Area Forecast Discussion
Issued by NWS Miami, FL
Issued by NWS Miami, FL
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346 FXUS62 KMFL 110555 AFDMFL Area Forecast Discussion National Weather Service Miami FL 155 AM EDT Tue Jun 11 2024 ...New SHORT TERM, LONG TERM, MARINE... .SHORT TERM... (Today through Wednesday) Issued at 152 AM EDT Tue Jun 11 2024 A cold front and associated weak surface low is currently progressing into northern Florida this morning, with the front projected to stall in that general area through the short-term period. At the mid-lvls, longwave troughing will be in place over the eastern CONUS with ridging pinned to our southeast (centered to the SW of the Turks and Caicos). This configuration will result in strengthening deep-layer SWrly flow overspreading our area, which will in turn transport rich tropical moisture, characterized by PWATs around 2.5 inches (approx 3 SD above climo) NEwrd into SFL today. This anomalous moisture plume, which will largely remain pooled over South and Central Florida over the next several days, will set the stage for an active and wet pattern over our area. In terms of forecast details, the overnight CAMs continue to highlight the threat of heavy rainfall and locally very heavy rainfall over portions of our area through Wednesday. In large the highest totals look to be focused over SWFL where low-lvl convergence will be maximized in the SWrly regime. However, the anomalous moisture and deep warm-cloud layer will enable efficient warm-rain processes, and any convective elements that can form (in the limited instability tropical environment) will be capable of high rain rates and localized flooding concerns... with the more widespread flooding concern being dictated by which areas can receive repeated rounds from these heavy rainers. Consequently the flood watch remains in effect for the entire area through Wednesday night, although as will be discussed in the long term, the hydro threat will likely linger into the latter half of the workweek. In terms of specific rainfall amounts, the HREF means yield widespread totals of 2-4 inches across SEFL through Wednesday afternoon, with 3-7 inch totals over SWFL. The Probability Matched Mean (PMM), which is likely more representative of higher-end (but not necessarily the absolute maximum values) in this regime, would bump those ranges to 3-6 inches over the east coast and 6-10 inches over portions of SWFL. Individual CAMS even depict some very localized maxima of 10+ inches (in just the next 36-48 hours) largely over SWFL. Our forecast QPF values are a blend of the more conservative (but likely decent as an area-average) HREF mean, and the more aggressive PMM values that may better capture the higher end possibilities. However, it must be emphasized that large spatial gradients in totals are very likely given that the tracks of individual poorly-organized convective cells will likely drive totals, and these tracks are nearly impossible to predict with much lead-time. Outside of the periods of heavy rain and associated flooding concerns, a silver lining will be the somewhat cooler temperatures as abundant cloud cover and periods of rainfall should keep highs only in the low to mid 80s through Wednesday. && .LONG TERM... (Wednesday night through Monday) Issued at 152 AM EDT Tue Jun 11 2024 The wet and active period will continue for the first half of the extended period as the boundary to our north remains stalled and the tropical moisture remains focused over south-Central Florida. A mid- lvl shortwave trough will pivot southeastward and phase with the longwave east-coast trough in the Wednesday night-Thursday time frame, amplifying and elongating the trough from SW-NE. Ultimately the building ridge to our north will cause the increasingly enlongated trough to split Saturday, with the northern split lifting northeast while the southern split looks to retrograde into the Central GOM. This will hopefully result in the tropical moisture plume being reoriented west of the area by Sunday-Monday with mid- lvl ridging then building into the eastern CONUS in that time period. In terms of sensible weather, the main concern will remain the flooding potential Thursday/Friday as the lingering tropical moisture will interact with upper-lvl disturbances pivoting through the base of the trough. Although raw totals don`t look quite as high as the initial surge on Tuesday/Wednesday (although they could be comparable over SEFL) it is possible the ground will be already saturated from the earlier week rainfall, so any additional heavy rainfall could exacerbate hydro issues. Consequently, assuming the Tues/Wed rainfall more or less pans out as expected, the flood watch will likely need to be extended into the Thursday/Friday timeframe. Assuming the aforementioned synoptic evolution occurs, Saturday will hopefully mark the end of the heavy rainfall threat, as the retrograding trough and building ridge combination should direct the deep tropical moisture to our west. Although lingering low-lvl moisture will support at least scattered showers and storms through the period, the strengthening easterly flow and building heights should limit the chances for widespread heavy rainfall beyond Friday night/early Saturday (although exact forecast details remain uncertain). && .AVIATION... (06Z TAFS) Issued at 1251 AM EDT Tue Jun 11 2024 Challenging period as conditions will gradually deteriorate with periods of prevailing MVFR or even IFR conditions intermittently. Numerous showers and scattered thunderstorms will encroach on TAF sites beginning early this morning, and continuing through the vast majority of the period. CIGs less than 1000 ft AGL and significant VIS reductions are the primary impacts, as well as lightning and locally strong wind gusts embedded near/around TSRA. && .MARINE... Issued at 152 AM EDT Tue Jun 11 2024 Periods of strong showers and thunderstorms are expected over the area waters the next several days, which will result in locally hazardous winds and seas. Outside of thunderstorms, cautionary- level (at time near hazardous) south-southwesterly winds can be expected through Wednesday with seas 3 ft or less. && .PRELIMINARY POINT TEMPS/POPS... Miami 86 78 87 78 / 90 90 90 90 West Kendall 87 76 88 76 / 90 90 90 90 Opa-Locka 87 77 89 77 / 90 90 90 90 Homestead 87 78 88 77 / 90 90 90 90 Fort Lauderdale 86 78 86 77 / 90 90 100 90 N Ft Lauderdale 86 78 87 77 / 90 90 100 90 Pembroke Pines 89 78 89 78 / 90 90 90 90 West Palm Beach 86 76 87 75 / 100 70 100 90 Boca Raton 87 77 88 76 / 90 90 100 90 Naples 87 77 86 77 / 100 70 100 90 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...Flood Watch through Wednesday evening for FLZ063-066>075-168- 172>174. AM...None. GM...None. && $$ SHORT TERM...Carr LONG TERM....Carr AVIATION...Rizzuto