National Weather Service
JetStream Max - Online School for Weather
Weather on the Web
Point Forecasts
In the past, after hours of analysis, the forecaster would sit at the computer and type the forecast for each weather "zone" in his/her area of responsibility. A "zone" is a region where weather tends to be similar. However, it was not a perfect system as we all know the weather can vary significantly over short distances in the same zones.
Today, after the analysis, the NWS forecaster essentially "draws" the forecast and a computer takes his/her input to create the local forecast you currently see on the web. Since the information is drawn over an area, the computer can interpolate between values. For example, if the forecaster draws a temperature line of 60°F at the north end and a 70°F line at the south end of his/her area of responsibility, the computer will interpolate the remaining values (61-69°F) over the region between the two lines.
In addition to the air temperature, this drawing process is repeated for each of the following weather parameters:
- Dewpoint
- Wind speed
- Wind direction
- Cloud cover
- Amount of precipitation
- Type of precipitation
- Percent chance of precipitation
From these forecast parameters, additional parameters are created such as heat index, wind chill and relative humidity.
Because our computers interpolate between the values drawn by the forecaster, we are able to forecast for many more locations. In fact, we currently produce these forecast values as small as every 1.6 miles (2½ km)!
What this means is for even small counties and parishes, there are many "gridpoints" where we can extract meteorological forecast information.
For example, the size of Tarrant County in North Central Texas is approximately a 30 mile by 30 mile square. In this 900 square mile region, there are over 360 gridpoints (forecast points) from which we can generate weather forecast information for you.
As a result, you can "pinpoint" the forecast you received since the region you click is typically no more than about a mile away from a forecast gridpoint. And not only is your forecast relevant for your location but we also can provide your forecast for each hour out to 72 hours. This hourly information is available for the following parameters:
- Air Temperature
- Dewpoint
- Relative Humidity
- Wind Chill/Heat Index (seasonal)
- Percent Chance of Precipitation
- Percent of skycover
- Wind Direction
- Wind Speed
- Wind Gusts
- Likelihood of:
- Thunderstorms
- Rain
- Freezing rain
- Snow
We present the point forecast in two formats; The Hourly Weather Graph and Tabular Forecast. The hourly weather graph (right) is essentially a graph of the various elements you chose to be presented. This is an hourly forecast for the next 48 hours. In addition to hourly temperatures, the time and temperature of the maximum and minimum temperature each day are included.
We employ standardized wind staffs and barbs in the wind forecast section. The staffs point to the direction the wind is coming FROM with the barbs indicating the speed rounded to the nearest 5 knots. Read more information on how to interpret the wind speed. To aid in reading any specific hour, just click on that hour then read each forecast value at the bottom of the graph.
If you prefer, you can view your forecast in the tabular format (left). Essentially, this is a large table with forecasted values each hour out to 72 hours.
Neither the hourly weather graph nor tabular forecast hold any advantage over the other in which presents a better forecast. 
All information is the same in both formats other than an additional 24 hours of forecast information on the digital/tabular version. Chose which format works best for you.
In both forecast formats, you can select as many or as few elements you would like to view via the check boxes located at the top of each page. Once you press "Submit" the forecast presentation is recreated. When you customize the forecast to your liking, be sure to bookmark the page so you will have it the next time you need it.
How do you get to these two forecasts? You can find links to these two version of your forecast in the section labeled Additional Forecasts & Information of the "Forecast-at-a-Glance".
