Area Forecast Discussion
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328 FXUS62 KTAE 220616 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 216 AM EDT Tue Jul 22 2014 .Near Term [Through Tonight]...
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The 11 pm EDT regional surface analysis showed a decaying, wavy, quasi-stationary, front from SC, through central GA, extending southwestward to a broad, 1015 mb low centered over southern MS. There was an east-west trough along I-10 in the FL Panhandle. Vapor imagery and upper air data showed a cutoff low centered over southwest GA, with a well-defined dry slot wrapping around the west and southwest flank of the low, over the FL Panhandle and adjacent coastal waters. The GFS and ECMWF forecast the upper low to translate slowly westward, providing weak Q-G forcing across GA & AL today. It also appears that there will be slightly more deep layer moisture in this region as well. Although they differ somewhat in magnitude, the consensus of MOS and the Convection Allowing Models (ECAM) PoPs generally range from 40 to 60% across our forecast area today. The most concentrated area of deep moist convection will initially be across Apalachee Bay and the FL Big Bend/North FL this morning. This activity will gradually move inland and diminish later this morning, but scattered storms will develop across GA and AL this afternoon in association with the forcing from the upper low and any mesoscale boundary interactions that occur. Given the very weak wind field aloft and lackluster forecast SBCAPE values (1500 J/kg or less), we`re expecting a less than 5% chance of severe storms (within 25 miles of a point) today. We expect high temperatures to be a little warmer today than in recent days- around 90. .Short Term [Wednesday Through Thursday Night]... A mid-upper level low will continue to retrograde westward along the Gulf coast and eventually get sheared out near coastal Louisiana or Texas by Thursday. For Wednesday, this will allow for a ridge to build into the area with negative vorticity advection in those same layers. Computer models are in good agreement in showing suppressed convective activity on Wednesday despite PWATs very close to seasonal normals (around 1.9"). While this may be the case, we think that the approx 20% PoPs the models are advertising for the afternoon hours are too low without any substantial drying - either at the surface or aloft. By Thursday, another trough begins to dig into the region from the northwest and could provide some additional large scale forcing for storms. Therefore, we indicated scattered thunderstorms both afternoons with PoPs around 30-40% in most areas. Temperatures should be warmer than in recent days, with highs in the mid 90s likely. .Long Term [Friday Through Tuesday]... The large scale pattern commences rather amplified with ridging over west, troughing over east and ridge over extreme Wrn Atlc. At surface, ridge from Wrn Atlc to over local region with cold front draped over mid-south. During the rest of the period, Wrn ridge shifts Ewd with downstream trough pivoting and deepening Ewd over local region on Fri before lifting Newd and flattening Sat into Sun. Front inches swd shunting Gulf ridge further Swd allowing for a return to a more WLY flow and normal summer time sea breeze dominated regime. Will go with generally 30-40% aftn/eve POPs thru the period. Expect highs generally in the low to mid 90s, lows low to mid 70s.
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&& .Aviation...
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[Through 06Z Wednesday] The latest HRRR runs and GFS MOS suggest a good chance of low-end MVFR/IFR CIGS through mid morning at every site but KTLH. Conditions will improve to VFR by late morning, outside of scattered TSRA. Initially the TSRA will be concentrated near KTLH, but will spread to KVLD, KABY, and KDHN by afternoon. The probability of TSRA at each terminal is 40-50% today, except 30% at KECP. Of course gusty winds and brief period of poor VIS/CIGS are expected with the stronger storms, but we were not yet confident enough to explicitly forecast these conditions at any site on the 06 UTC TAF package.
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&& .Marine...
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Winds and seas should be relatively calm during the period - winds generally 10 knots or less and seas generally 2 feet or less.
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&& .Fire Weather...
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Red flag conditions are not expected this week.
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&& .Hydrology...
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The Shoal River at Mossy Head briefly approached flood stage early yesterday morning, but the river levels are now falling. There will likely be some heavy rain rates today, and the storm motion will be unusually slow (around 5 kt). This would suggest at least some potential for flooding. However, there appears to be one negative factor that will keep the risk of flooding rather low- the influx of dry air aloft from the south and west. This should help dampen deep moist convection somewhat, preventing updrafts from persisting over any one location for too long. We think the probability of exceeding local flash flood guidance today is about 5% (within 25mi of a point), which is not high enough for a watch.
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&& .Preliminary Point Temps/PoPs...
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Tallahassee 90 72 95 73 95 / 50 30 50 20 50 Panama City 87 75 90 76 90 / 30 20 30 20 30 Dothan 89 72 93 73 93 / 40 20 40 20 40 Albany 90 72 94 73 94 / 40 40 30 20 30 Valdosta 90 70 96 72 96 / 40 40 40 20 40 Cross City 90 71 94 73 92 / 60 30 40 20 40 Apalachicola 87 74 88 76 88 / 50 20 30 20 30
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&& .TAE Watches/Warnings/Advisories... FL...None. GA...None. AL...None. GM...None. && $$ NEAR TERM...FOURNIER SHORT TERM...LAMERS LONG TERM...BLOCK AVIATION...FOURNIER MARINE...LAMERS FIRE WEATHER...FOURNIER HYDROLOGY...LAMERS

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