FXUS62 KMLB 200627 AFDMLB

Area Forecast Discussion National Weather Service Melbourne FL 227 AM EDT Fri Sep 20 2024

New DISCUSSION, MARINE, HYDROLOGY

DISCUSSION
Issued at 227 AM EDT Fri Sep 20 2024

KEY MESSAGES:

- The best chance (30-50%) for a few lightning storms today resides closer to the Treasure Coast. This weekend, 30-40% shower/storm chances continue.

- Minor coastal flooding remains possible, particularly during the late morning high tides through the upcoming weekend. Low- lying streets, yards, and docks along the barrier islands and Intracoastal may experience minor flooding.

- There is a medium chance (40%) for tropical development in the northwest Caribbean or southern Gulf of Mexico next week. It is too early to determine what, if any, impacts this would bring to East Central Florida. Continue to monitor the forecast for updates.

----------Synoptic Overview----------

This morning, a weak trough extends down the U.S. East Coast. To the west, upper high pressure resides over Texas, out ahead of deep low pressure over California. Florida will remain influenced by the trough through Saturday before the upper high migrates eastward early next week. By Tuesday or Wednesday, ensemble guidance suggests ridging will become anchored near Florida as a trough pushes across the Upper Mississippi River Valley.

At the surface, weak high pressure will slowly settle across the Appalachians through this weekend. Northeasterly boundary layer flow will result, and moisture values will remain near to somewhat below normal for mid/late September.

The Central American Gyre is still forecast to become active over the NW Caribbean by early next week. A propensity of ensemble members eventually develops negative pressure anomalies near the Yucatan Channel. There is a medium chance of eventual tropical development from this feature. However, it's too early to determine whether impacts will occur locally.

-------Sensible Weather & Impacts-------

Today & Tonight...

We should start our day off fairly quietly. Some patchy fog is possible around dawn. Boundary-layer flow turns onshore today, with a few gusts to around 20 mph especially north of Cape Canaveral.
Weak cyclonic flow and associated vorticity remain overhead, but moisture is limited above H7. This supports only 20-30% shower/storm chances near I-4 and the Space Coast and 40-50% chances for the Treasure Coast. Any stronger storms would have the potential to produce occasional lightning strikes, gusty winds 40-45 mph, and brief torrential rain which could cause minor flooding. Highs should reach the upper 80s to around 90F. Later tonight, a few showers may try to skirt the coast in the increasing NE flow. Lows 70-77F, warmest beachside.

Minor coastal flooding is anticipated at high tide today, with water levels likely at their peak between 8 AM and noon.

This Weekend...

Northeast surface flow becomes well-established across the Sunshine State as high pressure nestles over the Appalachians. Ripples of moisture in the boundary layer, and lingering mid-level vorticity, lend to broad 30-40% chances for showers and a few storms. Some of this activity will extend into the overnight hours, particularly along the coast.

It will be breezy at times, with a few gusts up to 20 mph each day.
Highs will again range from the upper 80s to the low 90s, with lows in the low/mid 70s.

A minor coastal flooding threat persists during high tide cycles through at least Sunday. The highest water levels are forecast in the late morning hours with a lesser peak in the late evening.
Beach-goers should be mindful that surf will be slowly building and the rip current risk will be at least moderate, and potentially even high!

Monday-Wednesday...

Ensembles strongly indicate that upper ridging becomes entrenched over Florida. With increased subsidence and a further diminution of available moisture, rain/storm coverage still looks below normal for late September. At the surface, east winds will remain breezy at times, which could push a few low-topped showers onshore. We are currently carrying 10-30% measurable rain chances each day, except 20-40% for the Treasure Coast. Steady-state temperature trends are in order, with each day ranging from the upper 80s to the low 90s.

Later Next Week...

All eyes remain on the extended forecast as most ensemble members and their respective means congeal deep tropical moisture and lower surface pressures over the NW Caribbean or southern Gulf of Mexico.
Unfortunately, that's about where the agreement stops. The National Hurricane Center still highlights a 40% chance of tropical development with this disturbance. At this time, however, there is currently no well-defined system for models to track. Furthermore, the mid-latitude longwave pattern will be in the process of realignment. A weak trough is expected to push into the Midwest as ridging builds over the West ahead of an enhanced Pacific jet.
There is a significant spread in the depth and timing of the Midwestern trough and its embedded vort maxima. All told, one should not expect a lot of clarity on this setup for 2-3 more days at least.

It's still way too early to determine whether any local impacts from this potential disturbance will occur. For now, we are showing a gradual uptick in shower/storm chances late next week. Keep checking weather.gov/mlb for updates over the next few days.
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