CHAMONIX VALLEY AND MONT-BLANC AREA WEATHER FORECAST


Matsuo Bashō
How glorious
Young green leaves
Flash in the sun
ISSUED AT 19:15 ON FRIDAY JULY 21, 2017
VALID FROM : FRIDAY JULY 21 -- UNTIL : THURSDAY JULY 27 2017

GENERAL SYNOPSIS
Surface pressure field featuring median to low value and loose gradient, Mediterranean to Alps. • Low whirling almost stationary over the British Isles, currently 994 hpa Ireland. • Resulting southwesterly stream is warm, humid and very unstable; it is expected to persisting until Sunday. • Weather will improve ovenight, once away this afternoon's rainy-thundery spell. • Thunder storm trend will however resume on Saturday afternoon. • Further outlook is still uncertain in detail, but global evolution should lead to a fairly active cold front passing on Monday, likely to causing gloomy condition, moreover unseasonably cool.
FRIDAY EVENING JULY 21 - AND OVERNIGHT
Disturbance moving away northeastward - clear outbreaks later - windy high up
SKY CONDITION : overcast or mostly cloudy in the first part of the night - clear spells spreading later, high up at first - fog patches likely to persisting along the slopes.
PRECIPITATION : shower becoming scattered in the first part of the night, then ending soon - rain-snow limit towards 3500-3600 m.
WIND - ground level : SW light or calm.
WIND - mid mountain : SW moderate - light to moderate at times.
WIND - high mountain : SW moderate -> moderate to strong.
TEMPERATURE : low +11°C.
ISOTHERM 0°C : 3800 -> 3900 m.
ISOTHERM -10°C : 5400 -> 5600 m.
Same kind of weather all over the Region.
TOMORROW - SATURDAY JULY 22
Fair sunny spell, then cloudy and warm with trend toward thunderstorm ‑ windy high up
SKY CONDITION : remaining cloud patches by dawn - becoming partly cloudy - increasing cloud over the massifs in the afternoon leading to overcast skies later. Period of sunshine close to 50%.
PRECIPITATION : thundery shower or thunderstomr likely towards the end of the afternoon, locally fairly heavy - rain-snow limit towards 3600 m.
WIND - ground level : calm or variable light - SW light to moderate at times toward noon.
WIND - mid mountain : SW moderate - light to moderate at times.
WIND - high mountain : SW moderate -> WSW moderate to strong.
TEMPERATURE : low +11°C - high +23°C.
ISOTHERM 0°C : 3900 m.
ISOTHERM -10°C : 5600 -> 5500 m.
Uncertain.
SATURDAY TO SUNDAY NIGHT - JULY 22 TO 23
Thunderstorm trend probably persisting - shy improvement before dawn
SKY CONDITION  : mostly cloudy to overcast - becoming cloudy with clear spells later.
PRECIPITATION : short lull after evening's precipitation, then fairly fast moving rainy-thundery disturbance towards the middle or the latter part of the night - rain-snow limit dropping towards 3400 m.
WIND - aloft : SW -> WSW moderate to strong.
TEMPERATURE : low +11°C.
Uncertain.
SUNDAY JULY 23
Partly sunny ‑ warm in the afternoon ‑ windy high up
SKY CONDITION : cloudy with sunny spells - spreading for a short while towards noon - at times mostly cloudy in the afternoon. Period of sunshine close to 45%.
PRECIPITATION : probably none.
WIND - aloft : WSW -> W moderate to strong - strong at times.
TEMPERATURE : low +11 °C - high +23°C.
Very uncertain.
MONDAY JULY 24
Cold front crossing over the area will cause a gloomy Monday
SKY CONDITION : mostly cloudy to overcast. Period of sunshine close to 15%.
PRECIPITATION : continuous and light - moderate to heavy at times towards the middle of the day - rain-snow limit towards 3000 m, dropping suddenly towards 2400 m in the middle of the afternoon.
WIND - aloft : WSW -> NW moderate to strong.
TEMPERATURE : low +10°C - high +17°C.
Very uncertain.
EXTENDED OUTLOOK UNTIL THURSDAY JULY 27

Tuesday : often mainly cloudy with some showers - fleeting sunny spells ‑ cooler than average ‑ fairly strong NNW high up at times. Wednesday : fairly sunny ‑ cumulus cloud growing over the massifs in the afternoon ‑ cooler than average. Thursday : fair weather likely ‑ fairly strong NW high up at times. Very uncertain.

Forecast reliability : poor.

ReportsAs a reminder, today in Chamonix, the sun rises at 06:04:36 and goes down at 21:13:25.
45.55 N 6.51 E - Altitude 1040 m
July 22 07:00
Temperature +11°C
Relative humidity 88%
Wind 0 km/h
Sea level pressure 1017 hpa - falling slowly
Pressure at 1042 m 900 mb
Precipitation last 6h 0.3 mm
Skies cloudy
Visibility 60000 m
Altitude 3845 m
July 22 07:00
Temperature -1°C
Wind SW 35 km/h
Altitude 2250 m
July 22 05:00
Snow depth 0 cm
Wind 20 km/h
Gusts 35 km/h
Temperature +8°C