Area Forecast Discussion
Issued by NWS Miami, FL
Issued by NWS Miami, FL
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344 FXUS62 KMFL 201918 AFDMFL Area Forecast Discussion National Weather Service Miami FL 318 PM EDT Thu Jun 20 2024 ...New LONG TERM... .SHORT TERM... (Rest of today through Friday) Issued at 147 PM EDT Thu Jun 20 2024 Typical summertime conditions will be on tap for South Florida today, with chances for scattered showers and a few thunderstorms across the interior and southwest Florida coastline. Sounding date from the 12Z MFL launch and ACARS flights show moderate instability and lapse rates in place across the area, with dry air in the mid- levels with near climo moisture near the surface. The combination of these factors has allowed for a few isolated low-topped showers along the East Coast earlier today, but the dry air aloft has helped limit ascent and further vertical development. Activity will continue through the afternoon, mainly over the interior and Gulf Coast as the dominant easterlies quickly push the East coast sea breeze further inland. On Friday, models show a large area of enhanced moisture associated with a weak surface trough over the southwest Atlantic gradually migrating towards the region. Some of these models show dry air potentially wrapping around the southwestern side of the trough and over our region, which could help limit widespread rainfall across South FL. Winds will veer slightly from the southeast, which will help in concentrating scattered showers and thunderstorm activity towards the Lake region in the afternoon hours. Temperatures across the East Coast today will benefit from the breezy easterly flow, with highs topping off in the upper 80s. Interior and southwest FL will see further warming throughout the day, with highs in the low 90s. Conditions on Friday could get slightly warmer, with temperatures along the East Coast potentially reaching the 90s. Temperatures indexes will hit triple digits each afternoon but should remain below advisory criteria. && .LONG TERM... (Friday night through next Wednesday) Issued at 318 PM EDT Thu Jun 20 2024 Expansive mid-level ridging across the southeastern United States will continue to remain in firm control of our prevailing weather pattern as we enter the upcoming weekend. At the surface, the long- persistent surface ridging in place across the western Atlantic waters will prevail easterly to southeasterly flow across the region on Saturday. Peripheral moisture from a large and expansive Central American Gyre (C.A.G.) will begin to filter into the region on Saturday with notably higher precipitable water values in the 2.0- 2.4 inch range. This moistening in the vertical column will allow for a greater abundance of convection, albeit with still relatively warm 500mb temperatures as mid-level ridging remains in place aloft. Given the prevailing easterly flow, convection will favor the east coast metro areas in the morning with a increase in shower and thunderstorm activity across inland areas and southwestern Florida during the afternoon hours in conjunction with peak diurnal heating. Given the relatively weak/light 500mb flow during this time frame and moist forecast soundings, cannot rule out localized flooding along the Gulf coast metro areas on Saturday afternoon. The formation of a gulf breeze due to the weakening influence of the surface ridge could also aid in thunderstorm development along the gulf breeze during the afternoon hours. Although synoptic parameters don`t appear very conducive for strong storms, mesoscale ascent could aid the development of a few strong multi-cellular pulse storms before they move off of the boundary and into unfavorable residual cold pools. As a mid-level trough dips southward across the Great Lakes on Sunday, the aforementioned mid-level ridging will begin to break down and weaken in spatial extent. Easterly surface flow will begin to weaken as the previously expansive surface ridging over the western Atlantic waters begins to weaken and retreat out of the region. There will still be just enough of an easterly component to see a foci of convection across the western half of South Florida, with a gulf breeze once again providing convergence of convective development and potential localized flooding concerns given the light 500mb flow. By Monday, surface flow will become more southerly in nature as the influence of the surface ridge of high pressure continues to wane. This will act to focus the bulk of convection during the start of the work-week across inland areas which would favor Lake Okeechobee and other inland locales as boundary collisions occur inland and away from the coast. Throughout this time period, pockets of deeper tropical moisture associated with the periphery of the ongoing Central American Gyre (C.A.G.) will rotate into South Florida which will keep rain chances in the 50-60% chance each afternoon. As mid-level troughing finally settles into place across the eastern United States on Tuesday, an associated surface frontal boundary will be displaced across the southeastern United States. Our prevailing surface winds will respond to this feature as background winds begin to veer to a more southwesterly direction. This slight detail will mar a notable change in our prevailing weather pattern beginning on Tuesday. Southwesterly flow will aid with the inland propagation of the gulf sea-breeze and act to pin the Atlantic sea- breeze along the east coast. If forecast trends were to continue, this would act to forecast the highest concentration of convection along the east coast metros each afternoon beginning on Tuesday/Wednesday. With precipitable water values still in the 1.8 to 2.2 range throughout the work week and relatively light 500mb flow still in place, localized flooding could be in the cards once again... especially in urban areas. While the most favorable kinematics stay to the north of the region from a synoptic forcing perspective, once again cannot rule out some strong pulse storms along boundary collisions. To summarize the analysis above, the extended period features a transition between mid-level ridging and the arrival of a mid-level trough. We remain on the periphery of a deep plume of tropical moisture associated with a large and expansive Central American Gyre (C.A.G.) which will at times advect deeper moisture into our area. The combination of a decrease in surface winds and a lack of synoptic flow across the region could result in slow-moving convection this upcoming weekend and into next week. This could result in localized flooding concerns as storms generally drift/move along boundary collisions. Temperatures will remain near norms with highs in the upper 80s to mid 90s, largely dictated by convective trends as well as anvil cloud debris. With the abundance of moisture in the vertical column, it will certainly feel quite muggy out there with heat indices in the 100`s. && .AVIATION... (18Z TAFS) Issued at 147 PM EDT Thu Jun 20 2024 Generally VFR through the period. KAPF could see brief periods of MVFR conditions later today as SHRA/TSRA develop along the Gulf Coast, which could prompt short-fuse amendments. Gusty easterly flow prevails through the evening, with wind speeds decreasing overnight and into tomorrow, when flow veer from the southeast. && .MARINE... Issued at 147 PM EDT Thu Jun 20 2024 Winds begin relaxing a little with both wind speeds and seas gradually dropping to below advisory criteria on both sides of the peninsula later today. The SCA will expire this morning for the Gulf, and in the early afternoon for the Atlantic waters. Moderate E/ESE winds will prevail through the end of the work week, but brief periods of rough seas and gusty winds will accompany any thunderstorm that forms. && .BEACHES... Issued at 147 PM EDT Thu Jun 20 2024 Persisting robust coastal easterly winds will keep a high risk of rip currents across all the Atlantic beaches through Friday, then relaxing enough for risk level to drop to moderate during the weekend. Surf should also gradually decrease today and tomorrow. && .PRELIMINARY POINT TEMPS/POPS... Miami 78 89 81 90 / 10 40 30 40 West Kendall 76 91 79 90 / 10 50 30 50 Opa-Locka 77 91 81 91 / 10 40 30 40 Homestead 78 89 80 89 / 10 40 40 50 Fort Lauderdale 78 88 81 88 / 10 40 30 40 N Ft Lauderdale 77 89 81 89 / 10 40 30 40 Pembroke Pines 79 92 81 92 / 10 40 30 40 West Palm Beach 75 90 79 90 / 10 30 30 40 Boca Raton 77 90 81 90 / 10 30 30 40 Naples 75 92 78 92 / 20 50 30 50 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...High Rip Current Risk through Friday evening for FLZ168-172-173. AM...None. GM...None. && $$ SHORT TERM...ATV LONG TERM....Hadi AVIATION...ATV