Area Forecast Discussion
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934 FXUS62 KTAE 190922 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 422 AM EST Fri Dec 19 2014 .Near Term [Through Today]...
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Today will mark the onset of a much more active synoptic pattern across the SE U.S. which had been mired in a very quiet, fair, cool, and lately very near climatological temperature pattern as well. In fact, TLH has only received 0.09" of rain so far for the month of December, which is 2.20" below normal for the month so far. However, thanks to a developing low pressure system over TX and a warm frontal boundary which is just beginning to organize as it forms eastward across the NE Gulf from LA to offshore of the western FL Peninsula, a few periods of rain are likely on their way for our region during the next few days. While the heavier rainfall during this somewhat protracted event is expected later in the period, we are still expecting some rain to break out across most of the CWA before days end (with the possible exception pf the extreme SE FL Big Bend), with fairly widespread PoPs between 40 and 60 percent for much of the region. As for rainfall amounts, the best chances will be across western portions of the region today, with parts of the FL Panhandle and SE AL getting between 0.15" and 0.25" for just the first part of this event. The clouds and rain will also hold temperatures down today, with highs ranging from only in the middle 50s across parts of the FL Panhandle. to near 70 well to the SE across Dixie county. For most locations, highs of 60-65 will be the norm for this afternoon. .Short Term [Tonight Through Sunday]... Primary zone of moderate isentropic ascent on the north side of the weak Gulf low pressure area is expected to move across the far northwestern portion of the forecast area overnight into Saturday morning. By daybreak, the zone of best lift will be moving rapidly east across Middle Georgia and into South Carolina. As a result, rain chances should rapidly taper off after sunrise. However, the models do indicate that some weak ascent with a moist low level environment may be supportive of drizzle or possibly even some light measurable precipitation, so will keep rain chances in the forecast across northern areas on Saturday afternoon. By Saturday night, focus will shift back to the southwest where another storm system will be developing on a stalled frontal zone across the Gulf. A large broad trough will be transiting from the Rockies into the Central Plains Saturday night. With this system moving quickly east into the Mid South on Sunday, expect cloudiness and precipitation to develop quickly across the Eastern Gulf and lift northward in a strong isentropic lift regime. Numerical guidance typically under forecasts the intensity and timing of this ascent by several hours, so have increased PoPs on Sunday higher than the MOS. Some elevated instability late Sunday afternoon may be supportive of isolated thunderstorms across the area. .Long Term [Sunday Night Through Friday]... At the start of the period, the trough will continue lifting NE across the Southern Appalachians with the primary zone of isentropic ascent shifting to the foothills. Even with the loss of this lift, large scale QG forcing will likely be sufficient to keep rainfall ongoing overnight, especially across the eastern portion of the region. PoPs during this period have been increased to the 70 to 80 percent range. The region will effectively be between systems on Monday, but with plenty of moisture still around, can`t completely rule out a shower or two. By Monday night and especially into Tuesday, rain will once again return as the broad trough across the Central Plains further amplifies and begins to shift eastward. Initially a frontal zone will lift north back into the region on Tuesday focusing a corridor of moderate to locally heavy rain Monday night and into early Tuesday. By Tuesday afternoon, as stronger deep layer forcing arrives, this surface boundary should retreat northward into our region. Model guidance differs on how far northward this boundary will get before a potent cold front surges across the Gulf Coast States. For now, the warm front appears to set up across North Central Florida, suggesting the environment most favorable for surface-based convection would remain over Central Florida. As a result, will only include Iso-T in the forecast for Tuesday into Tuesday night. Nevertheless, this system bears watching, not only for the heavy rainfall potential but for an outside shot at severe weather if surface-based instability can materialize in the strongly sheared environment.
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&& .Aviation...
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[Through 12Z Saturday] Despite the BKN-OVC conditions that are predominating the terminals overnight and will continue to do so for the bulk of entire Taf Period, all of the Cigs are expected to remain at VFR levels. Even the Vis is expected to hold at VFR for most of the time period, with just a few interludes of MVFR level Vis in a few of the showers.
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&& .Marine...
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Though winds may increase to 10 to 15 knots at times ahead of an approaching weak low pressure area, headline conditions are not expected through the weekend. Rainy conditions will develop by Sunday afternoon and unsettled conditions will continue through Tuesday. A significant increase in winds and seas are expected after Tuesday with advisory conditions possible by Wednesday.
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&& .Fire Weather...
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Plenty of clouds, low level moisture, and high rain chances will inhibit any fire weather concerns over the next several days.
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&& .Hydrology...
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The initial system today and into Saturday is only expected to produce up to a quarter of an inch of rain, which will have little or no impact on area river levels. The combination of the storm system on Sunday afternoon and the next system arriving on Tuesday will signal an increase in flood potential, initially as an areal flood threat in the Tuesday-Wednesday time frame with possible river flooding to follow late in the week.
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&& .Preliminary Point Temps/PoPs...
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Tallahassee 65 46 67 52 65 / 40 30 20 20 60 Panama City 61 50 65 55 63 / 40 40 20 20 70 Dothan 61 46 58 49 58 / 60 70 50 20 60 Albany 63 45 59 49 60 / 50 70 50 20 60 Valdosta 65 45 66 51 64 / 40 30 20 20 60 Cross City 70 44 69 54 69 / 10 10 10 20 60 Apalachicola 64 50 67 57 64 / 20 30 20 20 70
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&& .TAE Watches/Warnings/Advisories... FL...None. GA...None. AL...None. GM...None. && $$ NEAR TERM...GOULD SHORT TERM...GODSEY LONG TERM...GODSEY AVIATION...GOULD MARINE...GODSEY FIRE WEATHER...GOULD HYDROLOGY...GODSEY

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