[{"data":1,"prerenderedAt":507},["ShallowReactive",2],{"learn-\u002Flearn\u002Fdecoding-a-snowtam":3,"learn-nav-\u002Flearn\u002Fdecoding-a-snowtam":475},{"id":4,"title":5,"body":6,"date":401,"dateModified":402,"description":403,"draft":404,"extension":405,"faqs":406,"howTo":416,"keyTakeaways":425,"meta":431,"metaDescription":432,"navigation":433,"path":434,"quiz":435,"seo":460,"series":402,"seriesOrder":402,"sources":461,"stem":472,"topic":473,"__hash__":474},"learn\u002Flearn\u002Fdecoding-a-snowtam.md","Decoding a SNOWTAM",{"type":7,"value":8,"toc":387},"minimark",[9,13,19,24,69,73,103,130,146,150,153,196,199,203,218,222,238,242,279,283,301,305,324,344,348,380,384],[10,11,12],"p",{},"A SNOWTAM is the message that tells you what state a runway is actually in when the weather has been at it: how much snow, slush or ice is on the surface, and how good the braking is likely to be. It looks like a wall of codes, but it follows a fixed format built around one idea, the runway split into thirds, each with a condition code.",[14,15,16],"blockquote",{},[10,17,18],{},"This is general educational information, not operational, legal, or regulatory advice. Rules differ by authority and change over time. Always verify against current official sources and follow your operator's approved procedures.",[20,21,23],"h2",{"id":22},"what-a-snowtam-is","What a SNOWTAM is",[10,25,26,27,38,39,42,43,46,47,50,51,57,58,63,64,68],{},"A SNOWTAM is a ",[28,29,30,31],"strong",{},"special-series ",[32,33,37],"a",{"href":34,"className":35},"\u002Flearn\u002Fglossary#gt-notam",[36],"glossary-link","NOTAM"," that reports the ",[28,40,41],{},"surface condition"," of an aerodrome's movement area when it is affected by ",[28,44,45],{},"snow, ice, slush, standing water, frost"," or similar contaminants. It is issued in a ",[28,48,49],{},"standardised format",", set out in the ",[32,52,56],{"href":53,"rel":54},"https:\u002F\u002Fstore.icao.int\u002Fen\u002Fprocedures-for-air-navigation-services-aeronautical-information-management-doc-10066",[55],"nofollow","PANS-AIM (Doc 10066)"," under the parent ",[32,59,62],{"href":60,"rel":61},"https:\u002F\u002Fstore.icao.int\u002Fen\u002Fannex-15-aeronautical-information-services",[55],"ICAO Annex 15"," aeronautical-information standards, so a SNOWTAM from one country reads the same way as one from another. Because it is a NOTAM, it sits within the same briefing system as the rest of the ",[32,65,67],{"href":66},"\u002Flearn\u002Funderstanding-notams","NOTAMs"," you read before a flight, but it carries a specific, weather-driven payload about the surface.",[20,70,72],{"id":71},"the-runway-condition-code-and-the-thirds","The runway condition code and the thirds",[10,74,75,76,85,86,94,95,98,99,102],{},"Since the worldwide adoption of the ",[28,77,78,79,84],{},"Global Reporting Format (",[32,80,83],{"href":81,"className":82},"\u002Flearn\u002Fglossary#gt-grf",[36],"GRF",")",", the heart of a SNOWTAM is the ",[28,87,88,89,84],{},"runway condition code (",[32,90,93],{"href":91,"className":92},"\u002Flearn\u002Fglossary#gt-rwycc",[36],"RWYCC",", and the key thing to know is that the runway is divided into ",[28,96,97],{},"three thirds",", each reported separately. The codes run from ",[28,100,101],{},"6 down to 0",":",[104,105,106,117,120],"ul",{},[107,108,109,112,113,116],"li",{},[28,110,111],{},"6"," is a ",[28,114,115],{},"dry"," runway, the best braking;",[107,118,119],{},"the middle values describe progressively more contaminated surfaces with poorer braking;",[107,121,122,125,126,129],{},[28,123,124],{},"0"," is the ",[28,127,128],{},"worst",", where braking is essentially nil.",[10,131,132,133,136,137,140,141,145],{},"So a runway reported as ",[28,134,135],{},"5\u002F5\u002F3"," means good conditions on the first two thirds and a poorer surface on the last third, read in the direction of the ",[28,138,139],{},"lower runway designator",". Our guide to ",[32,142,144],{"href":143},"\u002Flearn\u002Fthe-global-reporting-format-for-runway-conditions","the global reporting format for runway conditions"," explains how those codes are assessed and what each means for braking and for the crosswind you should accept; this guide is about reading the SNOWTAM that delivers them.",[20,147,149],{"id":148},"the-runway-condition-section","The runway condition section",[10,151,152],{},"The runway condition part of a SNOWTAM, group by group, identifies:",[104,154,155,166,172,178,184,190],{},[107,156,157,158,161,162,165],{},"the ",[28,159,160],{},"aerodrome"," by its location indicator, and the ",[28,163,164],{},"date and time"," the assessment was made;",[107,167,157,168,171],{},[28,169,170],{},"runway designator",";",[107,173,157,174,177],{},[28,175,176],{},"three runway condition codes",", one per third;",[107,179,157,180,183],{},[28,181,182],{},"percentage