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Area Forecast Discussion
Issued by NWS Melbourne, FL
Issued by NWS Melbourne, FL
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291 FXUS62 KMLB 142359 AFDMLB Area Forecast Discussion National Weather Service Melbourne FL 759 PM EDT Sun Jul 14 2024 ...New AVIATION... .AVIATION... (00Z TAFs) Issued at 759 PM EDT Sun Jul 14 2024 Storms and lingering debris cloud rainfall along to northwest of the I-4 corridor will gradually diminish through late evening. Despite some -RA and stray lightning strikes from this much of this activity, VFR conditions should prevail. No additional shower or thunderstorm development expected overnight, except for isolated showers that may still be able to redevelop over the coastal waters through early morning. Some drier air will begin to move in from the east later tonight, moving into the Treasure Coast region by daybreak. Earlier onset of the sea breeze in this area from KVRB-KSUA and the drier air should limit any shower/storm development at these sites tomorrow. However, scattered to numerous showers and storms should still be able to develop along the inland moving sea breeze boundaries and any collisions across the interior through the afternoon/early evening hours. Have VCTS mentioned for KDAB-KMLB and across all inland TAF sites. Will likely need to add tempo TSRA groups for inland sites with next TAF package, where greatest potential for this activity is forecast tomorrow afternoon, roughly between 20-00Z. && .PREVIOUS DISCUSSION... Issued at 216 PM EDT Sun Jul 14 2024 KEY MESSAGES: - Through this evening, scattered to numerous storms (40-80%) are expected to develop with the highest coverage along the I-4 corridor. Heat and humidity have reached hazardous levels in a few locations, especially along the Treasure Coast. - Unusually hot temperatures, even for Florida, continue this week. A risk for heat-related illness will extend to anyone without proper access to hydration and air conditioning. - Daily scattered storms persist, but coverage is forecast to drop below normal by midweek before increasing again next weekend. ---------Synoptic Overview---------- Positive H5 height anomalies continue across the southern half of the U.S. today with anticyclones located over NM and FL. Mid-level heights will build over the W Atlantic this week as a longwave trough forms over the Mississippi Valley. 14/00Z Cluster analysis from the grand ensemble strongly suggests this trough will get stuck well northwest of Florida. Therefore, the Bermuda High remains the dominant influence on our weather. The near-surface ridge axis will stay very close to Central Florida over the next week, allowing light S/SE background flow in the lower troposphere. Deep tropical moisture remains in place today (and tomorrow along the I-4 corridor), but the middle troposphere dries out some as we move into the work week. A propensity of members advect lower PW (total moisture) values, perhaps as low as 1.4-1.5", across the state through mid-week on the western flank of a weak TUTT. Thereafter, moisture is forecast to increase late in the week (and especially next weekend) out of the tropics. H85 T`s remain near the maximum moving climatological average for mid-July (+19 to +20C). Above-normal temperatures persist, particularly through the work week as lightning storm coverage is now expected to drop below normal for at least 2-3 days. -----Sensible Weather & Impacts----- Through Tonight... A Heat Advisory continues for Indian River, St Lucie, Okeechobee, and Martin Cos. for maximum heat indices locally exceeding 108F this afternoon. Stuart (SUA) reported a heat index of 111F an hour or so ago! A scattering of more reliable mesonet stations, including the WeatherStem network, are also reporting heat indices of 108F or greater in this area. The remainder of east Central FL is reaching heat index readings of 102-107F, which can still be dangerous but falls just below our advisory threshold. Be sure to take frequent water breaks, seek shade and A/C, and listen to your body: heat illness can creep up on you in a hurry. A ribbon of higher moisture is pushing across the peninsula today, evidenced by PW`s over 2" on this morning`s XMR sounding (14/10Z). In addition, H7 RH values exceed 70% near and north of Melbourne to Winter Haven. This is sometimes a good indicator of where convection is favored. Beneath that, a robust sea breeze circulation is underway, and an eventual collision should occur amid an uncapped environment. A few storms have already bubbled up along the sea breeze. Later this afternoon/early evening, our highest (60-80%) rain/storm chances shift into a zone from near Daytona down through Greater Orlando. Heavy rain is possible, with the 14/12Z HREF indicating a reasonable worst-case scenario of 3"+ in 6 hours from the strongest storms. This could lead to localized flooding. Storms will diminish by mid/late evening, and it will be quiet overnight with lows in the mid 70s. Monday... Quite a gradient in storm coverage tomorrow afternoon as drier air aloft starts to drift overhead from the east. We have 30-40% coverage for the Space/Treasure Coasts increasing to 50-70% near and northwest of Interstate 4 where the deeper moisture looks to reside a bit longer. Locally heavy rain and frequent lightning will be the primary hazards from storms on Monday. High temperatures should again reach 90-95F across the area, hottest over the interior. Peak heat indices likely will rise to around 102-107F yet again as well. Tuesday - Thursday... Guidance has backed off on storm chances during the middle of the week - especially Tue/Wed - as they hone in on this pocket of dry air that floats across the peninsula. This required some changes, namely taking out `likely` (>55%) coverage on storm potential on Tue and Wed and pinning the highest coverage to areas west of Orlando even into Thu. While widely scattered PM storms are still forecast on the sea breeze, there will be a lot of dry time. Any storm that manages to mature could produce gusty winds to 40-50 MPH as it collapses. The beaches may remain rain-free with quite a bit of sunshine. This downturn in rain/cloud coverage will have the opposite effect on temperatures. Statistical guidance now indicates many areas reaching 94-96F (except 90-93F along the coast) each afternoon. Heat indices up to 107F will continue to occur, perhaps as high as 109F especially near our lakes and on the advancing sea breeze. Little relief is expected at night (mid/upper 70s), and our experimental HeatRisk forecast (which considers climatology) is major to locally extreme near Greater Orlando. This level of heat affects anyone without effective cooling and/or adequate hydration. Friday - Next Weekend... Ridging will persist in the W Atlantic, nosing over Florida. Beneath the upper high, some members hint that a low-amplitude easterly wave will approach Florida from the tropics next weekend. Moisture would increase in this scenario, leading to a return of more scattered/numerous (50-70%) storm coverage. Highs are forecast to remain in the low/mid 90s, hottest Friday before perhaps trending down a couple degrees as storm chances pick up by Sat/Sun. Peak heat indices will remain elevated, as high as 107F. && .MARINE... Issued at 216 PM EDT Sun Jul 14 2024 Rather tranquil marine weather persists as a ridge of surface high pressure extends westward into the local Atlantic through this week. Isolated showers and storms are forecast, but long stretches dry weather are likely. Southeast winds 5-12 KT through at least mid- week, except ESE 10-15 KT nearshore in the afternoon as the sea breeze forms. Seas 2-3 FT, except up to 4 FT well offshore north of Sebastian Inlet through early Tuesday. && .PRELIMINARY POINT TEMPS/POPS... DAB 75 93 76 93 / 20 60 20 40 MCO 77 95 76 95 / 50 60 20 50 MLB 77 91 76 90 / 10 40 10 30 VRB 76 92 76 92 / 10 30 10 30 LEE 77 95 78 95 / 50 70 40 50 SFB 77 94 76 95 / 40 60 30 50 ORL 77 95 78 95 / 50 60 30 50 FPR 75 92 75 91 / 10 20 10 30 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ DISCUSSION...Heil AVIATION...Weitlich