Weather to Fly

The aviation weather reporting system can be confusing.  This article from the FAA gives tips on How to Obtain a Good Weather Briefing.  To it I add, my advice:

  • If you are calling for a weather briefing, back that up by using the Duats site. It is easier for me to look at a report in writing than to hear a briefer ramble on about it. Check weather online first and then you can ask your briefer for trends and clarification on the phone rather than trying to get everything from them. If you can only call, listen closely.
  • Learning WX codes can be difficult.  Duats will give you long text and WX codes if you specify – so use both for learning. You can also download a short training pamphlet that covers the codes HERE.  A more thorough guide comes with our Airplane Pilot Training Kit and many of the other kits.  
  • My best advice is that it gets easier with time so keep working on it.  Eventually, codes will become faster and easier than reading long text description of conditions.


The “Anatomy” of a Good Weather Briefing

Here are some “tips” on how to get a good weather briefing. A good weather briefing starts with developing an awareness of the overall “big picture” before attempting to get a detailed weather briefing. At many locations, you can learn about the big picture by listening to the TWEB, an acronym for Transcribed Weather Broadcast; the TIBS for Telephone Information Briefing Service (automated FSSs); or PATWAS, for Pilot’s Automatic Telephone Weather Answering Service (nonautomated FSSs); IVRS, for Interim Voice Response System; or by watching a good television weather report such as AM Weather. The Airport Facility Directory, the AOPA Handbook for Pilots, and other aviation reference materials list the sources of weather information. When you are ready to call for a weather briefing, the telephone number for the Federal Aviation Administration (FAA) may be found in these same references.

In a telephone book, look under United States Government/Department of Transportation/Federal Aviation Administration/Flight Service Station. Make sure your planned route of flight is worked out and your flight plan partially completed before you make the telephone call.

A universal toll free number for Flight Service Stations (FSS) is being established in conjunction with the FSS Modernization Program. In the areas of the country where this system is operational, you can dial 1-800 WX BRIEF (1-800-992-7433) and you will be switched automatically to the FSS or automated flight service station that serves the area from which you are calling. When you reach the FSS, you will be answered by a briefer. If you are connected to one of our automated FSSs, you will be answered by a recorded announcement which includes the name of the facility, followed by instructions for both touch-tone and rotary dial telephone users. Touch-tone users can elect to talk to a briefer or any of the direct access services, or can select a menu which identifies those services and the associated codes for each. The direct access services available from an automated FSS are recorded weather and aeronautical information and “fast file” flight plan filing. If you are using a rotary dial or pulse-tone equipped telephone, you will be switched automatically to a briefer, who will provide the information desired; or, if requested, can connect you to one of the direct access services.

So that your preflight briefing can be tailored to your needs, give the briefer the following information:

– Your qualifications, e.g., student, private, commercial, and whether instrument rated. – The type of flight contemplated, either VFR or IFR. – The aircraft’s N-number identification. If you do not know the N-number, the pilot’s name. – The aircraft type. – Your departure point. – Your proposed route of flight. – Your destination. – Your proposed flight altitude(s). – Your estimated time of departure (ETD). – Your estimated time enroute.

Request that the briefer provide you with a standard weather briefing. Then LISTEN to the briefer. The briefer will be following procedures and phraseology used by FAA personnel providing flight services. The briefer will advise you of any adverse conditions along your proposed route of flight. When a VFR flight is proposed and actual or forecast conditions make VFR flight questionable, the briefer will describe the conditions and may advise you that “VFR flight (is) not recommended.” If this occurs, or if you feel that the weather conditions are clearly beyond your capabilities (or that of your aircraft or equipment), you should consider terminating the briefing. This will free the briefer to handle other incoming calls.

The briefer will summarize weather reports and forecasts. After the conclusion of the briefing, if there is anything that you do not understand about the weather briefing, let the briefer know. If terminology is used that you do not understand, ask the briefer to explain it. A briefer who talks too fast should be asked to speak more slowly. The amount of detail in your weather briefing will depend upon how complicated the weather situation really is. Remember, if the weather situation really is “iffy,” expect – and insist upon – a standard weather briefing. It is both your legal responsibility and your prerogative as a pilot to do so.

