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Gridpoint Forecast Help
Table of Contents


General Overview


Of the many forecast products produced by our meteorologists at the Weather Forecast Office (WFO) in Caribou, Maine, one type is our gridpoint forecasts.

These forecasts are plotted on maps divided into 2.5 kilometer per side grid squares. Each grid square therefore contains 6.25 square km, which equates to 2.41, or roughly two and a half square miles. The point at the center of a grid square becomes the square's gridpoint, whose latitude and longitude are used to identify the grid square.

WFO Caribou meteorologists forecast such weather elements as temperature, wind speed, chance of precipitation, etc. Their predictions reach out seven days into the future. Take only one weather element prediction for only one time period from this seven day span, then plot it on the map of grid squares: call this plot a grid.

You can see these grids on our Cartographic Forecast pages. If you are curious, jump to these, take a look, then press your browser's Back button until you return to this page to read on.

There are hundreds of these grids, since there are dozens of weather elements and scores of time periods which make up the 7-day forecast. Viewing and understanding these hundreds of grids to form an overall picture of the 7-day weather forecast would be a difficult and time consuming process. That's where our point & click, gridpoint forecasts come in!

You simply choose a forecast format, then select a gridpoint by clicking on the desired location on a map of our area. That specific 2.5 square mile grid square is analyzed across all of the hundreds of grids, formatted as requested, and presented as a modern web graphic for your use.

The analysis is dynamic. It happens every time you click, to ensure that your forecast reflects any recent changes we may have made to the grids.

 
7-Day Forecast

The 7-Day Forecast is our most web-suited prognosis. It conveys information in both pictures and text, and it is interactive, with links to other sources of weather information. It looks like this:

7-Day Forecast graphic. Shows what a 7-day forecast looks like.

We will now cover the various parts of this document so you can benefit most from this forecast.

At the very top of your browser's window is its title bar, in which appears the web page's title. With one of our 7-Day Forecasts displayed in the browser window, this title bar includes the latitude and longitude of the gridpoint on which you clicked:

Title bar graphic. Shows title referencing a point with a latitude of 46.83 north and a longitude of -68.01 west.

If you intend to read forecasts for this location over and over again, as you might for your home, your farm, or your place of business, you will probably want to bookmark the page or make it one of your favorites. Once you do, this title becomes the identifier of the bookmark/favorite. You may prefer a different id, in order to make your bookmark/favorite more easily recognizable. For example: you might prefer Forecast for Jones' Farm to your gridpoint's default title of, let's say, 7-Day Forecast for Latitude 45.01N and Longitude -67.99W. If so, simply use your browser's bookmark or favorite management capability to rename the link.

More information about the gridpoint appears at the top of the page contents. If cities or towns exist in the grid square, the one closest to the gridpoint clicked will be shown between the NOAA and NWS logos:

Closest town/city graphic. Shows Pauls, Maine as an example of the closest town/city to a point on the map that was clicked on.

This is not necessarily the town or city with the largest population, it is just the one that was closest to the point you clicked on, even if you clicked on one of the labeled dots on the map. For example, click on the Caribou dot on the map and the 7-Day Forecast will most likely id Pauls, Maine instead of Caribou. If no city or town is in the vicinity, the 7-Day Forecast will identify the location with a phrase like Rural Northern Somerset, ME, for example.

At the left side, directly above the header for the Forecast at a Glance section, are three items of information:

Three items of interest graphic. Shows the town/city repeated, Pauls, ME, repeated and the lat/long repeated.

The first item identifies the WFO that produced the forecast you are looking at. We will assume you clicked on a spot in WFO Caribou's area of responsibility and that this reads "NWS Caribou, ME." This text also links to our home page. The second item repeats the closest city/town name, unless one does not exist, then it will id the spot you picked with a phrase like "13 Miles ESE Daaquam ME," meaning that your point was 13 miles East-Southeast of Daquaam, Maine, for example. Finally, the last item re-displays the latitude and longitude.

