Area Forecast Discussion
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531 FXUS62 KTAE 131048 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 642 AM EDT Sat Sep 13 2014 .Near Term [Through Today]... The 11 pm EDT regional surface analysis showed a cold front from the Piedmont of SC through southeast LA, with a weak frontal wave near Columbus, GA. A trough/convergence zone extended south of this low through Apalachicola, where scattered showers and thunderstorms were developing this early morning. The weak 1014 mb low pressure system that tracked across South FL Friday had emerged off the Naples coast, with no signs of tropical cyclone development. Vapor imagery and upper air data showed a narrow ridge over portions of the Southeast. A band of warm, dry, sinking area (associated with a PV anomaly) was spreading westward across North FL and southeast GA. We expect the showers & thunderstorms (ongoing as of 230 am) to diminish somewhat over the next several hours, but there is enough moisture, instability, & forcing for at least a few to survive into this morning. Though the details differ, there was relatively good agreement among the various MOS and ECAM with regards to how today`s showers and thunderstorms will develop. After a morning lull, we expect numerous thunderstorms to develop in the FL Panhandle, southeast AL, and southwest GA, as the aforementioned cold front enters our northwest zones and stalls. Across the FL Big Bend and south central GA, the PoP is lower due to the approaching drier air aloft. Our PoP ranges from 60% around Dothan and Panama City, to 20-30% to the east. With plentiful deep layer moisture, especially north and west of Tallahassee, some of the slow-moving storms will produce very heavy rain amounts (isolated 2-4 inches). However, the threat appears isolated enough so that a Flash Flood Watch is not needed at this time. With weak forcing, rather light winds aloft, and unspectacular 700-500mb lapse rates, we`re not anticipating organized or numerous severe storms today; though a "pulse" severe storm can`t be ruled out. .Short Term [Tonight Through Monday]... Although weak upper level ridging will continue to dominate the northern Gulf Coast and SE U.S during the remainder of the weekend and into early next week (before it is eventually replaced by a trof towards mid week), plenty of deep layer tropical moisture will continue to flow into the region from the Gulf of Mexico and western Atlantic. This will keep PoPs above climo through the short term period with daytime rain chances generally in the 40-50% range, with decent PoPs continuing well into the evening hours, especially tonight over NW portions of the CWA. Temps are expected to remain above normal as well, with highs mainly in the lower to a few mid 90s away from the coast, with overnight lows in the lower to middle 70s. .Long Term [Monday Night Through Friday]... The main uncertainty for the extended forecast is to what extent the weak system moving westward into the Gulf will impact our area. The collaborated NHC/WPC forecast takes the system westward to a position south of Houston by mid-week and keeps it weak. Deep moisture will continue to increase across the area with a stalled frontal boundary also in the vicinity. These ingredients point to an unsettled period coming up with an above average chance of rain by mid-week. Some locally heavy rain is possible given the weak boundary and deep tropical moisture expected to be in place. This could be further enhanced by the Gulf system depending on its evolution, but that evolution is much more uncertain. Daytime highs are expected to be held down in the mid 80s from Tuesday through most of the week given the expected cloud cover and increased rain coverage. && .Aviation...
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[through 12z Sunday] Other than brief patchy fog early, generally VFR conditions are expected. Scattered to numerous SHRA/TSRA will develop this afternoon & evening across southeast AL, the FL Panhandle, & southwest GA, affecting KDHN, KABY, & KECP with occasional gusty winds, low cigs, and poor vis. Elsewhere VFR conditions will continue. SHRA/TSRA should slowly diminish around midnight or shortly after.
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&& .Marine... Winds and seas will be slightly elevated this weekend as a weak tropical disturbance passes well to the south of the coastal waters. Thereafter, a very weak surface pressure pattern will return to the marine area, with typically low summertime winds and seas expected once again. && .Fire Weather... Red Flag conditions are not expected through at least this weekend. && .Hydrology... As mentioned above, some locally heavy rainfall (with up to 2" to 4" amounts) will be possible today in some of the slow moving storms to the north and west of Tallahassee, but any heavy amounts should be isolated in nature and not have much of a hydrological impact through early next week. By the middle of the week, however, an upper level trof will replace the current ridge which will be retreating westward, and before the cooler and drier air is allowed to seep into the region by late in the week or next weekend, more widespread heavy rainfall could fall over the CWA. Should this occur, some more significant rises along area rivers and streams could take place, so this situation will be worth monitoring. && .Preliminary Point Temps/PoPs... Tallahassee 93 73 93 72 92 / 30 20 40 20 50 Panama City 90 76 89 76 89 / 50 30 40 20 50 Dothan 92 72 92 72 92 / 60 50 50 30 50 Albany 92 72 92 73 92 / 50 40 50 30 50 Valdosta 93 71 94 71 93 / 20 20 40 30 50 Cross City 93 72 92 71 92 / 20 30 40 20 50 Apalachicola 89 77 89 76 88 / 20 20 40 20 40 && .TAE Watches/Warnings/Advisories... FL...None. GA...None. AL...None. GM...None. && $$ NEAR TERM...FOURNIER SHORT TERM...GOULD LONG TERM...DVD AVIATION...FOURNIER MARINE...GOULD FIRE WEATHER...FOURNIER HYDROLOGY...GOULD is the U.S. government's official web portal to all federal, state and local government web resources and services.