ECMWF Ensemble Mean and GFS Ensemble Mean continue to signal strong ridging building back in to start the week.
For the Dakotas, highs of 90+ degrees should be common each day from Saturday through at least Tuesday, with the peak heat likely to occur on Monday.
Triple digits possible again Sunday and Monday from the Bismarck-Mobridge-Pierre area. For those days, 850mb temps are forecast to reach +24C on the 00z ensemble runs of the ECMWF and GFS. Operational runs have 850mb temps of +26C and +28C, respectively, for those models. As a comparison, the evening BIS sounding on Tuesday indicated an 850mb temp of +25.6C - a day in which their surface high temperature was 102F (20130821_00z BIS Sounding Tabular Data).
There is disagreement as to whether the ridge flattens a bit around the middle to late next week. Even if that happens though, it looks like we will just go from hot (highs in the 90s) to seasonably warm (highs in the 80s). However, if the operational GFS is correct, the ridge reloads and is potentially even stronger to close the week. It should be noted, that the more reliable medium range option - the ECMWF Ensemble mean - has a flattened ridge to close the work week, but then it too builds in a stronger ridge for next weekend, albeit a couple days later than the operational GFS.
It is ironic I have returned to blogging by mentioning another opportunity for triple digit heat in Bismarck, when my last post in April, detailed their 23.5" snowstorm. I'm looking forward to blogging again, with my next post likely examining whether this heat verifies to start the week, and re-investigate how much and how long the ridge flattens to close the week.