Standard Preflight Weather Briefing

At a minimum, your preflight briefing should include the following elements:

– Adverse Conditions – Significant meteorological and aeronautical information that might influence you, the pilot, to alter your proposed route of flight or even cancel your flight entirely (e.g., thunderstorms, icing, turbulence, low ceilings or visibilities, airport closures). Expect the briefer to emphasize conditions that are particularly significant, such as low level wind shear, embedded thunderstorms, reported icing, or frontal zones.

– Synopsis – A brief statement as to the cause of the weather (e.g., fronts or pressure systems) which might affect your proposed route of flight.

– Current Conditions – When your proposed time of departure is within 2 hours, a summary of the current weather, including PIREPs, applicable to your flight will be given.

– Enroute Forecast – Expect the briefer to summarize forecast conditions along your proposed route in a logical order, i.e., climbout, enroute, and descent.

– Destination Forecast – The destination forecast for your planned ETA will be provided, including any significant changes within 1 hour before and after your planned time of arrival.

– Winds Aloft – The briefer will summarize forecast winds aloft for the proposed route. Temperature information will be provided on request.

– Notice to Airmen (NOTAMs) – “Current” NOTAMs pertinent to your proposed route of flight will be provided. However, information on military training routes and areas (MTR and MOA), along with PUBLISHED NOTAMs and Special Notices, must be specifically requested.


The Standard Preflight Briefing

In person or by phone from an FSS, your preflight weather briefing should include:

* Adverse conditions, Including SIGMETs, convective SIGMETs, AIRMETs, and CWAs. * Synopsis * Current conditions, including PIREPs * Enroute forecast * Destination forecast * Winds aloft forecast * NOTAMs

Don’t forget – first give the briefer the flight information needed to compile a good briefing; then listen to the briefer. Ask questions If you don’t understand or need more information.

Abbreviated Preflight Briefing

Request an Abbreviated Briefing when you need information to supplement mass disseminated data, update a previous briefing, or when you need only one or two specific items. Provide the briefer with appropriate background information, the time you received the previous information, and/or the specific items needed. You should indicate the source of the information already received so that the briefer can limit the briefing to the information that you have not received, and/or appreciable changes in meteorological conditions since your previous briefing. To the extent possible, the briefer will provide the information in the sequence shown for a Standard Briefing. If you request only one or two specific items, the briefer will advise you if adverse conditions are present or forecast. Details on these conditions will be provided at your request.

Outlook Preflight Briefing

You should request an Outlook Briefing whenever your proposed time of departure is 6 or more hours from the time of the briefing. The briefer will provide available forecast data applicable to the proposed flight. This type of briefing is provided for planning purposes only. You should obtain a Standard Briefing prior to departure in order to obtain such items as current conditions, updated forecasts, winds aloft and NOTAMs.

Inflight Briefing

You are encouraged to obtain your preflight briefing by telephone or in person before departure. In those cases where you need to obtain a preflight briefing or an update to a previous briefing by radio, you should contact the nearest FSS to obtain this information. After communications have been established, advise the specialist of the type of briefing you require and provide appropriate background information. You will be provided information as specified in the above paragraphs, depending on the type of briefing requested. In addition, the specialist will recommend shifting to the FLIGHT WATCH frequency when conditions along the intended route indicate that it would be advantageous to do so.

Following any briefing, feel free to ask for any information that you or the briefer may have missed. It helps to save your questions until the briefing has been completed. This enables the briefer to present the information in a logical sequence, and reduces the chance of important items being overlooked.

Weather Judgment

Judgment, which may be defined as the power of arriving at a wise decision, is the combined result of knowledge, skills, and experience. You can improve your “Go or No-Go” weather judgment by setting personal weather minimums that are higher than the legal minimums. For instance, use a 2,000 foot ceiling and 5 miles visibility, instead of the legal 1,000 and 3, until you are familiar with flight under those conditions. You may then gradually reduce your personal minimums to whatever limits you find comfortable, a or above the legal limits.

Here are some obvious “DO NOTS” for everyone beginner and pro alike:

* DO NOT fly in or near thunderstorms. Scattered thunderstorms may be safely circumnavigated, but do not try to fly through or under one.

* DO NOT continue VFR into IFR weather conditions at any time unless you are IFR rated and have the appropriate Air Traffic Control (ATC) clearance. Wait it out or turn around if you find enroute weather lowering to IFR conditions. Do not forget there will be areas enroute – or even near airports – which are below VFR minimums, whenever reporting stations are at or near VFR minimums. Be especially cautious when the temperature and dewpoint spread is 50 or less – fog may result.

