CHAMONIX VALLEY AND MONT-BLANC AREA WEATHER FORECAST


Matsuo Bashō
On a mountain path
Something might charm you
A wild violet
ISSUED AT 18:00 ON SATURDAY SEPTEMBER 20, 2014
VALID FROM : SATURDAY SEPTEMBER 20 -- UNTIL : FRIDAY SEPTEMBER 26 2014

GENERAL SYNOPSIS
Low 1006 hpa northwest of Portugal, drifting south while filling. Resulting altitude stream over the Alps is southwest in the evening to west overnight, still moderate, mild, humid and unsettled, likely to causing scattered showers with possible local thunderstorm. High cell setting up over the British Isles on Sunday. Cooler air mass sliding along its eastern flank towards the Alps. Resulting front, fairly weak over the Western Alps, is expected to crossing over by Sunday afternoon or evening. High pattern then allowing for two sunny days on Monday and Tuesday, with a fairly strong N wind spell on Monday.
SATURDAY EVENING SEPTEMBER 20 - AND OVERNIGHT
Cloud patches crossing over - thundery shower risk
SKY CONDITION : cloudy or mostly cloudy at times.
PRECIPITATION : thundery shower risk, probably higher towards the middle of the night - rain-snow limit towards 3000 m.
WIND - ground level : variable light.
WIND - mid mountain : W -> variable light.
WIND - high mountain : W moderate - at times light to moderate.
TEMPERATURE : low +11°C.
ISOTHERM 0°C : 3300 -> 3100 m.
ISOTHERM -10°C : 5000 -> 4900 m.
Same kind of weather over the Upper Aosta Valley and the bordering Valais. Uncertain.
TOMORROW - SUNDAY SEPTEMBER 21
Changeable - cloud patches - sunny spells - light scattered showers - deterioration later
SKY CONDITION : mostly cloudy early in the morning - becoming cloudy with sunny spells - resuming mostly cloudy during the afternoon - overcast in the evening. period of sunshine close to 40%.
PRECIPITATION : light and scattered - probably slightly heavier in the afternoon - rain-snow limit towards 2800 m, dropping.
WIND - ground level : variable light to moderate.
WIND - mid mountain : variable -> NW light.
WIND - high mountain : W -> NW moderate.
TEMPERATURE : low +11°C - high +20°C.
ISOTHERM 0°C : 3100 -> 2900 m.
ISOTHERM -10°C : 4900 -> 4800 m.
Same kind of weather over the Upper Aosta Valley and the bordering Valais. Uncertain.
SUNDAY TO MONDAY NIGHT - SEPTEMBER 21 TO 22
Mainly cloudy at first - becoming partly cloudy and windy high up
SKY CONDITION  : mostly cloudy early in the night - becoming partly cloudy, high up at first.
PRECIPITATION : shower slight risk still persisting early in the night - otherwise dry.
WIND - aloft : NW moderate -> NNW moderate to strong.
TEMPERATURE : low +9°C.
Incertain.
MONDAY SEPTEMBER 22
Sunny ‑ windy high up - cool in the morning - milder in the afternoon
SKY CONDITION : partly cloudy in the morning - clear in the afternoon. Period of sunshine close to 95%.
PRECIPITATION : none.
WIND - aloft : NNW moderate to strong.
TEMPERATURE : low +9 °C - high +18°C.
Noticeably milder over the Upper Aosta Valley due to northerly fœhn wind.
TUESDAY SEPTEMBER 23
Fine sunny weather - almost cold in the morning - very mild in the afternoon
SKY CONDITION : clear. Period of sunshine close to 100%.
PRECIPITATION : none.
WIND - aloft : N -> NE light.
TEMPERATURE : low +6°C - high +21°C.
Fine weather all over the three bordering alpine regions.
EXTENDED OUTLOOK UNTIL FRIDAY SEPTEMBER 26 2014

Wednesday and Thursday : fairly sunny and mild - cloud patches crossing over during the night in-between. Friday : sunny and mild.

Forecast reliability : poor in the short term.

ReportsAs a reminder, today in Chamonix, the sun rises at 07:18:39 and goes down at 19:32:17.
45.55 N 6.51 E - Altitude 1040 m
20 September 08:00
Temperature +12°C
Relative humidity 95%
Wind 0 km/h
Sea level pressure 1018 hpa - rising
Pressure at 1042 m 900 mb
Precipitation last 6h 3.0 mm
Skies cloudy - fairly thick high cloud
Visibility 50000 m
Altitude 3845 m
20 September 08:00
Temperature -3°C
Wind W 50 km/h
Altitude 2250 m
20 September 08:00
Snow depth 0 cm
Wind 20 km/h
Gusts 35 km/h
Temperature +6°C