To the right, directly across from those three items, is a section that identifies times associated with the forecast:

Times graphic. Shows various times associated with the forecast and Spanish language link.

The time labeled Last Update tells you when the forecast grids were last modified. Simply put, this tells you how old the forecast is. The next item is a time range labeled Forecast Valid. This range describes the 7 days which the forecast covers. The first time of this range is important. As you read the textual Detailed 7-Day Forecast section below, the beginning time tells you, within Today or Tonight, when the forecast starts. At the top, for Spanish readers, is a link to present the forecast en Español.

Now, for the forecast!. The next section, extending across the whole of the near-top of the page, is the Forecast at a Glance:

Picture of the Forecast at a Glance Graphic. Shows the whole Forcast at a Glance section.

It is an iconic and textual summary of the weather for the next few days. Reading from left to right, It covers at least the next 9 day/night periods, or 4 and one half days. If the weather for consecutive periods is unchanging, then it will combine periods and show more days. The period in question is described textually above each icon

Icons show weather during each period and convey, at a glance, concepts such as bright and sunny, partly cloudy, snowy, foggy, windy, day, night, etc. The icon that is circled in the example above (Tonight) depicts a night whose only significant weather will be mostly cloudy. If a major shift in the weather is predicted or the weather could be variable during that period then the picture is split diagonally, and two weather patterns are depicted in one icon.

The probability of precipitation is shown textually within the icon, if equal to or greater than 20%. The probability of precipitation circled above (Wednesday) is 30%, meaning that there is a 30% chance it will snow and a 70% chance it will not.

Beneath each icon a very brief textual description of the weather appears. The circled example above (Wednesday Night) reads Chance Snow.

Finally, at the bottom of each icon's cell, the high or low temperature is shown: highs for day periods and lows for nights. The circled high above (this Afternoon) is 19 degrees Fahrenheit. The circled low (Tonight) is 5 degrees Fahrenheit below zero.

After the Forecast at a Glance section, the 7-Day Forecast splits into two columns. Appearing first in the left-hand column is the Detailed 7-Day Forecast, a pure, textual description of the weather over the next 7 days:

7-Day Forecast textual graphic. Shows the text portion of the forecast with its 7 days of textual description of the forecast weather.

If any hazardous weather watches, warnings, advisories, statements, etc., currently exist for your gridpoint's containing county, links to each will appear at the top of this section. If a Hazardous Weather Outlook forecasts a possible hazard within the next 7 days, a link to it will also appear, as in the circled example above.

Next, all the 7-day periods are covered one by one, near-term first and day 7 last. The weather is described in more detail for the short-term. Broader generalities are used as the forecasts progress into the future. Find the circled example above for the third period, a day period for a Wednesday. It shows good detail. The expected overall weather is mostly cloudy with a 30% chance of snow. The expected high temperature, wind speed and direction are described. A projected snowfall amount is included.

After the Detailed 7-Day Forecast section, at the bottom of the left-hand column, is a section for the combined grids for all the WFOs across the country: the National Digital Forecast Database:

National Digital Forecast Database (NDFD) graphic. Shows two NDFD maps, which link to NDFD.

This section shows two pictures which are both links to this NDFD database. The first picture depicts the maximum temperature grid for the current time period for all of New England and links to the full grid-viewing interface. The second picture shows the overall weather grid for the same and also links to the same.

Back up to the top of the right-hand column! This section is called Current Conditions. We have 8 automated sensors across our area of responsibility that come into play here:

  • Bangor International Airport
  • Bar Harbor Automatic Weather Observing / Reporting
  • Caribou Municipal Airport
  • Frenchville, Northern Aroostook Regional Airport
  • Greenville
  • Houlton International Airport
  • Millinocket Municipal Airport
  • Presque Isle

Your 7-Day Forecast picks the site that is closest to the point you clicked on and shows you the current observations from that sensor:

Current conditions graphic. Shows an example from Caribou Municipal Airport.

