8.2 TAF and Graphical Forecast Products

ACS PA.I.C.K2c is the TAF. PA.I.C.K2d is the Graphical Forecasts for Aviation (GFA). PA.I.C.K2b is the surface analysis chart and the Ceiling and Visibility Analysis (CVA). PA.I.C.K2f is the Convective Outlook (AC). Together they answer the question a METAR cannot: what will the airport and the route look like at your ETA.

What a TAF covers — and what it does not

A TAF is a concise forecast of expected weather within about 5 statute miles of the center of the airport’s runway complex. It is a point forecast, not a route forecast. Weather 15 miles from the field can ruin a VFR arrival and never appear in that airport’s TAF. VC (vicinity) is the 5-to-10 SM ring and, in NWS TAFs, is used only with selected phenomena such as fog, showers, or thunderstorms.

AIM 7-1: TAFs are prepared by NWS Weather Forecast Offices for hundreds of U.S. airports. They are valid for 24 or 30 hours and amended as required. Most locations get a 24-hour TAF; some (typically larger) airports get a 30-hour TAF. Scheduled TAFs are issued at least four times a day, every six hours (commonly around 0000, 0600, 1200, and 1800Z). An amended TAF (TAF AMD) supersedes the previous issue and may have a shorter remaining valid period. A delayed or corrected TAF may also be shorter than 24 hours. Do not memorize a single “all TAFs are 30 hours” line — AIM states both periods.

TAFs reuse METAR weather and sky codes. Visibility P6SM means greater than 6 statute miles. Cloud heights are still AGL. NSW means no significant weather.

Change groups: FM, TEMPO, PROB30, and BECMG

This is the highest-rate TAF trap on PAR.

FM versus TEMPO is the decision that fails students. FM141800 16010G18KT 5SM -SHRA BKN040 means that from 1800Z the forecast is 5 SM in light rain showers and a 4,000-foot broken ceiling. TEMPO 1420/1423 2SM TSRA BKN025CB means that between 2000Z and 2300Z those worse conditions may occur temporarily, then the prevailing group returns. You do not plan a VFR arrival at 2115Z as if 2 SM and a thunderstorm were guaranteed for three hours — and you also do not ignore TEMPO TSRA because “it is only temporary.” A thunderstorm you cannot legally or safely fly through is still a thunderstorm.

Worked TAF — 30-hour Denver issue

TAF KDEN 141130Z 1412/1518 02012KT P6SM FEW080 SCT140 FM141800 16010G18KT 5SM -SHRA BKN040 TEMPO 1420/1423 2SM TSRA BKN025CB FM150200 28014KT P6SM SCT060 PROB30 1508/1512 4SM -SN BKN020

• Issued 1130Z on the 14th. Valid 1200Z the 14th to 1800Z the 15th — that is a 30-hour TAF.
• From 12Z: wind 020° at 12, visibility greater than 6 SM, few 8,000 / scattered 14,000. No ceiling.
• From 1800Z: a lasting change to 160° at 10 gusting 18, 5 SM, light rain showers, broken 4,000. That 4,000-foot layer is the new ceiling.
• TEMPO 2000–2300Z: periods of 2 SM, thunderstorm and rain, broken 2,500 with CB. Not the whole three hours; still a convective no-go window for a VFR arrival.
• From 0200Z on the 15th: lasting improvement to 280° at 14, P6SM, scattered 6,000. Ceiling gone again.
• PROB30 0800–1200Z on the 15th: a 30 percent chance of 4 SM, light snow, broken 2,000. That group sits well after the first nine hours, which is where NWS is allowed to put PROB30.

Jordan’s 2130Z arrival sits inside the TEMPO TSRA window and after the FM 1800Z 5 SM / BKN040 change. He does not read only the first line and call it VFR. Maya’s 0400Z night arrival sits after FM150200 — better, but she still checks the overnight PROB30 snow if her flight slides late.

GFA replaced the CONUS Area Forecast

The Graphical Forecasts for Aviation (GFA) tool at aviationweather.gov/gfa is the CONUS product AIM 7-1-4 describes as replacing the legacy textual Area Forecast (FA). Do not study old FA text as the current primary CONUS en-route forecast. The GFA is a continuously updated map of aviation weather. Forecast tabs include TAF locations, ceiling and visibility, clouds, precipitation/weather, thunderstorms, winds, turbulence, and icing. Observation/warning tabs include METAR, PIREP, radar/satellite, and current ceiling and visibility. Icing, turbulence, and wind fields are three-dimensional; you select altitude and valid time rather than reading one paragraph for a whole state.

Static GFA-related images (Aviation Cloud Forecast and Aviation Surface Forecast) are issued for users with limited connectivity: ten maps (CONUS plus nine regions), updated every 3 hours, snapshots at 3, 6, 9, 12, 15, and 18 hours. Cloud images overlay mountain-obscuration and icing AIRMETs; surface images overlay IFR and ≥30-knot surface-wind AIRMETs.

Surface analysis, CVA, and the Convective Outlook

The surface analysis chart is a now picture: isobars, highs and lows, fronts, and plotted observations. It is not a TAF and it is not a 24-hour forecast. Use it to see which air mass and which front sit on your route this hour, then read the GFA and TAF for what that system will do later.

The Ceiling and Visibility Analysis (CVA) is a real-time analysis of current ceiling and visibility — typically updated on the order of every five minutes. It is ACS K2b for a reason: it shows where IFR and MVFR exist now, including between reporting stations. It is not a forecast. Do not use a CVA snapshot from this morning as tonight’s destination briefing.

The Convective Outlook (AC) from the Storm Prediction Center is a planning product, not a SIGMET. Categorical risk, from lowest to highest organized severe threat: general thunderstorms (TSTM), Marginal (MRGL), Slight (SLGT), Enhanced (ENH), Moderate (MDT), and High (HIGH). A “slight risk” is still a day on which a light airplane should treat convection as a go/no-go and diversion problem. The outlook says organized severe weather is possible in an area; it does not clear you to thread cells. Pair it with Convective SIGMETs (next section) for the now and next two hours.

Trap: the TAF is not the route

A green TAF at departure and a green TAF at destination can still hide IFR mountain obscuration, icing, or a squall line on the GFA between them. Decode the TAF for the terminals. Use the GFA, CVA, surface analysis, and convective outlook for everything in between.