WMS Layer

<style>
#map {
  height: 350px;
  position: relative;
  width: 100%;
}

</style>
<div id="map"></div>

<script>
var NPMap = {
  div: 'map',
  overlays: [{
    attribution: 'NOAA',
    format: 'image/png',
    layers: '1',
    transparent: true,
    type: 'wms',
    url: 'https://idpgis.ncep.noaa.gov/arcgis/services/NWS_Observations/radar_base_reflectivity/MapServer/WMSServer'
  }]
};

(function () {
  var s = document.createElement('script');
  s.src = 'https://www.nps.gov/lib/npmap.js/4.0.0/npmap-bootstrap.js';
  document.body.appendChild(s);
})();

</script>