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Preflight Briefing Tutorial Video







Tutorial on how to use AviationWeather.gov for self-briefing to get your weather information before you fly.









GFA Tutorial Video







Tutorial for the Beta version of the Aviation Weather Center's Graphical Forecasts for Aviation.









Cross Section Tutorial Video







Tutorial on how to use the cross section tool and draw a flight route






Graphical Forecasts for Aviation (GFA) Help

Overview

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The Graphical Forecasts for Aviation (GFA) web page is intended to provide the necessary aviation weather information to give users a complete picture of the weather that may impact flight in the United States (including Alaska & Hawaii), the Gulf and Caribbean, and portions of the Atlantic and Pacific Oceans. The web page includes observational data, forecasts, and warnings that can be viewed from 18 hours in the past to 18 hours in the future. Hourly model data and forecasts, including information on clouds, flight category, precipitation, icing, turbulence, wind, and graphical output from the National Weather Service’s National Digital Forecast Data (NDFD), are available. Low altitude data, previously found within the Helicopter Emergency Medical Services (HEMS) tool, is available to aid the Helicopter Air Ambulance (HAA) community and other low altitude flights. Built with modern geospatial information tools, users can pan and zoom to focus on areas of greatest interest.






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Product Overview



The Graphical Forecasts for Aviation (GFA) include gridded displays of various weather parameters as well as National Weather Service (NWS) textual weather observations, forecasts and warnings. Icing, turbulence, and wind gridded data are three-dimensional. Other gridded data are two-dimensional and may represent a “composite” of a three-dimensional weather phenomenon or a surface weather variable such as horizontal visibility.

The weather observations and forecasted data are listed under the Weather dropdown menu within the page header. Forecaster produced warnings and advisories can be found under the Products dropdown menu, along with TAF forecasts, Prog Charts, and Forecast Discussions. Note: The weather that extends beyond the outlined region have been masked out for this page, and therefore does not indicate the absence of such phenomena in these areas.





Observations



Station plots showing the METARs valid for the selected time from the time slider are displayed with PIREPs overlaid, a lowest angle reflectivity radar, SIGMETs and NWS Warnings.

Station Plots





Station model plots are used to depict current surface weather conditions.

Temp: temperature plotted in the upper left in Fahrenheit (Celsius)

Wx: present weather plotted left of the center circle with the symbol indicating weather occurring (see symbols table)

Vis: horizontal visibility plotted to the left of the present weather in miles (km)

Dew: dew point temperature plotted in the lower left in Fahrenheit (Celsius)

Wind/gust: plotted as a barb from the center circle in the direction the wind is from. Full lines off the main barb indicated 10 kts, half lines 5 kts, and triangular flags 50 kts. A circle indicated calm or variable winds.

Alt: altimeter setting plotted in the upper right as the last three digits in inches Hg (hPa)

Cig: cloud ceiling plotted to the right in hundreds of feet

Id: four letter station identifier plotted in the lower right

Flt cat/cover: cloud cover symbol (see symbols) plotted in the center. Color indicates flight condition.



Satellite

A global satellite mosaic constructed from the five geostationary satellites plus appropriate polar orbiter imagery is available. The resulting image is created every 30 minutes from available imagery. There are three types of images available:

Infrared — This is a 10 kilometer image where brighter grays show colder cloud temperatures. The infrared images display the Earth in a manner that correlates with temperature. Generally speaking, the warmer an object, the more infrared energy it emits (gives off). The satellite sensor measures this energy and calibrates it to temperature using a very simple physical relationship (Planck's Law).

Visible — This is a 5 kilometer image showing visible reflection from clouds and ground surface. The visible images display the Earth similarly to how humans see it with their eyes or how typical cameras view it. Clouds and snow appear bright white (high albedo/reflectance) but oceans and trees are much dimmer. Consequently, these images will be black at night.

Water vapor — This is a 10 kilometer image where brighter grays show higher areas of water vapor. This is useful for showing jet stream and thunderstorms. The water vapor images display the Earth in a manner that correlates to quantity of water vapor in the upper portions of the atmosphere (25,000 feet and higher in general). The actual numbers displayed on the water vapor images correspond to temperature but there is no direct relationship between these values and the temperatures of clouds (as is the case for infrared images) since this channel doesn't really "see" clouds but "sees" high-level water vapor instead.

