FXUS62 KMLB 262013 AFDMLB

Area Forecast Discussion National Weather Service Melbourne FL 413 PM EDT Fri Jul 26 2024

DISCUSSION
Issued at 400 PM EDT Fri Jul 26 2024

Key Messages:

- Moistening trend this weekend and especially early next week should bring some needed rain to coastal sections.
- Heat indices reaching up to 103-106 daily.

Thru Tonight...A more well defined east coast sea breeze will continue to push inland into early evening, aided by outflow from showers and storms that spark along the boundary. Late morning Cape sounding shows some of that low level moisture has entrained some of the drier air in the mid levels and that has allowed dewpoints to fall into the upper 60s and lower 70s. Convective initiation occurred earlier this afternoon across the far north where deeper moisture resides. Expect an increase in storm coverage across the interior as boundary collisions occur. Slow and erratic cell motions will produce heavy rain with a quick 1-2 inches in some areas creating temporary flooding esp in urban areas and where recent heavy rains have occurred. Lightning strikes will be the primary threat. Once again the immediate coast has remained rain-free but outflow boundaries may push back to the Volusia and Brevard coasts and bring some shower activity with them after sunset. The good news for the coast is rain chances will be increasing over the next few days as deep moisture becomes more widespread and the steering flow (though weak)
increasingly favors the eastern peninsula.

Saturday-Tuesday (previous)...The mid-term forecast has become a little more unsure as a complicated upper-air pattern develops. A mid- level low developing over Texas gets swept up by a broad trough over the western US, while the mid-level trough over the eastern seaboard develops into mid-level low of its own as it pushes offshore into the western Atlantic. The upstream low is absorbed into the broad trough Sunday, cutting off the low over the western Atlantic until it too is absorbed late Monday or so.
GFS and ECM have slightly different results of this evolution, with ECM building a trough over the eastern US that digs all the way down to Florida, possibly supporting some stronger storms, while the GFS tilts the trough out into the western Atlantic instead.

For Florida, a surface low developing in the western Atlantic in response to the trough and mid-level low aloft is still expected to pull higher moisture associated with a frontal boundary across the CONUS down into Florida and further increase rain chances. If anything, there's now better agreement the drier air north of the boundary will stay offshore, keeping rain chances high. The question is how soon and how much the Atlantic high can build back, depending on where the mid-level trough ends up. As long as the high stays suppressed offshore, a loose pressure gradient will remain in place with little to no steering flow, which looks to be the scenario through Tuesday at this juncture. Thus, slow and erratic storm motion combined with the high rain chances will continue to pose a threat for localized minor flooding.

Once again no significant changes to forecast temperatures. While the humidity will certainly be back, the increasing rain chances and cloud cover will subtly lower afternoon highs a few degrees from the L-M90s Saturday to the U80s-L90s Tuesday. Heat indices follow a similar trend, peaking up to 107 Saturday, and 102 Tuesday.

Wednesday-Friday (previous)...The Atlantic high looks to build back to Florida by Wednesday or Thursday, reestablishing southerly to southeasterly flow depending where the ridge axis lands. Deep tropical moisture is transported across Florida in this flow, keeping daily rain chances at least 50-60 pct (continue to cap at 60 pct due to the time scale). Temperatures creep back up to the L-M90s, bringing heat indices back up towards 106.
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