Area Forecast Discussion
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957 FXUS62 KTAE 230755 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 255 AM EST Mon Feb 23 2015 ...HEAVY RAINFALL EXPECTED ACROSS THE AREA ON WEDNESDAY WITH THUNDERSTORMS POSSIBLE ACROSS THE SOUTHEAST BIG BEND... .Near Term [Through Today]...
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Zonal flow continues aloft with the only mentionable feature locally being a weak southern stream +PV anomaly passing through the Southeast today. At 07z this anomaly was placed, via WV imagery, over the Mississippi River at the LA/AR/MS border. At the surface, a quasi-stationary front is draped southwest to northeast from the LA/MS coasts, through central AL & GA, up the lee side of the Appalachians. Behind this front, is another front delineating a moist airmass ahead of a strong surface ridge, from the dry air behind it. Through today, the southern stream anomaly will move east into the western Atlantic, taking with it the large area of rain over the Southeast this morning. However, the advancing surface ridge will force the stationary boundary into motion, pushing it into the southeast Big Bend by this evening. Rain chances will be highest today across southeast Alabama and southwest Georgia where the passing shortwave will have the greatest impact locally. Then, as the front passes through the Tri-State region, scattered light to moderate rain will accompany it, though much of the area won`t have more than a 30% chance of getting any measurable rain. One last feature of note is an expected area of isentropic ascent across the southeast Big Bend this morning through early afternoon. Most of the hires guidance shows this feature while the lower resolution models don`t quite pick up on it. This is most likely because they are missing out on the shallow cool layer over the Suwannee Valley this morning. The local hires guidance seems to be handling the boundary layer quite well this morning w.r.t. T, Td, and wind, so this forecast will bite on the isentropic rain later this morning. Either way, it should be fairly light as it is being forced primarily along the 290K surface, and not much above that. Generally, rainfall amounts in this area will be less than a tenth of an inch this morning. .Short Term [Tonight Through Wednesday]... The short term will be unsettled. A weak upper level disturbance will bring an increase in moisture and light showers during the day on Tuesday. Widespread cloud cover will also hold high temperatures down into the 50s across most of the area for Tuesday. The unsettled conditions will culminate on Wednesday as a vigorous upper level shortwave crosses the region. A surface area of low pressure is expected to develop somewhere near the coast and track across our forecast area on Wednesday. This will likely spread moderate to heavy rainfall across the area. Some thunderstorms are also possible along and to the southeast of the low track. The low has trended a little stronger and farther north compared to earlier runs, so a chance of thunderstorms was included across the southeast big bend. In fact, both the 00z GFS and ECMWF have a 60 knot low level jet crossing the southeast big bend on Wednesday evening with non-zero instability. There may be a non-zero severe threat Wednesday afternoon and evening right along the coast and into the southeast big bend depending on the exact low track, although that threat looks more likely for the coastal waters than the land area currently. .Long Term [Wednesday Night Through Monday]... The system will move out of the area on Wednesday night with dry conditions expected to return for the remainder of the work week. By the weekend, the 00z ECMWF has moisture returning while the GFS is dry. The weekend forecast has shown a lot of variability over the last couple of days. A slight chance of rain is shown for both Saturday and Sunday with a warming trend back to the mid 60s to near 70 for daytime highs on Sunday.
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&& .Aviation...
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[Through 12z Tuesday] A mix of MVFR ceilings to LIFR ceilings and visibilities exists across the region this morning. A front will gradually move past DHN and possibly ABY and ECP this morning, clearing out the LIFR visibilities, though IFR ceilings will remain. By 14z all sites should be clear of restrictions in fog, a ceilings will gradually raise through the day to VFR at all sites by around 20z. Expect another round of low ceilings tonight.
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&& .Marine...
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Light to moderate northerly winds will prevail today behind a cold front. Winds and seas will increase again on Wednesday as an area of low pressure moves near the coast with advisory conditions likely. In fact, it could be rather stormy with gale force gusts possible in addition to a squall line cross the area on Wednesday. The low will move out of the area by Thursday with light to moderate winds returning for the remainder of the week.
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&& .Fire Weather...
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Hazardous fire weather conditions are not expected over the next several days as a couple of rounds of rain will keep things quite wet.
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&& .Hydrology...
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An areawide moderate to heavy rain event is still expected on Wednesday. Total rainfall is generally expected to be in the 2-3 inch range with isolated higher totals possible. This will cause rises on area rivers and may bring a few of our sites back up to action stage. At this time, flooding is not expected, although if widespread rainfall amounts were to increase above 3 inches, then the Kinchafoonee Creek as well as the Ochlockonee, Aucilla, and Upper Withlacoochee Rivers could come close to minor flood stage.
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&& .Preliminary Point Temps/PoPs...
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Tallahassee 65 49 56 46 55 / 20 60 60 40 90 Panama City 63 47 54 47 55 / 30 50 60 50 90 Dothan 58 42 51 42 48 / 50 60 60 40 90 Albany 59 42 51 41 50 / 60 60 60 30 90 Valdosta 65 47 52 44 53 / 30 60 60 40 90 Cross City 71 51 59 48 61 / 50 30 50 40 90 Apalachicola 68 51 57 50 60 / 20 30 50 50 90
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&& .TAE Watches/Warnings/Advisories...
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FL...Dense Fog Advisory until 9 AM EST /8 AM CST/ this morning for Calhoun-Central Walton-Coastal Bay-Coastal Dixie-Coastal Franklin-Coastal Gulf-Coastal Jefferson-Coastal Taylor- Coastal Wakulla-Gadsden-Holmes-Inland Bay-Inland Dixie- Inland Franklin-Inland Gulf-Inland Jefferson-Inland Taylor- Inland Wakulla-Inland Walton-Jackson-Lafayette-Leon-Liberty- Madison-South Walton-Washington. GA...Dense Fog Advisory until 9 AM EST this morning for Brooks- Decatur-Grady-Lowndes-Seminole-Thomas. AL...None. GM...None.
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&& $$ NEAR TERM...HARRIGAN SHORT TERM...DVD LONG TERM...DVD AVIATION...HARRIGAN MARINE...DVD FIRE WEATHER...HARRIGAN HYDROLOGY...DVD

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