Area Forecast Discussion
Issued by NWS Melbourne, FL
Issued by NWS Melbourne, FL
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189 FXUS62 KMLB 190030 AFDMLB Area Forecast Discussion National Weather Service Melbourne FL 830 PM EDT Wed Sep 18 2024 .AVIATION... (00Z TAFs) Issued at 825 PM EDT Wed Sep 18 2024 Primary concern this eve is for ongoing strong storms INVOF KTIX with potential for sliding southward toward MLB. Lessening convective potential from VRB-SUA as well as MCO/SFB. Light SW flow overnight becoming NW 5-10 knots after sunrise, veering NE- ENE along the coast aft 17Z behind a sea breeze. Expect late day storms to focus again near the coast terminals on Thu. && .PREVIOUS DISCUSSION... Issued at 410 PM EDT Wed Sep 18 2024 Key Messages: - Afternoon shower and lightning storm chances persist through late week, lowering this weekend - High astronomical tides promote elevated water levels this week, a Coastal Flood Advisory continues - Saint Johns River at Astor forecast to remain in Moderate Flood Now-Tonight...A warm Wednesday afternoon is well under way as low-mid level cumulus clouds billow from southwest to northeast across central Florida. Despite some of these clouds, it is practically impossible to avoid the heat today with plenty of sunshine pushing temperatures into the low 90s. Heat indices are eclipsing the 100 degree mark in several locations, especially along the Atlantic coast. Conditions will remain hot through early evening, except where a rain shower moves overhead. Speaking of rain, showers and lightning storms are expected to build in coverage over the next few hours, especially from Cape Canaveral to the Treasure Coast. With the east coast sea breeze pinned along the immediate coast (and rather diffuse in most locations), any sea breeze collision that leads to additional showers and storms will be skewed to the late afternoon or early evening. RAP analysis shows 2000-2500+ J/kg of MLCAPE, little in the way of bulk shear, and a sharp contrast between steep low- level lapse rates (8.0 C/km) and weak mid-level lapse rates (5.5-6.0 C/km). GOES-derived PW indicates better moisture availability across the southern half of the forecast area, and hi-res models show a brief surge of ~2.0" PW through 00z up and down the FL Atlantic coast. Therefore, the primary window for scattered lightning storms will likely be between 5 PM and 11 PM tonight. Gusty winds, frequent lightning strikes, and brief heavy rainfall will be the main threats. However, any microscale convective collisions (sea breeze/outflow boundaries) may allow a more organized storm to exhibit brief low-level rotation. That said, the tornado and waterspout threat remain very low. Rain and storms will be moving offshore or dissipating across southern locations by midnight, leaving behind gradually clearing skies and temperatures falling into the 70s. A Coastal Flood Advisory remains in effect for some flooding of low-lying areas along the Atlantic shoreline, mainly around times of high tide. A high risk of life-threatening rip currents also continues at area beaches. Thursday-Friday...Thursday`s forecast is very similar to today`s, with lows starting out in the 70s under mostly clear conditions. Light northwesterly flow in the morning will turn onshore in the afternoon as the east coast breeze makes more of an attempt to meander inland. Isolated to scattered showers and a few lightning storms are expected, mainly toward late afternoon and early evening, with a focus from Melbourne southward to Lake Okeechobee. A good number of locations, especially farther north, will escape without a raindrop Thursday afternoon. This means temperatures will be able to climb into the low 90s with no issue, and heat index values are forecast to push into the low 100s once again. Weak mid level troughing and northwesterly flow sticks around through Friday. An approaching (weak) surface front arrives Friday morning and continues south through the remainder of the day, eventually stalling across the Florida Straits into this weekend. PoPs decrease to around 20-30 percent (north) and 40-50 percent (south) on Friday as a result of the frontal passage and some dry air advection. Winds do increase a bit behind the front as they veer to the northeast during the afternoon. Temperatures will not reflect much of a frontal passage, but a degree or two cooler for highs (upper 80s/low 90s) is reflected in Friday`s forecast. Saturday-Tuesday...Drier conditions are expected this weekend with the highest rain chances confined to south Florida. Northeasterly winds may become gusty each afternoon, especially from Sunday into next week. Mid level ridging builds east from the western Gulf of Mexico to the southeast U.S. early in the week, while surface high pressure expands over the eastern U.S. Our next formidable rain opportunity could arrive with a push of tropical moisture by mid to late week. The National Hurricane Center continues to highlight an area for potential tropical development over the northwestern Caribbean next week (20 percent chance of cyclone formation in 7 days). However, it is still way too early and models are still in far-reaching disagreement regarding the general synoptic pattern, much less the potential for tropical development, beyond days 6-7. && .MARINE... Issued at 410 PM EDT Wed Sep 18 2024 Now-Tonight...Light onshore flow turns offshore tonight. Seas remain generally favorable, around 3-4 ft, outside of any isolated/scattered lightning storms that push offshore this evening. Thursday-Sunday...Another day of winds becoming onshore around 10 kt Thursday afternoon, with isolated/scattered showers possible by the late afternoon and evening (mainly south of Cape Canaveral). Seas decrease further, around 2-4 ft. A surface front traverses the local waters on Friday, settling across south Florida and the Florida Straits this weekend. Northeast winds increase persistently each day, especially in the afternoon hours, gusting as high as 15-20 kt by Sunday. Seas gradually build Saturday into Sunday as a result, up to 5 ft offshore by Sunday afternoon/night. && .PRELIMINARY POINT TEMPS/POPS... DAB 73 90 73 89 / 50 30 10 20 MCO 74 92 73 91 / 30 50 10 30 MLB 74 90 75 88 / 60 40 40 30 VRB 73 90 73 89 / 60 50 40 40 LEE 74 90 73 90 / 20 40 10 20 SFB 73 91 73 90 / 30 50 10 30 ORL 75 92 75 91 / 30 50 10 30 FPR 73 90 73 89 / 60 60 40 50 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...Coastal Flood Advisory until 2 PM EDT Friday for FLZ141-154-159- 164-347-447-647-747. AM...None. && $$ DISCUSSION...Schaper AVIATION...Kelly