Drought is again expanding over the US West. Oregon, after a very rapid April and May snowmelt, is being advised to conserve water. And with high pressure building in over the Southwest, weather models are predicting the emergence of an extreme heatwave by late this weekend. One that current guidance is indicating will bring 100 to 120 degree (F) temperatures to a wide region stretching from California’s Central Valley, through Southern California, Northwestern Mexico, Arizona, Nevada and into Southern Utah.

(The US is expected to swelter under a heat dome that is predicted to form this weekend and expand on into next week. Record heat is predicted to first impact the US Southwest before building into the Central US by late next week. Image source: NCEP/NOAA.)

The trigger for what may become a record-shattering heatwave is the predicted development of a powerful atmospheric ridge. Model guidance now…