How 5/8 cloud cover at 10,000 feet AGL becomes BKN100 in LAWRS reports

Understanding the sky’s shorthand in LAWRS reports

If you’re staring at a LAWRS-style weather snippet and wondering what those three little letters mean, you’re not alone. The sky loves to speak in a language that looks tiny at first glance but carries a lot of weight for a pilot planning a flight. Let’s unpack one classic example you’ll come across: five-eighths cloud cover at 10,000 feet AGL. How is that encoded in column 10? And why does it matter?

What the cloud codes really say

Think of cloud coverage as a simple meter for how full the canopy looks overhead. In aviation weather reporting, we use four main terms to describe the sky:

• SCT — scattered clouds. That means about 1/8 to 4/8 of the sky is covered.

• BKN — broken clouds. That’s 5/8 to 7/8 coverage.

• OVC — overcast. The ceiling is 8/8, or the whole sky is covered.

• CLR — clear. No significant clouds in the sky.

These aren’t random letters; they’re a compact way to flag how much of the sky is cloudy. A pilot uses this, along with altitude data, to judge whether there’s a good chance of cloud layers affecting visibility, instrument approaches, or airspace procedures.

Now, the catch: the number after the cloud code

When you see a code like BKN100, you’re looking at two pieces of information rolled into one:

• The cloud cover indicator (BKN for broken).

• The base altitude of that cloud deck, expressed in hundreds of feet.

So, BKN100 means broken clouds with the base at 10,000 feet. The “100” isn’t 100 feet; it’s 100 hundreds of feet — i.e., 10,000 feet.

Here’s how that plays out in the example you asked about

• The sky cover is five-eighths, which falls into the category of broken clouds (BKN). That part matches the “five-eighths” description.

• The cloud base is at 10,000 feet above ground level (AGL). In the code, that’s written as 100 (10,000 feet ÷ 100).

• Put together, the correct encoding is BKN100.

Let me explain why the pieces fit

Breaking down the logic helps you remember it on the spot:

• Five-eighths to seven-eighths cloud cover = BKN. The weather world reserves SCT for lighter coverage and OVC for the sky’s ceiling being fully covered.

• The height after the code is a simple math shortcut. Aviation folks love quick references. Instead of writing 10,000 feet, they use the base altitude in hundreds of feet, so you get a compact “100.”

• The combination BKN100 tells a pilot not only how much of the sky is cloudy but also where that cloud layer sits, which is critical for flight planning, instrument conditions, and decision-making.

How this differs if the numbers change

If the sky were completely filled with clouds, you’d see OVC followed by a height, like OVC065 for an overcast layer with a base at 6,500 feet. If only a small puff of cloud was there, SCT050 or SCT020 would show up, meaning 1/8–4/8 coverage with a base higher or lower than 2,000 feet, depending on the exact data. CLR would indicate a clear sky, no significant clouds nearby.

The altitude piece matters more than you might think

Altitude isn’t just “how high the clouds are.” It’s about what a pilot will encounter along the route or during a landing. A cloud base at 10,000 feet AGL can affect climb-out and cruise segments in ways that matter for performance calculations, airspace separation, and even fuel planning. When you’re scanning the METAR-like fields in LAWRS, the base height helps you map out potential weather-related hazards, from instrument meteorological conditions (IMC) to stepping-stone ceilings for transition levels.

A quick mental model you can rely on

• Cloud cover equals a quick opacity check: SCT is light, BKN is substantial but not a full blanket, OVC is a full cover, CLR is no significant clouds.

• The number after the code equals the base height in hundreds of feet, with the example here translating to 10,000 feet.

• Put together, BKN100 means “there’s a broken deck starting at 10,000 feet,” a useful cue for wind shear plans, route adjustments, or approach selection.

Why pilots care about this exact pairing

Cloud ceilings aren’t just an aesthetic detail. They influence:

• Visual vs. instrument flight rules (VFR vs. IFR) decisions. A higher or lower deck can tip the balance.

• Approach and departure procedures. If the base is down around 2,500 feet or 4,000 feet, it changes safe glide paths and missed-approach criteria.

• Terrain and obstacle clearance. Higher bases can offer more night visibility, but may still interact with mountain waves or desert haze.

A few practical takeaways

• Memorize the main cloud codes: SCT, BKN, OVC, CLR. They’re the alphabet you’ll see again and again.

