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175 FXUS62 KTAE 291347 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 945 AM EDT Fri Aug 29 2014 .Update... The influx of deep moisture across the region has begun and the 12z KTAE sounding shows PW has increased to near 1.50". Forecast soundings further increase PWs to around 2.0" this afternoon. Local radars indicate a large area of showers and thunderstorms mainly south of our panhandle coastal waters (beyond 60 nm) with only isolated to scattered convection across our marine area. This activity will continue to lift northward through the day. This along with daytime heating and convection initiating along the sea breeze will bring scattered to numerous showers and thunderstorms to the Tri-state area this afternoon and evening. PoPs for today look reasonable as well as forecast max temps. Max temperatures across the Florida zones have been adjusted down a few degrees to account for the increasing cloud cover and higher rain chanceS. .Aviation... [Through 12Z Saturday] In general, conditions are expected to remain in the VFR range through the period. However, increasing showers and thunderstorms are expected by late morning and into the afternoon. IFR VIS will be possible in the heavier rain showers or storms, but those should be brief reductions in VIS. The best chance of TSRA will be at ECP, and slightly lower at TLH. Chances will diminish much more to the north and east at DHN, ABY, and VLD. The most likely time for TSRA will be starting around 16Z near the Florida Panhandle coast, to around 23Z further inland. .Prev Discussion [233 AM EDT]... .Near Term [Through Tonight]... Deep layer southerly flow is expected to develop today, which will enable moisture advection in our area through much of the depth of the troposphere. The end result will be a return to a more humid air mass, and increased rain chances - particularly in our Florida counties. There is some evidence of a weak surface warm front in the 05Z observations and objective MSAS analysis with a pressure trough, surface wind shift, and thetae gradient existing about 120 miles south of Apalachicola. Most available model guidance suggests this will lift north with the surge of low-level moisture this morning, and could be a focus for convection. In fact, a cluster of cooling cloud tops was noted on IR satellite, along with lightning, in the general vicinity of this front (also around 05Z). The timing on the models is fairly consistent, and suggests a marked increase in rain chances in the late morning to around midday (15-17Z) near the Florida Panhandle coast. The convection would then slowly spread inland and into parts of the Big Bend during the course of the afternoon, eventually diminishing around 00Z. We placed 60-70% PoPs in the Florida Panhandle west of the Ochlockonee River for this afternoon, with 30-50% PoPs in most other locations. Far northern parts of our area in the Albany to Tifton corridor and to the north may actually remain dry today. High temperatures were adjusted according to greatest rain chances and sky cover, and we leaned toward the consensus of the convection-allowing models (CAM) which indicated mid-90s in the northern parts of our area that should remain relatively cloud free, and upper 80s to around 90 south of Interstate 10 in Florida. Convection will diminish in the evening, setting up a fairly typical late summer night with dry weather and lows in the lower 70s. Despite the fact that the 00Z Tallahassee sounding from yesterday evening only showed 1.09" precipitable water (PWAT) values, there should be a substantial surge of moisture today, and models consistently show 2"+ PWATs by late afternoon over the southern half of our area. Combined with storm motions under 10 knots, this could lead to a threat of localized heavy rainfall, and some of our local CAM ensemble members are showing small areas of 4-6" of rain. We have added heavy rain wording to the forecast, mainly in Florida. .Short Term [Saturday Through Sunday]... Although the tropical wave across the Gulf will have lifted north of the area by Saturday, deep moisture will remain in place with PWAT values near 2 inches. This will support diurnal convection with 50-60% PoPs across the area for Saturday and 40-50% for Sunday. Although locally heavy rainfall rates are possible with the deep moisture in place, widespread heavy rainfall does not appear likely with the lack significant upper level dynamics or a low level jet. Highs are expected to be in the low to mid 90s with lows in the low to mid 70s. .Long Term [Sunday Night Through Friday]... Medium range guidance is all in good agreement that deep layer ridging will dominate over the southeastern states through much of next week. Without a source of deep moisture in place, PoPs will remain below climo, with temperatures continuing to run above normal. && .Marine... Winds will be southerly today as a weak tropical wave moves northward across the Gulf of Mexico. The onshore flow, which should remain near or below 15 knots, will continue into early next week. && .Fire Weather... Increasing moisture today will lead to higher afternoon RH values, and no threat of red flag conditions across the area. There is the potential for some wetting rains in the Florida Panhandle this afternoon. && .Hydrology... A decent coverage of showers and thunderstorms is expected today across the southern portions of the area, spreading north to include most of the area on Saturday. Some locally heavy rainfall amounts are possible, but widespread heavy rain does not look likely. There are no flooding concerns at this time since river levels are already very low due to a drier than average summer. && .Preliminary Point Temps/PoPs... Tallahassee 91 74 94 74 94 / 50 30 50 30 50 Panama City 87 79 91 77 92 / 70 40 50 30 40 Dothan 95 73 94 73 95 / 30 20 60 30 40 Albany 96 74 96 74 94 / 20 10 60 40 50 Valdosta 95 73 93 72 94 / 30 20 50 30 50 Cross City 90 74 93 72 93 / 50 30 50 30 40 Apalachicola 86 77 91 76 91 / 60 40 40 30 30 && .TAE Watches/Warnings/Advisories... FL...None. GA...None. AL...None. GM...None. && $$ UPDATE...BARRY NEAR TERM...LAMERS SHORT TERM...DVD LONG TERM...CAMP AVIATION...LAMERS MARINE...DVD FIRE WEATHER...LAMERS HYDROLOGY...DVD

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