* DO NOT proceed “on top,” hoping to find a hole at the other end or hoping to get ATC to “talk you down” if you get caught on top.

* Allow more margin for weather at night. Scud and lower clouds do not show up very far ahead, particularly when it is a really dark night.

* DO NOT fly into areas of rain when the air temperature is near freezing. Ice on the windshield and on the wings makes for poor VFR flying conditions. Remember too, flight into known icing conditions is prohibited for all aircraft not properly equipped.

And finally, if you do get caught in weather, tell an FSS or another ATC facility. They will do their utmost to help you.


Preliminary Flight Planning – Getting the “Big Picture”

* Media:

– AM Weather on public television stations (consult local TV listings for exact time) – Newspaper weather maps – TV and radio weather reports

* Transcribed Radio Broadcasts:

– National Oceanic and Atmospheric Administration (NOAA) Weather Radio – Transcribed Weather Broadcast (TWEB) on NDBs, VORs, and available by telephone at some locations

* Recorded Telephone Weather:

– Interim Voice Response System (IVRS) – Pilot’s Automatic Telephone Weather Answering Service (PATWAS) – Telephone Information Briefing Service (TIBS)

To Obtain a Standard Preflight Weather Briefing:

* In person or by telephone:

– An FSS

If You Go …

Inflight Weather Update – Sources of inflight weather include:

* Via VHF radio:

– EFAS (FLIGHT WATCH on 122.0 MHz below FL 180 and as published at FL 180 and above for “real time” weather. – FSS -Centers and terminal area facilities will broadcast a SIGMET or CWA alert once on all frequencies upon receipt. – To the extent possible, centers and terminal area facilities will issue pertinent information on weather and assist pilots in avoiding hazardous weather areas, when requested.

* Transcribed radio broadcasts:

– Transcribed Weather Broadcasts (TWEBs) – Hazardous Inflight Weather Advisory Service (HIWAS)

Destination/Arrival Weather can be obtained from the following sources as available:

* Via VHF radio from:

– Enroute Flight Advisory Service (EFAS) – FSSs or other air traffic control facilities – Unicom

* Transcribed VHF radio broadcasts:

– Automatic Terminal Information Service (ATIS)

– On site automated weather observations

If You Don’t Go … Your Alternatives

* Delay/postpone (and get a later preflight weather briefing), or

* Cancel


Area Forecasts (FA)

What are they? Area Forecasts are 12 hour aviation forecasts plus a 6 hour categorical outlook giving general descriptions of cloud cover, weather conditions, and potentially hazardous weather which could impact aircraft operations.

Heights of cloud bases, tops, freezing level, icing, and turbulence, are referenced to mean sea level (MSL). Ceilings, however, are given in heights above ground level (AGL). SIGMET type information affecting a particular area is included in the Area Forecast and, in addition, a separate SIGMET is always issued. AIRMETs are issued only when hazardous conditions develop or are expected to develop which were not adequately covered in the original forecast.

Categorical outlook terms, describing general ceiling and visibility conditions for advanced planning purposes, are defined as follows:

* LIFR (Low IFR) – Ceiling less than 500 feet and/or visibility less than 1 statute mile. * IFR – Ceiling 500 feet to less than 1,000 feet and/or visibility 1 to less than 3 statute miles. * MVFR (Marginal VFR) – Ceiling 1,000 to 3,000 feet and/or visibility 3 to 5 statute miles, inclusive. * VFR – Ceiling greater than 3,000 feet and visibility greater than 5 statute miles; includes sky “clear.”

The causes of LIFR, IFR, or MVFR are indicated by either ceiling or restrictions to visibility, or both. The contraction CIG (for ceiling) and/or weather and obstruction to visibility symbols are used. If winds (or gusts) of 25 knots or greater are forecast for the outlook period, the word WIND is also included for all categories, including VFR.

Example: LIFR CIG – Low IFR due to a low ceiling. Example. IFRF – IFR due to visibility restricted by fog. Example: MVFR CIG H K – Marginal VFR due both to ceiling and to visibility restricted by haze and smoke. Example: IFR CIG R WIND – IFR due both to low ceiling and to visibility restricted by rain; the wind is expected to be 25 knots or greater.

