safety
Scotland's Avalanche Forecast: How to Read and Use SAIS
How to read the Scottish Avalanche Information Service (SAIS) forecast before any winter hill day — hazard ratings, aspect diagrams, and what each level means in practice.
Quick Summary
- SAIS (Scottish Avalanche Information Service) publishes forecasts for 6 regions from December to April — Northern Cairngorms, Southern Cairngorms, Creag Meagaidh, Lochaber, Glencoe and Torridon
- The hazard scale runs 1–5 (Low to Very High) — in Scotland, most avalanche fatalities occur at Considerable (3) because walkers underestimate it
- Check SAIS every day before a winter hill day — conditions can change overnight after wind and snowfall
- SAIS is free at sais.gov.uk — bookmark it on your phone before you need it
Scotland has a real avalanche problem every winter. The SAIS site reports 321 avalanches recorded last season. Most do not involve people. The ones that do are frequently fatal. Knowing how to read the forecast before any winter hill day — and understanding what the numbers mean in practice — is a non-negotiable winter skill.
Quick Answer: Scotland's avalanche forecast is produced by the Scottish Avalanche Information Service (SAIS) at sais.gov.uk. It covers 6 regions from December to April. The hazard scale runs 1 (Low) to 5 (Very High). Check it the evening before and again the morning of your hill day — pay particular attention to the aspect and elevation diagrams, which tell you which slopes and which heights are dangerous. At Considerable (3), hazards are described as "human-triggered avalanches likely" — this is the level at which most Scottish avalanche accidents occur, partly because the rating is easy to underestimate.
What SAIS covers
SAIS runs six forecast regions, each based around a mountain area with a dedicated observer:
| Region | Key hills |
|---|---|
| Northern Cairngorms | Cairn Gorm, Ben Macdui, Braeriach, the Northern Corries |
| Southern Cairngorms | Lochnagar, Glas Maol, The Cairnwell, the Glenshee hills |
| Creag Meagaidh | Creag Meagaidh, Coire Ardair, the Ardverikie hills |
| Lochaber | Ben Nevis, Aonach Mor, Mamores, Grey Corries |
| Glencoe | Bidean nam Bian, Buachaille Etive Mor, Aonach Eagach, Meall a' Bhuiridh |
| Torridon | Liathach, Beinn Eighe, Beinn Alligin, the Fannichs |
If you are hillwalking in any of these areas between December and April, you should check the relevant region before going.
Most Scottish hills are not in any of them. Six areas is six massifs — the Trossachs, Ben Lawers, Glen Affric, Knoydart, Skye, Assynt, the eastern Mounth, Arran and the Southern Uplands all sit outside the network, and no avalanche forecast is published for them. That does not mean no avalanche hazard: it means nobody is measuring it for you, and the judgement is yours on the day. Picking the "nearest" area instead is worse than having none — a stable rating for a different massif, with a different aspect and a different storm history, reads like reassurance.
The five-point hazard scale
SAIS uses the European Avalanche Warning Services' Avalanche Danger Scale, which runs from 1 to 5:
| Level | Description | What it means in practice |
|---|---|---|
| 1 — Low | Generally stable snowpack | Avalanche triggering possible only on very steep slopes with very heavy loads. Rare in Scotland. |
| 2 — Moderate | Heightened conditions on specific terrain features | Triggering possible, mainly by high additional loads such as a group, on the steep slopes the forecast names. |
| 3 — Considerable | Unstable slabs on steep slopes | Human-triggered avalanches likely on steep slopes. Natural avalanches possible. Most Scottish fatalities occur here. |
| 4 — High | Very unstable snowpack | Triggering likely on many steep slopes, even by a single walker. Large natural avalanches possible. Runout extends further than expected. |
| 5 — Very High | Extremely unstable snowpack | Numerous large natural avalanches, even in moderately steep terrain. Rare in Scotland, but occurs. |
Reading the aspect and elevation diagrams
The hazard number alone tells you little. The forecast also shows:
The aspect rose
A compass rose coloured to show which aspects (compass directions) are dangerous at each hazard level. In Scotland, north and northeast-facing slopes load most heavily because prevailing southwesterly winds deposit snow on them. But after unusual wind events, any aspect can be dangerous.
The elevation diagram
Shows which elevation bands carry the highest risk — typically above 900m or above 700m depending on the snowpack. Below the affected elevation, the risk is typically lower.
How to use them together: If the forecast shows Considerable on N–NE aspects above 800m, and your planned route crosses north-facing slopes at 900m, you have a problem to plan around — either avoid those slopes, or cross them very early before solar heating, or accept the risk.
The avalanche problem type
SAIS also identifies the problem type:
- Wind slab — the most common Scottish problem. A layer of compacted, wind-deposited snow on lee slopes that can release as a slab. Hard to see from above.
- Persistent slab — an old weak layer buried by subsequent snowfall. Can be triggered days or weeks after it forms; very unpredictable.
- Wet slab — warming temperature causes surface melt, lubricating a weak layer. Afternoon problem in spring.
- Loose snow / point release — unconsolidated snow releasing from a point and spreading downward. Lower consequences than slab but a risk on steep slopes.
