Things are quiet and sunny in mid-MO this afternoon. WPC surface analysis resolves a weak cold front in northern MO as of 18z, with a surface high located just off to its north. An ongoing region of heavy clouds and rainfall was located across much of the South. This large area of unsettled weather was forming in response to a slow-moving cold front, which (as of ~20 UTC) was supported by an upper-air circulation that was nearly cut off from the main jet stream at 250-mb.
For this forecast period, the 12 UTC GFS/GEFS and the 20 UTC RAP and 18 UTC extended HRRR were used, with the SREF also employed for temperature guidance.
This evening and overnight, the surface cold front is progged to slide southward into mid-MO. This will result in a wind shift from westerly to northerly, but there is little to no real cold air located behind the front. Short range models have the surface high behind the front slipping by quickly to the northeast of COU. The high should be almost due east of mid-MO by sunrise, setting up decent southerly flow and WAA for Tuesday. Lows overnight will likely fall into the upper 20s with clear skies and light winds.
For Tuesday, all signs point towards sunny skies and modest WAA. It could even be a bit on the breezy side, with gusts as high as 15-20 mph possible. The WAA and sunny skies will combine to allow temperatures to warm into the middle to upper 50s. SREF and GEFS means are around 53-54 degrees, with the HRRR indicating the potential for a high as warm as 57-58. Given the recent outstanding performance of the HRRR and the cool bias of the ensemble models, a range of 54-58 degrees seems well in order.
Tuesday night into Wednesday, continued southerly flow and WAA will combine to keep temperatures above climatological averages. The aforementioned area of precipitation and clouds - supported by an upper-level circulation that had nearly become cut off as of 20 UTC Monday - will shift eastward and remain well south of COU as the circulation is re-absorbed into the jet. This will leave the mid and upper levels of the atmosphere dry over mid-MO, ensuring mostly sunny conditions through midweek. Both ensemble and deterministic models are consistent with well-defined ridging at 500-mb by Wednesday and Thursday, supporting the idea of warm weather and sunny skies during this period.
Wednesday currently looks to be the warmest day of the two, with highs in the 60s and sunny skies. However, Thursday has the potential to be very warm as well, since southerly flow will be maximized out ahead of the next storm system. Deterministic and ensemble models are both consistent on a disturbance approaching from the west by Thursday night, with the 12 UTC GFS indicating a semi cut-off and closed upper low. Based upon GEFS model guidance, this may either be a closed cut-off low or a rather deep and well-defined shortwave. Either way, moisture advection will support increasing clouds Thursday night, with the potential for precipitation just beyond the forecast period.