When disseminated? Area Forecasts, each covering a broad geographical area are issued three times a day in the contiguous United States and Alaska, and four times a day in Hawaii.

The dissemination time differs from area to area. Specific schedule times for your location can be obtained by calling the nearest FSS. These forecasts are amended as required.

Sequence (or hourly) Weather Reports (SA)

What are they? Sequence (or hourly) weather reports are specific aviation weather observations taken at designated reporting sites throughout the United States. Usually, but not always, these sites are located on airports.

When produced? Observations are usually made hourly at about 50 minutes past each hour. These observations are transmitted between 55 minutes past each hour and 3 minutes past the hour, and are generally available at all FSSs within 10 minutes of transmission time. Of course, special observations are taken whenever changing weather conditions warrant.

Example of an Hourly Sequence Report:

RDU SA 0150 M50 OVC 10RW – 094/74/59/1009/982/ RB 40/OCNL LTG DSNT SW

Translation – Raleigh-Durham, observation at 0150 ZULU, measured ceiling 5,000 feet overcast, visibility 10 statute miles; light rain showers; sea level pressure 1009.4 millibars; temperature 74° F; dewpoint 59° F; wind from 100° true at 9 knots; altimeter 29.82 inches. Remarks: Rain began at 40 minutes past the hour; occasional lightning to the distant southwest. (Note: When providing advisories to departing or arriving aircraft, air traffic control will give current winds relative to magnetic north.)

Terminal Forecasts (FT)

What are they? Terminal forecasts are issued for specific airports and generally cover a 5 nautical mile radius from the center of the runway complex. They contain information on the expected ceilings, cloud heights and coverage, visibility, weather, obstructions to vision, and surface winds. They are valid for a 24 hour period. The last 6 hours of each forecast contains a categorical outlook statement indicating whether VFR, MVFR, IFR, or LIFR conditions are expected.

Terminal forecasts are written in the following format:

* Station identifier * Date/time group * Ceilings are identified by the letter “C”. * Cloud heights in terminal forecasts are always reported in hundreds of feet above ground level (AGL). This differs from area forecasts where, except for ceilings, the bases of clouds are reported in feet above mean sea level (MSL). * Cloud layers are stated in ascending order of height. * Visibility is reported in statute miles (or fractions thereof up to 2 statute miles), but omitted if the visibility is greater than 6 statute miles. * Weather and obstructions to vision are displayed in standard weather and obstructions to visibility symbols. * Surface wind is reported in tens of degrees from true north and in knots; omitted when less than 10 knots. (Note: Wind direction indicates the direction from which the wind is blowing.) * Remarks

When disseminated? Terminal forecasts are issued three times a day based on the time zone in which the forecast office is located and they are disseminated within 20 minutes after release. Each forecast is amended according to prescribed criteria when required. For specific issuance times contact your local FSS.

Example of a Terminal Forecast:

BOS FT 221010 10 SCT C18 BKN 5SW- 3415G25 OCNL C8X1/2SW 12Z C50 BKN 3312G22 04Z MVFR CIG

Translation – Boston terminal forecast for the 22nd day of the month, valid time 10Z-10Z. Scattered clouds at 1,000 feet (AGL); ceiling 1,800 feet broken (AGL), visibility 5 statute miles; light snow showers; surface wind from 3400 at 15 knots with peak gusts to 25 knots; occasionally, ceiling 800 feet obscured; visibility one-half mile in moderate snow showers. After 12Z, becoming ceiling 5,000 feet broken (AGL); surface wind from 3300 at 12 knots with gusts to 22 knots. After 04Z and for the last 6 hours of the terminal forecast, becoming marginal VFR due to ceiling.

Wind and Temperatures Aloft Forecasts (FD)

What are they? Winds and temperatures aloft forecasts contain upper air velocity and temperature forecasts for some 160 locations in 48 states. Winds for in between points can be calculated by interpolation. Winds and temperatures aloft forecasts are 6 hour, 12 hour, and 24 hour forecasts of wind direction to the nearest 10 degrees relative to true north along with wind speed, in knots, for selected altitudes.

Temperatures aloft, always in degrees Celsius, are given for all but the lowest forecast level (with the possible exception of mountainous areas where temperatures for the lowest level may also be available, depending upon the elevation of the reporting station).

