Area Forecast Discussion
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469 FXUS62 KTAE 292003 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 403 PM EDT Wed Oct 29 2014 .Near Term [Through Tonight]...
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A weakening cold front will push through the region during the overnight hours. Dynamics are not overly strong and deep layer moisture is only around average for this time of year. Scattered showers will be gradually decreasing through the overnight hours. Overnight lows will range from near 50 in the far northwest areas to the lower 60s across the southeast big bend. There is also the chance of some areas of fog ahead of the front where higher low level moisture exists across the far southeast big bend including portions of Taylor, Lafayette, and Dixie counties late tonight. .Short Term [Thursday Through Friday Night]... The aforementioned cold front should push south of the forecast area either late tonight or Thursday morning. There may be some lingering showers 12-18Z Thursday near the surface cold front, but significant dry air advection is expected through the day, so a mostly dry forecast is expected and clouds should quickly clear out. The boundary layer temperatures should not decrease much behind the initial cold front, and therefore highs on Thursday are expected to be close to normal (mid-upper 70s). Continued clear skies and dry weather are expected into Friday with slightly below normal temperatures. A more substantial cold front is expected to arrive Friday evening, associated with a potent, digging +PV anomaly on the backside of a broad trough in the eastern United States. By 12Z Saturday, the latest operational ECMWF and GFS generate sub-538 DKM closed low at 500mb near South Carolina with the digging +PV anomaly aloft. This is highly anomalous for late October, around 5 standard deviations below normal. In fact, many fields on the latest numerical model runs are quite anomalous in the Southeast. For example, the GEFS ensemble mean forecast 850mb temperatures at 12Z Saturday are 4-5 standard deviations below normal across south Georgia. In other words, this should be a stronger cold front than normal for early October, despite the fact that no precipitation is expected with the front. Because of this we have trended temperatures down for Friday Night with lows generally between 40 and 45 degrees. However, there should be a limit to how cold the air temperature can get as a strong pressure gradient should keep near-surface winds and boundary layer mixing up overnight. Therefore the forecast reflects lows several degrees below the multi-model consensus. .Long Term [Saturday Through Wednesday]... Strong cold air advection will continue on Saturday, which should produce daytime maximum temperatures well below normal. The record coolest max temp on November 1st at Tallahassee was 57 in 1993. We could get close to that sort of value on Saturday given the highly anomalous low-level temperature profile. The raw GFS and ECMWF have highs of 55 and 56 respectively, but most MOS guidance is in the low 60s. We trended the high temperature forecast down with increasing confidence in an anomalously cool air mass, but not as extreme as some of the raw model guidance for now. For Saturday Night, the surface ridge axis should drift closer which will lead to lighter boundary layer winds and reduced mixing. This should create the coldest night of the forecast period with lows away from the coast in the mid-upper 30s. This could be our first shot at frost of the winter season, but RH values could be a little too low for widespread frost. After that, a building ridge in the eastern US and transition to a +NAO/+AO state will lead to a gradual moderation in temperatures into next week with continued dry weather.
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&& .Aviation...
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[Through 18z Thursday] There is a chance of showers and perhaps an isolated thunderstorm through this evening in association with a weakening cold front, but the impacts are expected to be brief. Otherwise, VFR conditions are expected to prevail at the terminals.
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&& .Marine...
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A slight increase in offshore winds tonight behind a cold front has prompted a SCEC headline over the western half of the coastal waters with 15-20 knot winds. Otherwise, conditions should be relatively benign until a stronger cold front arrives on Friday evening. Advisory level winds are likely, and a few gale (34kt) force gusts cannot be ruled out. With warm water temperatures, and an unusually cold low-level air mass just above the surface, lapse rates over the waters should be very steep and support efficient transfer of stronger winds aloft to the surface. Later in the weekend and into next week, winds should veer to the east and periodic SCEC conditions are possible - especially at night.
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&& .Fire Weather...
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Red flag criteria are not forecast to be met until Saturday in the wake of a dry cold front. On Saturday, much of the tri-state area will likely see red flag conditions. Saturday will mark the return to cool season criteria in Alabama.
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&& .Hydrology...
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Rainfall amounts through tonight are expected to be mainly on the light side with no impact to rivers and streams expected over the next several days.
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&& .Preliminary Point Temps/PoPs...
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Tallahassee 60 78 46 75 44 / 30 10 0 0 0 Panama City 61 74 52 73 47 / 30 10 0 0 0 Dothan 50 73 44 73 40 / 30 0 0 0 0 Albany 52 74 44 73 41 / 30 0 0 0 0 Valdosta 57 77 49 73 44 / 30 10 0 0 0 Cross City 62 81 54 76 48 / 10 20 10 0 0 Apalachicola 62 77 51 74 49 / 20 10 0 0 0
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&& .TAE Watches/Warnings/Advisories... FL...None. GA...None. AL...None. GM...None. && $$ NEAR TERM...DVD SHORT TERM...LAMERS LONG TERM...LAMERS AVIATION...DVD MARINE...LAMERS FIRE WEATHER...MOORE HYDROLOGY...DVD

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