coverage"," of contaminant on each third;",[107,185,157,186,189],{},[28,187,188],{},"depth"," of contaminant where relevant;",[107,191,157,192,195],{},[28,193,194],{},"type of contaminant",", such as dry snow, wet snow, slush, compacted snow or ice.",[10,197,198],{},"Read together, these tell you not just a single number but a picture: how much of each third is covered, how deep, with what, and the resulting condition code. That detail is what feeds an aircraft's landing and take-off performance assessment, which is why the report is so structured.",[20,200,202],{"id":201},"the-situational-awareness-section","The situational-awareness section",[10,204,205,206,209,210,213,214,217],{},"After the runway condition section comes a ",[28,207,208],{},"situational-awareness"," section, which carries the wider picture: the state of ",[28,211,212],{},"taxiways and aprons",", ",[28,215,216],{},"drifting snow",", reduced runway width, snowbanks, or any other hazard on the movement area. It is plain-language and free-format compared with the coded runway section, but it matters, because a runway can read well while a taxiway or apron is treacherous, and drifting snow can change the runway itself between assessments. Reading the situational-awareness section stops you from fixating on the runway codes and missing a hazard on the way to or from it.",[20,219,221],{"id":220},"how-it-reaches-you-and-why-the-time-matters","How it reaches you, and why the time matters",[10,223,224,225,229,230,233,234,237],{},"A SNOWTAM arrives through the AIS and NOTAM system as part of your ",[32,226,228],{"href":227},"\u002Flearn\u002Fthe-preflight-information-bulletin","briefing",", and like any surface report it has a ",[28,231,232],{},"shelf life",". The condition described is the condition at the ",[28,235,236],{},"assessment time","; fresh snow, a thaw, or treatment of the surface can change it quickly, so a new assessment supersedes the old. The assessment time is therefore one of the first things to read and one of the last things to forget: an hour-old SNOWTAM in active snowfall is describing a runway that may no longer exist in that state.",[20,239,241],{"id":240},"what-the-contaminant-types-mean","What the contaminant types mean",[10,243,244,245,247,248,251,252,255,256,251,259,262,263,266,267,270,271,274,275,278],{},"The condition code summarises the surface, but the ",[28,246,194],{}," the SNOWTAM names tells you why, and the types behave very differently. ",[28,249,250],{},"Dry snow"," and ",[28,253,254],{},"frost"," are the least slippery of the winter contaminants; ",[28,257,258],{},"wet snow",[28,260,261],{},"slush"," are worse and can also create drag and spray that affect the take-off; ",[28,264,265],{},"compacted snow"," packs to a firm but slippery surface; and ",[28,268,269],{},"ice",", especially ",[28,272,273],{},"wet ice",", is the worst, sitting at the bottom of the condition-code scale. ",[28,276,277],{},"Standing water"," brings its own hazard of aquaplaning at speed. The SNOWTAM reports the type for each third precisely because the same depth of two different contaminants gives very different braking, and because the type, not just the code, feeds the aircraft's performance assessment.",[20,280,282],{"id":281},"when-a-snowtam-is-issued-and-cancelled","When a SNOWTAM is issued and cancelled",[10,284,285,286,289,290,293,294,297,298,300],{},"A SNOWTAM is issued when the surface condition changes significantly and is ",[28,287,288],{},"re-issued"," as conditions change again, so a sequence of them traces the runway through a snow event. It is ",[28,291,292],{},"cancelled"," when the contaminant is cleared and the runway returns to a normal state, or it lapses after its validity. The practical consequence is that you read the ",[28,295,296],{},"latest"," SNOWTAM, check its ",[28,299,236],{}," against the current weather, and treat an older one as superseded. In active snowfall, the gap between when the runway was assessed and when you will land is the number that matters most, because the surface you touch down on is the one at your landing time, not the one in the report.",[20,302,304],{"id":303},"a-worked-example","A worked example",[10,306,307,308,310,311,313,314,317,318,320,321,323],{},"You pull the SNOWTAM for your destination. It identifies the ",[28,309,160],{}," and the ",[28,312,236],{},", which you note is recent. For ",[28,315,316],{},"runway 27"," it reports condition codes ",[28,319,135],{},": good on the first two thirds and poorer on the last. The contaminant section shows the first two thirds with a thin coverage and the last third reporting ",[28,322,265],{}," over a high percentage of its area, which is why its code dropped to 3.",[10,325,326,327,330,331,333,334,337,338,340,341,343],{},"You