Area Forecast Discussion
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501 FXUS62 KTAE 200928 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 428 AM EST Sat Dec 20 2014 .Near Term [Through Today]...
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A weak surface low pressure area south of the Louisiana coast will continue to move slowly eastward today. An area of isentropic ascent on the NE side of this low pressure area will weaken and move NE into the Carolinas by the afternoon. As a result, areas of rain should weaken with time across our forecast area, likely ending by midday if not sooner. Even with the rain ending, cloudiness should persist through the day, especially across western areas, resulting in cool high temperatures, ranging from the upper 50s in Southern Alabama to the upper 60s in the SE Florida Big Bend. .Short Term [Tonight Through Monday]... The aforementioned surface low, separated from its mid-level counterpart, will meander slowly into our northeast Gulf waters overnight. Surface high pressure will strengthen over the eastern half of the country in the wake of a passing shortwave. This will set up a weak CAD pattern with low-level cool air spilling into the Tri-State region from the northeast. Although the approaching surface low will be weak, the southerly low-layer flow will glide over a cool near-surface dome generated primarily by the cool shelf waters along the northeast Gulf coast. This rain will gradually spread inland through the night, initially impacting the Florida Big Bend region. Through the first part of the day on Sunday, rain will spread north into south Georgia as the aforementioned wedge of cool air keeps isentropic surfaces sloped in the lowest layers. Late Sunday afternoon, into Sunday night a shortwave will roll into the Southeast and link up with the ongoing low-level forcing to create a period of more widespread heavy rainfall. As the shortwave moves into the Mid-Atlantic on Monday, it will pull the surface low through north-central Florida focusing much of the heavier rain in this region on Monday. In its wake, the cold wedge will strengthen once again with another round of low-level isentropic rain is expected late Monday afternoon through Monday night. .Long Term [Monday Night Through Saturday]... Although rain will continue throughout the night Monday into Tuesday morning, a strong low pressure system moving through the Plains into the Mississippi Valley will weaken the cool wedge of high pressure and allow for the more "tropical" airmass to spread inland on Tuesday. Dewpoints are forecast to surge into the middle 60s, with PWATs between 1.5"-2" (>+2 sigma) accompanying. When the upper-level low pressure links up with the low-level forcing on Tuesday afternoon the potential for some very heavy rainfall will exist. Furthermore, the strong low and mid level wind fields generated by the prolonged stratiform rain will combine with a destabilizing airmass on Tuesday afternoon to yield the potential for some strong to severe thunderstorms as well. Confidence in severe weather remains low at this time, but should be monitored closely over the next few days. Finally, on Wednesday we`ll clear out the rain and the clouds and usher in a burst of cold air for Christmas Eve. At this time, temperatures appear as though they`ll be a few degrees below average, in the middle 30s area-wide. Near average to slightly below afternoon highs and overnight lows are expected to finish the week.
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&& .Aviation...
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[Through 12Z Sunday] Conditions will gradually change to MVFR at ECP/ABY/DHN overnight along with periods of light rain. Ceilings may lower to IFR at DHN before sunrise. Expect a period of MVFR conditions to last until early afternoon at these sites when all terminals should return to VFR. After 00z Sunday, a large area of at least MVFR ceilings will move back in from the east affecting all terminals.
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&& .Marine...
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Easterly winds will near cautionary levels this afternoon, primarily west of Apalachicola. Thereafter, sub-headline easterly winds will continue through the weekend before veering southerly on Monday ahead of an approaching low pressure system. A strong cold front will increase winds to advisory levels beginning Tuesday night, with an increase to Gale conditions possible on Wednesday. By Thursday, winds will fall to below headline levels once again with seas lagging about 12 hours behind.
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&& .Fire Weather...
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Moist conditions through at least Wednesday will prevent any red flag criteria from being met.
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&& .Hydrology...
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Rain will continue on-and-off for the next several days. A couple rounds of heavy rain will be possible Sunday night and Tuesday, with the heaviest expected on Tuesday. 7-day rainfall totals range from 3 inches across southeast Alabama to 5 inches across the southeast Big Bend of Florida. These totals are expected to be widespread averages, with isolated higher amounts possible. The potential for river flooding exists primarily early next week when the heaviest rain will fall on well primed basins.
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&& .Preliminary Point Temps/PoPs...
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Tallahassee 65 54 60 56 67 / 20 30 70 90 50 Panama City 63 56 61 58 68 / 20 30 80 100 50 Dothan 57 47 57 53 64 / 50 20 60 80 40 Albany 59 47 57 51 62 / 60 20 60 80 50 Valdosta 65 52 60 56 67 / 20 30 70 90 70 Cross City 70 58 66 61 67 / 10 40 70 90 70 Apalachicola 66 58 63 61 69 / 10 40 80 100 50
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&& .TAE Watches/Warnings/Advisories... FL...None. GA...None. AL...None. GM...None. && $$ NEAR TERM...GODSEY SHORT TERM...HARRIGAN LONG TERM...HARRIGAN AVIATION...GODSEY MARINE...HARRIGAN FIRE WEATHER...GODSEY HYDROLOGY...HARRIGAN

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