Area Forecast Discussion
Issued by NWS Miami, FL
Issued by NWS Miami, FL
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208 FXUS62 KMFL 121249 AFDMFL Area Forecast Discussion National Weather Service Miami FL 849 AM EDT Wed Jun 12 2024 ...New UPDATE, AVIATION... .UPDATE... Issued at 823 AM EDT Wed Jun 12 2024 After a nice lull overnight, convection has fired up once again along a convergence boundary along central FL near the Lake region. Portions of this line have moved over Glades, Hendry and Collier county, with an estimated 1-3 inches of rain already over some areas. This line is forecast to drift eastward through the day, bringing more rain across the rest of the CWA. Additionally, ACARS sounding data and the 12Z MFL sounding show favorable conditions for additional rounds of rainfall to develop along the East Coast ahead of this line. As such, the flash flooding risk will persist across the area, especially for locations that received multiple inches of rain yesterday. A very conditional, very marginal chance for isolated landspouts or tornados will also be possible this afternoon with the stronger "overachieving" storms that manage to develop, but this possibility will hinge on having enough instability and shear for a storm to organize, which still looks uncertain at this time. && .SHORT TERM... (Today through Thursday) Issued at 147 AM EDT Wed Jun 12 2024 Somewhat drier mid-lvl air has filtered into SFL in the wake of the earlier (convectively-enhanced) shortwave passage Tuesday afternoon/evening. This combined with diurnal stabilization has allowed for a general lull in heavier rainfall over the area early this morning. This lull will likely not last very long as additional convective development looks likely over portions of the area by mid-morning (and potentially even by sunrise), as additional shortwave impulses pivot into the area and interact with the anomalous tropical moisture (PWATs 2.3-2.5 inches) that remains pooled over South Florida. The forecast for today remains complex, as the overnight guidance suite hints at a plethora of plausible but sometimes conflicting scenarios for how the day will evolve. There is a general consensus that the best low-lvl convergence and moisture pooling will be over northern areas of our CWA in the Lake region, and many of the global models place their QPF maximum in this vicinity (or even north of our area altogether). However, many of the higher-res guidance hint at greater convective coverage/intensity south of this zone of broader ascent likely fueled by greater diurnal destabilization and potentially a weak differential heating boundary. Both the northern and southern foci seem plausible so went with a broadbrushed approach for QPF, giving slightly more weight to the southern solution as it is favored by the CAMs and we are only 6-18 hours out. Whether the northern or southern solution pans out will have impacts on today`s hydrology concerns, as the northern third or so of the area saw significantly less rainfall (generally 2 inches or less) on Tuesday compared to the region between Tamiami Trail and Alligator Alley which observed a widespread 3-6 inches, with localized amounts of up to 8 inches. This observed rainfall gradient is evident in FFG with 6 hour FFG varying from around 2 inches in coastal Collier and Miami-Dade to 4-5 inches in Palm Beach/Glades/Hendry counties. Consequently a southern solution would likely result in greater hydrologic impacts, as several inches of rain would be likely over already saturated areas, while the northern solution would be more "equitable" and ideally less impactful (unless it focused over urban portions of PB county). The only notable change to the synoptic pattern on Thursday will be the development of an intensifying sfc. low over the stalled boundary to our north, just off the SE Coast. This low (which may eventually acquire subtropical characteristics over the Gulf Stream) will shift NE in the late week period, but looks to at least in the short term keep the subtropical moisture tap in place over our area through Thursday (i.e. the classic cyclone moisture tail). With the potential for significant additional rainfall (HREF PMMs would indicate areas of 2-4 inch totals possible) and likely saturated ground made the decision to extend the Flood Watch through Thursday evening with this morning update. && .LONG TERM... (Wednesday night through next Monday) Issued at 256 PM EDT Tue Jun 11 2024 An active subtropical jetstream will become entrenched over central Florida, just downstream of a positively tilted major short-wave trough that will impart on the Gulf of Mexico. This will allow for a fetch of deep tropical moisture to remain entrenched over South Florida, thus resulting in a prolonged period of widespread rainfall will continue through the remainder of the week. Hydrologic concerns will be the primary focus through the remainder of the week, primarily owing to antecedent rainfall from previous days, and the repeated bouts of strong thunderstorms capable of producing very high tropical rainfall rates. With precipitable water remaining above 2.0 inches, expect favorable conditions for flooding and even flashing flooding - particularly for urban locations. The most intense rainfall will develop in tandem with upper level impulses that trek through the CWA through this period. As far as rainfall totals through Friday, expect 4-8 inches for the western half of the region, and 2-6 inches for the eastern half of CWA (including metropolitan east coast), with locally higher totals possible. These totals are subject to deviate based on how the forecast evolves in the coming days. A stationary frontal boundary will gradually dissolve, as low-level circulations develop over the southern Gulf of Mexico and coastal FL/GA respectively. This will likely stretch/divert moisture away in opposite directions away from the region, though there will still be lingering deep tropical moisture such that heavy rainfall will still be a concern through the weekend. By late Saturday/early Sunday, a backing of low-level winds will be realized as expansive Bermuda ridge of high pressure expands southwestward. An easterly flow regime will likely become re-established, which will allow for periods of heavy rainfall in the morning along the east coast, with more coverage generally along interior and western portions of the CWA. Heavy rainfall and flooding will be the primary concerns again, though the threat should be diminished in comparison to earlier in the week. Nevertheless, cannot rule out the potential for flooding through the weekend, mostly conditional on measured rainfall up to this point. High temperatures will begin to increase slightly through the period with mid 80s expected on Friday and slightly increasing each afternoon. Highs will reach the lower 90s again by the Tuesday- Wednesday time frame. && .AVIATION... (12Z TAFS) Issued at 823 AM EDT Wed Jun 12 2024 Periods of sub-VFR conditions likely today as rounds of SHRA/TSRA push through today. Convective activity is forecast to spread NW to SE through the day. Several TEMPOs are already in place but short- fuse amendments could be needed as conditions evolve. Outside of storm outflows generally southerly winds - gusty at times - will prevail through the daytime hours. && .MARINE... Issued at 147 AM EDT Wed Jun 12 2024 Near hazardous southerly winds will persist over the area waters today, as the area remains south of a stalled front and associated surface low. These winds will decrease Thursday into the late week period as the low progresses northeast into the Atlantic waters. Numerous showers and thunderstorms remain likely through much of the upcoming week resulting in periods of locally higher winds and seas. Outside of storms wave heights should remain 3 ft or less through the forecast period. && .BEACHES... Issued at 147 AM EDT Wed Jun 12 2024 The moderate risk of rip currents will continue today for the beaches of Collier county as breezy SW flow persists. && .PRELIMINARY POINT TEMPS/POPS... Miami 86 78 85 76 / 90 90 90 90 West Kendall 87 75 87 74 / 90 100 90 90 Opa-Locka 87 77 87 76 / 90 80 90 90 Homestead 87 76 87 75 / 80 100 90 90 Fort Lauderdale 85 77 84 77 / 90 80 90 90 N Ft Lauderdale 86 77 85 76 / 90 80 90 90 Pembroke Pines 89 77 88 77 / 90 80 90 90 West Palm Beach 86 75 85 75 / 90 70 100 90 Boca Raton 87 76 86 76 / 90 80 90 90 Naples 87 77 86 76 / 90 90 90 100 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...Flood Watch through Thursday evening for FLZ063-066>075-168- 172>174. AM...None. GM...None. && $$ SHORT TERM...Carr LONG TERM....SRB AVIATION...ATV