take that to the ",[32,328,329],{"href":143},"global reporting format"," to understand what a 3 on the rollout third means for your braking and crosswind. Then you read the ",[28,332,208],{}," section, which warns of a ",[28,335,336],{},"snowbank"," beside the runway and ",[28,339,216],{}," on a taxiway, both of which you factor into your taxi plan. Last, you re-check the ",[28,342,236],{}," against the current weather: snow is still falling, so you treat the report as a snapshot that may worsen and plan accordingly. The block of codes has become a clear picture of a runway that is mostly good but degraded at the far end, with hazards beside it and a forecast that could change it.",[20,345,347],{"id":346},"common-pitfalls","Common pitfalls",[104,349,350,356,362,368,374],{},[107,351,352,355],{},[28,353,354],{},"Reading one code for the whole runway."," The report gives three codes, one per third; the worst third often matters most.",[107,357,358,361],{},[28,359,360],{},"Ignoring the contaminant type and coverage."," The code summarises, but the type and percentage tell you why, and feed performance.",[107,363,364,367],{},[28,365,366],{},"Skipping the situational-awareness section."," Taxiways, aprons, snowbanks and drifting snow can be worse than the runway.",[107,369,370,373],{},[28,371,372],{},"Forgetting the assessment time."," Surface conditions change fast; an old SNOWTAM in active weather may no longer be true.",[107,375,376,379],{},[28,377,378],{},"Reading the thirds in the wrong direction."," They run in the direction of the lower runway designator, so confirm which end is which.",[20,381,383],{"id":382},"in-pilot-efb","In Pilot EFB",[10,385,386],{},"Pilot EFB is a study and planning companion that keeps your NOTAMs, including SNOWTAMs, and the rest of a briefing in one offline-first place, so a briefing you have already pulled stays readable away from a signal. It helps you read and study the format, but it does not assess the runway, compute your performance, or replace the official report, and pulling a fresh SNOWTAM needs a connection. Pilot EFB is not a certified Electronic Flight Bag, so treat it as a study and planning aid and brief from your official source of record.",{"title":388,"searchDepth":389,"depth":389,"links":390},"",2,[391,392,393,394,395,396,397,398,399,400],{"id":22,"depth":389,"text":23},{"id":71,"depth":389,"text":72},{"id":148,"depth":389,"text":149},{"id":201,"depth":389,"text":202},{"id":220,"depth":389,"text":221},{"id":240,"depth":389,"text":241},{"id":281,"depth":389,"text":282},{"id":303,"depth":389,"text":304},{"id":346,"depth":389,"text":347},{"id":382,"depth":389,"text":383},"2026-05-12",null,"What a SNOWTAM reports, how it carries the runway condition code for each third of the runway under the global reporting format, and how to read one.",false,"md",[407,410,413],{"q":408,"a":409},"What does a SNOWTAM report?","A SNOWTAM is a special-series NOTAM reporting the surface condition of an aerodrome movement area affected by snow, ice, slush, standing water or frost, in a standardised format. Under the global reporting format its heart is the runway condition code, with the runway split into three thirds, each given a code from 6 (a dry runway) down to 0 (the worst).",{"q":411,"a":412},"How do you read the runway condition codes?","The runway is divided into three thirds, read in the direction of the lower runway designator, and each third gets a condition code. So a runway reported as 5\u002F5\u002F3 means good conditions on the first two thirds and a poorer surface on the last. The report also gives the percentage coverage, the depth and the type of contaminant for each third, which feed the aircraft's performance assessment.",{"q":414,"a":415},"Why does the time on a SNOWTAM matter?","Because a surface report goes out of date as conditions change. The condition described is the condition at the assessment time, and fresh snow, a thaw or treatment of the surface can change it quickly, so a new assessment supersedes the old. In active snowfall the gap between the assessment time and your landing time is the number that matters most.",{"name":417,"steps":418},"How to decode a SNOWTAM",[419,420,421,422,423,424],"Identify the aerodrome by its location indicator and read the date and time the runway was assessed.","For the runway, read the three runway condition codes, one for each third in the direction of lower runway designator.","Read the percentage coverage, the depth and the type of contaminant reported for each third.","Read the situational-awareness section for taxiways, aprons, drifting snow and other hazards.","Cross-reference the runway condition code against the global reporting format to understand the expected braking.","Check the assessment time and validity, because a