Area Forecast Discussion
Issued by NWS Melbourne, FL
Issued by NWS Melbourne, FL
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650 FXUS62 KMLB 101133 AFDMLB Area Forecast Discussion National Weather Service Melbourne FL 733 AM EDT Mon Jun 10 2024 ...New AVIATION... .AVIATION... (12Z TAFs) Issued at 733 AM EDT Mon Jun 10 2024 VFR persist thru the TAF until coverage of RA/TSRA increases through the day. FEW-SCT mid and high level clouds grow in coverage after 15z-16z with VCTS/VCSH beginning at most terminals 18z-20z. TEMPOs included from MCO/SFB east to TIX/MLB, including SUA, for TSRA. CIG/VIS reductions to IFR and brief gusty winds are possible. Outside of storms, WSW winds remain around 10 kt or less, backing to the SE at the coast after 17z. TSRA will decrease in coverage, leaving lingering SHRA after 02-03z. However, another push of moisture toward the end of the TAF period will bring at least VCTS conditions back to the sites. && .PREVIOUS DISCUSSION... Issued at 536 AM EDT Mon Jun 10 2024 Today-Tonight...One last day of abnormally hot weather, then the streak finally comes to an end as the mid-upper level ridge responsible is shunted to the southeast by broad troughing over the CONUS digging down to the Atlantic seaboard. An attendant surface front associated with the trough stalls near or just north of North Florida, while the Atlantic high retreats south and seaward a bit, backing low-level flow southwesterly, and lifting copious (and much needed) tropical moisture to Florida. Increasing cloud cover brings temperatures down a notch from previous days, but still well above normal in the M-U90s inland and L-M90s along the coastal corridor. A couple high temperature records could be broken again today, with Leesburg and Vero Beach the most likely candidates. Heat index values also come down a notch, but remain just below Heat Advisory criteria at 100-107, highest from Osceola and southern Brevard south. Winds WSW-SW 5-10 mph pick up to 10-15 mph and a bit gusty in the afternoon , especially along the coast. As for rain chances, we`ll start the day with a fairly sharp PWAT gradient across ECFL from around 1.8-1.9" in Martin County to 1.2-1.3" in northern Lake and Volusia counties, which are forecast to increase to 1.7"-2.1" (between the climatological 75th percentile and daily maximum) by the evening. This will support increasing rain chances through the day, starting at 20 pct across the southern counties by late morning, 30-50 pct across most of ECFL by the afternoon, and topping out at 60-70 pct from Orlando to Titusville south. CAMs have a bit of variation in timing, for example the HRRR getting things going mainly in the afternoon, but overall coverage is in pretty good agreement. While 500mb temperatures are a somewhat unimpressive at -6C to -4C, the additional instability provided by the increasing moisture looks to push MUCAPE values over 2,500 J/kg in the afternoon, and those hot conditions will cause low-level lapse rates to exceed 7-8 C/km, resulting in a favorable environment for clusters of pulse thunderstorms after 2 PM. Dry mid-levels could enhance downdrafts, and indeed soundings show DCAPE values 900-1,000 J/kg, leading to gusty thunderstorm winds to 50 mph, and a locally severe/damaging gust to 60 mph can`t be ruled out. Other storm hazards will be occasional to frequent lightning, and torrential downpours. Adequate low-mid level flow should keep storms on the move, but repeated rounds could result in locally high rainfall amounts of 2-3", with a upper limit of 4" not out of the question. Additional rounds of showers and storms are expected through the night, and while they won`t pack the same punch as those this afternoon as we lose instability from daytime heating, we`ll continue to see those rainfall totals increase. Tuesday-Friday...Fairly straight forward forecast at this point. Southwesterly flow around the Atlantic high transports juicy tropical moisture across Florida, which combined with a broadening shortwave trough becoming quasi-stationary over the GOMEX and Florida, will result in high rain chances and an increasing