For this example, this 7-Day Forecast picked Caribou Municipal Airport. It is identified, as shown in the oval labeled Site. The time of the latest automated observation is also shown. These automated sensors do break. While one is inoperative and not reporting, this display may show the phrase Not a Current Observation, instead.

Selected weather elements follow. Overall weather, temperature, humidity, wind speed, gust speed, wind direction, barometric pressure, dewpoint, wind chill/heat index, and visibility may be shown, depending on what that sensor supports.

Finishing off this section are two links that let you see more observations. One link shows you other sensors' obs., the other shows you more obs. for this sensor.

Continuing down the right-hand column, we next come to Radar and Satellite Images:

Radar and Satellite graphic. Shows two links. One to a Caribou radar website and the other to the national satellite imagery website.

The two small pictures shown there are not static icons but actual snapshots of recent radar and satellite coverage. They are also links. Click on them and they will expand to full sized displays.

Next, down the right-hand column, is the Detailed Point Forecast map:

Picture of the Detailed Point Forecast map

This map gives you a chance to refine your aim, if your first "point & click" missed. Simply click on this map and another 7-Day Forecast will be generated for that new point. You can see that the task is a little easier with this map. It is rendered at a smaller scale (more zoomed-in) than the one on our home page. It shows more towns and cities. And it shows a little topography to help you out.

At the bottom of the right-hand column is the Additional Forecasts & Information section. It contains links to other forecasts or formats. Here's an example of what this may look like:

Additional Forecasts & Information graphic. Shows links to other information, each described below.

Air Quality Forecasts
shows a 36-hour ozone prediction forecast for Caribou, ME.
 
Printable Forecast
isolates the forecast elements and reformats them, ready for printing on 8.5 x 11 inch paper.
 
Text-Only Forecast
further isolates only the textual forecast elements (Detailed 7-Day Forecast) for printing on 8.5 x 11 inch paper.
 
Text Forecast(°C)
redisplays the full 7-Day Forecast with temperatures shown in Centigrade rather than Fahrenheit. Once displayed in Centigrade, the Printable Forecast and Text-Only Forecast links will honor the conversion and report in Centigrade too. Temperature is the only metric conversion performed. Depths are still in inches, distances in miles, and speeds in mph.
 
About Point Forecasts
displays a help page with a subset of the information on this page.
 
Hourly Weather Graph
allows you to quickly switch to the Hourly Weather Graph Forecast format for the gridpoint already displayed.
 
Tabular Forecast
does the same thing for the Tabular Forecast format.
 
Help for This Page
displays this page.
 
Gridpoint Forecasts Central
switches to our complete Gridpoint Forecasts page, which gives more flexibility for choosing the gridpoint to be forecast. There are four ways to select the gridpoint, by: clicking on a map to indicate the point, choosing a town/city, choosing a zip code, or entering a latitude and longitude for the point.
 
All Caribou Forecasts
switches to our Local Weather Forecasts page, which shows all our forecast products, not just point & click, gridpoint forecasts.
 
Area Forecast Discussion (AFD)
links to that specific product.
 
Caribou, ME Home
links to our home page.

Hourly Weather Graph Forecast

The Hourly Weather Graph Forecast is great for finding out when we think weather is going to occur. It plots weather elements you choose on a graph where the x-axis depicts time over a two-day period. This switch from a 7-day forecast down to 48 hours lets you know that our confidence level drops off rapidly on hourly forecasting as forecast time progresses. The Hourly Weather Graph Forecast, once displayed, gives you the ability to extend our predictions out further in time; however, the further into the future you go, the less likely that any hourly changes predicted will actually hold true. The forecast looks like this:

Hourly Weather Graph Forecast graphic. Shows what a Hourly Weather Graph Forecast looks like.

At the very top of your browser's window is its title bar, in which appears the web page's title. With the Hourly Weather Graph Forecast displayed in the browser window, this title bar includes the latitude and longitude of the gridpoint on which you clicked.

