Mesoscale Precipitation Discussion 1463 NWS Weather Prediction Center College Park MD 425 PM EDT Fri Oct 09 2026

The Florida Peninsula is caught between a tightening pressure gradient with high pressure to the north and northeast, and powerful Hurricane Isaias to the west. This is fostering a SErly 925-850mb flow pattern over the Florida Peninsula and off the Gulf Stream that is forecast to push this frontal boundary northward as a warm front this evening. Instability is highest over northern FL where as much as 2,000 J/kg is available. There also remains no shortage of tropical moisture available, highlighted by >2.25" PWs that will stick around through this evening.

As Isaias tracks north, so will the frontal boundary as 1000-850mb layer warm-air advection (WAA) advances northward. The tightening theta-e gradient will develop additional storms along the both I-95 and I-10 corridors into this evening. Low-level easterly winds off the Carolina coast will accelerate and provide additional moisture just north of the frontal boundary. RAP guidance shows a narrow zone of 925-850mb mass flux convergence over northern FL beyond 00Z. This area is likely to become the focus for increasing thunderstorm coverage, and potential for some back-building storms given the gradual northward advancement of the frontal boundary.

FFGs are lowest from the Jacksonville metro area on north along I-95 into southeast GA and along I-10 where 1hr FFGs are as low as 2.5" in some cases. Given the highly saturated soundings that include increasing instability and warm cloud layer depths of at least 13,000ft, highly efficient rainfall rates up to 3"/hr are anticipated late afternoon and into this evening. Flash flooding is possible with more heavily urbanized communities and low-lying, poor drainage areas most at-risk.