Area Forecast Discussion
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644 FXUS62 KTAE 251527 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 1127 AM EDT Thu Sep 25 2014 .Near Term [Through Today]...
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An upper level trough lies over the Appalachian mountains with surface high pressure in place over the Ern CONUS. This surface high pressure is lifting north, meaning the pressure gradient will be weaker, so it won`t be as windy today as it was yesterday. It will be another cool and cloudy day particularly for the GA counties. Clouds will likely scatter out this afternoon in FL and AL counties. Highs today will be in the low 70s in GA and mid-upper 70s elsewhere.
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&& .Marine...
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Expect cautionary level easterly winds with waves in the 3-4 foot range until Sunday. Thereafter, winds will weaken as a broad area of weak low pressure moves across the Southeast.
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&& .Prev Discussion [319 AM EDT]...
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.Short Term [Tonight Through Saturday]... Under the influence of middle and upper level ridging, essentially no deep-layer synoptic forcing for ascent is expected through Saturday. Instead, any showers or isolated storms that do develop will be forced in the lower-levels. The primary mechanism for showers and storms will be an inverted surface trough currently bending down the Southeast coastline. Although the cutoff low that initially forced this trough has moved away, its presence has been maintained by the strong temperature gradient between the warm Gulf Stream waters and the very cool adjacent land temperatures as a result of the persistent low cloud deck yesterday that is expected once again today. Through tonight, southerly steering flow will force a low-level PV anomaly forced by ongoing convection off of the southeast Florida coastline, northward along the Florida east coast. This low-level support will further enhance the already pronounced surface trough. By Friday, the mid-level ridge axis will pivot to a more east-west orientation. This will result in a more easterly steering regime over the Peninsula, thereby forcing the coupled low/mid-level trough system west into the northeast Gulf by Friday night. What this all means is that rain chances will drastically increase beginning Friday afternoon over the southeast Big Bend of Florida and south-central Georgia. The highest threat for rain will shift westward through the first part of the weekend with the best chance for rain Saturday along and south of the southern tier of counties in Georgia and Alabama. The environment will not be favorable for the development of severe storms, though heavy rain will be a possibility; see the hydrology discussion below. .Long Term [Saturday Night Through Thursday]... By late in the weekend a developing trough over the Southern Plains will pull the aforementioned surface trough and moisture further north, with enhanced rain chances across the remainder of the area. With precipitable water values possibly exceeding 2 inches, the potential for locally heavy rainfall will continue. Into Monday and Tuesday, the global guidance diverges with the ECMWF cutting off an upper low over the Arklatex and pushing a strong front into the Deep South. The GFS is much weaker and more progressive with its evolution. At this time, have leaned more towards the wetter ECMWF solution for Monday and Monday night. With the approach of the inverted trough and it`s more tropical airmass, temperatures will likely be a bit above normal for the weekend into early next week (especially for min temps). .Aviation... [Through 12Z Friday] MVFR-IFR cigs will affect all local terminals this morning except ECP (and possibly briefly there as well, although confidence is lower). Skies are expected to start clearing out from west to east starting in the late morning and into the afternoon, except at VLD where they may hang in through the period. .Fire Weather... Relative humidity values will remain above critical thresholds through the period. Red flag conditions will not be met. .Hydrology... The above mentioned period of wet weather (Friday through at least Sunday) could produce, on average, 1 to 3 inches of rain across north Florida. Elsewhere, averages on the order of an inch or less are more likely. These amounts are not expected to result in any river flooding due to the widespread low flows. Depending on whether the heavy rain persists through Tuesday, which is uncertain, there may be some minor river flooding issues.
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&& .Preliminary Point Temps/PoPs...
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Tallahassee 79 64 85 73 84 / 0 10 40 40 60 Panama City 79 67 83 73 82 / 0 0 30 30 70 Dothan 79 63 82 69 81 / 0 0 10 20 40 Albany 74 64 81 69 82 / 0 10 10 20 40 Valdosta 74 66 83 71 85 / 10 10 50 40 60 Cross City 79 69 85 72 85 / 10 10 70 60 50 Apalachicola 79 70 83 75 82 / 0 10 40 40 70
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&& .TAE Watches/Warnings/Advisories... FL...None. GA...None. AL...None. GM...None. && $$ NEAR TERM...MCDERMOTT/MOORE SHORT TERM...HARRIGAN LONG TERM...CAMP/HARRIGAN AVIATION...MOORE MARINE...MCDERMOTT FIRE WEATHER...MOORE HYDROLOGY...HARRIGAN

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