Area Forecast Discussion
Issued by NWS Melbourne, FL
Issued by NWS Melbourne, FL
421 FXUS62 KMLB 111454 AFDMLB Area Forecast Discussion National Weather Service Melbourne FL 1054 AM EDT Sat May 11 2024 ...New UPDATE, AVIATION... .UPDATE... Issued at 1049 AM EDT Sat May 11 2024 The KMLB radar shows scattered showers and isolated lightning storms across the Treasure coast and Okeechobee counties this morning. These showers and storms are moving southeast at around 20 mph. Satellite and surface observations show some low level clouds streaming over the Florida peninsula. The weak frontal boundary will continue to shift southward today. Increasing moisture across the Treasure Coast (PW values ranging from 1.8-1.9") will support isolated to scattered showers (PoP 20-40 percent) to continue across the treasure Coast and Okeechobee county into the afternoon. Instability will also increase today across the south, with MUCAPE around 2200 J/kg across the Treasure Coast. This will support isolated lightning storm chances through the afternoon across that area. Some storms may be strong. Storms that develop today will be capable of producing occasional to frequent lightning strikes, gusty winds of 40-50 mph, and locally heavy rainfall. Otherwise, expect mostly dry conditions today, with partly to mostly sunny skies. Hot conditions will remain in place despite the frontal boundary. Afternoon highs will range from the mid 80s to low 90s along the coast where a sea breeze will form and shift inland, and low to mid 90s over the interior. Forecast remains on track with only minor adjustments to rain and storm chances through the afternoon. && .AVIATION... (12Z TAFs) Issued at 1049 AM EDT Sat May 11 2024 Isolated showers ongoing across the Treasure Coast and Okeechobee counties this morning. Have included VCSH for VRB-FPR through 15Z, and VCSH for SUA through 20Z when it transitions to VCTS. The frontal boundary will continue to slowly progress southward through today, clearing the Treasure Coast into this afternoon. Isolated showers and lightning storms will remain possible along the Treasure Coast and Okeechobee counties through the Afternoon. IFR/MVFR conditions will occur with any showers or storms, with some BKN MVFR cigs at times this morning, mainly from Cape Canaveral southward. Otherwise, VFR conditions expected today into tonight. W/NW winds up to 10-12 knots expected into this afternoon, with east coast sea breeze switching winds to the NE 8-12 knots along the coast as it forms and shifts inland. Light and variable winds once again overnight. && .PREVIOUS MARINE... Issued at 504 AM EDT Sat May 11 2024 Today-Tonight...W/NW winds this morning up to 10-15 knots will become N/NE across much of the waters this afternoon, as passing front continues slowly southward into the Treasure Coast waters, and the east coast sea breeze forms and shifts inland. Seas will range from 2-3 feet nearshore and up to 4-5 feet offshore this morning, falling to 2-4 feet this afternoon and into tonight. Isolated offshore moving storms producing gusty winds and frequent lightning will continue to be possible through this morning south of the Cape, and near to south of Fort Pierce into the afternoon. && .PREVIOUS FIRE WEATHER... Issued at 504 AM EDT Sat May 11 2024 Fire sensitive conditions continue into the weekend with drier air that builds in behind the passing front. Min RH values fall into the 30s across the interior, west of I-95, this afternoon, and will be as low as the mid 30s to low 40s inland on Sunday afternoon. Winds may still be gusty today out of the W/NW across inland areas, but sustained winds look to remain just below 15 mph. E/NE winds into Sunday will be even a tad weaker around 5-10 mph. Moisture and shower/storm chances then rise into early next week, with Min RH values forecast to remain above critical values. && .PREVIOUS DISCUSSION... Issued at 504 AM EDT Sat May 11 2024 Today-Tonight...Weak frontal boundary will continue to shift southward into today, with isolated showers and storms still possible across Okeechobee County and the Treasure Coast past sunrise this morning. Moisture will then continue to increase across the southern Treasure Coast this afternoon as boundary continues to slowly shift southward through this region, with PW values up to 1.8- 1.9 inches. Instability will also be on the rise with daytime heating, and SBCAPE values jump up to ~2000 J/kg across St. Lucie/Martin counties. This will continue scattered shower and isolated thunderstorm development across this area into the afternoon, with any storms potentially producing frequent lightning strikes, gusty winds up to 40-50 mph and locally heavy rainfall as they shift offshore. Rain chances range from 20-40 percent south of a line from Melbourne to Lake Kissimmee today, with drier conditions forecast to the north. Despite the frontal passage, it will still be unseasonably hot, especially inland, with highs ranging from the mid 80s to low 90s along the coast where a sea breeze will form