Area Forecast Discussion
Issued by NWS Melbourne, FL
Issued by NWS Melbourne, FL
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969 FXUS62 KMLB 210644 AFDMLB Area Forecast Discussion National Weather Service Melbourne FL 244 AM EDT Sat Sep 21 2024 ...New DISCUSSION, MARINE, HYDROLOGY... .DISCUSSION... Issued at 244 AM EDT Sat Sep 21 2024 KEY MESSAGES: - Onshore winds and a northeasterly swell will promote a Moderate to High Risk of life-threatening rip currents at Central Florida`s Atlantic beaches. - Minor coastal flooding remains possible, particularly during the late morning high tides through this weekend. Low-lying streets, yards, and docks along the barrier islands and Intracoastal Waterway may experience minor flooding. - There is a medium chance (60%) for tropical development in the northwest Caribbean or southern Gulf of Mexico next week. It is too early to determine if and what impacts this may bring to East Central Florida. Continue to monitor the forecast for updates. ----------Synoptic Overview---------- A weakening mid-level trough resides over the Eastern U.S. this morning. Lingering pockets of vorticity will stream overhead while the trough dissipates this weekend. Upper-level high pressure remains over the Ark-La-Tex region, but a cut-off low over Arizona has started to nudge it eastward. Over the next few days, this ridge will become anchored very close to Florida as multiple shortwaves form a trough across the Upper Midwest. Beneath the upper high, H5 temperatures are expected to approach the 99th percentile of climatology. At the surface, high pressure will slowly move from the Appalachians this weekend into the Atlantic early next week, reinforcing onshore NE to E winds across the Florida Peninsula. Total atmospheric moisture will remain near to just below normal through this weekend before dropping further below average early next week. The marine influence keeps temperatures very close to normal for the opening days of autumn. Ensemble guidance indicates deep tropical moisture and convection will consolidate early this week over the northwestern Caribbean Sea. By Wednesday, ensemble-averaged negative pressure anomalies are generally centered just offshore of the Yucatan Peninsula. Those negative pressure anomalies and associated tropical moisture are forecast to lift into the Gulf of Mexico late next week. There is a medium chance of tropical development with this feature. -------Sensible Weather & Impacts------- Through The Weekend... Seasonable moisture values remain over the state, however much of that moisture resides in the lowest 10 KFT. Weak ripples of vorticity streaming off the Atlantic in the northeast flow will be enough to spark widely scattered (30-40%) low-topped showers and a few storms, with some of this activity persisting overnight along the coast. High temps reach the upper 80s to around 90F, with lows in the low/mid 70s. Northeast winds will become breezy at times, with gusts up to 20 mph, especially near the coastline. Beach-goers should expect surf of 3-4 FT and a moderate to high risk of rip currents, especially surrounding low tide in the afternoon and early evening. Additionally, minor coastal flooding remains a concern during high tide. The highest water levels are forecast in the late morning hours with a secondary peak in the late evening. Remember never to drive through salt water! Autumn begins at 8:43 am ET on Sunday. Monday-Wednesday... Quiet early autumn weather as we head back to work and school. Deep-layer ridging continues to build as drier air drifts overhead. H5 T`s soar to a very suppressive -3 or -4C as H5 heights reach 591 dam in the grand ensemble mean by early Wednesday. Bottom line, shower/storm chances lessen to 10-20% from Orlando northward and 20-30% to the south each day. Surface high pressure drifting into the Atlantic will deliver breezy easterly winds. Expect partly to mostly sunny skies with highs in the upper 80s to low 90s. Thursday & Beyond... The weather during this timeframe will be almost entirely dictated by the ultimate evolution and movement of lower pressures and rich tropical moisture rising from the Caribbean into the Gulf. Most ensemble members show this disturbance making it into the southern Gulf of Mexico by Wednesday or Thursday. After that time, significant uncertainty remains, which is expected at this stage. Guidance on potential tropical development may take several days to resolve, due to the initial absence of a trackable feature and the evolving upper air pattern over North America. The depth and position of a trough over the Midwest still look to be the ultimate variables in when and whether this disturbance gets a kick north/northeastward. The National Hurricane Center has increased the chance of tropical development in the southern Gulf to 60%. It remains too early to determine local impacts. We continue to advertise an increase in rain/storm chances (40-60%) from Thursday into next weekend, which is supported by the expected uptick in tropical moisture over the state. We are now in peak hurricane season. Check weather.gov/mlb and hurricanes.gov for the latest updates, and take the time to check on your hurricane preparedness kits and plans. && .MARINE... Issued at 244 AM EDT Sat Sep 21 2024 This Weekend... High pressure holds over the Southeast U.S., ensuring northeast winds 8-15 KT. Nearshore seas 3-4 FT building to 4-5 FT in the Gulf Stream beyond 20 nm. Scattered showers and isolated lightning storms will persist over the next couple days. Monday-Wednesday... Occasionally poor boating conditions. High pressure pushes into the W Atlantic, allowing winds to turn from ENE to E 10-15 KT. Seas 3-5 FT, except up to 6 FT well offshore. Rain shower coverage becomes more isolated late Monday through mid-week. && .AVIATION... (06Z TAFs) Issued at 131 AM EDT Sat Sep 21 2024 MVFR conditions occurring at LEE due to BR will likely continue through the overnight hours. Otherwise, VFR conditions prevailing. Showers will continue to occasionally stream onshore into coastal areas, at times approaching coastal terminals. VCSH has been included into the early afternoon (18Z) in these locations. Isolated to widely scattered showers will then progress inland along onshore flow, diminishing by around 0Z. Showers will then be possible once again overnight along the coast. Breezy onshore winds today will increase to around 12kts, with gusts around 20kts this afternoon, especially for coastal terminals. Winds will diminish this evening. && .HYDROLOGY... Issued at 244 AM EDT Sat Sep 21 2024 The Saint Johns River at Astor is forecast to remain in Moderate Flood stage through at least the weekend. Farther upstream, the Saint Johns at Deland and Sanford will remain near or slightly above Action Stage. && .PRELIMINARY POINT TEMPS/POPS... DAB 87 75 89 75 / 30 20 30 10 MCO 89 74 91 74 / 30 10 30 10 MLB 88 76 89 76 / 40 20 30 20 VRB 88 74 89 75 / 40 20 30 30 LEE 90 73 91 73 / 20 0 20 0 SFB 88 74 89 73 / 30 10 30 0 ORL 90 75 91 75 / 30 10 30 0 FPR 88 74 89 75 / 40 20 40 30 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...Coastal Flood Advisory until 2 PM EDT Sunday for FLZ141-154-159- 164-347-447-647-747. AM...None. && $$ DISCUSSION...Heil AVIATION...Leahy