Area Forecast Discussion
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197 FXUS62 KTAE 161955 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 355 PM EDT Wed Apr 16 2014 .Near Term [Through Tonight]...
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With the very chilly start to the day with lows ranging from the mid 30s to the mid 40s, temperatures have struggled to climb through the 50s and into the 60s during the afternoon despite plenty of insolation. The gusty NE winds have also aided in keeping the temperatures down, but these should diminish over most areas by sunset. For tonight, temps may initially fall fairly quickly under the still dry air, mostly clear skies, and lighter winds, but should then level off and possibly even rise during the overnight hours as low level moisture and low cloudiness begin to increase over the region from the southeast. That said, expect minimum temperatures to reach the lower to mid 40s over the NW half of the CWA, to the upper 40s to lower 50s further to the SE. Also, besides putting a cap on the temperatures, once the low level clouds become more widespread (especially in the remaining hours before sunrise), a few sprinkles will be possible across much of the FL Big Bend and eastern Panhandle and near the Valdosta area in GA where the moisture advection will initially be greatest. The chance for sprinkles (or even some measurable light rain) will be even greater across the marine area late tonight. .Short Term [Thursday through Saturday]... Much of the focus in the short term period was centered around the evolution of a Gulf low from Thursday Night onward, and the amount of rain that it will produce in our area. Numerical models have begun to converge on a similar solution as the digging shortwaves that will eventually lead to surface cyclogenesis are finally being sampled by the upper air network over the western US. Generally speaking, a low-amplitude shortwave trough in the mid- upper levels will dig ESE to around 90W longitude by 00z Friday. This will place the base of the shortwave trough and RFQ of a strengthening upper level jet streak over the north-central Gulf of Mexico, setting the stage for a surface low to develop. The low should then move in the general direction of the I-4 corridor in the Florida Peninsula by Saturday morning. On Thursday and into Thursday evening, low-level isentropic ascent will gradually increase, paired with a trend for higher RH and lower condensation pressure deficits. This should lead to the development of scattered showers in that time period, and perhaps an isolated thunderstorm over the southern part of the area. By late Thursday Night and early Friday, cyclogenesis over the Gulf will be well underway. Model forecast cross sections NE of the low from DHN-TPA show increasing mid-level frontogenesis over our forecast area around 18z Friday. There is good model agreement showing the development of a band of heavy rain around that time, especially over the southeastern half of our forecast area. Overall, the instability levels seem to be very limited so this looks to be more of a general rain event forced by a combination of isentropic ascent and mid-level FGEN. With PWATs expected to be around 1.6-1.7 inches in the southeast part of our area (around +2 standard deviations above normal) and very strong forcing for ascent, the ingredients are there for heavy rainfall. Given the lack of instability and the long duration of rain (12-24 hours), it seems like river and areal flooding threats would be higher in this event than flash flooding. QPF totals are relatively close to a model consensus and range from 2-4 inches over much of the Florida Big Bend region and adjacent far southern Georgia, to around 1 inch in southeast Alabama. The 16Apr.12z runs of the ECMWF, UKMET, GFS, CMC, and NAM all show a band of 3-4 inches of rainfall across the southeast part of our area. We did not issue a Flood Watch yet, but one could become necessary overnight if model consensus continues to grow around this particular solution. .Long Term [Saturday Night through Wednesday]... By Sunday, slight ridging will begin to settle in the area allowing for a break from precipitation. The next chance of rain occurs Tuesday when the flow will become more zonal and a shortwave to the north of our area will bring a slight chance of rain and isolated thunderstorms to the northern counties. Throughout the entire period, temperatures will be near climatology with highs in the lower 80s, and lows in the upper 50s.
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&& .Aviation...
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[Through 18Z Thursday] VFR conditions will hold at the terminals through the remainder of this afternoon and much of tonight, with the gusty NE winds diminishing by sunset. However, by very late tonight and into Thursday morning, MVFR level CIGS may be poised to overtake the TAF sites from SE to NW, as low level moisture is expected to quickly return to the region from the southeast.
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&& .Marine...
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After a brief break in the Advisory level conditions this afternoon, winds and seas will be back on the increase tonight out of the east to northeast as the pressure pattern tightens once again. Therefore, issued a new Small Craft Advisory which will begin at 8 pm EDT this evening for the easternmost legs, and at 2 am EDT overnight for the rest of the marine area. This Advisory will remain in effect until 8 am EDT Friday morning, but will very likely need to be extended for some time into the upcoming weekend, as a new low pressure system develops in the northern Gulf of Mexico.
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&& .Fire Weather...
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After the brief shot of much cooler and drier air over the region today, low level moisture will quickly be on the increase once again on Thursday and Friday. A developing low pressure system in the Gulf of Mexico will then lead to yet another batch of rain over the area on Friday and into the upcoming weekend. These inclement conditions will ensure no fire weather concerns during the next several days across the Tri-state area.
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&& .Hydrology...
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Heavy rains across the FL Panhandle yesterday resulted in sharp rises on the Chipola River where the Altha gage is cresting about two feet above moderate flood stage. Only minor rises occurred on the Choctawhatchee, Apalachicola and Ochlockonee Rivers. Most of the area rivers have crested and are falling steadily, except for the Choctawhatchee River near Bruce, which is currently at its crest but will remain in moderate flood stage until Sunday. More rain is expected Friday. Rain totals of 1 to 3 inches are possible with 2 to 4 inches possible in the Florida Big Bend region. Isolated areas may see higher totals. As rain rates should be more gradual, with the above rainfall totals expected to fall over 12-24 hours, the flooding threat with this next round of rain should be of the areal/river variety. The flash flooding threat should be lower. In other words, areas of existing high water or flooding may worsen... and areas of high water could also develop in places like fields or low-lying areas. River flooding will also be possible - particularly in rivers around the Florida Big Bend and Apalachee Bay region. The most up-to-date river forecast information can always be found on our AHPS page (below): http:/water.weather.gov/ahps2/index.php?wfo=tae.
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&& .Preliminary Point Temps/PoPs...
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Tallahassee 49 70 61 67 55 / 10 30 70 80 80 Panama City 49 71 63 67 58 / 10 30 80 80 60 Dothan 44 68 57 65 53 / 0 10 50 60 50 Albany 44 70 55 66 52 / 0 10 50 70 50 Valdosta 49 70 59 67 56 / 10 20 60 80 80 Cross City 53 74 63 73 57 / 10 30 60 80 80 Apalachicola 49 70 65 68 60 / 10 30 80 80 80
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&& .TAE Watches/Warnings/Advisories...
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FL...High Rip Current Risk until Midnight EDT tonight for Coastal Franklin. GA...None. AL...None. GM...Small Craft Advisory from 8 PM this evening to 8 AM EDT Friday for Apalachee Bay-Coastal waters from Suwannee River to Keaton Beach FL out 20 NM. Small Craft Advisory from 2 AM Thursday to 8 AM EDT Friday for Coastal waters From Ochlockonee River to Apalachicola FL out to 20 NM-Coastal waters from Apalachicola to Destin FL out 20 NM-Waters from Suwannee River to Apalachicola FL from 20 to 60 NM-Waters from Apalachicola to Destin FL from 20 to 60 NM.
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&& $$ NEAR TERM...GOULD SHORT TERM...LAMERS LONG TERM...LAMERS/HELLER AVIATION...GOULD MARINE...GOULD FIRE WEATHER...GOULD HYDROLOGY...MCDERMOTT/LAMERS

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