Area Forecast Discussion
Issued by NWS Melbourne, FL
Issued by NWS Melbourne, FL
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828 FXUS62 KMLB 031451 AFDMLB Area Forecast Discussion National Weather Service Melbourne FL 1051 AM EDT Wed Jul 3 2024 .UPDATE... Issued at 1050 AM EDT Wed Jul 3 2024 Sfc analysis shows weak Atlc low level ridge axis continues to lift north, currently located across NE FL. A more dominant onshore flow on the south side of this ridge will produce an earlier sea breeze onset. In fact, radar, satellite and sfc observations indicate the sea breeze boundary has formed along the entire EC FL coast with a little better momentum south of the Cape. Isolated showers have formed along the boundary and these will progress inland with the sea breeze and develop into lightning storms. The isolated showers over the Atlc will diminish as they approach the coast due to the subsidence behind the sea breeze. Early morning Cape sounding shows considerable low level moisture so not surprising diurnal cu field has been quick to form but some drier air is present above 700 mb producing DCAPE of 1000J/kg which should support a better chance for stronger wind gusts in storms. Rain/storm chances will be highest over the interior late this aftn and early this evening as a result of sea/lake/outflow boundary collisions. Widespread mid 90s across the interior and lower 90s coast will combine with high dewpoints to produce peak heat indices 103 to 107 for most of the area. Heat stress will be a concern for those spending long durations outside esp in direct sun. && .PREVIOUS DISCUSSION... Issued at 255 AM EDT Wed Jul 3 2024 KEY MESSAGES: - An extended period of above-normal temperatures continues through Independence Day and this weekend. Residents and visitors will need to take extra precautions to prevent heat- related illness. - Daily chances for showers and storms hold near 30% to 60% from today through the weekend. Overall, storm coverage will be near to below normal, lowest Friday and Saturday. - As Hurricane Beryl churns toward Jamaica and the Western Caribbean, high pressure will prevent any impacts for Florida. ---------Synoptic Overview---------- Upper heights are building across the Southeast this morning as an H5 anticyclone has nudged eastward, now centered over Alabama. This is in response to a broad trough that has entered the northern High Plains. Relatively flat upper ridging, characterized by H5 heights exceeding 590 dam, extends from California to the subtropical Atlantic. As the mid-latitude trough works through the Great Lakes by this weekend, the H5 high will sink toward North Florida and remain nearby through at least Monday. Hurricane Beryl continues to be steered beneath this ridge on a track WNW through the Caribbean Sea, well south of Florida. 02/12Z ensemble cluster analysis continued to indicate that large-scale agreement in the mass fields remains excellent over Florida over the next several days. Surface high pressure and relatively light background winds persist throughout the next week. Its axis will also sink slowly southward, reaching Central Florida late Saturday and then slipping toward the FL Straits by late Sunday or Monday. The daily sea breeze circulation will be unimpeded within this pattern. Near-normal tropospheric moisture will remain in place, except late Friday through early Sunday when somewhat drier air briefly filters in aloft. This overall pattern will continue to support scattered afternoon/early evening storms and above-normal temperatures which will pose a Moderate to Major HeatRisk across Central Florida. -----Sensible Weather & Impacts----- Today - Independence Day: Whether you`re heading to the beach, an area attraction, attending a holiday celebration, or just spending time in the backyard - be sure to stay hydrated and find a way to dip out of the hot sun from time to time! Keep an eye to the sky, and head indoors when thunder roars! Statistical guidance remains biased way too high on rainfall potential. Therefore, we relied heavily on 03/00Z HREF probabilistic guidance for storm chances for the next couple of days while considering persistence. Only isolated showers are forecast near the coast in the morning hours, then expect 30-40% coverage of a few storms on the advancing sea breeze near and west of I-95 in the afternoon. Our highest storm chances, at 50-60%, lie roughly northwest of I-4 late afternoon/early evening. This is where slightly deeper moisture is forecast to reside atop the sea breeze collision. Proximity soundings