The header across the top of the page contents identifies the forecasting office. We will assume you clicked on a spot in WFO Caribou's area of responsibility and that this reads Caribou, ME, as in this graphic:

Forecasting WFO graphic. Shows Caribou, Maine as an example of the responsible forecasting office for the point on the map that you clicked on.

Note that this is different from the 7-Day Forecast: it is not a dynamic element that identifies the closest city/town to the point on which you clicked. It is a static display of the location of the Weather Forecast Office that produced your Hourly Weather Graph Forecast.

Next, above the Hourly Weather Forecast Graph, on the left side of the page, is relevant information:

Relevant information graphic. Shows the repeated latitude and longitude and the list of town/cities within 5 miles of the point you clicked on.

The closest city/town to the point on which you clicked is identified. The latitude and longitude are repeated.

To the right, directly across from those items, is a section that identifies when the forecast grids were last modified:

Times graphic. Shows update time associated with the forecast and Spanish language link.

This information is labeled Last Update. This time tells you when the forecast grids were last modified. Simply put, this tells you how old the forecast is. One line above this, for Spanish readers, is a link to present the forecast en Español.

Next is a section of controls which allow you to re-specify how you want your Hourly Weather Graph Forecast to appear. The default checked weather element boxes show you what the graph displays initially:

Graph control graphic. Shows the weather elements to graph controls with the default set checked.

Temperature, Dewpoint, Wind (speed and direction), Sky Cover and Precipitation Potential are selected and graphed by default. If you wish to change what is graphed, check and un-check elements as desired, then press the Submit button with a left-mouse click. Your gridpoint will stay the same and the graph will be reproduced with your new weather element choices displayed.

The next control, labeled 48-hour period starting, both provides information and lets you control the graph:

Time control graphic. Shows the drop-down menu form control that allows you to pick a new time to start the forecast with.

The date/time shown initially indicates the origin of the x-axis: the starting time of the 48-hour period graphed. If you want to change this, pick a new date/time with this drop-down menu, then press the Submit button mentioned above (the one that appears to the right of the weather element check boxes). Your gridpoint will remain the same and the graph regenerated with your new date/time at the left of the graph as the x-axis' origin.

A shortcut button exists to the right of the date/time menu control:

Ahead 2 day button graphic. Shows the button form control that allows you to skip ahead 2 days at a time.

The Ahead 2 Days button does what it says: it moves the graph ahead 48-hours. The result equates to selecting the date/time for exactly 48 hours in the future from the date/time menu drop-down, then pressing the Submit button.

Next, we come to the meat of the Hourly Weather Graph Forecast:

Forecast table graphic. Shows a tabular forecast table with weather element values along the y-axis and hours along the x-axix

The following weather elements are presented in a line with markers chart, plotted on an hourly basis:

  • Temperature (°F)
  • Dewpoint (°F)
  • Relative Humidity (%)
  • Sky Cover (%)
  • Wind Chill or Heat Index (°F / switched seasonally)
  • Wind Speed and Direction (mph)
  • Precipitation Potential (%)

    Wind Speed and Direction

In addition to the plotted magnitude of the wind speed, the wind direction is also shown using what is called a wind barb.

A wind barb shows both direction and speed all in one. The direction is shown by a line oriented in normal map fashion (north is up, south is down, east is right, and west is left). The speed is shown by attaching what are called barbs (see next graphic) to the end of the line. A short barb indicates 5 mph, a long barb is 10 mph, and a triangular barb is 50 mph. The line and the barbs together are called a wind barb.

The wind blows in the direction from the end of the line with the wind barbs to the other, bare end. If you think of the barbs as feathers on the shaft of an arrow and mentally put an arrowhead on the bare end, you will never have a problem. The wind blows in the direction the arrow points:

Wind barb graphic. Shows examples of wind barbs.

Wind barbs are never shown unless the speed is over 5 mph, so you will never have a problem deciding which way the shaft points. And you do not have to do the math, since the speed is plotted on the line graph. Just pay attention to the barbs to see which way the wind is blowing.

