The warming trend is on! Weekend highs will creep above the freezing mark for the first time since early February (2/5 to be exact). A fair weather day Saturday will lead into a cloudy Sunday with a slight chance of rain Sunday afternoon and evening as a cold front passes through the Midwest. Despite the front temperatures will continue to rebound to near seasonal normals Monday.
Mid-Missouri is on a warming trend thanks to the retreat of the large upper level low that has been dominating over southeast Canada, the Upper Mississippi Valley, and the Great Lakes regions. A quick diagnostic of the GFS and NAM show the NAM running about 10 degrees warm for Friday’s daytime high while the GFS was more or less spot on. As such the GFS was mainly used alongside consultation with ensemble plumes for temperatures. The main focus of this forecast is the extent mid-Missouri warms up through this weekend, and a system set to move in by Sunday.
As mentioned above, the longwave trough that has been plaguing much of the CONUS with subzero temperatures further north and sub freezing temperatures as far south as the Gulf of Mexico is finally breaking down and retreating to the northeast as is seen on GFS 250-hPa plots of heights and winds. This will allow upper level flow to turn more zonal Friday into Saturday with an upper-level ridge setting up over the Upper Mississippi Valley and Upper Great Lakes regions. This will keep Friday evening into Saturday evening quiet and pleasant.
An upper-level jet max will set up over the Missouri-Iowa border. This will become important later on as this helps keep the storm track north of Columbia. The story is much the same at 500 hPa until Sunday when the system of interest will move in. A broad circulation associated with a s/w digs in from the northwest. The system, while looking dynamically juicy, will have little moisture to work with. GFS 700-hPa RH shows the bulk of saturated air staying north of the location of the aforementioned jet maximum. Additionally, GFS 850-hPa plots of winds show a fairly strong LLJ setting up ahead of the surface mid-latitude cyclone, but originates from the cT airmass of the southwestern CONUS rather than the moisture rich mT airmass of the Gulf. The result will be a system starved of moisture. GFS soundings for Sunday afternoon show saturation from the surface to only about 750 hPa beginning 15z Sunday lasting until cold frontal passage around 00z Monday. With PWATs of about 0.50 inches, some possible light precipitation ahead of the approaching surface cold front cannot be completely ruled out Sunday afternoon.
This cold front will not knock temperatures down significantly. In fact, temperatures rebound quite nicely Monday as GFS soundings suggest a veering profile of the winds returns by Monday. After the dangerously cold temperatures the region has seen over the past 10 days, temperatures in the mid 40s will seem very pleasant.