Area Forecast Discussion
Issued by NWS Miami, FL
Issued by NWS Miami, FL
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238 FXUS62 KMFL 161248 AFDMFL Area Forecast Discussion National Weather Service Miami FL 848 AM EDT Mon Sep 16 2024 ...New UPDATE... .UPDATE... Issued at 845 AM EDT Mon Sep 16 2024 A warm start to this Monday across southern Florida with morning convection over the local waters. Forecast is on track with observed trends matching recent guidance runs well. Slow-moving strong thunderstorms this afternoon could produce strong to locally damaging wind gusts, localized flooding from excessive rainfall, and frequent to excessive lightning. The morning high tide has reached minor flood stage at most locations with the potential for localized minor coastal flooding slowly subsiding through the morning as the tide falls. No major updates are anticipated through midday. Have a wonderful Monday morning! && .SHORT TERM... (Today through Tuesday) Issued at 250 AM EDT Mon Sep 16 2024 The persistent Rex Block synoptic pattern over the eastern United States today will gradually begin to break down today as a complex capture interaction of Potential Tropical Cyclone Eight takes place in conjunction with an upper level low over the southeastern United States. This interaction of the two lobes of vorticity will weaken the existing mid-level ridge across the northeastern United States and usher in a period of troughing across a large swath of the eastern United States by late Monday. This will usher in cooler temperatures aloft (-6C to -7C at 500mb) and facilitate the development of stronger southwesterly 500mb flow across the region. The CAMs (Convection Allowing Models) such as the HRRR, RAP, etc depict a residual column of drier mid-level air aloft today as well. At the surface, light and variable surface winds will continue to prevail at the surface which may facilitate the development of fairly patchy inland fog this morning that should quickly burn off after sunrise. With the onset of diurnal heating, the mesoscale-driven sea-breeze circulations will gradually begin to develop during the late morning hours into the early afternoon hours. Ample heating and initially clear skies will result in another day of warm and toasty temperatures across the region. Factor in the ample humidity courtesy of a stalled frontal boundary just to the north of our area, and peak heat index values will once again be in the triple digits before convective initiation occurs. For this reason, a Heat Advisory has been issued for Miami-Dade and Broward counties from 10am to 6pm today as peak heat indices of 104-107 degrees fahrenheit are forecast. With ample surface heat and cooler values aloft, lapse rates will steepen today with the potential of mid-level lapse rates of 6.0 to 6.5 C/km. The increased influence of synoptic troughing will favor southwesterly background flow and the continued evolution of convection developing over inland areas before shifting towards the east coast metro. Combining the mesoscale and synoptic factors listed above, there is the potential for a few strong to marginally severe storms across the east coast metro this afternoon. With background southwesterly flow, the Atlantic sea-breeze will remain pinned along the east coast metro which could provide localized ascent and allow for the development of a few pulse storms reaching strong to marginally severe levels. Residual dry air aloft may result in wet microbursts with the collapse of the tallest cores producing strong to marginally severe wind gusts. In addition, given the veering of winds with height along the pinned Atlantic sea-breeze, a brief tornado cannot be ruled out. The most favorable region for a potential spin-up would be across coastal Broward & Palm Beach counties as the Atlantic sea-breeze struggles to make much inland progress. Aside from convective hazards, the pinned Atlantic sea-breeze may also result in some limited scope of a localized flooding hazard in localized pockets where heavy rainfall falls. The latest HREF LPMM (localized probability- matched mean) depicts the potential of a few localized pockets of 1-2 inches across the east coast metro areas which could result in some localized flooding, especially if timed with the elevated high tide cycles (King Tides). The combination of heavy rainfall and higher than normal tides could result in slow drainage and a lower threshold of localized flooding across coastal areas. By Tuesday, the two lobes of 500mb vorticity across the southeastern United States will merge into one concise area of low pressure. This will keep southwesterly synoptic flow across the region and a similar setup to what will be experienced across the region today. 