When disseminated? Prepared twice daily from 0000Z and 1200Z radiosonde upper air observations. These forecasts are available about 4 hours after each observation.

Example and Format of a Winds and Temperatures Aloft Forecast:

Altitude 3,000, 6,000, 9,000, etc. JFK 2925 2833 00 2930-04, etc.

Partial Translation – Kennedy Airport, at 6,000 feet MSL, the forecast wind is from 2800 true north at 33 knots with a temperature of 0°C.

Inflight Advisories (WS, WST, WA, CWA)

What are they?


An advisory of hazardous weather conditions of concern to all aircraft issued as necessary.

Convective SIGMET (WST)

An advisory also of concern to all aircraft issued hourly during periods of hazardous convective weather.


An advisory of hazardous conditions, mainly of concern to small aircraft issued as necessary except when already part of an area forecast.

Center Weather Advisory (CWA)

An unscheduled inflight flow control air traffic and aircrew advisory. CWAs are considered as “nowcast,” rather than a flight planning product. They normally provide a narration of conditions existing at the time of issuance and a forecast for the next 2 hours.

SIGMETs and AIRMETs warn pilots of potentially hazardous weather. SIGMETs warn of severe and extreme conditions of importance to all aircraft, e.g., icing, turbulence, dust storms, sandstorms, etc. Convective SIGMETs are issued by the National Severe Storms Forecast Center in Kansas City for the continental United States and warn of tornadoes, thunderstorms, and hail. Appended hourly to convective SIGMETs is a 2 to 6 hour outlook that describes the area where and why expected convective conditions may meet issuance criteria. AIRMETs concern weather of less severity than SIGMETs or convective SIGMETs which may be hazardous to aircraft having limited capability because of lack of equipment, instrumentation, or pilot qualifications.

When produced? SIGMETs and convective SIGMETs are produced whenever conditions dictate. Convective SIGMETs are updated on an hourly basis. AIRMETs are issued only when the conditions were not adequately described in the area forecast.

Example of an inflight advisory relayed by ATC: “Attention all aircraft, a line of thunderstorms exists from Williamsport, PA, southeast to Norfolk, VA. Line moving east at one five knots, maximum tops to flight level four five zero. Possibility of strong winds, hail, and heavy rain. Expected to continue beyond two three zero zero ZULU”.


What are they? The best way to eliminate (or at least reduce) enroute weather surprises is to give – and obtain – pilot reported inflight weather observations, or PIREPs. A PIREP gives a pilot valuable information on weather conditions actually being experienced inflight by other pilots. This information supplements data reported by ground stations.

When disseminated? Pilot reports are utilized in the receiving facility immediately, and disseminated to other FAA facilities, the NWS, and pilots as soon as possible after receipt. They remain in the system for approximately 3 hours.

Example of PIREP:

LYH UA /OV RIC-LYH 180010/TM 1415/FL065/TP C152/SK 030 SCT-BKN 040 100 OVC/WX FV5 H/TA 06 /TB LGT/RM MDT TURBC SFC-045 DURGC RIC

Translation – Pilot report; from Richmond, VA, to 10 nautical miles south of Lynchburg, VA; time-1415 UTC; altitude 6,500 feet MSL; type aircraft, Cessna 152; cloud bases 3,000 feet MSL, coverage scattered to broken, tops 4,000 feet MSL, higher cloud bases 10,000 feet MSL, coverage overcast; flight visibility 5 statute miles, haze; temperature 6° C; light turbulence; remarks – moderate turbulence from the surface to 4,500 feet MSL during climb from Richmond.

How to Put PIREPs into the System

The best way to get PIREPs into the system is via Flight Watch, FAA’s real time weather service to pilots. Contact Flight Watch and give (or ask for) PIREPs along your route of flight. If you are unable to reach Flight Watch, PIREP information should be reported to the nearest FSS, approach or departure control, or the Air Route Traffic Control Center (ARTCC) controller. Remember, by providing real time weather input to the system you will be improving the quality of the weather information available to pilots following you over the same area or route. A good PIREP consists of the following:

* Your type of aircraft, altitude, and location (ideally, in reference to a VOR or significant geographical landmark) * Cloud cover, including base and top reports * Turbulence and icing * Visibility restrictions * Outside air temperature (OAT) * Other significant weather data


One Response to Weather to Fly

  1. Anwering Service says:

    Great information for new pilots

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