National Weather Service United States Department of Commerce

Dangerous Heat in the Northeast and Northwest U.S.; Areas of Excessive Rainfall In the Ohio Valley and Southwest

Dangerous heat will continue to impact portions of the Northwest and Northeast U.S. through this evening. Monsoon showers and thunderstorms may result in flash flooding and debris flows from the Four Corners region into the Great Basin this week. A slow moving cold front will bring heavy thunderstorms which may produce excessive rainfall over the Ohio Valley and Mid-Atlantic through Wednesday. Read More >

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Collecting Meteorological Data by Automated Surface Observing System (ASOS)


The Automated Surface Observing System (ASOS) program is a joint effort between the National Weather Service (NWS), the Federal Aviation Administration (FAA), and the Department of Defense (DOD). The ASOS system serves as the nation's primary surface weather observing network. ASOS is designed to support weather forecast activities and aviation operations and, at the same time, support the needs of the meteorological, hydrological, and climatological research communities. For complete details on the ASOS program, click here.
View of an ASOS unit - click to enlarge
In the NWS Raleigh County Warning Area, there are 9 ASOS units, including: Raleigh-Durham (KRDU), Piedmont Triad (KGSO), Fayetteville (KFAY), Laurinburg-Maxton (KMEB), Burlington (KBUY), Chapel Hill (KIGX), Roanoke Rapids (KRZZ), Rocky Mount-Wilson (KRWI), and Winston Salem (KINT).
With the largest and most modern complement of weather sensors, the ASOS system has significantly expanded the information available to forecasters and the aviation community. The ASOS network has more than doubled the number of full-time surface weather observing locations. ASOS works non-stop, updating observations every minute, 24 hours a day, every day of the year. Getting more information on the atmosphere, more frequently and from more locations is the key to improving forecasts and warnings. Thus, ASOS information helps the NWS increase the accuracy and timeliness of its forecasts and warnings.

ASOS reports the following basic weather elements:

  • Sky conditions such as cloud height and cloud amount up to 12,000 feet,
  • Surface visibility up to at least 10 statute miles,
  • Basic present weather information such as the type and intensity for rain, snow, and freezing rain,
  • Obstructions to vision like fog, haze, and/or dust,
  • Sea-level pressure and altimeter settings,
  • Air and dew point temperatures,
  • Wind direction, speed and character (gusts, squalls),
  • Precipitation accumulation, and
  • Selected significant remarks including variable cloud height, variable visibility, precipitation beginning/ending times, rapid pressure changes, pressure change tendency, wind shift, peak wind.