As surface high pressure scoots off to the east of Missouri, it will set up dominant southerly flow that will help keep temperatures on a warming trend through Saturday. As a low pressure system to the north approaches the Midwest, an associated cold front will bring with it showers and thunderstorms Saturday afternoon. Stay weather aware as some storms may be on the stronger side. The bulk of the severe threat should stay to the southeast of the region. The cold front will pass through Columbia by sunset on Saturday after which thunderstorms will be pushed out of the area while trailing showers will linger into late Saturday night into very early Sunday morning. Skies will clear up as and temperatures will be substantially cooler Sunday behind the front.
*** The Mizzou Campus Weather Forecast will be on spring break next week and will return on Monday April 5th at 10am***
For the Friday afternoon forecast a blend of the NAM and GFS was used for this forecast period. NAM was dealing with the placement of low pressure to the west a bit better than GFS. GFS on the other hand was running much closer to reality in terms of current temperatures in which NAM was 10 degrees warmer than observed. Both SREF and GEFS plumes were also analyzed to determine model efficiency through the weekend. Model soundings were heavily utilized to deal with the main issue of this forecast period which was probability and potential timing of convective development over the weekend.
250-mb NAM model analysis is featuring a broad yet well amplified trough over the western two-thirds of the CONUS with its axis draped from central Canada down into the Rockies where its base just off the southern California coast. This promotes west-southwest flow over mid-Missouri today and this evening. Over the course of tonight and tomorrow this upper level trough will swing its base across the desert southwest. The jet embedded in its upstream flow will promote divergence aloft tomorrow afternoon and evening which should be kept in mind for convective potential Saturday. The axis of the trough will push through the central CONUS Sunday and open the Midwest up to upper level ridging by the end of the forecast period Monday afternoon.
500-mb analysis reveals bountiful vorticity values embedded in the base of the trough just off the west coast. Over the course of the evening and tonight said vorticity along with energy being advected into the region from the northwest thanks to a deepening trough over northern Plains will merge over the Midwest and provide the catalyst needed for convective activity tomorrow afternoon. These high values of vorticity will advect to the east away from central Missouri by 15Z Sunday morning as the ridge to the west begins its influence on the area. A lack of vorticity exists for the rest of the forecast period.
Low level model analyses suggests a tale of two advections. WAA will dominate the early portions of the period lending to the warm temperatures this afternoon and moreso Saturday ahead of the encroaching cold front. Frontal passage looks to occur by 23Z tomorrow evening and the transition to a CAA regime will begin. A post frontal regime will build into Missouri from the northwest with northwesterly flow advecting those colder temperatures over the state promoting colder temperatures Sunday. Convergence at 700 mb Saturday afternoon lends confidence to the chances for convective development at that time.
Model sounding analysis was critical in determining timing and convective potential tomorrow afternoon. The profile moistens up significantly after 18Z Saturday as PWAT values climb rapidly to around 1.10 inches by 21Z. While the majority of that moisture exists near the 850-mb level Omega values at that layer support sufficient lift to move that moisture to a necessary height for convective development. CAPE values are ample topping out between 1500-2000 J/kg tomorrow afternoon with the slight capping inversion breaking shortly after 18Z. These CAPE values will maintain through early evening when the wind profile suggests front passage at roughly 22-23Z. Total totals in the 60 and K-index values in the mid 30's at these times suggest brief heavy convective rain. This all adds up to perhaps a strong line of showers and thunderstorms developing over central Missouri tomorrow afternoon before racing to the east-southeast where even strong convective environments exist. PWAT values will persist into the late evening promote a chance for some post-frontal precipitation. Accumulations all depend on exactly where in central Missouri that convective line develops. If the line forms to the north-northwest Columbia could see as much as 0.25 inches as the line pushes through. Otherwise Columbia could see as little as a trace of rain from this system.