Area Forecast Discussion
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569 FXUS62 KTAE 221102 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 602 AM EST Mon Dec 22 2014 ...Severe Weather and Flooding Possible Across the Region on Tuesday and Wednesday... .Near Term [Through Today]...
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Deep southwesterly flow will cover the Southeast today underneath the Subtropical jet. The ribbon of +PV responsible for the jet is clearly visible on water vapor imagery this morning with a large area of middle/upper level dry air spreading from the western Gulf through the Southern Mississippi Valley. This dry air will gradually spread eastward through the day today as the leading edge of a northern stream shortwave noses the southern stream east. Although this may sound like a limiting factor for rain across the region today, it will merely limit the intensity of rain as deep layer synoptic moisture and ascent is removed. The primary forcing mechanism for rain today will be rooted in the lower troposphere, below 700 mb. Strong warm, moist advection in this layer will break down the high pressure wedge that has plagued our region over the past couple days and gradually spread broad troughing and an associated warm front north to the northern Gulf Coast. Isentropic ascent, primarily along the 295K surface will result in continued light to moderate rain spreading inland through the day. Again, without much deep layer forcing to speak of, expect a somewhat ragged rain shield today with on-and-off breaks and overall low QPF. High temperatures will most likely be 5 to 10 degrees warmer across north Florida today, even with the rain and cloud cover. While temperatures will struggle to climb into the middle 50s closer to the retrograding wedge across our northern most Georgia counties. .Short Term [Tonight Through Wednesday]... A developing low pressure system off to our west will begin to amplify across the lower MS Valley region during the next couple of days and eventually form a potent and moisture laden system over the SE on Tuesday. This very energetic low is then expected to move rapidly north-northeast from the Central Gulf coast states into the eastern Great Lakes by Wednesday night and Thursday, pushing a strong cold front through our region later on Wednesday. Along with the potential for strong to severe thunderstorms with the pre-frontal squall line, a band of very heavy rainfall with potential flooding is quite possible as well, and this has prompted a Flash Flood Watch across our region from Tuesday morning through Wednesday evening. Storm total rainfall amounts of 4 to 6 inches (with locally higher amounts) are definitely possible during this time frame, which unfortunately, is centered around Christmas Eve. .Long Term [Wednesday Night Through Monday]... After the passage of the strong cold front on Wednesday night, conditions will rapidly return to normal on Thursday (Christmas Day) with fair and seasonably cool weather to return for much of the extended period.
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&& .Aviation...
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IFR ceilings will prevail for most of the TAF for all terminals. There may, however, be a brief period of time in the afternoon where ceilings lift to MVFR levels, though no scattering is expected. Visibility restrictions in fog will clear shortly after sunrise, but MVFR to IFR visibilities could still be possible in rain through the day.
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&& .Marine...
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A developing low pressure system to our west will will continue to tighten the pressure pattern over the the marine area during the next few days. This will result in steadily increasing onshore winds and seas, with Small Craft Advisory Conditions developing on Tuesday and Wednesday. Boating conditions are expected to become quite hazardous on Wednesday and Wednesday night with seas peaking at 8 to 10 feet. Conditions across the coastal waters will rapidly improve on Thursday and Friday as the strong cold front moves much further away from the marine area.
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&& .Fire Weather...
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A stretch of wet weather will preclude any hazardous fire weather conditions over the next several days.
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&& .Hydrology...
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A developing low pressure system off to our west will continue to open up plenty of moisture in the Gulf of Mexico through the middle of this week, with a strong low pressure system expected to develop and sweep a strong cold front through our region by Wednesday evening. This system, with its vast onshore flow, will have the potential to bring heavy rain to much of our region on both Tuesday and Wednesday. With embedded heavy thunderstorms, some of which could be severe, the potential for widespread rainfall totals of 4 to 6 inches (with locally higher amounts) could cause flash flooding in certain locations. The most likely areas for flooding will be low lying and poor drainage areas, but widespread 4 to 6 inch amounts could cause flooding on some of of our more vulnerable rivers and streams as well.
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&& .Preliminary Point Temps/PoPs...
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Tallahassee 65 62 72 63 71 / 80 50 80 90 80 Panama City 66 64 71 66 68 / 80 50 90 100 70 Dothan 63 58 71 61 69 / 70 50 90 100 70 Albany 58 57 71 60 67 / 60 50 90 100 80 Valdosta 61 60 73 63 73 / 80 50 80 90 80 Cross City 72 62 73 64 73 / 80 50 60 90 80 Apalachicola 67 63 69 65 69 / 80 50 80 90 80
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&& .TAE Watches/Warnings/Advisories...
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FL...Flash Flood Watch from Tuesday morning through Wednesday evening 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...Flash Flood Watch from Tuesday morning through Wednesday evening for Baker-Ben Hill-Berrien-Brooks-Calhoun-Clay-Colquitt- Cook-Decatur-Dougherty-Early-Grady-Irwin-Lanier-Lee-Lowndes- Miller-Mitchell-Quitman-Randolph-Seminole-Terrell-Thomas- Tift-Turner-Worth. AL...Flash Flood Watch from Tuesday morning through Wednesday afternoon for Coffee-Dale-Geneva-Henry-Houston. GM...None.
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&& $$ NEAR TERM...HARRIGAN SHORT TERM...GOULD LONG TERM...GOULD AVIATION...HARRIGAN MARINE...GOULD FIRE WEATHER...HARRIGAN HYDROLOGY...GOULD

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