h 0.0 mm
Skies clear
Visibility 70000 m
Altitude 3845 m
30 April 07:00
Temperature -12°C
Wind SW 45 km/h
Altitude 2250 m
30 April 06:00
Snow depth 255 cm
Wind 10 km/h
Gusts 15 km/h
Temperature -3°C