Area Forecast Discussion
Issued by NWS Melbourne, FL
Issued by NWS Melbourne, FL
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753 FXUS62 KMLB 190758 AFDMLB Area Forecast Discussion National Weather Service Melbourne FL 358 AM EDT Thu Sep 19 2024 ...New DISCUSSION, MARINE, HYDROLOGY... .DISCUSSION... Issued at 358 AM EDT Thu Sep 19 2024 KEY MESSAGES: - Shower and storm chances today will peak (40-70%) generally south of Orlando. From Friday through early next week, chances of rain will fall below normal. - Minor coastal flooding remains possible, particularly during late morning high tides from Friday through the upcoming weekend. Low-lying streets, yards, and docks may flood along the barrier islands and Intracoastal. - There is a medium chance (40%) for tropical development in the NW Caribbean or Southern Gulf of Mexico by next week. It is too early to determine what, if any, impacts for East Central Florida. However, continue to monitor the forecast for updates. ----------Synoptic Overview---------- A mid-level trough extends down the Eastern Seaboard to Florida this morning with ridging over Texas. This pattern remains stagnant for the rest of the week before a shortwave in the Desert Southwest is forecast to push ridging eastward toward Florida by early next week. At the surface, high pressure will settle into the Appalachians by this weekend, with easterly boundary layer flow gradually resuming. With the northerly-component mid-level flow, somewhat below normal total moisture (PWATs) will be advected over Central Florida late this week through early next week. Occasional perturbations in the boundary layer may introduce transient increases in moisture. With H85 T`s near normal, temperatures should hold close to seasonal averages through early next week. By the mid to latter portion of next week, the grand ensemble indicates that the Central American Gyre is forecast to become more active. Many members indicate deep tropical moisture will lift northward toward the Gulf and perhaps even Florida. The National Hurricane Center indicates a 40% chance of tropical development over the next 7 days, potentially in the NW Caribbean or southern Gulf of Mexico. -------Sensible Weather & Impacts------- Today & Tonight... Early this morning, we continue to monitor some remnant showers and storms along the Treasure Coast. Once this activity pushes offshore, it should be a fairly quiet morning. This afternoon, HREF members and RAP guidance show that the juxtaposition of deeper moisture and subtle convergence will generally lie south of Orlando. Storm chances vary between 20-30% north of Orlando to 50-70% along much of the Treasure Coast. Main threats include brief gusty winds of 35-45 mph, occasional lightning, and heavy rain leading to minor flooding. Storms may linger after sunset across our southern counties before diminishing overnight. Highs should range in the lower 90s with peak heat indices from 98-103. Expect lows in the low/mid 70s. Friday-Saturday... Broad troughing persists over Florida along with lingering weak vorticity at H5. Meanwhile, moisture values continue to decrease, stymieing the potential for widespread showers and storms. Northeasterly surface flow will develop, allowing for an increasingly dominant Atlantic breeze each day. For now, we have limited shower/storm chances to 20-30% from Melbourne north and 30- 40% Treasure Coast on Friday. Afterward, only 20-30% shower/storm chances return on Saturday. Highs will reach the upper 80s to around 90F. High astronomical tides and onshore flow will introduce the threat of minor coastal flooding at high tide, particularly with the late morning high tide cycles each day. The Coastal Flood Advisory has been extended to include Saturday, and may eventually need to be extended to Sunday. Sunday-Tuesday... Ridging overtakes Florida aloft and surface high pressure remains to our north, keeping easterly boundary-layer flow in place. With continued below-normal available moisture, rain/storm chances will remain muted at 20-30%. Highs continue to range from the upper 80s to around 90 with lows in the low 70s inland and mid/upper 70s along the coast. Wave guidance shows increasing swells late this weekend which could make surf conditions hazardous for beach-goers. Mid/late next week... Confidence is quite low as we move deeper into next week. The latest (19/00z) grand ensemble suite continues to indicate the Central American Gyre (CAG) will consolidate waves of convection and deep moisture in the NW Caribbean. In the mid-latitudes, the ensembles also indicate substantial spread in the depth and speed of movement of a trough riding atop a flat and weakening ridge axis extending from Texas to Florida . Therefore, the guidance is split on where this disturbance will be drawn and exactly when. At a bare minimum, that has local implications on when rain and storm chances increase. There is currently a medium (40%) potential for tropical development in the NW Caribbean or So. Gulf, near or within the developing CAG, over the next 7 days. The timing and depth of the aforementioned mid-latitude trough appears to be critical in the movement of any tropical feature, if one were to develop. There is much speculation regarding whether a tropical cyclone will form, and if so, where it will ultimately go. Presently, the guidance shows a wide gamut of potential outcomes. Ultimately, the impacts on our area are unclear at this time - but it`s yet another reminder: we are now in the heart of hurricane season. Let`s take this opportunity to go over our hurricane preparation kits and plans. && .MARINE... Issued at 358 AM EDT Thu Sep 19 2024 Today-Tonight... Lingering showers/storms over the Treasure Coast waters are expected to weaken this morning. Generally 3-4 FT seas today with winds becoming NE 5-12 KT north of Sebastian Inlet and more variable to the south. Scattered showers and storms are forecast today especially south of Cape Canaveral. Some of the storms could be offshore-moving and gusty. Friday-Monday... 2-4 FT seas persist through at least Saturday before building to 3-5 FT from Sunday into Monday as northeast onshore winds increase to 8-15 KT and a northeast swell enters the local Atlantic. Shower and thunderstorm activity will be more isolated. && .AVIATION... (06Z TAFs) Issued at 140 AM EDT Thu Sep 19 2024 VFR conditions prevailing. Ongoing TSRA along the Treasure Coast should taper off by around 7Z. Then, dry conditions forecast through late morning. Initially offshore winds will veer easterly along the coast by around 18Z, as the east coast sea breeze develops. The sea breeze will then push inland through the day, reaching inland terminals by mid to late afternoon. Winds around 10kts or less. VCTS possible along the sea breeze in the afternoon hours. The highest chance for showers and storms looks to be the Treasure Coast, though confidence is too low to include TEMPOs at this time. && .HYDROLOGY... Issued at 358 AM EDT Thu Sep 19 2024 The Saint Johns River at Astor is forecast to remain in Moderate Flood stage into the upcoming weekend. The potential exists for small additional rises if locally heavy rainfall develops over the river basin. Farther upstream, the Saint Johns at Deland, Sanford, and above Lake Harney has become nearly steady either just below or within Action Stage. Interests along the river should monitor for future forecast updates. && .PRELIMINARY POINT TEMPS/POPS... DAB 89 73 88 74 / 20 10 20 10 MCO 92 74 90 73 / 40 20 20 0 MLB 90 74 88 74 / 40 30 30 10 VRB 90 73 88 73 / 50 50 40 20 LEE 90 73 90 73 / 30 10 10 0 SFB 90 73 89 72 / 40 10 20 0 ORL 92 75 90 74 / 40 10 20 0 FPR 90 73 88 72 / 60 50 40 20 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...Coastal Flood Advisory until 2 PM EDT Saturday for FLZ141-154- 159-164-347-447-647-747. AM...None. && $$ DISCUSSION...Heil AVIATION...Leahy