Area Forecast Discussion
Issued by NWS Melbourne, FL
Issued by NWS Melbourne, FL
055 FXUS62 KMLB 090840 AFDMLB Area Forecast Discussion National Weather Service Melbourne FL 440 AM EDT Thu May 9 2024 .DISCUSSION... Issued at 445 AM EDT Thu May 9 2024 Key Messages... -Early-season heat impacts persist as near-record temperatures are expected through Friday. -A few showers/storms late Friday into Saturday, with gusty winds and brief heavy rain possible. -Conditions and localized drought continue to pose increased fire weather potential through the weekend. -A conditional risk for strong storms will be monitored for the early to middle portions of next week. Today/Tonight...Atlc ridge axis has reached south Florida which will result in a hot SW flow across the area. This offshore flow will delay onset of the sea breeze south of the Cape and produce max temps around 90F at the beaches with widespread mid to upper 90s on the mainland and interior. This will result in near record highs for many areas. Vero Beach appears to have the best chance to equal/exceed their record of 93F (1977) and there will prob be at least one or two others (see below). Peak heat indices are forecast to reach 99-101 across much of the area. While these conditions are fairly common during FL summers and do not reach our Heat Advisory criteria, most people are not yet acclimated to the heat this season. For those exposed to the direct sun for extended periods, this heat can be dangerous to anyone without proper hydration or access to adequate cooling breaks. Areas will remain rain-free today. Will be watching storms pushing E/SE this aftn across AL/GA and eventually into the eastern panhandle and north FL late in the day. Some model guidance shows weakening convection pushing south into our northern counties around or shortly after sunset producing gusty outflow winds from the north and brief showers/storms mainly across Volusia county and the adjacent Atlc waters. Other reliable guidance keeps the convection north of the area tonight. For now, have kept a silent 10 PoP across the north this evening. Synoptic Overview For Friday Through The Middle Of Next Week: Florida will remain near the southern extent of a belt of strong westerlies aloft, sandwiched between a series of shortwave troughs across the mid-latitudes and a ridge of high pressure from the Southern Gulf into the Caribbean Sea. In particular, two shortwaves will have the highest potential to affect our weather. First, a disturbance will quickly shift from the Midwest to the Delmarva on Friday, allowing a weakening cold front to settle through the state by Saturday. A secondary cut-off low is projected to slide from the Great Basin to the Ohio Valley by around Tuesday. As it does, a diffuse warm front and appreciable theta-E advection out of the tropics will quickly re-introduce deeper moisture across the Southeast U.S. by early next week. As is typical with cut-off ejections, timing and depth differences are evident early next week. This will have significant implications on local impacts (see below). Later next week, heights are expected to build back above normal. Sensible Weather & Impacts: Friday-Sunday... We will sit well ahead of the front on Friday, with west/southwest winds likely preventing sea breeze formation. This, along with dry soils and a healthy dose of sunshine, will allow for a deeply-mixed boundary layer. So long as any outflows remain north of the area, H85 T`s from +18C to +21C should yield widespread mid/upper 90s on Friday afternoon. Locales from Orlando to Titusville and southward, including the coastal corridor, have 50-80% odds of reaching 95F or warmer. Co-located with our driest communities, areas west of I-95 in Indian River, St Lucie, and Okeechobee Counties have a 20-30% chance of reaching 100F! Many areas will see maximum heat indices from 98-103F, which constitutes a Moderate HeatRisk. Those susceptible to heat illness should remain inside during the hottest portion of the day. We will likely be keeping our eye on bands of storms up near I-10 on Friday afternoon. A minority of the HREF membership maintains that some outflow-driven storms could make it into our northern communities (think north of Orlando to Titusville) late day or