What to do with the forecast
Before you go
- Check SAIS the evening before — get the overview and understand the problem type
- Check again the morning of your walk — overnight wind can transform conditions
- Cross-reference with the MWIS mountain weather forecast for your region — high winds + fresh snow overnight means dramatically elevated risk the next day
- Adjust your route to avoid the forecast problem aspects and elevations, or choose a lower-altitude objective
On the hill
The forecast is a starting point, not a guarantee. Conditions can vary significantly from the forecast, and the observer covers a wide area. On the hill, watch for:
- Recent avalanche activity — debris on slopes indicates instability. Do not cross the slope above fresh debris.
- Cracking or "whumpfing" — sounds and cracks radiating from your footsteps indicate an unstable slab. Leave the slope immediately and gently.
- Wind loading — plumes of snow streaming from ridges, cornices building, hollow-sounding snow underfoot on a lee slope
- Rapid temperature rise — warming above 0°C after snow can trigger wet avalanches on sun-facing slopes within hours
SAIS vs MWIS: which to check?
Both. They give different information:
- SAIS (sais.gov.uk) — avalanche hazard, snowpack conditions, aspect and elevation diagrams. Updated once daily from December to April. Check this for winter hill days.
- MWIS (Mountain Weather Information Service, mwis.org.uk) — mountain weather forecast (wind, temperature, cloud, precipitation) for hillwalkers. Updated daily, year-round. Check this for any hill day.
For a winter day, you need both. The hazard level is set by SAIS, not worked out from the wind, but strong winds and heavy snow overnight in the MWIS forecast are a warning that the hill may be worse than the last avalanche report. Read the newest SAIS report before you go.
Where to learn more
The avalanche forecast is a tool for informed decision-making — it is not a substitute for avalanche education. Mountaineering Scotland runs avalanche awareness courses and Glenmore Lodge runs snow and avalanche courses; check its site for current dates and prices. If you plan to spend regular winter days in the Scottish hills above 600m, this training is worth doing before you need it.
Try it yourself
gives a summer baseline for your route. Snow and ice slow you down, so allow plenty of extra time on a winter day.
No sign-up required.Frequently Asked Questions
What is the SAIS avalanche forecast?
SAIS — the Scottish Avalanche Information Service — is the publicly funded body that produces daily avalanche hazard forecasts for six mountain regions in Scotland from December to April. Forecasts are produced by field observers who physically check snowpack conditions each day. The service is free at sais.gov.uk and is the primary avalanche safety resource for Scottish hillwalkers.
What time is the SAIS forecast updated?
SAIS publishes a daily report in season, and the site does not state a fixed publication time. Check the report the evening before for the broad picture, then check sais.gov.uk again on the morning of your walk in case a newer report is up.
Is there an avalanche risk on all Scottish Munros in winter?
No. Avalanche risk is specific to slopes above about 30-35° gradient that hold significant snow loading. Lower-angle Munros with rounded tops and gentle ridges carry minimal risk even when the regional forecast is Considerable. The risk is highest in corried mountains with north and northeast-facing hollows: Ben Nevis, Aonach Mor, Cairn Gorm, Beinn Eighe, Liathach, Creag Meagaidh. Flatter plateau hills (e.g. Ben Hope, Ben Klibreck) carry lower risk but are not immune.
What does Considerable (Level 3) mean in practice?
Considerable means human-triggered avalanches are likely on steep slopes. This is the most dangerous rating in practice because it sounds manageable — but it is the level at which the majority of Scottish avalanche accidents occur. Route choice is critical: avoid lee slopes, avoid steep (30°+) snow-covered ground, do not travel beneath loaded slopes, and be ready to turn back if conditions on the hill look worse than the forecast suggested.
Do I need avalanche safety equipment for Scottish hills?
Not as standard for winter walking. Mountaineering Scotland's ThinkWINTER kit list for winter hillwalkers does not include an avalanche transceiver, probe or shovel; it says you may also consider a snow shovel. For a walker the main defence is route choice — read the SAIS forecast where your hill is covered, and keep off steep, snow-loaded slopes. Transceiver, probe and shovel are carried for ski touring and off-piste skiing, and they only help if everyone in the party carries all three and has practised searching with them.
Where can I learn more about Scottish avalanche safety?
Mountaineering Scotland runs avalanche awareness events and the Glenmore Lodge offers snow and avalanche courses at glenmorelodge.org.uk. The SAIS website also has an extensive archive of forecast reports and avalanche incident summaries that are worth reading before your first winter season in the hills.
Related articles
- Winter Hillwalking in Scotland: The Beginner's Guide — ice axe, crampons, and getting started safely
- How to Read the Mountain Weather Forecast — using MWIS and Met Office for hill days
- How to Start Hillwalking in Scotland — the broader beginner guide
- Munros section — individual hill pages with SAIS region links and winter notes
This article is for informational purposes only. Avalanche safety requires practical training and qualified instruction — the information here is not a substitute. Never enter avalanche terrain without appropriate training, equipment and experience. OutdoorSCOT is not liable for any incidents arising from the use of this information.
Sources
- SAIS avalanche forecast — Scottish Avalanche Information Service (six areas; last season's avalanche count; read 2026-10-28)
- Avalanche awareness — Mountaineering Scotland
- ThinkWINTER: clothing and equipment — Mountaineering Scotland, read 2026-10-28
- Avalanche Danger Scale — European Avalanche Warning Services, read 2026-10-28
- MWIS mountain forecasts — Mountain Weather Information Service
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