and shift inland, and low to mid 90s over the interior. Any lingering rain chances across the southern Treasure Coast gradually end into this evening, as front continues southward and drier air continues to build in. Temperatures will be a little cooler, but still near to slightly above normal into tonight, with lows in the 60s for most locations. Synoptic Overview For Sunday Through Next Saturday... The extended forecast begins with a trough across the Northeast U.S., zonal flow over the South, and another shortwave trough exiting from the Rockies into the Central Plains. Weak ridging will transit across the state on Monday before the effects of the second trough begin to affect our weather from Tuesday into Wednesday. On its southern flank, the subtropical jet will strengthen with H5 zonal wind anomalies exceeding the 95th percentile of climatology toward Wednesday. Exhibited by IVT values also exceeding the 95th percentile, extremely rich moisture will be advected into the Southeast U.S. ahead of the feature. Later in the week, weak ridging will again flex northward, but anomalously high moisture looks to remain in place. Aided by essentially uninterrupted south to southwest flow, boundary-layer temperatures will run above normal through the period. In summary, this pattern should yield opportunities for showers and storms. Some storms could be strong to severe. Days that end up drier will turn quite hot. Sensible Weather & Impacts: Sunday-Monday... The combo of residual dry air and nearby surface high pressure should keep us quiet on Sunday. Rain chances are below 15%. Some guidance suggests bands of mid and high clouds and perhaps even some sprinkles on Sunday afternoon. No impactful weather is forecast to finish the weekend. Highs should bounce toward the mid/upper 80s, except low 90s south of Orlando along the Kissimmee Basin. As the high pressure dome moves into the Atlantic on Monday, moisture quickly returns to the area. This will be a transition day of sorts as we will still feel the influence of shortwave ridging aloft, which will act to suppress widespread convection. However, the increase in total moisture and an embedded seabreeze should spark 30- 40% coverage of mainly afternoon and early evening showers/storms. The severe threat on Monday looks limited, but non-zero as we will have sufficient low-level and bulk shear for perhaps gusty winds or a tornado. The limiting factor will be poor mid-level lapse rates with the ridge axis overhead. Expect mid/upper 80s beachside and upper 80s/low 90s elsewhere. Tuesday-Wednesday... Times of active weather still appear likely for the middle of the coming week as the next trough moves into the Tennessee Valley. With strong ridging to our south, this will act to increase the subtropical jet over the Southeast, including Florida. Perturbations within the jet are expected to interact with a ribbon of deep moisture to produce rounds of showers and storms somewhere from GA/AL into at least the northern half of Florida. The parameter space continues to look concerning for the potential for severe storms and locally heavy rain. The rich thermodynamic environment will attempt to combine with unseasonably high wind shear. 10/12Z EPS EFIs for CAPE-Shear remain high (> 0.8 w/ some shift of tails), indicative of unusually favorable conditions for strong/severe storms with potentially all hazards. As mentioned in previous discussions, timing out these waves of showers and storms are notoriously difficult this far out. Cluster analysis also shows that there is disagreement in placement of the highest storm chances, with around 30% of members still favoring much of this activity holding just north of much of our area. Bottom line, shower and storm chances increase during this timeframe, with a conditional risk of severe weather that increases as you travel north across our forecast area. Breezy southwest winds are forecast. Areas that remain rain-free will continue to heat up to above normal levels. Places along the Treasure Coast and around Lake O may reach the mid 90s. Thursday & Beyond... Once the trough exits, ensembles suggest that heights will increase across Florida. However, with no front to clear the area, near to above normal moisture will remain in place leading to diurnally- driven scattered showers and storms. Temperatures look to remain above normal as H85 temperatures hold between +18C and +20C. Fairly widespread low/mid 90s are forecast, and peak heat indices will likely soar to 100-105F each afternoon. Ensembles are also hinting at another disturbance approaching the Deep South sometime next weekend, which may eventually bump up our shower/storm chances once again. && .PRELIMINARY POINT TEMPS/POPS... DAB 86 67 85 69 / 0 0 10 0 MCO 93 69 89 71 / 10 0 10 0 MLB 88 70 85 72 / 10 0 10 0 VRB 90 69 86 71 / 30 10 10 0 LEE 91 68 89 71 / 0 0 10 0 SFB 92 68 89 69 / 10 0 10 0 ORL 93 69 89 71 / 10 0 10 0 FPR 91 69 87 70 / 30 10 10 0 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ Watson/Sedlock