CHAMONIX VALLEY AND MONT-BLANC AREA WEATHER FORECAST


Matsuo Bashō
Ah spring spring
How great is spring !
and so on
ISSUED AT 19:30 ON SATURDAY APRIL 21, 2018
VALID FROM : SATURDAY APRIL 21 -- UNTIL : FRIDAY APRIL 27 2018

GENERAL SYNOPSIS
High 1022-1018 hpa, North Sea to Southern France, going along with an altitude anticyclonic component over the Alpine Range. The whole system is weakening slowly, and will be withdrawing over the Mediterranean by Sunday evening, although being no threat to the current fair weather, outstandingly warm compared to seasonal average, especially in the median altitude range. • Deepening low coming in north of Scotland during the night to Monday will make the altitude stream veer west, cooler on the whole, and somewhat unstable at times. • Disintegrating cold front might trigger showers over the massifs on Monday afternoon. • Expected sunny improvement on Tuesday, then more pronounced deterioration likely by Wednesday afternoon, with possible local thunderstorm.
SATURDAY EVENING APRIL 21 - AND OVERNIGHT
Clear - cool in the valley by dawn - mild in the median altitude range
SKY CONDITION : clear or partly cloudy - thin high cloud from the southwest before dawn.
PRECIPITATION : none.
WIND - ground level : calm -> NE light.
WIND - mid mountain : SW -> S light.
WIND - high mountain : S -> SW light.
TEMPERATURE : low +4°C.
ISOTHERM 0°C : 3400 -> 3200 m.
ISOTHERM -10°C : 4900 -> 4800 m.
Temperature inversion towards 1200 m by dawn. Same kind of weather all around the neighbouring massifs.
TOMORROW - SUNDAY APRIL 22
Fair weather - cool in the morning - warm with cumulus cloud later
SKY CONDITION : clear or partly cloudy - thin high cloud early in the morning - cumulus cloud growing over the slopes in the afternoon. Period of sunshine close to 85%.
PRECIPITATION : none.
WIND - ground level : NE -> variable light.
WIND - mid mountain : S -> WSW light.
WIND - high mountain : SW -> W light.
TEMPERATURE : low +3°C - high +24°C.
ISOTHERM 0°C : 3200 -> 3400 m.
ISOTHERM -10°C : 4800 -> 4900 m.
Same kind of weather all around the neighbouring massifs.
SUNDAY TO MONDAY NIGHT - APRIL 22 TO 23
Almost clear in the first part of the night - cloudy deterioration later
SKY CONDITION  : partly cloudy or even clear after possible cumulus cloud dispelling - becoming cloudy - high cloud patches becoming more frequent from the west towards the latter part of the night.
PRECIPITATION : none.
WIND - aloft : W light -> WNW light to moderate.
TEMPERATURE : low +6°C.
Incertain.
MONDAY APRIL 23
Changeable and cooler - shower risk during the afternoon
SKY CONDITION : cloudy with sunny spells early in the morning - high cloud patches - becoming mostly cloudy. Period of sunshine close to 35%.
PRECIPITATION : shower risk in the afternoon - rain-snow limit towards 2700 m, dropping trend.
WIND - aloft : WNW light to moderate -> W moderate.
TEMPERATURE : low +6 °C - high +18°C.
Uncertain.
TUESDAY APRIL 24
Sunny - cool in the morning ‑ warm in the afternoon
SKY CONDITION : partly cloudy, becoming clear - high cloud patches from the northwest early in the morning. Period of sunshine close to 85%.
PRECIPITATION : none.
WIND - aloft : NNW light to moderate -> WSW light.
TEMPERATURE : low +4°C - high +21°C.
Uncertain.
EXTENDED OUTLOOK UNTIL FRI. APRIL 27

Wednesday : unstable ‑ sunny spells in the morning ‑ cloudy with thundery shower risk later. Thursday : mostly cloudy with showers - changeable rain-snow limit around 2000 m. Friday : persistent instability - partly cloudy in the morning - becoming mostly cloudy with shower risk in the afternoon. • Westerly stream fairly strong at times high up during the latter two days.

Forecast reliability : fairly good until Sunday ‑ poor thereafter.

ReportsAs a reminder, today in Chamonix, the sun rises at 06:33:16 and goes down at 20:28:39.
45.55 N 6.51 E - Altitude 1040 m
April 21 07:00
Temperature +3°C
Relative humidity 80%
Wind 0 km/h
Sea level pressure 1023 hpa - rising slowly
Pressure at 1042 m 906 mb
Precipitation last 6h 0.0 mm
Skies clear
Visibility 90000 m
Altitude 3845 m
April 21 07:00
Temperature -5°C
Wind SE 10 km/h
Altitude 2250 m
April 21 06:00
Snow depth 325 cm
Wind 5 km/h
Gusts 10 km/h
Temperature +7°C