Monday, April 30th – Afternoon Forecast
Tuesday Night: Small chance for a brief thunderstorm Low: 61°F
Wednesday Partly cloudy. 79°F
Wednesday Night: Thunderstorms possible (30-50%). Low: 63°F
Thursday: Partly Cloudy. High: 82°F
Thursday Night: Strong-to-severe thunderstorms possible (30-50%). Low: 58°F
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General Discussion:
Temperatures across the board are very warm (70s and 80s) but there are a few chances of thunderstorms coming up this week. Wednesday evening shows the first chance (30-50%) of thunderstorms occurring with rain totals ranging between 0.25″ and 0.5″. Strong-to-severe thunderstorms will be possible (30-50%) on Thursday, but timing and hazards remain uncertain.
-Yost
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Forecasters: Yost, Thee
Date Issued: 04/30/2024 5:00 PM
Technical Discussion:
Key Messages:
- Small chance (10-20%) for a brief pop-up thunderstorm Tuesday night.
- Thunderstorms are possible (30-50%) on Wednesday night
- Chance (30-50%) of thunderstorms Thursday evening/night with locally strong-to-severe thunderstorms.
Current visible satellite imagery displays widespread clearing in central MO with a line of supercells firing off the cold front/triple-point in the NE/IA/KS region. This convection is tracking east-northeastward into central IA and northwestern MO along a thin instability axis ahead of the cold front. Instability in central MO will be lackluster throughout the night but a small chance of a small pop-up thunderstorm remains low (10-20%). The surface cyclone in northern NE will continue to track eastward throughout early-Tuesday evening, advecting a favorable plume a Gulf-moisture into central MO between 00Z – 03Z Wednesday. Steep mid-level lapse rates (>7.0 C/km) will overspread central MO at the same time, allowing for some elevated destabilization. Model soundings after 00Z Wednesday shows a stout capping inversion over central MO which decreases confidence that any thunderstorms can maintain themself moving into this environment. Additionally, dominant dry air intrusions in the PBL suggests efficient evaporational cooling of any precipitation that does fall which will limit accumulation to a trace or less. A pop-up thunderstorm cannot be ruled out as the cold front shifts through the region between 00Z and 06Z Wednesday.
On Wednesday, broad troughing in the Pacific Northwest will slowly eject eastward into portions of the Upper-Midwest. This feature will linger in the Intermoutain West and induce renewed cyclogenesis in the TX/OK panhandles. The SFC low will strengthen low-level southerly flow throughout Wednesday and lift a warm front north alongside a thin instability axis. By 00Z Thursday, the SFC low will linger to the west and the warm front will drape along and north of the I-70 corridor in MO, with a favorable plume of upper-60s dewpoints. Warm surface temperatures alongside steep mid-level lapse rates will allow for meager destabilization (500-1000 J/kg MUCAPE) in the CWA. There will be an opportunity (30-50%) for convection after 21Z as the warm front lifts north throughout the day. However, robust capping and a lack of forcing for ascent decreases confidence in widespread storm coverage. If thunderstorm initiation is realized, rain totals could range between 0.25″ and 0.5″ with locally stronger thunderstorms.
The upper-level trough will fully eject into the Upper-Midwest throughout Thursday afternoon, reinforcing the surface cyclone to track northeast with the mid-level flow. The surface cyclone will track through central KS in the afternoon before translating along and north of the I-70 corridor in MO throughout the evening. The aforementioned warm front from Wednesday will continue to retreat north alongside strengthening southerly surface winds, pooling a large swath of 60s dewpoints into the CWA. Deterministic model soundings (NAM) shows steep mid-level lapse rates overspreading the moist boundary layer throughout Thursday afternoon allowing for rapid destabilization (1500-2000 J/kg MLCAPE). This would be conducive of some large hail (>1+ inches) throughout afternoon/evening hours given enough dry air aloft. The hail threat should decrease into the nighttime hours as model soundings suggests a water-loaded vertical profile after 00Z. Shear profiles on Thursday afternoon are impressive (100 m^2/s^2 of 0-1km SRH), but not supportive of any tornadoes at this time. Rain totals are likely to exceed 0.5″ due to the convective nature of the storms and greater forcing for ascent compared to Wednesday. Severe weather remains possible (30-50%) for portions of central MO on Thursday afternoon into the evening, but there is low confidence in the specific hazards that will be in play.
-Yost