At 7:57am, the fissure opened. Whereas last time the fissure opened up far to the north and east of Grindavik, they were not so lucky this time. The fissure has now spread much more south in the Hagafell region. It seemed to me as though it erupted at the southern end of the fissure that erupted in December. At the time of this post (11:00am), magma is only a few hundred feet from the greenhouse and maybe a mile from Grindavik.
A considerable portion of the rift spread under the protective berm they created over the last few weeks. While the berm was effective (Think sandbags stacked up to stop flood waters, but with dirt and stone), It could only ever stop a certain amount of liquid flow. This spreading of the fissure effectively circumvented it's protection for areas of the fissure inside the berm. The best case scenario now is that the southern end of the fissure ceases and cools before it can eject enough matter to overwhelm the town, which is now downhill.
Send hope that Grindavik and it's populace are spared. This is close to a worst case scenario.