CHAMONIX VALLEY AND MONT-BLANC AREA WEATHER FORECAST


Matsuo Bashō
Summertime in the mountains
Straw sandals I am
Bowing to – and leave
ISSUED AT 20:55 ON SATURDAY JULY 20, 2019
VALID FROM : SATURDAY JULY 20 -- UNTIL : FRIDAY JULY 26 2019

GENERAL SYNOPSIS
Loose gradient pressure area over Central Europe and the Alpine Range. • Low 1000 hpa, between Scotland and Southwestern Norway, driving east a cold front whose southern tip will brush past the nortwestern slopes of the high massifs overnight. Increasing westerly stream high up is therefore expected to driving several tiny rainy-thundery cells towards our Region, with precise pathes quite difficult to figure out. Sunny condition will be resuming on Sunday afternoon, causing noticeable heat increase. • Scorching heat spell to be expected, Monday-Thursday, with surface Azores High ridge and African altitude high ridge once more resuming simultaneously.
SATURDAY EVENING JULY 20 - AND OVERNIGHT
Cloud passing - scattered shower, with possible local thunderstorm
SKY CONDITION : cloudy or mostly cloudy at times.
PRECIPITATION : isolated or scattered shower, randomly breaking out, with possible local thunderstorm - rain-snow limit towards 3700 m - expected amount of water in the valley < 2 mm.
WIND - ground level : SW light.
WIND - mid mountain : WSW light to moderate -> moderate.
WIND - high mountain : W moderate - occasionally moderate to strong.
TEMPERATURE : low +14°C.
ISOTHERM 0°C : 4000 m.
ISOTHERM -10°C : 5800 -> 5900 m.
Same kind of weather in Valais. Shower risk seems quite light in the Upper Aosta Valley.
TOMORROW - SUNDAY JULY 21
Some persistent cloud in the morning - becoming sunny and hot later
SKY CONDITION : mostly cloudy, then quickly cloudy with sunny spells - becoming clear or partly cloudy in the afternoon - persistent cumulus cloud over the massifs. Period of sunshine close to 70%.
PRECIPITATION : probably none.
WIND - ground level : SW light.
WIND - mid mountain : WSW moderate -> W light.
WIND - high mountain : W moderate -> WNW light to moderate.
TEMPERATURE : low +13°C - high +30°C.
ISOTHERM 0°C : 4000 -> 4400 m.
ISOTHERM -10°C : 5900 -> 6100 m.
Same kind of weather, Valais and Upper Aosta Valley.
SUNDAY TO MONDAY NIGHT - JULY 21 TO 22
Veiled skies at times - barely cool by dawn
SKY CONDITION  : partly cloudy - thin high cloud from north.
PRECIPITATION : none.
WIND - aloft : WNW -> NW light to moderate.
TEMPERATURE : low +12°C.
Same kind of weather, Valais and Upper Aosta Valley.
MONDAY JULY 22
Fair weather, outstandingly hot and dry - very light winds high up
SKY CONDITION : clear or partly cloudy - scarce cumulus cloud in the afternoon - some high cloud passing. Period of sunshine close to 85%.
PRECIPITATION : none.
WIND - aloft : NW light to moderate -> NNW very light.
TEMPERATURE : low +12 °C - high +32°C.
Same kind of weather, Valais and Upper Aosta Valley.
TUESDAY JULY 23
Fair and outstandingly hot ‑ very light winds high up
SKY CONDITION : clear. Period of sunshine close to 100%.
PRECIPITATION : none.
WIND - aloft : SE -> S light.
TEMPERATURE : low +15°C - high +35°C.
Same kind of weather, Valais and Upper Aosta Valley.
EXTENDED OUTLOOK UNTIL FRI. JULY 26

Wednesday and Thursday : sunny morning ‑ large cumulus cloud locally in the afternoon, yet without triggering any precipitation ‑ temperatures about 8 to 10°C above seasonal averages - mainly S high up, very light. Friday : altitude stream veering southwest and increasing - thundery deterioration likely in the afternoon.

Forecast reliability : fairly good until Tuesday.

ReportsAs a reminder, today in Chamonix, the sun rises at 06:01:58 and goes down at 21:15:51.
45.55 N 6.51 E - Altitude 1040 m
July 20 07:00
Temperature +12°C
Relative humidity 73%
Wind 0 km/h
Sea level pressure 1018 hpa - rising slowly
Pressure at 1042 m 902 mb
Precipitation last 6h 0.0 mm
Skies clear - cloudy towards italian slopes
Visibility 70000 m
Altitude 3845 m
July 20 07:00
Temperature 0°C
Wind SW 30 km/h
Altitude 2250 m
July 19 06:00
Snow depth 0 cm
Wind 10 km/h
Gusts -- km/h
Temperature +7°C