Please also note that wind gust speeds are forecast. They will be plotted here if the Winds element is checked, the gusts are expected to be 20 mph or above, and are more than 10 mph stronger than wind speed itself.

The following weather elements are presented in a column chart, giving the chances for each type of weather event categorically.

  • Rain
  • Thunder
  • Snow
  • Freezing Rain

The column charts look like this:

Column chart graphic. Shows an example of a column chart for snow.

From bottom to top, the categories on the y-axis are:

Abbreviation on Chart Meaning
  No Chance
SChc Slight Chance
Chc Chance
Lkly Likely
Ocnl* Occasional / Periods of or Definitely

* Please note that Ocnl (occasional) represents definite rainfall; however, the rainfall may not be continuous but may stop and start at times.

In addition, expected rainfall and snowfall amounts are shown at the top of these column charts.

At the very bottom of the forecast graphs is a readout section. As you move your mouse over the forecast graphs, this readout gives you the value of each element checked above, for the time slice you are pointing to. Snow and rainfall accumulations are not shown. The time slice is identified in the header:

Readout graphic. Shows a sample of the readout lines that appear under the graph and show the values of the time your mouse points to.

You will note that the wind direction is shown here also. In the example circled above, the winds are expected at 5 mph, coming out of the northwest. If you want to forget about wind barbs altogether, just move your mouse to the time slice of interest and read the wind direction and speed here. Remember, these forecasts always speak of the direction from which the winds are blowing. If wind gusts are graphed, they will show here also. For example, if gusts of 24 mph were expected in the time slice above, for Sunday, January 28 at 12am (midnight), the readout would have read: Wind: NW 5mphG24mph.

At the very bottom of the Hourly Weather Graph Forecast are two final sections side by side:

First, we have Radar and Satellite Images:

Radar and Satellite graphic. Shows two links. One to a Caribou radar website and the other to the national satellite imagery website.

The two small pictures shown there are not static icons but actual snapshots of recent radar and satellite coverage. They are also links. Click on them and they will expand to full sized displays.

Second, we have the Additional Forecasts & Information section. It contains links to other forecasts or formats. Here's an example of what this may look like:

Additional Forecasts & Information graphic. Shows links to other information, each described below.

7-Day Forecast
allows you to quickly switch to the 7-Day Forecast format for the gridpoint already displayed.
 
Tabular Forecast
does the same thing for the Tabular Forecast format.
 
Help for This Page
displays this page.
 
Gridpoint Forecasts Central
switches to our complete Gridpoint Forecasts page, which gives more flexibility for choosing the gridpoint to be forecast. There are four ways to select the gridpoint, by: clicking on a map to indicate the point, choosing a town/city, choosing a zip code, or entering a latitude and longitude for the point.
 
All Caribou Forecasts
switches to our Local Weather Forecasts page, which shows all our forecast products, not just point & click, gridpoint forecasts.
 
Area Forecast Discussion (AFD)
links to that specific product.
 
Caribou, ME Home
links to our home page.
 
Tabular Forecast

The Tabular Forecast is also hourly. It displays weather data in a table. Its duration is fixed at 72 hours with no option to extend the forecast. Once again, the shortening of the forecast period to 72 hours lets you know that our confidence level goes down rapidly on hourly forecasting. The further out you look into the future, the less likely that any hourly changes predicted will actually hold true. A Tabular Forecast looks like this:

Tabular Forecast graphic. Shows what a Tabular Forecast looks like.

At the very top of your browser's window is its title bar, in which appears the web page's title. With the Tabular Forecast displayed in the browser window, this title bar includes the latitude and longitude of the gridpoint on which you clicked:

The header across the top of the page contents identifies the forecasting office. We will assume you clicked on a spot in WFO Caribou's area of responsibility and that this reads Caribou, ME, as in this graphic:

Forecasting WFO graphic. Shows Caribou, Maine as an example of the responsible forecasting office for the point on the map that you clicked on.

