The updated forecast early this morning now includes all of South Florida under a Heat Advisory, as today looks to be the hottest day of the year so far. Promoting this heat is a strong 593+ dam ridge of high pressure at 500 hPa from the western Atlantic, with the 12z observed KMFL sounding recording a height of 594 dam. These heights are some of the highest typically seen for South Florida, and with above normal low-level temps also expected coupled with sultry dewpoints in theupper 70s to near 80, the stage is set for a dangerously hot day.The Heat Advisory is in effect from 11am to 6pm, when the highestheat index values are expected to occur. During this time, mostareas could see heat index values soar to around 110 degrees, witha few locations in inland Collier and Miami-Dade counties possiblyreaching or exceeding 113 degrees at times which would meet Excessive Heat Warning criteria.
Combination of dewpoints ranging in the low 80s to mid 70s will lead for another day of heat indices of 100-105F across most of South Florida with locations over inland Collier and Miami-Dade County could see heat indices above 108 today.
East coast metro and portion of the interior could see heat index values of above 108 to 110 for an hour during peak heating but return to around 105 for the rest of the afternoon.
Therefore, a heat advisory has been issued for Miami-Dade and Inland Collier starting mid morning.