CHAMONIX VALLEY AND MONT-BLANC AREA WEATHER FORECAST


Matsuo Bashō
On a mountain path
Something might charm you
A wild violet
ISSUED AT 19:10 ON MONDAY OCTOBER 20, 2014
VALID FROM : MONDAY OCTOBER 20 -- UNTIL : SUNDAY OCTOBER 26 2014

GENERAL SYNOPSIS
The Mediterranean high currently protecting the Alps is weakening, allowing for a moderately active disturbance to crossing over during the night in a still milder air than average. Former hurricane Gonzalo expected to crossing over from the Northern British Isles to Denmark on Tuesday, causing unsettled and humid polar air to burst over the area from the northwest. Therefore a sudden weather change is to be expected during the Tuesday to Wednesday night, triggering wintry condition with gale force wind on Wednesday. Milder high pattern resuming from Thursday afternoon and lasting until Sunday.
MONDAY EVENING OCTOBER 20 - AND OVERNIGHT
Showers crossing over the area - windy high up
SKY CONDITION : cloudy, then mostly cloudy to overcast.
PRECIPITATION : showers towards the latter part of the night - scattered, although locally fairly heavy - rain-snow limit towards 2900 m, dropping.
WIND - ground level : variable light.
WIND - mid mountain : WNW light to moderate.
WIND - high mountain : W -> NW moderate to strong.
TEMPERATURE : low +7°C.
ISOTHERM 0°C : 3400 -> 3000 m.
ISOTHERM -10°C : 5300 -> 5200 m.
Same kind of weather over the Upper Aosta Valley and the bordering Valais.
TOMORROW - TUESDAY OCTOBER 21
Showers early in the morning and in the evening ‑ gale high up
SKY CONDITION : often mostly cloudy - at times cloudy with sunny spells towards the middle of the day. period of sunshine close to 30%.
PRECIPITATION : isolated shower still possible early in the morning - resuming heavier towards the evening and even more during the following night - rain-snow limit towards 2700 m in the morning, dropping towards 1700 m at night.
WIND - ground level : variable light to moderate.
WIND - mid mountain : WNW light to moderate -> W moderate.
WIND - high mountain : NW moderate to strong -> WNW gale.
TEMPERATURE : low +7°C - high +15°C.
ISOTHERM 0°C : 3000 -> 2000 m.
ISOTHERM -10°C : 5200 -> 4300 m.
How much colder on Tuesday is still somewhat uncertain by now.
TUESDAY TO WEDNESDAY NIGHT - OCTOBER 21 TO 22
Very bad weather high up - snow likely in the valley
SKY CONDITION  : overcast or mostly cloudy.
PRECIPITATION : moderate or locally fairly heavy due to the barrier effect against the northern slopes - rain-snow limit probably dropping towards 1000 m bu dawn - expected snowfall towards 1500 m : 5-15 cm.
WIND - aloft : WNW -> NNW strong gale.
TEMPERATURE : low 0°C.
Uncertain.
WEDNESDAY OCTOBER 22
Bad wintry weather ‑ snow showers ‑ strong N gale high up
SKY CONDITION : overcast, then mostly cloudy - possible fleeting sunny spells later. Period of sunshine close to 10%.
PRECIPITATION : showers - frequent in the morning - getting scattered in the afternoon - rain-snow limit towards 1100 m.
WIND - aloft : NNW -> N stong gale.
TEMPERATURE : low 0 °C - high +3°C.
Uncertain.
THURSDAY OCTOBER 23
Improving very cool ‑ fairly sunny in the afternoon - decreasing N wind high up.
SKY CONDITION : cloudy or locally mostly cloudy early in the morning - becoming cloudy with sunny spells, then partly cloudy. Period of sunshine close to 70%.
PRECIPITATION : none.
WIND - aloft : N strong -> moderate to strong.
TEMPERATURE : low 0°C - high +7°C.
Uncertain.
EXTENDED OUTLOOK UNTIL SUNDAY OCTOBER 26 2014

Friday and Saturday : fairly sunny ‑ milder. Sunday : hazy sunshine - milder than seasonal average.

Forecast reliability : fairly good until Tuesday ‑ poor thereafter..

ReportsAs a reminder, today in Chamonix, the sun rises at 07:56:34 and goes down at 18:37:56.
45.55 N 6.51 E - Altitude 1040 m
20 October 08:00
Temperature +5°C
Relative humidity 100%
Wind 0 km/h
Sea level pressure 1026 hpa - falling slowly
Pressure at 1042 m 906 mb
Precipitation last 6h 0.0 mm
Skies partly cloudy
Visibility 55000 m
Altitude 3845 m
20 October 08:00
Temperature -3°C
Wind W 60 km/h
Altitude 2250 m
20 October 08:00
Snow depth 0 cm
Wind 10 km/h
Gusts 20 km/h
Temperature +10°C