Marine Weather and Tide Forecast for Boca Raton, FL

FXUS62 KMFL 210526 AFDMFL

Area Forecast Discussion National Weather Service Miami FL 126 AM EDT Wed May 21 2025

New SHORT TERM, LONG TERM, AVIATION, MARINE

SHORT TERM
(Today through Thursday)
Issued at 123 AM EDT Wed May 21 2025

The deamplification of stout deep-layer ridging across South Florida will begin today in response to an expansive mid-level trough slowly sliding eastward across the central United States. Although the atmospheric column will remain quite dry as indicated in forecasted CAMS model forecast soundings, low-level humidity coupled with a veering component of surface winds will led to well above average and impactful heat this afternoon across most of the region. A subtle but important shift from a southerly component yesterday to more of a southwesterly component today will stunt the inland progression of the Atlantic sea-breeze during the afternoon hours bringing the potential of higher temperatures further east across the region into the east coast metros. Records at our east coast sites are in the 95-96 degrees range this afternoon with the 75th percentile of model forecasts remaining near these record values.
The potential still exists that at least one of our long term observing sites ties or breaks a high temperature record this afternoon. Temperatures across the east coast metro will range from the low 90s along the immediate coast to temperatures in the middle 90s across inland metro locales. Heat indices will reach the low to mid 100s across the region this afternoon, just below Heat Advisory value and time (at least a two hour duration) thresholds. However, although conditions will just below these thresholds, the heat risk for most of South Florida today will be in the moderate range with a corridor directly over the east coast metro that will see heat risk values in the major to extreme level. While the dry air aloft may prevent an official designation of a heat advisory being issued for scientific criteria purposes, make no mistake, prolonged exposure in the heat today will cause issues and should be avoided if possible.
If you must be outdoors today, be sure to take frequent breaks in A/C and the shade and ensure proper hydration. Outside of the main concern for today, the heat, there is also the potential of an isolated shower or two along the pinned Atlantic sea-breeze.
However, convective coverage should overall be limited by copious amount of dry air in the vertical column.

After a prolonged period of subsidence and dry conditions, a pattern change is indeed on the near horizon for South Florida. The arrival of a mid-level trough across the northeastern United States tonight into Thursday will allow for a surface low to accelerate northeastward on the leeward side of the Appalachian mountains. The aforementioned surface low will drag an attendant surface boundary southeastwards across the Gulf and Florida Peninsula during the day on Thursday. An envelope of deeper atmospheric moisture will advect into the region in tandem with the front, depicted on the GFS and European models with precipitable water values in the 1.5 to 2.0 inch range. At the same time, mid-level flow will veer to a westerly direction and enhance as South Florida will be situated underneath the base of the mid-level trough. This upper-level flow regime in tandem with light southwesterly surface flow, will act to focus afternoon rain chances across the eastern half of the region as the aforementioned background southwesterly surface flow interacts with a pinned Atlantic sea-breeze. This prevailing wind pattern both aloft and at the surface, tends to favor the northeastern half of South Florida with the greatest chance of seeing convective activity and thus PoPs are the highest on Thursday afternoon in the aforementioned areas.

Residual mid-level dry air in the vertical column may act to initially limit spatial coverage of convection on Thursday afternoon, however if updraft cores are able to develop enough to tap into the background environment, the abundant dry air could actually led to an isolated strong to marginally severe storm or two along the pinned Atlantic sea-breeze. In fact, cooler 500mb values(-8C to -9C)
aloft combined with ample heat at the surface will act to steepen mid-level lapse rates and allow for more robust convective growth along the sea-breeze boundary. Small to marginally severe hail (lower freezing level) and strong to severe wind gusts (DCAPE >1000 J/kg) is possible in tandem with frequent lightning with any storm that develops directly along the localized ascent of the sea- breeze boundary. Heavy rainfall over urban areas cannot be ruled out as well, although dry antecedent conditons may limit the localized flooding threat.

Temperatures on Thursday will remain hot and well above average as convection will initiate later in the afternoon, allowing for ample instability (CAPE values above 1500-2000 J/kg). Forecast high temperatures will remain in the low to mid 90s across locations closer to the coast with inland locations potentially reaching the upper 90s once again.
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