Saturday: Parlty Cloudy. Low: 75
Saturday Night: Showers & T-Storm Possible. Low: 42
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Discussion:
Warm temperatures continue into Friday and Saturday. Our next chance of showers and thunderstorms come late night Saturday into early morning Sunday.Forecasters: Labit, Macko, McCormack
Date Issued: 4/13/2023 5:00 PM CDT
The last few days have seen clear conditions due to a Rex blocking pattern over the eastern portion of the United States. This involves a high pressure system over the Ohio Valley and a low in the deep south. Due to a strengthening trough over the Colorado Basin, this will help move this blocking pattern to the northeast and bringing with it a active weather pattern. The NAM and GFS have been accurately forecasting flow patterns. The NAM seems to have a better placement of observed rainfall and with both of these in consideration, the NAM will be used for this forecast.
This aforementioned upper-level trough will help break apart the Rex pattern resulting in the low-pressure system to move into the New England region by late Saturday afternoon. There shouldn't be much of a weather shift through this time frame since southerly flow will remain until the trough passes through central Missouri. By the time the trough is in the Mid-Mississippi Valley, it'll begin to amply and gain a more negative tilt to it meaning a strengthening upper-level system. By Sunday 03Z this trough should be positioned over Missouri which is about the timing when the most intense line of precipitation is expected. Additionally, there's elevated levels of divergence aloft further supporting this idea.
While looking at instability at the 500mb level, there are a few pulses of vorticity coming from the low as it moves to the northeast overnight Thursday into early Friday morning. This will in turn kick up moisture keeping confidence that early morning cloud development is possible, but no driving force will maintain this moisture resulting in a mostly clear sky by the afternoon. Another pulse of energy bringing with it WAA, negative omega, and moisture making it likely resulting in cloud development by early Saturday morning. After analyzing soundings, the likelyhood of rain is low due to a dry intrusion near the surface. Moisture starts to carry into our area more promptly as the trough digs deeper into the south. This will supply a much more consistent stream of moisture by Saturday afternoon, and combined with a multitude of forcing mechanisms, should expect to see more overcast conditions by this time. No precipitation is expected with moisture filtering in during this time due to the same reasoning mentioned above for Saturday morning. Moisture continues to build Sunday 00Z, but total saturation doesn't occur until Sunday 03Z-09Z which is the timing expected for precipitation to impact our area. This will also be the timing when the trough begins to amplify due to it becoming negatively tilted. As this happens significantly greater values of instability becomes present and if combined with moisture, a QLCS is becoming more likely.
At the surface, the biggest feature to point out is the surface cold front which will be passing through Columbia Sunday 00Z-06Z. This will act as the main forcing mechanism to prompt precipitation development and after looking at forecasted sounding from the NAM, CAPE values just before the passage are at ~2400J/kg. However, CIN values sit at around -60 J/kg meaning there's a significant amount of capping that would need to be overtaken for the development of stronger thunderstorms. Once the system does traverse into our area, very limited energy will remain with ~200 J/kg which could result in some thunderstorm development.
A not for future forecasters, watch for any change in the capping and dry inversion in forecasted soundings. If enough of a change occurs, precipitation could start earlier than originally forecasted.
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