Note that this is different from the 7-Day Forecast: it is not a dynamic element that identifies the closest city/town to the point on which you clicked. It is a static display of the location of the Weather Forecast Office that produced your Tabular Forecast.

Next, above the Digital Forecast, on the left side of the page, is relevant information:

Relevant information graphic. Shows the repeated latitude and longitude of the point you clicked on.

The closest city/town to the point on which you clicked is identified. The latitude and longitude are repeated.

To the right, directly across from those items, is a section that identifies when the forecast grids were last modified:

Times graphic. Shows update time associated with the forecast and Spanish language link.

This information is labeled Last Update. This time tells you when the forecast grids were last modified. Simply put, this tells you how old the forecast is. One line above this, for Spanish readers, is a link to present the forecast en Español.

Next is a section of controls which allow you to re-specify how you want your Tabular Forecast to appear. The default checked weather element boxes show you what the table displays initially:

Graph control graphic. Shows the weather elements to graph controls with the default set checked.

Temperature, Dewpoint, Wind (speed and direction), Sky Cover and Precipitation Potential are selected and matrixed by default. If you wish to change what is tabulated, check and un-check elements as desired, then press the Submit button with a left-mouse click. Your gridpoint will stay the same and the table will be reproduced with your new weather element choices displayed.

All weather elements are displayed in a tabular format. Columns are shown with hour labels across the top and rows with weather element labels down the left side. Values are placed at the appropriate row / column intersections.

Wind Speed and Direction

No wind barbs here. Wind speed is shown in mph. Wind direction is shown as a point on a 16-point compass. Wind direction once again shows the compass point from which winds are blowing. An additional element for wind gusts will appear. It will value when gusts are over 20 mph and are more than 10 mph stronger than wind speed itself.

The following weather elements are again shown categorically.

  • Rain
  • Thunder
  • Snow (seasonal)
  • Freezing Rain (seasonal)

The categories are:

Abbreviation on Chart Meaning
  No Chance
SChc Slight Chance
Chc Chance
Lkly Likely
Def* Definitely or Occasional / Periods of

* Please note that Def represents definite rainfall; however, the rainfall may not be continuous but may stop and start at times.

Rainfall and snowfall amounts are not shown in the Tabular Forecast format.

At the very bottom of the Tabular Forecast are two final sections side by side:

First, we have Radar and Satellite Images:

Radar and Satellite graphic. Shows two links. One to a Caribou radar website and the other to the national satellite imagery website.

The two small pictures shown there are not static icons but actual snapshots of recent radar and satellite coverage. They are also links. Click on them and they will expand to full sized displays.

Second, we have the Additional Forecasts & Information section. It contains links to other forecasts or formats. Here's an example of what this may look like:

Additional Forecasts & Information graphic. Shows links to other information, each described below.

7-Day Forecast
allows you to quickly switch to the 7-Day Forecast format for the gridpoint already displayed.
 
Hourly Weather Graph
does the same thing for the Hourly Weather Graph Forecast format.
 
Help for This Page
displays this page.
 
Gridpoint Forecasts Central
switches to our complete Gridpoint Forecasts page, which gives more flexibility for choosing the gridpoint to be forecast. There are four ways to select the gridpoint, by: clicking on a map to indicate the point, choosing a town/city, choosing a zip code, or entering a latitude and longitude for the point.
 
All Caribou Forecasts
switches to our Local Weather Forecasts page, which shows all our forecast products, not just point & click, gridpoint forecasts.
 
Area Forecast Discussion (AFD)
links to that specific product.
 
Caribou, ME Home
links to our home page.

Links to More Info

The gridpoint forecast is just a small part of the National Weather Service's efforts towards a National Digital Forecast Database (NDFD). Go to the NDFD Home Page for complete information.







































Home—NWS Forecast Office—Caribou, Maine


National Weather Service
Caribou Weather Forecast Office
810 Main St
Caribou ME 04736
(207) 492-0170
carwebmaster@noaa.gov
Page last modified: January 8, 2010
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