Current Conditions at Sanborn Field
Friday Night - Cloudy with rain overnight. Low: 48-52
Saturday - Rain in the AM. High: 60-64
Saturday Night - Cloudy. Low: 38-42
Sunday - Decreasing clouds throughout the day and warmer. High: 64-68
Monday - Mostly sunny and hot. High: 78-82.
Cloudy skies and rain will usher in the weekend as the precip shield of a low pressure system passes to the south of the region overnight tonight. Rain will begin late this evening and last through the majority of the AM hours on Saturday. Rainfall accumulations look to fall somewhere between 0.5 and 0.75 inches though convective activity looks minimal at best. The remainder of the weekend looks dry and increasingly warmer as warm air advection from southerly winds helps push highs on Saturday and Sunday back into the 60's. Sunny skies and temperatures near 80 degrees will greet the new work as April comes to a close.
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Usual differences between the GFS and NAM has pushed more towards GFS guidance. NAM displayed its usual bullish tendencies for warm temperatures and seemed to handle the placement of the upper-level low over the central CONUS. As such, GFS and GEFS were primarily used. The main focus for this forecast period is an upper-level shortwave moving through the Midwest that will bring with it rain Friday night into Saturday.
At 250 hPa, two jet cores sit off to the south of the region. Interestingly, one sits directly north of the other, so their entrance regions should probably be dampening one another. The GFS has the northern jet strengthening and the southern weakening. As the strengthening jet core moves to the northeast, the trough in the west strengthen and a secondary jet streak forms directly downstream of the bend of the trough. The result is weak jet streak coupling between the stronger NE jet streak and the weaker SW jet streak. Increased divergence over the Lower Mississippi Valley suggests stronger forcing for ascent associated with this coupling. The bulk of the forcing will remain well to the south of mid-Missouri. The GFS does suggest increased upper-level divergence over Missouri moving in by Friday night and into Saturday morning. The upper-level low is more evident in 500-hPa plots of height and vorticity. The vortmax will pass just to the south of the region suggesting that the surface cyclone should do the same.
At 700 hPa, the GFS suggests that the mid levels will saturate Friday night with moisture moving in on the north side of the surface low. As the low slides to the northeast, moisture will stick around mid-Missouri into Saturday morning suggesting lingering rain. Moisture deficits should not be a problem either as low level winds at 850 hPa have turned southerly as strong high pressure in the low-levels and its anticyclonic flow has moved well east according to RAP analysis loops. This has set us on a warming trend that will continue for the remainder of the forecast.
GFS plots of MSLP and 1000-500-hPa thickness back up the idea of increasing WAA as solenoids tighten up as the surface low moves to the south of Missouri. Since the cyclone passes to the south, no distinguishable frontal boundary moves through which will prevent temperatures from being knocked down too far on Saturday. Surface winds briefly turn out of the north, but quickly return to southwesterly ahead of a system next week beyond the scope of this forecast.
GFS soundings show near complete saturation of the atmosphere over Columbia occurring by 00z Saturday. Would expect precip to begin near this time. Total saturation remains until 15z Saturday when the upper-to-mid-levels begin drying out. By 18z rain should push out of the area to the east. As mentioned above, moisture will not be in short supple and GFS soundings agree with PWATs maxing out at over an inch overnight Friday into Saturday. GEFS ensemble plumes average ~0.5 inches to 1 inch of rain. Thinking that this is a good range with totals increasing north to south. Monday’s shifts should watch closely the next system set to impact the region on Tuesday for threat of thunderstorms and precipitation.
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