500mb temperatures will still remain in the ballpark of -6C to -7C with mesoscale circulations and boundaries developing during the afternoon hours. A threat of a few locally strong to marginally severe storms across the east coast metro areas remains possible on Tuesday afternoon as the Atlantic sea-breeze will be pinned along the coast once again. Strong winds and the potential of a brief spin-up along the Atlantic sea-breeze remains possible on Tuesday afternoon. High temperatures will reach the lower 90s each afternoon before convective initiation will result in a cool down across affected areas. && .LONG TERM... (Tuesday night through Sunday) Issued at 250 AM EDT Mon Sep 16 2024 The mid-level low across the southeastern United States will gradually lift northward through the mid-week period which will veer 500mb flow across the region to a westerly then northwesterly direction. The elongation of troughing over the eastern United States will keep 500mb temperatures in the -6C to -7C range during the mid-week period with forecasted daily afternoon lapse rates in the 5.5 to 6.0 C/km range. At the surface, we will remain situated to the south of the weak yet quite persistent stationary boundary still draped across Central Florida. Ample precipitable water (PWAT) values of 2.0+ inches and a fairly moist saturated column will result in daily afternoon rain chances near climatological norms. The prevailing weak surface winds and the generally westerly flow aloft will keep a rain pattern favoring SoFlos interior and eastern metro areas. Deeper convection will again focus along sea breeze and outflow boundaries mainly in the afternoon hours, with the continued potential of a few isolated strong to marginally severe pulse storms when ascent is briefly maximized along those aforementioned mesoscale boundaries. Afternoon highs are expected to moderate a little and remain near seasonal normals (upper 80s to low 90s). However, peak heat indices will likely remain in the low triple digits, but should remain just below heat advisory criteria. && .AVIATION... (12Z TAFS) Issued at 745 AM EDT Mon Sep 16 2024 Generally VFR to start the morning though convection could start by mid-morning along the coast. As the sea breezes develop and advance inland slowly, the highest risk for sub-VFR comes in the afternoon hours. Short-fused AMDs for IFR/LIFR may be necessary for directly impacted terminals. Light wind flow will prevail through much of the period turning onshore briefly with the sea breezes in the afternoon. && .MARINE... Issued at 250 AM EDT Mon Sep 16 2024 Generally light south to westerly winds will prevail through most of this week as a weak surface boundary and Potential Tropical Cyclone Eight remain north of the area. Seas across the northern Atlantic waters will remain elevated through this afternoon as northerly swell generated by Potential Tropical Cyclone Eight offshore of the southeastern United States moves in. Scattered showers and thunderstorms will be possible each day through the period and could lead to locally higher winds and seas. && .BEACHES... Issued at 250 AM EDT Mon Sep 16 2024 Continued northerly swell from Potential Tropical Cyclone Eight offshore of the southeastern United States will result in a high risk of rip currents along the Palm Beaches today with a moderate risk of rip currents being realized elsewhere along the east coast. This ongoing northerly swell will result in a continued elevated rip current risk through the middle part of the work week along the east coast of South Florida as the swell gradually subsides. There will also be the continued potential for minor coastal flooding around periods of high tide due to astronomically higher tides associated with this full moon through mid-week. A Coastal Flood Statement is in effect through at least Wednesday. High Tide Times: Naples: 12:05 pm Monday, 1:01 am Tuesday, 12:56 pm Tuesday Lake Worth: 6:52 am Monday, 7:27 pm Monday, 7:46 am Tuesday Port Everglades: 7:12 am Monday, 7:44 pm Monday, 8:06 am Tuesday Virginia Key: 8:00 am Monday, 8:30 pm Monday, 8:53 am Tuesday && .PRELIMINARY POINT TEMPS/POPS... Miami 92 78 91 77 / 60 40 50 40 West Kendall 92 77 90 75 / 70 40 60 40 Opa-Locka 93 78 91 77 / 60 40 50 40 Homestead 92 77 90 76 / 70 40 50 40 Fort Lauderdale 91 78 91 77 / 60 40 50 40 N Ft Lauderdale 92 78 90 77 / 60 40 50 40 Pembroke Pines 94 79 91 77 / 60 40 50 40 West Palm Beach 93 78 90 76 / 50 40 50 30 Boca Raton 93 78 91 77 / 50 40 50 40 Naples 91 79 90 77 / 30 20 40 20 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...Heat Advisory until 6 PM EDT this evening for FLZ071>074-172>174. High Rip Current Risk through Tuesday evening for FLZ168. AM...None. GM...None. && $$ SHORT TERM...Hadi LONG TERM....Hadi AVIATION...RAG