Task I.B
Weather Information
To determine the applicant exhibits satisfactory knowledge, risk management, and skills associated with obtaining, understanding, and applying weather information for a flight under IFR.
Note: If K2 is selected, the evaluator must assess the applicant’s knowledge of at least three sub-elements. If K3 is selected, the evaluator must assess the applicant’s knowledge of at least three sub-elements.
References: 14 CFR part 91, AC 91-92; AIM; FAA-H-8083-2, FAA-H-8083-3, FAA-H-8083-25, FAA-H-8083-28
Quick Review
Conversational Q&A — quiz yourself before the oral.
Flight Service (phone or 1800wxbrief.com) and automated resources like aviationweather.gov — a self-briefing per AC 91-92 is regulatory compliant. Three briefing types:
- Standard — the full package for a flight you haven't briefed yet
- Abbreviated — to update specific items or supplement earlier data
- Outlook — when departure is 6 or more hours away; planning only, follow up with a standard briefing before departure
METAR: the routine report, issued hourly.
SPECI: a special, off-schedule report triggered by significant changes — for example a thunderstorm beginning or ending, or a cloud layer appearing below 1,000 ft that wasn't in the previous report.
Both are surface observations from automated systems, with human augmentation at some larger airports (AIM 7-1-2, TBL 7-1-1).
A Terminal Aerodrome Forecast — a concise statement of expected conditions at an airport for a specified period, using METAR code. Scheduled four times daily at 0000Z, 0600Z, 1200Z, and 1800Z; most locations get a 24-hour forecast period, some get 30 hours. Amended as required — always check the date-time group: FM100000 is 0000Z on the 10th, not 1000Z (AIM 7-1-28).
UA is a routine pilot report; UUA is urgent. Facilities are required to solicit PIREPs when reported or forecast:
- Ceilings at or below 5,000 ft, or visibility at or below 5 miles
- Thunderstorms, or icing of light degree or greater
- Turbulence of moderate degree or greater, wind shear, or volcanic ash
Heights in PIREPs are MSL. Give them freely — they're the best real-time truth about ice and turbulence.
AIRMETs cover en route weather hazardous at intensities below SIGMET criteria:
- Sierra — IFR conditions and extensive mountain obscuration
- Tango — moderate turbulence, sustained surface winds of 30 knots or greater, and nonconvective low-level wind shear
- Zulu — moderate icing and freezing level heights
Over the contiguous U.S. they're graphical, valid at discrete times up to 12 hours out (AIM 7-1-6).
Non-convective weather affecting the safety of all aircraft:
- Severe icing not associated with thunderstorms
- Severe or extreme turbulence or clear air turbulence (CAT) not associated with thunderstorms
- Dust storms or sandstorms lowering surface visibility below 3 miles
- Volcanic ash
Unscheduled; valid 4 hours — except 6 hours for SIGMETs associated with tropical cyclones or volcanic ash clouds (AIM 7-1-6).
Issued for any of:
- Severe thunderstorms: surface winds 50 knots or greater, or hail at the surface 3/4 inch or greater, or tornadoes
- Embedded thunderstorms
- A line of thunderstorms
- Heavy precipitation affecting 40 percent or more of an area of at least 3,000 square miles
Bulletins are issued hourly at H+55, forecast valid up to 1 hour. Any Convective SIGMET implies severe or greater turbulence, severe icing, and low-level wind shear (AIM 7-1-6).
The GFA (aviationweather.gov/gfa) replaced the legacy text area forecast: an interactive display of observations, forecasts, and warnings viewable from 14 hours in the past to 15 hours in the future — thunderstorms, clouds, flight category, precipitation, icing, turbulence, and wind. Icing, turbulence, and wind are forecast in 3,000-ft increments up to 30,000 ft MSL. Static Aviation Cloud/Surface Forecast images are updated every 3 hours with snapshots at 3–18 hours (AIM 7-1-4).
Each station line gives forecast wind and temperature at standard altitudes: direction in tens of degrees true, speed in knots, then temperature in Celsius — 2615+12 means 260° true at 15 knots, +12 °C. Heights are MSL, and briefers interpolate between levels and stations for your cruising altitude (AIM 7-1-5). Every FB carries the reminder "TEMPS NEG ABV 24000" — above 24,000 ft the sign is dropped because temperatures are always negative.
The Storm Prediction Center's forecast of general and severe thunderstorm areas: Day 1, Day 2, and Day 3 outlooks plus a combined Day 4–8 severe weather outlook. Categorical risks, in ascending order: TSTM (general thunderstorms), MRGL, SLGT, ENH, MDT, HIGH (SPC). For IFR planning it's your earliest look at whether convection will own your route.
