{"id":181,"date":"2014-06-30T14:47:28","date_gmt":"2014-06-30T14:47:28","guid":{"rendered":"http:\/\/flyfiesch.co.nf\/?page_id=181"},"modified":"2026-03-23T18:21:52","modified_gmt":"2026-03-23T18:21:52","slug":"181-2","status":"publish","type":"page","link":"https:\/\/www.flyfiesch.com\/?page_id=181","title":{"rendered":"F\u00f6hn"},"content":{"rendered":"

I strongly recommend this page on Meteoschweiz<\/a> for an explanation of f\u00f6hn as it affects the Swiss Alps.\u00a0 In particular, you should note this image showing wind directions which indicate f\u00f6hn:<\/p>\n

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Valley wind directions indicating f\u00f6hn<\/p><\/div>\n

Fiesch is \u2013 in theory \u2013 vulnerable to f\u00f6hn from the north as well as the south, but this word is generally used in German-speaking Switzerland to refer to conditions with a southerly origin.\u00a0 Also, some pilots here apply the term somewhat loosely to any adverse winds on the lee side of a mountain range (which are, after all, what we need to be concerned about) so for the purposes of explanation, I have adopted those two conventions here.<\/p>\n

Although getting caught in full-on f\u00f6hn in these big mountains would be unpleasant and dangerous, a forecast of \u201cmild f\u00f6hn tendency\u201d is often associated with excellent flying conditions here, particularly for long one-way XCs to the east, so you may find that you are having to balance this risk against the potential for a good flight.\u00a0 Also, f\u00f6hn may develop gradually during the day, requiring a decision as to whether to continue or abandon flying, so it\u2019s important to be able not only to predict it, but also to recognise its early manifestations.<\/p>\n

When assessing the risk of f\u00f6hn, I start off by taking a glance at the synoptic chart to get an idea of the general weather situation and to put other information in context.\u00a0 An approaching Atlantic depression and cold front usually guarantees its development, which can often start even when the front is still located in the western half of France.\u00a0 This chart shows the typical pattern, with the classic \u201cf\u00f6hn knee\u201d feature in somewhat exaggerated form:<\/p>\n

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Classic synoptic chart associated with f\u00f6hn<\/p><\/div>\n

I then check out a prediction of ground level north-south \u201coverpressure<\/a>\u201d (explained on a separate page) \u2013\u00a0 the\u00a0 difference in atmospheric pressure between Lugano (to the south) and Z\u00fcrich (to the north), which is available at Profiwetter<\/a>:<\/p>\n

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It\u2019s said that the likelihood of f\u00f6hn becomes significant if the value exceeds 4 hPa.\u00a0 However,\u00a0 it really isn\u2019t as simple as that; on that basis 21.09.24 should have been ok, but as the two charts below (from that date) show, it wasn\u2019t.\u00a0 In the spring, 2 hPa can be enough, and higher humidity (or precipitation) on the side of the Alps from which the airflow originates can also increase its likelihood.\u00a0 Another issue is that the pressure difference at altitude may be completely different from the value at ground level (but impossible to determine).\u00a0 In August 2024 there was even one day when this chart showed 5 hPa of north overpressure, but south f\u00f6hn arose around Fiesch because of a significant gradient in the opposite direction higher up.\u00a0 I have also often noticed that a rapid change of pressure in either direction is associated with unexpected winds, not always because that indicates some general weather disturbance around.<\/p>\n

In assessing the risk of f\u00f6hn I pay the greatest attention to the wind forecasts at XCTherm<\/a>, in particular the charts showing the flows at 2,000m.\u00a0 This example shows unmistakeable signs of f\u00f6hn, with an easterly breeze at Visp (when the normal direction would be from the west), a southerly flow in the Haslital to the north of Oberwald (where the Grimseler would usually be blowing from the north), a southerly breeze to the north of Andermatt (when a vigorous northerly is almost always present on a thermic day) and a southerly wind blowing into Disentis (instead of the usual easterly):<\/p>\n

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XCTherm chart predicting winds at 2,000m, showing typical features of f\u00f6hn<\/p><\/div>\n

In the morning, an overall review of the weather stations<\/a> may also reveal f\u00f6hn, as shown here:<\/p>\n

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Wind pattern typical of f\u00f6hn<\/p><\/div>\n

The important features to note on this chart are the same as those in the XCTherm prediction, and also in particular how the winds at lower altitudes in the valley are stronger than those at the peaks, and blowing downwards, not upwards as one would expect in thermic conditions.<\/p>\n

Once you are at any of the Fiescheralp takeoffs, you have a good view of the mountains which form the border between Switzerland and Italy, around 13km to the south-east.\u00a0 It\u2019s quite common to see \u201cf\u00f6hnmauer\u201d there \u2013 a wall of cloud on the ridge \u2013 even on days when f\u00f6hn doesn\u2019t materialise.\u00a0 Take some time to watch this closely; when the cloud appears stationary, the day may well be spared, but if you can see it pouring down the slope towards you like a waterfall, then it\u2019s likely that the flying conditions will be significantly affected (and I would be wondering whether I should be flying at all).<\/p>\n

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Typical appearance from Heimat<\/a> takeoff of \u201cf\u00f6hnmauer\u201d \u2013 a wall of cloud on the ridge across the valley to the south-east of takeoff<\/p><\/div>\n