potential for localized flooding through the week. To paraphrase WFO MLB wisdom, weather in Florida is often the mean of two extremes, and as we look at the potential of going from drought to flooding, this certainly holds true. We`ll see multiple rounds of showers and lightning storms through the period with daily rain chances 80-90 pct. The big question will be where we see those repeated rounds of heavy showers and storms, and how much rainfall accumulates. A fairly common theme across the various guidance is 24-hour rainfall amounts of 1-3 inches, with locally higher amounts up to 4" possible, and a total QPF through Friday night of 5-8" down south and 2-4" to the north. Based on these numbers and the cumulative effect over several days, the Weather Prediction Center has issued a Marginal Risk for excessive rainfall across all of ECFL through the period, and a Slight Risk starting across the south Tuesday that shifts further north each day, reaching Orlando to Titusville by Friday. Model soundings show mostly that long-skinny profile associated with high rainfall events, but CAPE values still manage to reach 1,000-1,500 J/kg in the afternoons, so storms capable of gusty winds and at least occasional cloud to ground lightning will be possible. Almost as good news as the rain will be temperatures, which are forecast to barely make it to 90 in northern Lake and Volusia counties Tuesday and Wednesday, but otherwise and elsewhere only make it to the M-U80s thanks to the cloud cover and rain. While not a cold snap by any means, they will be at or below normal, which is at least something. Saturday-Sunday...Guidance has further diverged and further decreased forecast confidence going into the weekend. GFS develops a surface cyclone in the Gulf of Mexico, while the ECM develops little more than a wave. This results in a much drier solution from the GFS while the ECM keeps some moisture across the area and continues rain chances. Official forecast reflects a compromise blend between the two, keeping relatively high rain chances and near to below normal temperatures through the weekend, but changes are likely as we drawn nearer. && .MARINE... Issued at 536 AM EDT Mon Jun 10 2024 Today-Tonight...The Atlantic high retreats southeastward as a frontal boundary stalls near or north of North Florida. Flow starts to become more SW-SSW later in the day as a result, but the sea breeze circulation remains the primary driver of winds, backing them to the S-SE at 10-15 kts in the afternoon, then returning to SW-WSW overnight. Another nocturnal offshore surge to 15-20 kts is expected, but limited to well offshore of the Volusia waters tonight. Increasing moisture from the SWrly flow will result in SCT-NUM offshore moving showers and lightning storms, some of which could become strong, capable of winds over 35 kts and locally higher seas. Outside of storms, seas 1-3. Tuesday-Friday...Pattern remains fairly static through Friday. SWrly winds Tuesday shift to Srly Wednesday and Thursday, then start to shift to the SE Friday as high pressure over the Atlantic builds back. High rain chances through the period with rounds of SCT-NUM showers and lightning storms. High cloud cover will prevent meaningful development of the sea breeze. Seas generally 1-3 ft outside of storms, maybe creeping up to 4 ft in the Gulf Stream Tuesday night. && .FIRE WEATHER... Issued at 536 AM EDT Mon Jun 10 2024 Sensitive fire weather conditions due to near record heat and drought conditions continue today, then a gradual improvement is expected through the request of the week as moisture and subsequent rain chances increase. Min RHs 50 pct or higher except north of I-4 at 35-40 pct today. SCT- NUM showers and lightning storms expected this afternoon. && .PRELIMINARY POINT TEMPS/POPS... DAB 96 73 89 73 / 30 60 80 50 MCO 95 76 87 75 / 60 60 80 50 MLB 93 74 87 74 / 70 70 90 70 VRB 93 75 87 73 / 60 70 90 70 LEE 95 76 90 76 / 30 60 80 40 SFB 96 76 89 75 / 50 60 80 50 ORL 96 76 89 75 / 60 60 80 50 FPR 93 74 87 73 / 60 70 80 70 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ DISCUSSION...Haley AVIATION...Schaper