Radar

The GFA uses the Multi-Radar/Multi-Sensor (MRMS) radar mosaic produced by the NWS. The radar image combines over 140 NEXRAD radars into a single mosaic. Each of these radars implements the WSR-88D technology. The "Doppler" capability of these radars uses shifts in the phase of the reflected energy to determine the velocity of the particles towards or away from the radar. The effective detection range is between 80 and 140 nautical miles, depending on the intensity of the precipitation. Additional post-processing is performed to remove some ground clutter and anomalous propagation (AP). The limitations of the radar such as blockage by mountains, lack of radar to radar overlap and over-processing of clutter and AP can cause the image to not show precipitation where there might be some. The display incorporates the latest radar image plus the previous 4 into a loop of radar data showing progression of precipitation echoes. By moving the time slider into the past, the radar loop will always show the latest 5 images ending in the time shown in the slider box. The valid time of the radar image is displayed in the top left corner of the map.

Lowest Angle (default) — Uses reflectivity from the lowest scan at each grid point.

Composite — Strongest radar echo return for each elevation level is combined into one image. The image gives you more information of what's happening at all elevations.

Composite 0-4km — Strongest radar echo return for each elevation level up to four kilometers is combined into one image. This image gives a better view of all precipitation for low altitude aviators.

Echo Top (18 dBZ) — At each horizontal 2D grid point, the reflectivity values at the vertical grid points are checked from the top-down. Once the 18Z threshold value is equalled or exceeded, that altitude and the altitude at the next-highest grid point are used to compute the echo top value using linear interpolation based on the slope of the reflectivity value between those two altitudes.

Layer Selector

Global Lightning

Gridded data from the Geostationary Operational Environmental Satellite (GOES) Geostationary Lightning Mapper (GLM) can be viewed within the GFA domain, as plotted below, by checking the Lightning box in the layer dropdown found in the top right corner of the display. The GLM provides enhanced visualization of convection beyond the extent of ground-based observations for GOES East and West up to 55 deg N as shown below. The map below displays GLM Coverage relative to the GFA domain. The GFA domain is outlined in red, with the satellite coverage from GOES West and GOES East in blue and yellow, respectively. The plotted GLM data is displayed in the shaded region.




Gridded Flight Category Analysis

The gridded analysis product provides near surface ceiling and visibility information every 15 minutes. It's important to note that the analysis is an interpolation between observation points, and therefore may not represent actual conditions occurring. The gridded guidance is using observations and interpolating between those points using background statistics The ceiling and visibility are used together to classify the flight category as VFR, MVFR, IFR, and LIFR (see table below). This set of rules is commonly used throughout the aviation industry. Ceiling grids are color-coded to show ceilings up to 3000 ft AGL, and visibility displays color-coded grids for visibility up to 5 miles. Values above 3000 ft AGL for ceilings, or 5 miles visibility are transparent.

Category	Ceiling		Visibility
LIFR	below 500 feet AGL	and/or	less than 1 mile
IFR	500 feet to below 1000 feet AGL	and/or	1 mile less than 3 miles
MVFR	1000 feet to 3000 feet AGL	and/or	3 to 5 miles
VFR	greater than 3000 feet AGL	and	greater than 5 miles

Turbulence NowCast

short-term (1- or 2-hour) forecast as a background state and is updated with recent observations to produce an analysis every 15 minutes. See Turbulence tab for additional informaiton on GTG. The Graphical Turbulence Guidance (GTG) Nowcast (GTG-N) is a high-frequency inflight turbulence analysis. Unlike the turbulence forecast, GTG-N uses a short-term (1- or 2-hour) forecast as a background state and is updated with recent observations to produce an analysis every 15 minutes. See the Turbulence information below for additional informaiton on GTG.

GTG-N data is available over the contiguous United States (CONUS) and adjacent coastal waters.

METAR

Weather stations from around the world report weather conditions typically once an hour using the WMO approved METAR format. These data are centrally collected by each country and distributed internationally by WMO and other services. AWC gathers data through a variety of feeds provided by NWS. The METAR observations are plotted using the standard station model where temperature, dewpoint, winds, altimeter setting, weather, ceiling and visibility are displayed around the station location. The data plotted comes from the latest available observation, including SPECIs. The stations displayed follow a progressive priority scheme that will show more stations depending on zoom level. Flight category and cloud coverage is indicated by the colored dots of the observation stations. Learn how to configure the data displayed by each METAR in the map options on the Tutorial tab to view only ceilings, visibility, or winds.

More information about METARs

Flight Cat

The flight category checkbox displays only the flight conditions at a particular airport as a colored dot. The dots are purple, red, blue, or green and represent LIRF, IFR, MVFR, and VFR, respectively. A yellow circle around the green VFR dot indicates there are cloud bases below 3,000 ft to indicate potential problems with low level flights. The flight category display uses the same priority filter system as the METAR plots but the density is much higher.

PIREPs

An aircraft report is a report of actual weather conditions encountered by an aircraft while in flight. A PIREP is reported by a pilot to indicate encounters of hazardous weather such as icing or turbulence and transmitted in real-time via radio to a ground station. Encoded and decoded PIREP text information is available by clicking on the individual report. The type, altitude, range, and report age of PIREPs that are displayed can be configured through the map options dialog.

