Originally answered here, there's a hack where if the page supports iframe embedding, you can open a document that embeds the page and then scrolls the document rather than the embedded page. The issue is that we can't get the height of the page, so instead we just hijack the scrolling event to make the document taller once we approach the bottom:
data:text/html,<html><body style="margin:0; padding:0;"><iframe id='i' src='http://forecast.weather.gov/MapClick.php?CityName=Las+Vegas&state=NV&site=VEF&textField1=36.175&textField2=-115.136&e=0' width=100% frameborder=0 margin=0 scrolling=no style="height: calc(100vh + 170px + 200px);"></iframe></body><script>window.scrollTo(0, 170);window.onscroll = function(e) {if((window.innerHeight + window.scrollY) >= document.body.offsetHeight - 200) {document.getElementById('i').style.height = window.innerHeight + window.scrollY + 200;}};</script></html>