The 12Z run of the GFS was utilized for this forecast period as it is more accurately placing the encroaching system to the west better than its NAM counterpart. GFS is also tracking temperatures better with a colder trend for the forecast period. The largest obstacle of this period will be timing and accumulation of rainfall Friday night through Saturday.
Persistent zonal flow aloft will reside over the Midwest through Monday afternoon. A jet streak draped from the Panhandles across SEC country to the Carolinas Friday afternoon will gradually erode to the east. Trough just to the northwest over the Central and Northern Plains will remain there through the period as well.
500-mb analysis reveals plenty of vorticity over the region Friday afternoon that will remain in place through Saturday and most of Sunday as the axis of a shortwave trough pushes across the state by 21Z Sunday.
The NAM40 was selected for this forecasting shift because of it's accurate placement of the approaching low pressure system. Additionally, both SREF and GEFS plumes were reviewed for analyzing total QPF .
At the 250-mb plot, the slight ridge that has developed over northern Missouri will begin to flatten out by 12Z Friday leaving behind zonal flow for the majority of the forecast period. A positively tilted trough will begin to develop to the west which will impact our weather later on throughout the week.
At 500-mb, the upper-level ridge is over Missouri, the LPS is approaching from the west. This system will be weakening over the weekend, though the circulation will be still supporting the system not to dissipate entirely. The NAM40 suggests that there will be another LPS developing over North Dakota by Sunday 12Z and will make the atmosphere cloudy over mid-Missouri.