CHAMONIX VALLEY AND MONT-BLANC AREA WEATHER FORECAST


Matsuo Bashō
Higher than the lark
Resting in the sky
Of the mountain pass
ISSUED AT 09:20 SUNDAY AUGUST 14 2022
VALID : SUNDAY 14 -- FRIDAY AUGUST 19 2022

GENERAL SYNOPSIS
SWIFT THUNDERY DETERIORATION • Previous protective high pressure area was refocusing E of the Scandinavian. • Remaining isobaric swamp over W Europe is currently turning into some slightly low pressure area (Sallanches, 1009 - Sion, 1012 - Innsbruck, 1015), locally very unstable, while a 1006 minimum was deepening last night towards S Brittany, linked to the altitude cut-off which was proceeding from W Portugal by the same time. • As a result, this small low system, currently drifting E, shapes a rainy-thundery limit, quite active in the Rhône Valley for now. It will affect W slopes of the Alpine Range as of 10:30-11:00. • After such a chaotic episode, further outlook remains quite uncertain in detail.
TODAY - SUNDAY AUGUST 14
Soon sultry under thick high cloud - waves of thundery disturbance approaching by noon
SKY CONDITION : already cloudy early in the morning, altocumulus and altostratus cloudy - becoming soon overcast from W, high up at first. Period of sunshine close to 25%.
PRECIPITATION : thundery shower starting up towards 11:00-12:00, locally heavy - several waves thereafter until nightfall - rain-snow limit towards 3700 m, dropping towards 3500 m.
WIND - ground level : calm -> SW light (10:00) - possible gusts ahead of thundery shower.
WIND - mid mountain : WSW light to moderate -> moderate - occasionally S.
WIND - high mountain : WNW light to moderate -> SSW moderate -> SW moderate to strong.
TEMPERATURE : low +12°C - high +25°C.
ISOTHERM 0°C : 4200 -> 3800 m.
ISOTHERM -10°C : 5800 -> 5400 m.
OVERNIGHT
Thunderstorm likely at first - then improving - clear outbreaks by dawn
SKY CONDITION : overcast or mostly cloudy until the middle of the night - clear outbreaks spreading randomly thereafter - iso 0°C towards 3600 m.
PRECIPITATION : last showery wave between 19:00 and 23:00 - rain-snow limit dropping towards 3200 m at times - expected water in the valley regarding the whole episode : 3-6 mm.
WIND - aloft : SW -> WSW moderate to strong - locally strong.
TEMPERATURE : low +10°C.
MONDAY AUGUST 15
Morning fog patches along the slopes - else, sunny outbreaks - windy high up
SKY CONDITION : changeable skies - fog patches sticking to the slopes at first, dispelling under direct sunshine thereafter - else sunny outbreaks, somewhat more widespread in the afternoon. Period of sunshine close to 60%.
PRECIPITATION : none.
WIND - aloft : WSW -> W moderate to strong - occasionally moderate.
TEMPERATURE : low +10 °C - high +24°C.
TUESDAY AUGUST 16
Fairly sunny - scorching heat in the afternoon - bulky cumulus cloud above the massifs
SKY CONDITION : clear or partly cloudy in the morning - locally cloudy in the afternoon, owing to cumulus cloud growth. Period of sunshine close to 70%.
PRECIPITATION : slight convection shower risk towards the latter part of the afternoon.
WIND - aloft : WSW light -> SW moderate.
TEMPERATURE : rising highs.
EXTENDED OUTLOOK UNTIL FRIDAY AUGUST 19 2022

Wednesday : uncertain - heavy deterioration likely in the afternoon, thunderstorm likely at first - SW by S occasionally strong high up in the morning. Thursday : uncertain - persistent unstable SW stream - mainly cloudy with frequent shower, often moderate - temperature highs dropping noticeably. Friday : very uncertain probably in the tail of previous disturbance - frequent shower until evening, though with some sunny spells towards noon. • 35-50 mm water during the three days, not unlikely.

Forecast reliability : fairly good until Monday - uncertain thereafter.

ReportsAs a reminder, today in Chamonix, the sun rises at 06:31:33 and goes down at 20:42:42.
Chamonix - ville
45.55 N 6.51 E - Altitude 1030 m
August 14, 2022 08:00
Temperature +12°C
Relative humidity 72%
Wind VAR 5 km/h
Sea level pressure 1010 hpa - falling quickly
Pressure at 1042 m 896 mb
Precipitation last 6h 0 mm
Skies mainly cloudy - ceiling > 4500 m
Visibility 70 000 m
Altitude 3845 m
August 14, 2022 08:00
Temperature +2°C
Wind SSW 10-45 km/h
Altitude 2250 m
August 14, 2022 08:00
Snow depth 0 cm
Wind S 7 km/h
Gusts 15 km/h
Temperature +13.9°C