CHAMONIX VALLEY AND MONT-BLANC AREA WEATHER FORECAST
ISSUED AT 07:45 MONDAY APRIL 27
VALID FROM : MONDAY APRIL 27 ‑‑ UNTIL : SATURDAY MAY 2 2015
Of a pilchard eye
Low trough 979‑1005 hpa, Norwegian Sea to Balearic Islands, driving a southwesterly to southeasterly altitude stream over the Alps, mild, humid and unsettled. Resulting fœhn wind effect is likely to shelter the valley from precipitation until the afternoon. Southern part of that low system is drifting east, followed by a polar air inflow. Active cold front therefore coming in towards the evening and crossing over during the night, triggering snowfall well below 1500 m and causing the altitude stream to veer northwest. Improving somewhat on Tuesday and Wednesday, before a new unsettled period from Thursday afternoon until Sunday at least.
TODAY - MONDAY APRIL 27
SKY CONDITION : cloudy with fœhn wind sunny spells in the morning ‑ becoming cloudy, then overcast in the afternoon. Period of sunshine close to 20%.
PRECIPITATION : isolated shower possibly running over from the south in the morning ‑ rain becoming continuous and moderate in the afternoon, and heavy with possible thunderstorm for a short while in the evening ‑ rain‑snow limit towards 2300 m, dropping sharply in the evening ‑ expected snowfall towards 2500 m : 25‑35 cm.
WIND - ground level : fœhn wind puffs still blowing in the morning ‑ variable light later.
WIND - mid mountain : SSE ‑> variable light ‑> NNW moderate.
WIND - high mountain : SSW light to moderate ‑> SE ‑> variable light.
TEMPERATURE : low +9°C - high +15°C.
ISOTHERM 0°C : 2700 ‑> 2200 m.
ISOTHERM -10°C : 4200 ‑> 4000 m.
ROAD CONDITION ••••• : @ 06:30, dry roadways.
SKY CONDITION : overcast.
PRECIPITATION : continuous and moderate, becoming light and scattered towards the end of the night ‑ rain‑snow limit dropping towards 1300 m ‑ expected snowfall towards 2500 m : 10‑15 cm.
WIND - aloft : variable faible ‑> WNW faible à modéré.
TEMPERATURE : low +3°C.
TUESDAY APRIL 28
SKY CONDITION : probably still mostly cloudy early in the morning ‑ low cloud ‑ becoming cloudy with fair sunny spells. Period of sunshine close to 50%.
PRECIPITATION : remaining drizzle still likely early in the morning ‑ rain‑snow limit towards 1300 m.
WIND - aloft : WNW light to moderate ‑> NW moderate.
TEMPERATURE : low +3 °C - high +12°C - temperature inversion toward Incertain m early in the morning.
WEDNESDAY APRIL 29
SKY CONDITION : clear or parly cloudy until the middle of the afternoon ‑ becoming cloudy due to cumulus cloud growth. Period of sunshine close to 80%.
PRECIPITATION : none.
WIND - aloft : SW moderate ‑ SSW at times.
TEMPERATURE : dropping lows ‑ rising highs.
EXTENDED OUTLOOK UNTIL SATURDAY MAY 2 2015
Thursday : westerly disturbance coming in from the west ‑ shower becoming frequent ‑ strong W wind high up towards the evening. Friday : gloomy morning ‑ snow towards 1600 m ‑ fleeting sunny spells in the afternoon ‑ fairly strong NW high up. Saturday : cloudy with sunny spells and probably without precipitation ‑ still windy high up.
Forecast reliability : poor.
Considerable avalanche risk (3/5) high up - stay posted.