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Beautiful weather has set up over mid-Missouri thanks to a strong surface high-pressure system. High pressure will stick around Friday night into Saturday keeping conditions much like Friday’s. Clouds will begin to build in overnight Saturday night ahead of an upper-level low-pressure system that has peaked our interest. This system will bring rain with it beginning around noon on Sunday. Some rumbles of thunder cannot be ruled out Sunday afternoon into Sunday night. Rain will stick around into Sunday night eventually tapering off by Monday morning. Early signs are pointing in the direction of severe weather Monday out ahead of a strong cold front set to blow through the region by 7pm Monday. If Monday morning rain sticks around longer than anticipated, possibility for severe weather will be hindered. If rain and clouds clear out when expected, the atmosphere will have plenty of time to prime itself for strong storms. This weekend is one to stay weather aware of as things will likely change by Monday.
Forecaster: Travis, Bongard
Issued: 5:00 PM CST 30 April 2021
Technical Discussion (The nerdy stuff we are discussing in class):
The NAM was utilized for this forecast period due to the better placement of the low to the southwest than that of the GFS which places it too far west over northern Mexico. The biggest challenge of the period was dealing with convective potential Sunday night and Monday.
Northwest flow Friday afternoon aloft places the forecast area in the downstream of a large trough over the Great Lakes and New England portions of the CONUS with a ridge to the west over the Northern Rockies. Upper level charts also reveal the presence of a cut off system to the southwest over west Texas that will meander slowly eastward this weekend. This will be the catalyst for precipitation and potential convection Sunday night and Monday. Through the weekend the ridge to the northwest will steer zonal flow into the Midwest as a trough begins to deepen out west over the Intermountain West. The system to the southwest of the region will slowly trek northeast and begin to get absorbed by Sunday afternoon into the flow to its north.
500-mb level vorticity is scarce to find Friday afternoon through Sunday morning in the region. The majority of energy lies to the southwest tied up with the cutoff low over the southern Plains and Texas. Some vorticity values creep into Missouri by 06Z Monday but the stronger vort values the system enjoyed while residing to the south are less apparent by the time the system arrives in the Midwest Monday.
Moisture values at 700 mb will stay to the south for the first half of the weekend. Sunday morning will see a rapid increase in moisture advection from the south bumping PWAT values on NAM model soundings up from 0.6 inches on Saturday to almost an inch better by Sunday at 18Z. The LLJ at 850 mb will be responsible for the slight increase in high temperatures Saturday afternoon but will wait to introduce more moisture into the region until Sunday morning. Timing of the start of precipitation looks to be late Sunday afternoon into Sunday evening. Model soundings also indicate the possibility of some convective activity Sunday night into Monday though the severe potential is low at that time.
Continued analysis of the model soundings through Monday at 21Z lends confidence that the potential for strong to severe convection exists during the day Monday. CAPE values will soar well above 1400 J/kg with the perfect amount of CIN (-25) in the morning to potentially cap activity until midday. Lifted and Total Totals point in the direction of possible severe potential beginning as soon as 17Z Monday. Also, the placement of the LLJ to the south puts the nose of the jet just to the southwest between Springfield and the Lake of the Ozarks by 15Z Monday. Currently, the SPC places a severe potential further south over northeastern Oklahoma, and western Arkansas. Indications at this time are that the convective potential may expand further north through the weekend.
Monday morning forecasters need to monitor this situation closely. Changes to the model will be important as well as Monday morning diagnostics of cloud cover and precipitation already occurring over Columbia. This will either help or hurt the convective potential Monday afternoon.