indicate 1200-1500 J/kg MLCAPE and dCAPE approaches 1000 J/kg, so there`s at least a low potential for gusty winds to 40-45 mph from any stronger storm that develops. Quick-hitting locally heavy rain of 1-3" leading to minor flooding and frequent lightning are also potential hazards. H85 T`s hold steady around +19C and 0-1 KM mixing ratios remain near 16 g/kg, so we fully expect the type of heat and humidity experienced yesterday to persist. Highs will reach the mid 90s over the interior and low 90s along the coast. Heat index values will peak between 102-107F. Low temperatures will continue to run above normal, in the mid/upper 70s - potentially threatening record warm minima. Friday - Weekend: Not a whole lot of change as we move forward in time. It`s going to stay hot (maybe even a degree or two hotter) and there remains a daily chance for a few storms. The upper high will reside very close to us this weekend. Its large- scale subsidence and warm mid-level temperatures (-3C to -4C at H5, above the maximum climatological moving average) will suppress sustained deep convection. PWAT values also briefly sneak below 2" from Friday through Saturday. The near-surface ridge axis will move southward through the weekend, veering the synoptic PBL flow more southerly by Sunday. This translates to roughly 30-50% storm chances Fri/Sat (lowest near the coast and highest far interior), increasing to 50-60% on Sunday as moisture values start creeping upward again. H85 T`s climb slightly this weekend to around +20C, so we would not be surprised if surface temperatures are also a degree or two hotter. Statistical guidance suggests at least a 40% chance of reaching 95 degrees near and northwest of I-4 each day. Combined with seasonably high humidity, peak heat indices should reach 102- 108F. Confidence in how hot our heat indices will get is somewhat challenged by an increase in interquartile dew point spread within the model suite. Two takeaways, 1) there is still a potential for portions of the area to reach Heat Advisory criteria, and 2) either way, the Moderate to Major HeatRisk will persist, indicating an unusually high potential for heat stress. Early Next Week: Deep-layer ridging is forecast to extend from the Bermuda High to the Gulf of Mexico. Meanwhile, a weakness in upper heights is indicated from the Midwest to Texas. Boundary-layer winds are forecast to hold southerly or even veer slightly SSW, and a slug of higher moisture extending north from a tropical wave over the N Caribbean may pass overhead. Thus, storm chances look a little higher on Monday. At least scattered storm chances (40-60%) will persist into the middle of next week, but confidence does drop off next Tue/Wed as the upper high holds close by and a SAL (Saharan air layer) may advance toward the state. Temperatures should continue to run near to above normal, with low/mid 90s by day and mid 70s at night. Heat indices will keep lurking at or just below the 108F advisory threshold. && .AVIATION... (12Z TAFs) Issued at 740 AM EDT Wed Jul 3 2024 VFR to continue thru much of the TAF period. ESE winds increase after 15z, up to 10 kt or less in the afternoon. As the ECSB moves inland, isolated/scattered TSRA are forecast to develop, with the highest chances along and west of MCO/ISM/SFB after 20z. Confidence remains low enough to maintain just VCTS but TEMPOs may be needed in future TAF updates. Activity dissipates after 02z Thu. Brief MVFR/IFR conditions may accompany organized TSRA inland. && .MARINE... Issued at 255 AM EDT Wed Jul 3 2024 Today-Sunday... A high pressure axis will hold north of Florida through Friday, leading to light daytime SE breezes up to 10 KT (locally enhanced at the coast during the afternoon). Winds become light SW late in the overnight hours. The high pressure axis will settle southward through the local Atlantic this weekend, with light (5-12 KT) S/SE winds by day turning offshore at night. Seas 2-3 FT through the period, with a light to moderate chop over the Intracoastal. A few showers or isolated storms are forecast during the overnight and early morning hours offshore, shifting closer to the coast in the late morning and early afternoon hours. && .PRELIMINARY POINT TEMPS/POPS... DAB 91 77 92 76 / 40 10 50 10 MCO 94 77 95 76 / 50 30 50 10 MLB 91 77 92 77 / 30 10 40 10 VRB 92 76 92 76 / 30 10 30 10 LEE 94 78 95 78 / 60 50 60 20 SFB 94 77 94 77 / 50 30 50 10 ORL 94 77 95 78 / 50 30 50 10 FPR 92 76 92 76 / 30 10 30 10 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ UPDATE...Kelly AVIATION...Schaper