in the evening hours. A mid-level cap should be in place, but if we can manage to break through it, MLCAPE is projected to be around 1000 J/kg with 0-6km shear values from 35-40 KT. A unidirectional profile suggests gusty winds and small hail are the primary threats. The SPC Day 2 Marginal (1 of 5) risk area extends north from Clermont to Sanford to Oak Hill. At this point, the threat on Friday appears quite conditional for Central Florida, due to the front still holding well to our north. This results in a tight gradient for rain chances Friday, from around 40% across N Volusia dropping to 20% near Orlando/Cocoa Beach and then less than 15% south of Melbourne. On Friday night, the front settles closer to the area leading to broad 20-30% chances for showers and a few storms. On Saturday, the front reaches South Florida, but upper-level support will be moving well out to sea. Will keep 20-30% storm chances south of Melbourne to Lake Kissimmee. With some drier air punching down the peninsula, even this could be generous. Hot temperatures will once again be found across the southern half of our district with mid 90s for the interior Treasure Coast. Low 90s will be common for Greater Orlando, dropping to the mid/upper 80s for the Daytona Beach area. Sunday looks to be the quiet day for us as shortwave ridging crosses the state and residual dry air squelches out any rain chances. Mid/upper 80s will be found at the coast with upper 80s/low 90s for the interior. This weekend may feature one of our last reprieves from the impending summer humidity as dew points briefly fall into the upper 50s to mid 60s. This will also allow widespread lows in the 60s on Sunday morning. Monday-Thursday... Needed rain opportunities increase, but the setup is still not a lock and could even accompanied by a round or two of stronger storms. Surface high pressure quickly scoots into the Atlantic on Monday as the next disturbance slides into the Plains. SSE flow will develop in the boundary layer, setting up a quick return of modified mT air across the Southeast U.S. Weakly favorable jet dynamics and PWs over 1.5" will be enough to introduce 30% shower/storm chances on Monday afternoon. Confidence then worsens as we push into Tuesday. The aforementioned trough over the Plains will reach the Tennessee Valley, with perturbations in the flow perhaps as far south as the Gulf Coast. Global models are beginning to hone in on bands of showers and storms across the Deep South & N Florida. 08/12Z cluster analysis revealed a significant spread in rainfall patterns, with 50- 60% of members indicating impacts as far south as Central Florida while others hold this activity just off to our north. Shear profiles are already suggestive of at least a conditional severe risk. CAPE-Shear EPS-EFI`s exceed 0.7 across much of Florida from Tuesday into Wednesday morning, indicating an unusual parameter space for mid-May. As the disturbance slowly moves eastward, the clusters remain split on how long to extend rain/storm chances into the middle of the week. For now, general 40-50% coverage seems warranted for Tue & Wed, with upside potential for one or more of these periods as confidence grows. With ridging attempting to build back north by late next week, we should see rain chances begin to drop off toward Thursday. Warm and humid weather is expected. For Monday and Tuesday, expect mid/upper 80s to around 90 along the coast with low 90s across the interior. Spread remains relatively high due to potential impacts from clouds and storms. Statistical guidance is highlighting another potential spell of hot temperatures for mid and late next week once the disturbance exits and ridging takes over. Mid 90s are back in the forecast by next Wed/Thu for our Okeechobee and interior Treasure Coast locales. && .AVIATION... (06Z TAFs) Issued at 445 AM EDT Thu May 9 2024 Patchy CIGs btwn 030-050 AGL through 13Z lifting north may affect interior terminals especially. Otherwise, VFR with SW wind flow increasing 10-12 knots gusting to 18 knots. Coastal terminals MLB-SUA will see a wind shift out of the SE 15-20 knots and gusty btwn 17Z-19Z. The sea breeze is unlikely to reach DAB though outflow from storms to the north may reach DAB around 00Z and produce a brief