Once you’re airborne, live readings from weather stations (and visual observation of indicators such as wind turbines and cloud movements) help you to assess if f\u00f6hn is developing.\u00a0 It’s important to realise that the wind direction in nearby passes is of vital importance; if it’s coming towards you then you’re at risk, but when blowing away from you, you’re safe.\u00a0 Local tandem pilots often use their smartphones on the way to takeoff to check out values at Binn, Ulrichen, Visp and Rosswald; winds of more than gentle strength with a significant easterly component ring alarm bells.\u00a0 The wind speed at Binn is the most relevant to Fiesch itself, with 30km\/hr considered by the Flying Center Oberwallis as the upper limit of safety (but note that the downslope direction here, indicating south f\u00f6hn, is from the north-east).\u00a0 Near Ulrichen, it’s helpful to observe the speed and direction in which the Griespass turbines are rotating (anticlockwise is dangerous).\u00a0 When you are flying along the Urserntal, it\u2019s relevant to monitor the readings at Andermatt, G\u00fctsch and B\u00e4lmeten, and to observe the wind turbines in the Gotthardpass and at G\u00fctsch.<\/p>\n

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Wind values indicating the arrival of f\u00f6hn<\/p><\/div>\n

If you are airborne around Fiesch and hazy conditions suddenly clear when the possibility of f\u00f6hn has been predicted for later, this is a sign that it may already have broken through down in the valley and suggests that you have outstayed your welcome.\u00a0 The safest option in this situation may be to land at takeoff level.\u00a0 A more typical scenario is that increasing wind readings or turbulence are approaching your “time to call it a day” threshold, so you decide it\u2019s best to land.\u00a0 In this situation, you should try to avoid locations exposed to wind from the side valleys mentioned above.\u00a0 The Fiesch landing field<\/a> is not exposed to the wind from the Binntal, but Lax (safer if Bise<\/a> has broken through) can be horrendous in that situation.\u00a0 It\u2019s best to avoid landing near Ulrichen<\/a> (or further east) but sufficient wind blowing out of the Agenetal there to cause concern will often be associated with thermodynamic lift on the slope directly opposite this outflow enabling you to gain sufficient height to reach Ritzingen<\/a>, which is likely to be your safest option.\u00a0 You should not overfly the M\u00fcnster sailplane runway<\/a> low (in June, July and August) but if it appears deserted, prioritising your safety may appeal.\u00a0 Near Brig, Bitsch<\/a> is less exposed to the wind blowing down from the Simplon pass than options further west.\u00a0 In the Urserntal<\/a>, Zumdorf (half way between Realp and Hospental, identifiable from the air from the gravel works) is probably your best bet, and near Disentis<\/a>, a downwind dash to Trun<\/a> is likely to be safer than landing there in f\u00f6hn.<\/p>\n

An anomaly to bear in mind is that f\u00f6hn is often associated with a breeze from the north-east in the Fiesch landing field<\/a>, for which there seems no obvious explanation.<\/p>\n

A case study<\/a>, including various charts, illustrates some of these points.<\/p>\n

I hesitate to include an example flight here, as flying with f\u00f6hn around is not to be recommended.\u00a0 This one took place in borderline Lugano\/Z\u00fcrich south overpressure of 4 hPa, with wind readings suggesting significant f\u00f6hn at valley level in Andermatt at the time I overflew the village, making me somewhat apprehensive about my landing options, but led to no problems higher up or when I landed near Ilanz:<\/p>\n

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Flight in borderline f\u00f6hnish conditions (click here<\/a> for 3D visualisation, here<\/a> for XContest details)<\/p><\/div>\n

The header image (showing f\u00f6hnmauer in the Gotthard pass) was taken on another day with excellent conditions for flying from Fiesch over the passes, to Flims<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

I strongly recommend this page on Meteoschweiz for an explanation of f\u00f6hn as it affects the Swiss Alps.\u00a0 In particular, you should note this image showing wind directions which indicate f\u00f6hn: Fiesch is \u2013 in theory \u2013 vulnerable to f\u00f6hn … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":4121,"parent":23,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-181","page","type-page","status-publish","has-post-thumbnail","hentry"],"_links":{"self":[{"href":"https:\/\/www.flyfiesch.com\/index.php?rest_route=\/wp\/v2\/pages\/181"}],"collection":[{"href":"https:\/\/www.flyfiesch.com\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.flyfiesch.com\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.flyfiesch.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.flyfiesch.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=181"}],"version-history":[{"count":90,"href":"https:\/\/www.flyfiesch.com\/index.php?rest_route=\/wp\/v2\/pages\/181\/revisions"}],"predecessor-version":[{"id":4178,"href":"https:\/\/www.flyfiesch.com\/index.php?rest_route=\/wp\/v2\/pages\/181\/revisions\/4178"}],"up":[{"embeddable":true,"href":"https:\/\/www.flyfiesch.com\/index.php?rest_route=\/wp\/v2\/pages\/23"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.flyfiesch.com\/index.php?rest_route=\/wp\/v2\/media\/4121"}],"wp:attachment":[{"href":"https:\/\/www.flyfiesch.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=181"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}