More information about PIREPs

Fronts

Surface analysis fronts, mean sea level pressure (MSLP) contours, and pressure centers from the Weather Prediction Center are available over North America including the contiguous US and Alaska. The data are produced every three hours and are generally available two hours after the valid time.
Forecasted fronts can be found under Prog Charts in the Products dropdown.

Warnings

All SIGMETs and National Weather Service (NWS) warnings that impact aviation are plotted. By clicking on the polygon or station plot, the user can view text information which displays the hazard name, the NWS Office that issued the warning, and the time the warning ends, or the full decoded METAR.

G-AIRMET

Various G-AIRMETs can be toggled on and off. For more information on G-AIRMETs, use the SIGMET/AIRMET/CWA/NWS Warnings tab below.

More information about G-AIRMETs





Ceiling & visibility



Model derived surface flight category forecast grids are displayed. Flight category is color-coded for MVFR, IFR and LIFR. Areas with VFR conditions (ceiling greater than 3000 ft AGL and greater than 5 miles of visibility) are transparent. MVFR conditions occur with a ceiling 1000 ft to 3000 ft AGL and/or visibility 3 miles to 5 miles. IFR conditions include ceiling height less than 1,000 feet AGL and/or visibility less than 3 miles. Low IFR (LIFR) is a sub-category of IFR where ceiling heights are below 500 ft AGL, and/or visibility is less than 1 mile.

Ceiling and visibility grids are available by selecting the dropdown button within the layer selector. Ceiling grids are color-coded to show ceilings up to 3000 ft AGL, and Visibility displays color-coded grids for visibility up to 5 SM. Values above 3000 ft AGL or 5 SM visibility are transparent. Additionally, Density Altitude at the surface is available in the same dropdown. The density altitude deviation depicts the aviation effect of high surface temperatures that lower the air density and require longer runway lengths before an aircraft may lift off the runway. The values range from zero to 4000 feet indicating the perceived additional altitude of the runway rather than the actual elevation.

The Weather Symbol overlays NDFD precipitation symbols on the graphic.

G-AIRMET and SIGMET polygons that affect ceiling and/or visibility (volcanic ash, blowing dust/sand (IFR), convective, tropical cyclone, and international thunderstorm SIGMETs and G-AIRMET Sierra) are overlaid on the graphic. NWS Hazards for Winter Storm, Blizzard, Blowing Dust, and Marine Dense Fog are overlaid on the graphic. Dense Fog and Freezing Fog will be added in the future.





Clouds



Model derived cloud fraction (few, scattered, broken, overcast) is displayed for clouds below FL180 each hour. Model bases and tops are available by selecting the dropdown button within the layer selector. All color-coded grids and text information relays cloud heights in feet above Mean Sea Level (MSL).

The Weather Symbol overlays grid circles which indicate the coverage at that particular location. The density of the grid circles increase as the user zooms in on the map. Text data displays layers and tops at each grid point. Cirrus or CI above indicate cirrus type clouds present above FL180.
NOTE: The color-coded grid and the grid circles are model-derived data. Users should check TAFs for forecast conditions.

Volcanic ash, convective, tropical cyclone, and international thunderstorm SIGMETs and G-AIRMETS for mountain obscuration are overlaid on the gridded display.





Precipitation



A color-coded grid, derived from the National Digital Forecast Database (NDFD), of weather type, severity, and likelihood is displayed to indicate forecast precipitation. The grids display 'chance' when the probability of precipitation is up to 50%, and 'likely' when the probability of precipitation is greater than 50%. Thunderstorm and winter weather grids are available by selecting the dropdown button within the layer selector.

The corresponding precipitation Weather Symbol is overlaid on the grid.

Convective, tropical cyclone, international thunderstorm, and volcanic ash SIGMET polygons are automatically displayed. NWS hazards associated with precipitation including, tornado, severe thunderstorm, winter storm, winter weather, ice storm, freezing rain and lake effect snow are displayed. Only Severe Thunderstorm and Tornado NWS warnings are included on the thunderstorm tab. A Severe Thunderstorm is defined as a thunderstorm that produces a tornado, winds of at least 58 mph (50 knots or ~93 km/h), and/or hail at least 1" in diameter.





Thunderstorms



A grid of thunderstorm coverage categories is displayed with the thunderstorm type/intensity symbol overlaid. A Severe Thunderstorm is defined as a thunderstorm that produces a tornado, winds of at least 58 mph (50 knots or ~93 km/h), and/or hail at least 1" in diameter.

Categories	Meaning
ISOL (isolated)	Limited in duration and/or coverage and/or intensity
SCT (scattered)	Short-lived and/or not widespread,isolated intense storms possible …(内容过长已截断)

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