• Remember the height rule: the digits after the code represent hundreds of feet. 100 = 10,000 feet, 060 = 6,000 feet, and so on.

• Pay attention to AGL vs. MSL. In the example, the base is given as 10,000 feet AGL. If you see MSL data, the meaning shifts a little because it’s tied to ground elevation rather than your immediate altitude.

Common pitfalls and how to avoid them

• Mixing up SCT and BKN ranges. SCT is 1/8–4/8; BKN is 5/8–7/8. If you’re unsure, picture the sky as a pizza: a few slices here and there vs. a big, uneven crust covering most of the dome.

• Reading the height as feet without the “hundreds” trick. The code’s number always multiplies by 100 to give feet. If you see 085, that’s 8,500 feet, not 85 feet.

• Forgetting AGL vs. MSL. If the report explicitly uses AGL, treat the base height as above the ground directly beneath you. LEVEL-correctness matters when you’re at different elevations.

A tiny practice scenario you can try

Here’s a straightforward thought exercise to lock in the idea:

• If you see SCT060 in column 10, what does that mean?

• Answer: Scattered clouds with a base at 6,000 feet. It’s a lighter sky condition than BKN, but you still have to plan for possible holes or climbs through a mid-level cloud layer.

Another one for the road:

• If the sky shows OVC100, what’s the likely impact?

• Answer: Overcast with a base at 10,000 feet. That’s a dense ceiling that could imply IFR conditions along parts of the route or during certain phases of flight.

Connecting these ideas to everyday flight planning

I’ll spare you the jargon soup and keep it real. When you’re plotting a flight, you look at the sky as a map—just a sky map instead of a ground map. The cloud coverage tells you where you can probably maintain visual reference and where you should switch to instruments. The base height tells you what altitude windows you might have for safe climbs, descents, and transitions through airway segments. It’s a practical puzzle, not a trivia test.

A friendly mnemonic to keep in mind

• BKN equals “breaks in the sky,” meaning more cloud between you and the ground, but not a complete ceiling.

• The number after the code equals the base height in hundreds of feet. So 100 means 10,000 feet, 060 means 6,000 feet, etc.

• CLR is clear, OVC is full cover, SCT is light-to-moderate cover. Put together, you can parse many weather reports quickly.

Why this matters in the broader picture

Cloud encoding is just one thread in the fabric of aviation weather. It ties in with visibility, wind, temperature, and icing potential. When you’re building mental maps of a route, these codes are the signposts. They help air traffic control people, flight planners, and crews coordinate safer, smoother operations. And yes, they’re worth committing to memory, because you’ll see them again and again—on raw METARs, in LAWRS-style reports, and in the little notes that pilots reference during preflight briefings.

A quick note about accuracy and clarity

The exact phrasing you’ll see in the field is precise for a reason. A wrong cloud base or the wrong coverage descriptor can lead to mistimed maneuvers or misjudged VFR conditions. That’s why it helps to internalize these basics, so you can skim a report and know what you’re facing in an instant. A fluent reader doesn’t waste time double-checking every digit in high-pressure moments. You want to be able to trust what you see and act on it.

Wrapping it up with a practical mindset

• Cloud coverage is a succinct weather barcode. SCT, BKN, OVC, CLR—these are your core codes.

• The number after the code is the altitude of the cloud base in hundreds of feet. In the example we walked through, 100 equals 10,000 feet.

• At the end of the day, this coding helps you assess risk, plan safe routes, and keep passengers comfortable and safe.

If you keep these ideas in your mental toolbox, you’ll spot patterns faster and read weather reports with more confidence. The sky talks in abbreviations, but the meaning isn’t cryptic once you know the rules. BKN100 isn’t just letters and digits—it’s a heads-up about altitude, ceilings, and how your flight will slice through the airspace. So the next time you see that line, you’ll recognize the story it’s telling: a broken deck at 10,000 feet, waiting to be navigated with care and competence.

Want a quick recap in your own words? Remember this: the cloud code tells you how crowded the sky is, and the number after it tells you how high that crowd begins. Put together, they guide you to safer skies.

If you’d like, I can whip up a few more example scenarios like this, so you can practice recognizing the encoding in everyday LAWRS-style reports. It’s a handy way to keep your mental weather map sharp and ready for real-world flights.