New and Difficult Weather Pattern

        Originally, this next "interesting" weather pattern looked like a classic heat wave/ridge style pattern when I last had a blog post several days ago. Things have changed significantly since then, with models trending towards, a Rex block pattern.  In a Rex blocking pattern, a significantly large trough of low pressure has cut itself (but not completely, as in the case of a cut-off low) off from the main jet stream flow, shoving itself into the middle of a ridge.  As long as there is no warm air advection into the trough, the blocking pattern can persist for quite a while.  As the ridge strengthens, the low "shoves" itself underneath the entire thing, causing the entire pattern to retrograde, or move in a direction opposite of the normal motion (which is moving eastward).  This kind of block is amplified by the fact that upper level blocking, even though it is still weak, is still persisting over Greenland.  This should cause a situation for our area that is extremely similar to the Greek story about Tantalus, who was in a lake of water up to his neck, but every time he tried to reach down for a drink, the water level would drop, not allowing him to get a drink. Around, a large upper level trough is going to build into the Northern Plains over the weekend, as a series of shortwaves "runs" into the amplifying ridge, which will cause the ridge to deamplify for a few days.  This series of shortwaves will carve out a rather large longwave trough over the Northern Plains, which will allow for a series of storm systems to traverse the upper plains. At the same time that the trough tries to dig into the Midwest and Great Lakes, the Rex blocking pattern will set up in the western Atlantic and near the East Coast.  This will cause these same storm systems to move across the same areas, Minnesota and South Dakota, causing several very heavy rain events. At the same, the heat wave will build north and westward into our area, with 500 millibar heights building into the 5900-5940 meter range, which is about as high as 500 millibar heights get (the highest 500 millibar heights were recorded last summer over Wichita, with heights of over 6000 meters above sea level!).  This will eventually lead to a strengthening of the heat by next Tuesday and Wednesday, with temperatures rising back into the mid 90's by Wednesday and Thursday of next week.  After that, there is incredible model uncertainty as to what will happen (there is a lot of uncertainty with what will happen this weekend!), but some of the models are indicating that the longwave trough will weaken and move over the area, causing temperatures to cool back into the 80's by next weekend.  Other models are indicating that either nothing will happen or keep flipping back and forth between solutions!  Ensemble consensus indicates that the longwave trough will retrograde back into the western United States (according to the HPC, or the Hydrometeorological Prediction Center), forcing the ridge to reamplify over the area.  In my opinion, the models are certainly having problems with the blocking pattern setting up and their forecasts should be considered with a grain of salt.  At this time, the GFS is probably the most progressive, while the ECMWF is probably the most amplified. If I had to use one model with the best forecast, I would say the ECMWF, as it seems to be handling the pattern quite well, as a Rex block will not allow the longwave patterns to progress very easily.  I would not take even the ECMWF for face value, as it breaks down the pattern quite rapidly, even though the Pacific ridge should retrograde, which would mean the entire pattern should shift west, including the trough in the Northern Plains, which would eventually cause the ridge axis to move back over the region.  I will have to keep updated on the pattern as it very confusing and not giving many meteorologists confidence.  There is always the possibility for cooler and wetter weather (hopefully)!
           As for this weekend, a shortwave will rapidly move through the upper Midwest by Saturday and Sunday, which could force a rather weak cold front close to the area.  Due to the amplifying ridge, I would highly doubt that the cold front will make it much past Chicago.  From my understanding, the only reason the NWS dropped temperatures into the upper 80's and lower 90's for Sunday and Monday is because of increasing clouds and lower low level temperatures associated with the approach of the cold front.  If the models end up having their well known moist bias, then they are likely having convective issues. Since they could be overestimating convection development, they may be forcing the cold front to far south, which could have a rather large effect on the entire weather pattern, especially with high temperatures and precipitation (for all of you who are hoping for rain, don't get your hopes up, rain chances for this weekend are less than 5%, in other words, don't expect rain). With a continuation of the drought (in fact, there is a moderate drought over most of the area, with the development of severe drought likely soon), expect high temperatures to be warmer than what is expected, and (possibly) cooler lows depending on the moisture profile of the low levels. Other than that, expect nice, sunny weather, with much warm and drier conditions developing. For more updates, I should have another blog post by tomorrow or Saturday, or you can come talk to me personally and I will answer your questions (usually I am at the West Bend News from 9 a.m. to 4 p.m.).