About the National Forecast Chart

Description
The WPC National Forecast Charts provide an overview of expected weather for up to the next three days, with emphasis on certain hazardous and significant weather. They summarize forecasts from several NCEP Service Centers including the Storm Prediction Center (for severe thunderstorm and tornado outlooks), the National Hurricane Center (for tropical storm and hurricane forecasts), and the Weather Prediction Center (for information concerning heavy rainfall, flooding, winter weather, and general weather). With overlaid frontal forecasts, these displays serve as a good overview of the expected weather for the next two days.

The Day 1 (today's) forecast chart is available in both English and Spanish. The Day 2 and Day 3 forecasts are currently available only in English.

Purpose
The charts are intended for use by anyone who needs a non-technical display of the expected weather including the general public, the media, and the emergency management community. They show the large-scale weather features and associated significant weather. These charts are especially useful to travelers or others needing a big picture forecast. They are not intended to provide detailed local forecasts for any particular area. See http://weather.gov/ for access to detailed local NWS forecasts and warnings.

Availability and Product Valid Times
The Day 1 (today's) National Forecast Chart is prepared twice daily at the WPC. The initial product is issued by 1000 UTC (5 a.m. EST), with an update provided at 2200 UTC (5 p.m. EST).

The Day 2 and Day 3 National Forecasts are prepared once daily and issued by 1000 UTC (5 a.m. EST).

Valid times of the features displayed in these products vary depending upon issuance time and the particular weather phenomenon of interest. Table 1 below provides detailed information regarding the valid times for these forecasts.

Feature	Valid Times for Day 1 - Today's Forecast	Valid Times for Day 2 (Tomorrow) and Day 3 Forecasts
Surface features such as highs, lows, and fronts	AM issuance: 1200 UTC (7 a.m. EST)	AM issuance: 1200 UTC (7 a.m. EST) tomorrow or 1200 UTC Day 3.
	PM issuance: 0000 UTC (7 p.m. EST)
General precipitation areas	AM issuance: 24-hour period starting at 1200 UTC (7 a.m. EST) of the current day.	AM issuance: 24-hour period starting at 1200 UTC (7 a.m. EST) tomorrow or 1200 UTC Day 3.
	PM issuance: 12-hour period from 0000 UTC to 1200 UTC (7 p.m.-7 a.m. EST)
Severe weather	AM issuance: 24-hour period starting at 1200 UTC (7 a.m. EST) of the current day.	AM issuance: 24-hour period starting at 1200 UTC (7 a.m. EST) tomorrow or 1200 UTC Day 3.
	PM issuance: 16-hour period starting at 2000 UTC (3 p.m. EST) of the current day.
Winter weather forecasts	AM issuance: 24-hour period starting at 1200 UTC (7 a.m. EST) of the current day.	AM issuance: 24-hour period starting at 1200 UTC (7 a.m. EST) tomorrow or 1200 UTC Day 3.
	PM issuance: 24-hour period starting at 0000 UTC (7 p.m. EST) of the current day.
Flash flooding forecasts	AM issuance: From issuance time through 1200 UTC (7 a.m. EST) tomorrow (~27-30 hour period).	AM issuance: 24-hour period starting at 1200 UTC (7 a.m. EST) tomorrow or 1200 UTC Day 3.
	PM issuance: From issuance time through 0000 UTC (7 p.m. EST tomorrow) (~27-30 hour period).

Table 1. Valid times for various features shown on the National Forecast Charts.

Basis of the National Forecast Charts
The National Forecast Charts depict the location of frontal systems and pressure centers over the continental United States and include several weather parameters derived from forecast charts prepared by other NCEP Service Centers. See Table 2 for the sources of the forecasts.

Weather Feature	Origin
Severe thunderstorms and tornados	SPC convective outlooks
Tropical Storms and Hurricanes	NHC forecasts
Heavy snow, sleet, and freezing rain	WPC winter weather forecasts
Flash flooding	WPC excessive rainfall forecasts
Fronts and general weather	WPC short-range public products

Table 2. Sources of forecasts depicted on the National Forecast Charts.

See http://www.wpc.ncep.noaa.gov/html/fntcodes2.shtml for an explanation of the symbols used to depict frontal systems on the National Forecast Charts and WPC surface charts.

Feedback
We are always seeking to improve our products based on user feedback. Comments concerning this and other WPC products can be sent through the “Contact Us” section of the WPC webpage at http://www.wpc.ncep.noaa.gov/mail_webmaster.