Area Forecast Discussion
Issued by NWS Melbourne, FL

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000 FXUS62 KMLB 181955 AFDMLB Area Forecast Discussion National Weather Service Melbourne FL 355 PM EDT Sun Apr 18 2021 .DISCUSSION... ...HEAVY RAINFALL AND STRONG STORMS EXPECTED TO IMPACT EAST CENTRAL FLORIDA THROUGH MID WEEK... Rest of Afternoon-Mon...A frontal boundary which was analyzed over northern FL this morning/early afternoon is forecast to slightly push south towards the Orange/Cape line tonight. As we sit on the warm sector in a SW flow and PWAT values of an inch and a half with dew points in the mid60-near 70 this afternoon, we expect another round of showers and thunderstorms to develop from Osceola/Lake counties to the northeast. These will be moving to the northeast and reach the coastal counties from Brevard to Volusia and the Atlantic waters. Strong to nearly severe gusty winds and small to isolated large hail remains possible with these storms. This round, reaching the Atlantic, could end later this evening. Then short term models show another round of a line of storms reaching the west coast around midnight and pushing east overnight. This will originate from the convection currently over the eastern gulf and it will bring heavy rain for most of the forecast area through Mon afternoon. So the start of the work week will be a messy one, as these storms will have the potential to generate heavy rain and thunderstorms causing localized flooding and strong gusty winds. Tuesday-Wednesday...Early to mid week trends are holding steady, as the frontal boundary dominating the local pattern dances over the FL peninsula. Late Monday night, the boundary will drop towards south FL, sending PoPs of 70-80% across the southern Space and Treasure Coasts overnight. The upper level support for strong to severe storms through the day exits over the Atlantic waters in the late evening hours, which may curb the potential for thunder towards midnight and through the early morning hours. The boundary then switches gears into reverse, trekking back northward on Tuesday, leading to the third consecutive day of PW values above 1.8-2.0" pumping across the Gulf of Mexico. These values are the 90th percentile for mid April, and close to daily maxima for the period of record. Needless to say, the threat for widespread heavy rain looks to be probable through mid week, especially on Tuesday, however, antecedent soil conditions suggest that the flood threat will remain marginal, largely dependent on rain totals over the next 48 hours. For now, do not anticipate the need for a Flood Watch, however, urban flooding could prompt the need for flood warnings, especially in training thunderstorms. Axis of broad mid-level trough crosses FL by late Wednesday, forcing surface front to drop south of the CWA by late in the day. Moisture axis gradually lessens, but still enough moisture convergence and lift for high POPs across the southern CWA (50-70%), with shower coverage lowering/ending across the north during the day (20-40 percent). Temperatures Tuesday fall to the low to mid 70s in the afternoon across the north and reach the mid 80s over the southern Treasure Coast following the movement of the boundary. Temps even out on Wednesday, reaching the low 80s areawide on Wednesday. Lows in the low to mid 60s. Modified Extended Discussion: Thursday-Friday...Zonal, unperturbed flow returns aloft with post- frontal surface high pressure well to the north ensuring a couple dry and relatively cool days/nights. Max temps ranging from lower 70s north to near 80 far south Thursday, and upper 70s/near 80 CWA- wide Friday. Thursday and Friday morning mins in the 50s, except 60- 65 along the coast south of the Cape. Longer range guidance suggests another mid-level trough approaches next weekend, with surface front and possible weak gulf low crossing the peninsula. This pattern would return rain chances and warmer temps starting Saturday. && .AVIATION... Convective activity took a pause early this afternoon but it should restart after 20z and impact KISM and KMLB northward. A few rounds of SHRA/TSRA with gusty winds are possible to impacts this afternoon, causing brief MVFR/IFR conditions. Then after midnight, another more widespread round of showers and storms will move in from the west and affect most of the terminals through Mon afternoon. These could reduce visibilities and cigs to IFR in pockets of heavy rain and produce strong gusty winds. && .MARINE... Tonight-Mon...Conditions across the local Atlantic waters will appear to be good for boating but as storms developing over east central FL move onshore, locally strong winds and higher seas will quickly change marine conditions. Outside any storm activity, winds will be variable up to 15 kt tonight and becoming SW towards Mon morning. Then a shift from the NW is forecast to start in the late afternoon from Volusia waters southward. Seas will be 2-3 ft outside any storm. Tuesday-Thursday...Prolonged period of daily scattered to numerous showers and strong thunderstorms will last through Wednesday, with the front finally pushing south of the area by Wednesday evening. Southeast winds 10-15 knots will veer NW on Wednesday as the front begins the southward shift, becoming NW to N by early Thursday and increasing over 15 knots. Seas Tue- Wed of 2-4 ft, increasing seas 4- 5 ft nearshore and up to 6 ft in the offshore waters. && .PRELIMINARY POINT TEMPS/POPS... DAB 65 76 63 77 / 80 80 60 80 MCO 68 79 66 79 / 80 80 70 80 MLB 68 82 67 82 / 80 80 70 80 VRB 69 85 66 84 / 50 80 70 80 LEE 67 75 65 76 / 80 80 60 80 SFB 67 77 65 78 / 80 80 70 80 ORL 70 79 67 80 / 80 80 70 80 FPR 67 86 67 85 / 40 80 70 70 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ Negron/Smith/Leahy/Haley is the U.S. government's official web portal to all federal, state and local government web resources and services.