The surface analysis chart shows where the pressure systems and fronts are — the IFH's planning scenario uses it, along with depictions of IFR-condition areas, to find where conditions are improving and where a diversion to VFR weather could go (IFH ch. 10). Ceiling and visibility products depict the standard flight categories (AIM 7-1-7):
- LIFR — ceiling below 500 ft and/or visibility below 1 SM
- IFR — 500 to below 1,000 ft and/or 1 to below 3 SM
- MVFR — 1,000 to 3,000 ft and/or 3 to 5 SM
- VFR — ceiling greater than 3,000 ft and visibility greater than 5 SM
The big limitation: data-linked NEXRAD mosaic imagery shows where the weather was, not where it is — it can be 15 to 20 minutes older than the age indication on the display, so use it strategically to route around weather, never tactically to pick through cells. FIS-B itself is a free broadcast over the 978 MHz UAT ADS-B network — line-of-sight to ground stations, with products like METARs, TAFs, AIRMETs/SIGMETs, and NEXRAD at defined update and look-ahead ranges (AIM 7-1-9).
Deep Dive
Hazards along an IFR route
The evaluator must assess at least three of the K3 meteorology sub-elements — and the evaluator picks the three, not you. Icing, thunderstorms, fog, and wind shear decide real IFR go/no-go calls, so know them cold; the survey cards further down cover the rest of the list.
Ice forms when supercooled visible moisture strikes the airframe at 0 °C or colder — clear ice near freezing, rime at colder temperatures, mixed in between (the ice types, their aerodynamic effects, and the in-flight escape drill are covered under Task II.A). The weather briefing is where the encounter is won:
- Find the freezing level from AIRMET Zulu and the GFA icing forecasts, and match it against your route altitudes (AIM 7-1-4, 7-1-6)
- Keep an out along the route — an altitude warmer than freezing, or air below the cloud bases
- PIREPs are the best real-time truth about where the ice actually is — give them and get them
A thunderstorm packs nearly every aviation hazard into one bundle — turbulence, hail, lightning, icing, updrafts and downdrafts.
- Circumnavigate strong cells by at least 20 miles; echoes separated by 20–30 miles may still hide severe turbulence
- Overflying: clear the top by 1,000 ft for every 10 knots of wind at that level
- Never fly under a thunderstorm
- Tops above 35,000 ft — extremely hazardous; embedded storms in large cloud masses are the IMC trap
- Radar shows precipitation, not turbulence; lightning risk peaks between –5 °C and +5 °C
Wind shear is dangerous because of the killer sequence: a headwind shear followed by a tailwind/downdraft — you've already pulled power and lowered the nose, leaving you nose-low and power-low near the ground. It's a change in wind speed and/or direction over a short distance, worst near thunderstorms and low-level temperature inversions: a tailwind shearing to a headwind balloons you above glidepath, and a headwind shearing to a tailwind drops you below it. Some airports have LLWAS alerts, and the answer to shear indications early on approach is a prompt missed approach, because recovery at low altitude may be impossible.
Fog needs air cooled to saturation or moisture added to it — expect it when the temperature/dewpoint spread is 5° or less and closing. The classic setup: arriving near dusk with falling temperatures. When fog is in play, plan extra fuel and solid alternates, and track trends en route via ATIS/ASOS/AWOS updates.
Air masses, fronts, and the rest of the K3 list
The remaining sub-elements — stability, moisture, fronts, clouds, frost, obscurations — are the theory behind every product you briefed above.
Heat exchange with the surface sets the character:
Warmed from below: convective currents make the mass unstable — cumulus clouds, showers, turbulence, but good surface visibility.
Cooled from below: the mass turns stable — low stratus clouds and fog, smooth air, and poor surface visibility, because smoke, dust, and haze stay trapped near the surface (PHAK ch. 12).
Add moisture and the pattern becomes your forecast: moist and stable means widespread low ceilings; moist and unstable means convection. Frontal and forecast products only tell you where these air masses are headed.
Warm front: moves slowly (10–25 mph) as warm air slides up over the retreating cold air — expect cirriform then stratiform clouds and fog in a wide band ahead of the boundary, a broad shield of low IFR ceilings, with thunderstorms possible in summer.
Cold front: faster (25–30 mph); the dense air plows under the warm mass like a snowplow, so the weather band is narrow and intense — towering cumulus and cumulonimbus, rain showers, gusty variable winds, and a fast-moving cold front can push a squall line ahead of it, then clear rapidly behind (PHAK ch. 12).
