CHAMONIX VALLEY AND MONT-BLANC AREA WEATHER FORECAST


Masaoka Shiki
A mountain village
Under the piled-up snow
The sound of water
ISSUED AT 19:20 ON FRIDAY MARCH 24, 2017
VALID FROM : FRIDAY MARCH 24 -- UNTIL : THURSDAY MARCH 30 2017

GENERAL SYNOPSIS
Pressure field is noticeably higher than 1020 hpa in Italian Piedmont and somewhat lower in French Savoy and Swiss Valais. An altitude cold low towards Northern Portugal creates an impressive cloud whirl around the Iberian Peninsula, driving a fairly strong and humid southeasterly stream high up across the Alps, causing a barrier effect against the Italian slopes of the High Massifs and allowing for intermittent fœhn wind to blow in the northern valleys. • Satellite minimum will be deepening overnight towards 1005 hpa north of the Balearic Islands, then will be moving towards the Biscaye Bay. Linked cold front is expected to crossing over the area during the Saturday to Sunday night, triggering locally fairly heavy precipitation on the Italian slopes, although much lighter on the northern slopes. • Easterly backings will then allow for gradual improvement, still humid and cool on Sunday, while sunny and mild on Monday.
FRIDAY EVENING MARCH 24 - AND OVERNIGHT
Erratic fœhn wind - fairly clear outbreaks in the valley - overcast and windy high up
SKY CONDITION : thick cloud veil until the latter part of the night, allowing for spreading clear outbreaks thereafter.
PRECIPITATION : none.
WIND - ground level : moderate fœhn wind, mainly NE - stronger in the upper valley.
WIND - mid mountain : SE gusty - light to moderate -> moderate to strong.
WIND - high mountain : SE moderate -> moderate to strong.
TEMPERATURE : low +4°C.
ISOTHERM 0°C : 2900 -> 3000 m.
ISOTHERM -10°C : 4200 m.
Uncertain.
TOMORROW - SATURDAY MARCH 25
Sunny spells at first - very mild at time - fœhn wind ending - overcast later
SKY CONDITION : cloudy with fœhn wind generated sunny spells - increasing cloud above the massifs during the afternoon - mostly cloudy to overcast in the evening. Period of sunshine close to 55%.
PRECIPITATION : probably none until the night.
WIND - ground level : moderate fœhn wind, mainly NE - stronger in the upper valley - decreasing in the afternoon.
WIND - mid mountain : SE moderate to strong or locally strong -> E light to moderate.
WIND - high mountain : SE moderate to strong.
TEMPERATURE : low +3°C - high +17°C.
ISOTHERM 0°C : 3000 -> 2600 m.
ISOTHERM -10°C : 4200 -> 3900 m.
Precipitation starting up towards the end of the afternoon on the Italian slopes. Uncertain.
SATURDAY TO SUNDAY NIGHT - MARCH 25 TO 26
Overcast - moderate showers - getting colder - windy high up
SKY CONDITION  : overcast to mostly cloudy.
PRECIPITATION : starting up in the first part of the night - light and scattered showers on the whole - at times more frequent and moderate towards the middle of the night - rain-snow limit towards 2100 m, dropping towards 1600 m by dawn - expected snowfall towards 2000 m : 5-10 cm.
WIND - aloft : SE modéré à fort -> E modéré.
TEMPERATURE : low +1°C.
Heavier precipitation on the Italian slope, with a lower rain-snow limit.
SUNDAY MARCH 26
Cool easterly cloud backings - probably dry - sunny spells in the afternoon
SKY CONDITION : mostly cloudy in the morning - becoming cloudy with sunny spells. Period of sunshine close to 40%.
PRECIPITATION : probably none.
WIND - aloft : E -> ENE moderate.
TEMPERATURE : low +2 °C - high +12°C.
Very uncertain.
MONDAY MARCH 27
Fairly sunny - diurnal instability causing cumulus cloud growth on the massifs
SKY CONDITION : clear morning - becoming partly cloudy or locally cloudy due to cumulus cloud growth in the afternoon. Period of sunshine close to 70%.
PRECIPITATION : evening shower slight risk in the massifs.
WIND - aloft : ESE -> SE moderate.
TEMPERATURE : low -1°C - high +16°C.
Very uncertain.
EXTENDED OUTLOOK UNTIL THURSDAY MARCH 30

Tuesday to Thursday : fair spring weather - almost cold in the morning - very mild later - outlook being still uncertain.

Forecast reliability : poor.

ReportsAs a reminder, today in Chamonix, the sun rises at 06:24:24 and goes down at 18:52:10.
45.55 N 6.51 E - Altitude 1040 m
24 march 07:00
Temperature +8°C
Relative humidity 60%
Wind NE 20 km/h
Sea level pressure 1015 hpa - rising slowly
Pressure at 1042 m 900 mb
Precipitation last 6h 0.0 mm
Skies mostly cloudy - fœhn wind in the valley
Visibility 12000 m
Altitude 3845 m
24 march 07:00
Temperature -11°C
Wind SE 60 km/h
Altitude 2250 m
24 march 06:00
Snow depth 130 cm
Wind 15 km/h
Gusts 35 km/h
Temperature +2°C