surface report goes out of date as conditions change.",[426,427,428,429,430],"A SNOWTAM is a special-series NOTAM reporting an aerodrome's surface condition under snow, ice, slush, water or frost.","Under the global reporting format the runway is split into three thirds, each with a runway condition code from 6 (dry) down to 0 (worst).","The runway section also gives the coverage, depth and type of contaminant for each third.","A situational-awareness section covers taxiways, aprons, snowbanks and drifting snow.","Conditions change fast, so read the latest SNOWTAM and check its assessment time against the current weather.",{},"What a SNOWTAM reports, how it carries the runway condition code per runway third under the global reporting format, and how to read one.",true,"\u002Flearn\u002Fdecoding-a-snowtam",[436,444,452],{"q":408,"options":437,"answer":442,"explanation":443},[438,439,440,441],"The forecast wind for the next day","The surface condition of an aerodrome movement area affected by snow, ice, slush, frost or water","The runway lighting schedule","The fuel prices at the aerodrome",1,"A SNOWTAM is a special-series NOTAM that reports the surface condition of an aerodrome movement area affected by snow, ice, slush, standing water, frost and similar contaminants, in a standardised format.",{"q":445,"options":446,"answer":442,"explanation":451},"Under the global reporting format, how is the runway condition reported along the runway?",[447,448,449,450],"A single code for the whole runway","A runway condition code for each of the three thirds of the runway","Only at the touchdown point","As a percentage only","The runway is divided into three thirds, and a runway condition code from 6 down to 0 is reported for each third, so a code like 5\u002F5\u002F3 describes the runway third by third.",{"q":453,"options":454,"answer":442,"explanation":459},"On the runway condition code scale, what does 6 represent?",[455,456,457,458],"The worst, nil braking","A dry runway, the best condition","A closed runway","A flooded runway","The runway condition code runs from 6, a dry runway with the best braking, down to 0, the worst. So a higher number is a better surface.",{"title":5,"description":403},[462,464,466,469],{"label":463,"url":60},"ICAO Annex 15: Aeronautical Information Services",{"label":465,"url":53},"ICAO Doc 10066: PANS-AIM (SNOWTAM format)",{"label":467,"url":468},"ICAO Annex 14: Aerodromes, Volume I (global reporting format)","https:\u002F\u002Fstore.icao.int\u002Fen\u002Fannex-14-aerodromes",{"label":470,"url":471},"FAA Aeronautical Information Manual, Chapter 4 Section 3 (runway condition reports)","https:\u002F\u002Fwww.faa.gov\u002Fair_traffic\u002Fpublications\u002Fatpubs\u002Faim_html\u002Fchap4_section_3.html","learn\u002Fdecoding-a-snowtam","Briefing","YF7-iqOX7hE2n0qHsrvVIc4YshseRytbLHO2PFtFDGk",{"related":476,"newer":494,"older":501,"series":402},[477,483,489],{"path":478,"title":479,"description":480,"date":481,"topic":473,"draft":404,"minutes":482,"series":402,"seriesOrder":402},"\u002Flearn\u002Freading-an-aerodrome-chart","Reading an aerodrome chart","How an aerodrome chart maps the runways, taxiways, holding positions, hot spots and aprons, and how to use it to plan a taxi and avoid a runway incursion.","2026-06-18",7,{"path":484,"title":485,"description":486,"date":487,"topic":473,"draft":404,"minutes":488,"series":402,"seriesOrder":402},"\u002Flearn\u002Ficao-vs-iata-codes","ICAO vs IATA codes explained","The 4-letter ICAO location indicators used for flight planning and weather versus the 3-letter IATA codes on your boarding pass, plus airline codes.","2026-06-08",3,{"path":490,"title":491,"description":492,"date":493,"topic":473,"draft":404,"minutes":482,"series":402,"seriesOrder":402},"\u002Flearn\u002Ftemporary-airspace-restrictions","Temporary airspace restrictions","What temporary flight restrictions are, why they are imposed, and how the US TFR compares with the UK restricted area and emergency restriction of flying.","2026-06-07",{"path":495,"title":496,"description":497,"date":498,"topic":499,"draft":404,"minutes":500,"series":402,"seriesOrder":402},"\u002Flearn\u002Frecency-and-currency","Recency and currency","The difference between being legally current and proficient, with the EASA and FAA recent-experience rules for passengers, night and instrument flight.","2026-05-13","Logbook",4,{"path":502,"title":503,"description":504,"date":505,"topic":506,"draft":404,"minutes":488,"series":402,"seriesOrder":402},"\u002Flearn\u002Fmach-number-and-true-airspeed","Mach number, true airspeed and the speed of sound","How the speed of sound depends on temperature, why Mach number rises as you climb at constant true airspeed, and how true airspeed and Mach relate.","2026-05-11","Operations",1782839404810]