Clouds are classified by base height:
- Low (up to 6,500 ft AGL — stratus, stratocumulus, nimbostratus): carry the ceiling and icing threats from supercooled droplets
- Middle: can hold moderate icing
- High: ice crystals, pose no icing threat
Towering cumulus and cumulonimbus mean instability, turbulence, and thunderstorms — including embedded ones hidden in other layers (PHAK ch. 12).
Frost deposits on cool, clear, calm nights when the surface cools below a below-freezing dew point. It disrupts airflow and can drastically reduce lift — remove it all before flight (effects detailed under Task I.C).
The go/no-go and continue/divert call
Every product you briefed has a shelf life: METARs age by the hour, TAFs get amended, and an AIRMET or SIGMET describes an area within which only part may hold the hazard at any one time (AIM 7-1-6). Brief the forecast, verify with current observations and PIREPs, and keep re-deciding in flight (IR.I.B.R2).
Divert while it's still easy:
- Destination weather trending below your personal minimums — or below approach minimums — while an alternate holds solid conditions (the IFH scenario keeps an MVFR alternate in its hip pocket the whole flight, IFH ch. 10)
- PIREPs of icing at your altitudes with a falling freezing level
- Convective SIGMETs filling in across the route
- Anything that erodes your 91.167 fuel reserve — holding, reroutes, stronger headwinds
The decision rule: if weather is below personal minimums, delaying or diverting is the good decision, not the failure (IFH ch. 10).
Do you need an alternate?
Apply the 1-2-3 rule: no alternate is required only if the destination has a published instrument approach (part 97 or special), and from 1 hour before to 1 hour after your ETA, forecasts show ceiling at least 2,000 ft above the airport elevation and visibility at least 3 SM (91.169(b)). Otherwise file an alternate — and carry the fuel to reach it (91.167). Whether a given airport can legally be your alternate (600-2 / 800-2 and friends) is covered under Task I.C.
Official ACS elementsreference
Knowledge23 elements
The applicant demonstrates understanding of:
IR.I.B.K1Sources of weather data (e.g., National Weather Service, Flight Service) for flight planning purposes.IR.I.B.K2Acceptable weather products and resources required for preflight planning, current and forecast weather for departure, en route, and arrival phases of flight such as:IR.I.B.K2aAirport Observations (METAR and SPECI) and Pilot Observations (PIREP)IR.I.B.K2bSurface Analysis Chart, Ceiling and Visibility Chart (CVA)IR.I.B.K2cTerminal Aerodrome Forecasts (TAF)IR.I.B.K2dGraphical Forecasts for Aviation (GFA)IR.I.B.K2eWind and Temperature Aloft Forecast (FB)IR.I.B.K2fConvective Outlook (AC)IR.I.B.K2gInflight Aviation Weather Advisories including Airmen's Meteorological Information (AIRMET), Significant Meteorological Information (SIGMET), and Convective SIGMETIR.I.B.K3Meteorology applicable to the departure, en route, alternate, and destination for flights conducted under Instrument Flight Rules (IFR) to include expected climate and hazardous conditions such as:IR.I.B.K3aAtmospheric composition and stabilityIR.I.B.K3bWind (e.g., windshear, mountain wave, factors affecting wind, etc.)IR.I.B.K3cTemperature and heat exchangeIR.I.B.K3dMoisture/precipitationIR.I.B.K3eWeather system formation, including air masses and frontsIR.I.B.K3fCloudsIR.I.B.K3gTurbulenceIR.I.B.K3hThunderstorms and microburstsIR.I.B.K3iIcing and freezing level informationIR.I.B.K3jFog/mistIR.I.B.K3kFrostIR.I.B.K3lObstructions to visibility (e.g., smoke, haze, volcanic ash, etc.)IR.I.B.K4Flight deck instrument displays of digital weather and aeronautical information.
Risk Management8 elements
The applicant is able to identify, assess, and mitigate risk associated with:
IR.I.B.R1Making the go/no-go and continue/divert decisions, including:IR.I.B.R1aCircumstances that would make diversion prudentIR.I.B.R1bPersonal weather minimumsIR.I.B.R1cHazardous weather conditions, including known or forecast icing or turbulence aloftIR.I.B.R2Use and limitations of:IR.I.B.R2aInstalled onboard weather equipmentIR.I.B.R2bAviation weather reports and forecastsIR.I.B.R2cInflight weather resources
Skills4 elements
The applicant exhibits the skill to:
IR.I.B.S1Use available aviation weather resources to obtain an adequate weather briefing.IR.I.B.S2Analyze the implications of at least three of the conditions listed in K3a through K3l, using actual weather or weather conditions provided by the evaluator.IR.I.B.S3Correlate weather information to make a go/no-go decision.IR.I.B.S4Determine whether an alternate airport is required, and, if required, whether the selected alternate airport meets regulatory requirements.