wind shift out of the north. Will not include this in the DAB TAF as confidence for this to occur is low at this time but it is an alternate scenario. && .MARINE... Issued at 445 AM EDT Thu May 9 2024 Today/Tonight...Low level ridge axis across south FL will produce a S to SW flow 10-14 knots over the local Atlc waters, turning onshore in a 15-20 knots SE seabreeze near the coast in the afternoon, esp south of the Cape. An increase in S/SW flow will occur this evening near 20 knots as the larger scale (synoptic) flow reasserts itself as the (mesoscale) sea breeze circulation diminishes. Do not plan on needing an Advisory for this as it will be rather short duration but will headline a Caution. Seas 3 to 4 FT. Convection passing by to the north may throw gusty outflow winds southward into the northern (Volusia) waters around or shortly after sunset. Will not forecast this explicitly unless/until confidence increases. Friday-Sunday... Breezy offshore winds on Friday from 10-15 KT across the local waters ahead of a cold front. Cautionary statements may be needed with the frontal passage Friday night due to a WNW wind surge of 15-20 KT, especially well offshore. A few storms could affect the waters late Friday through Saturday from north to south. Gusty winds exceeding 35 KT and briefly higher seas would be the primary threats from any storms. The front slides into S FL on Saturday, with NW winds veering NE from 8-15 KT. Winds continue to veer to E on Sunday from 6-12 KT. Seas 2-3 FT Friday for the entire local Atlantic, building to 3-5 FT in the Gulf Stream beginning Friday night. Through the weekend, nearshore seas 2-3 FT. && .FIRE WEATHER... Issued at 445 AM EDT Thu May 9 2024 Today...High fire weather danger in place due to hot temperatures, low humidity and SW winds 10-14 mph and gusty. Breezy sea breeze winds will develop along the coast. Critical RH values near 35% over the interior and inland portions of the coastal counties will produce near Red Flag conditions. Lowest RH values will hold between 40-45 percent along the coast due to effects of the sea breeze but winds behind the sea breeze will increase 15-20 mph with gusts up to 30 mph which could also produce rapid spread of any new or ongoing fires despite the higher RH values. Will coordinate with SPC Fire Desk to encourage an Elevated fire weather outlook for central FL in their fire weather Day1 update. IMPACT: High heat, breezy winds, and low RH will combine for near- critical or critical fire weather potential on Friday and Saturday. Friday-Sunday... As a cold front approaches from the north, breezy southwest winds from 12-17 MPH are forecast on Friday. Combined with well-above-normal temperatures and RH readings in the mid/high 30s (%) (especially south of Orlando), extremely fire-sensitive to critical fire weather conditions are possible Friday afternoon with the highest concern across Okeechobee & Osceola, as well as areas west of I-95 in St Lucie, Indian River, and Brevard Co`s. This also happens to be co-located with some of our driest locales. Behind the front on Saturday, even drier air punches down the peninsula as temperatures remain above normal for areas south of Orlando. The combination of WNW winds 12-17 MPH and low RH readings from 32-37% from Lake Co. down into the Kissimmee Basin may again yield near- critical to critical fire weather conditions Saturday afternoon. Deep mixing heights to 6-8 KFT will support excellent peak dispersion values Fri/Sat. By Sunday, winds lessen slightly to around 10 MPH. However, RH minima will once again fall to 30-40% over much of the interior. && .CLIMATE... Record highs Today and Fri. DAB 9-May 94 1978 LEE 9-May 96 2009 SFB 9-May 97 2009 MCO 9-May 98 1915 MLB 9-May 94 1978 VRB 9-May 93 1977 FPR 9-May 95 1967 DAB 10-May 94 2008 LEE 10-May 96 2009 SFB 10-May 98 2009 MCO 10-May 98 1916 MLB 10-May 95 1978 VRB 10-May 95 1976 FPR 10-May 96 2008 && .PRELIMINARY POINT TEMPS/POPS... DAB 96 72 93 70 / 10 10 40 30 MCO 97 74 95 73 / 0 0 20 30 MLB 93 72 95 72 / 10 0 10 30 VRB 94 70 97 70 / 0 0 10 30 LEE 94 75 92 72 / 0 0 30 30 SFB 97 74 95 72 / 0 0 30 30 ORL 97 74 95 74 / 10 0 20 30 FPR 93 69 96 69 / 0 0 10 20 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ SHORT TERM...Kelly LONG TERM...Heil