SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0154 PM CST Sun Dec 06 2020 Valid 062000Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN FLORIDA... ...SUMMARY... Locally damaging winds and a brief tornado are possible across south Florida and the Keys late tonight through early Monday morning. ...20Z Update... Will maintain severe probabilities for what is anticipated to be an increasing potential late tonight (mainly after 06Z) for a couple of thunderstorms capable of localized wind damage and/or a tornado. This will be as a cluster of storms likely moves in from the Gulf of Mexico and/or as other semi-discrete storms develop ahead of any such cluster. ..Guyer.. 12/06/2020 .PREV DISCUSSION... /ISSUED 1019 AM CST Sun Dec 06 2020/ ...South Florida... Southern-stream shortwave trough situated over TX late this morning will phase with a northern-stream trough and accelerate through the Southeast States tonight. Stalled front located just south of the FL Keys will return to deep South FL tonight. This will result in a small, moist warm sector spreading inland, while a southwesterly low-level jet strengthens across this region late tonight in response to the approaching shortwave trough. The atmosphere across south FL will undergo modest destabilization as upper 60s to near 70F dewpoints advect inland. However, very weak lapse rates (generally less than 5.5 C/km) will contribute to a marginal thermodynamic environment with MLCAPE below 800 J/kg. Numerous showers and thunderstorms will develop within the region of isentropic ascent north of the front, and widely scattered to scattered surface-based storms are also possible along and south of this boundary later tonight. Vertical wind profiles will strengthen with 40+ kt effective bulk shear, along with increasing 0-1 km hodograph size as the low-level jet evolves late tonight. A couple of bowing structures and embedded supercells are possible with an attendant threat for a few damaging gusts and a brief tornado. Due to the expected limiting factors imposed by an anticipated marginal thermodynamic environment, will maintain MRGL risk category this update but continue to monitor for a possible SLGT upgrade in later outlooks.
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