Area Forecast Discussion
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867 FXUS62 KTAE 140109 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 909 PM EDT Sun Apr 13 2014 .Near Term [Through Tonight]...
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An approaching low pressure system will bring southerly flow and increased moisture advection to the region. Cloud cover will increase after midnight as a low stratus deck forms due to radiational cooling and moisture advection. Patchy fog could briefly develop over the region shortly before sunrise. Expect mild low temps tonight in the low 60s.
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&& .Aviation...
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[Through 00Z Tuesday]... The consensus of the latest dynamical and statistical NWP guidance suggests the main forecast issue tonight- Monday morning will be low cigs- with MVFR cigs developing at most sites by 09 UTC, and occasional IFR between cigs 09 and 14 UTC. Fog is also possible, but the wind is likely to prevent it from being widespread or especially dense. Conditions will gradually improve to VFR by afternoon, except at KECP, where MVFR cigs are likely through the period. Rain from the cold front to our west will probably hold off until after 00 UTC.
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&& .Prev Discussion [339 PM EDT]...
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.Short Term [Monday Through Tuesday Night]... The recent stretch of fair and seasonably warm weather that we have experienced during the past several days will be coming to an abrupt end by Monday night and Tuesday, as the next system in a series of shortwaves digs SE towards the NE Gulf Coast. This upper level system is expected to develop a weak Sfc low which will race northeastward towards NY and New England on Tuesday. This low will drag a fairly strong cold front through the CWA on Tuesday and clear the region on Tuesday night, with much cooler and drier air to follow. Out ahead of the cold front, there will be some threat for severe weather, mainly across SE AL and western portions of the FL Panhandle where the Storm Prediction Center has placed its eastward extent of a Slight Risk. However, both wind shear and instability appear to be more limited for this event than the more significant one last week, and this is becoming apparent in many of the Hi-res mesoscale model runs which are now coming into temporal range for our region. Nevertheless, still have a period of Isolated Svr Storms in the grids in and around the Slight Risk area, with potential damaging wind gusts being the primary threat. As for rainfall amounts, which clearly caused the most widespread problems with the previous system, the prognosticated situation continues to gradually improve. While bands of heavy rainfall are still likely with this developing low, it now appears that the models are in good agreement that it will likely be too progressive to be an extreme rainfall producer for our area, with the heavier rain bands propagating very quickly to the east. Nevertheless, parts of SE AL could still see 1.5" to 2.0" of storm total rainfall (with locally higher amounts), but most areas across the CWA should generally see between 0.75" and 1.5" of rain before all is said and done. See the Hydrology section below for potential riverine impacts. Finally, with this upper level shortwave digging so far to the south for this time of year, it will be accompanied by a quick burst of some unseasonably cold air. Temps on Tuesday will likely fall from west to east during the day, and lows on Tuesday night could reach the mid to upper 30s over the interior. .Long Term [Wednesday Through Sunday]... Given the latest more progressive Global model runs where the ECMWF has come into very good agreement with the GFS, the overall fcst confidence has increased substantially across our CWA. This should result in a quick hitting, but quick exiting low pressure system as the very progressive upper level synoptic pattern should have swept any lingering showers or storms well off to our east by the beginning of the period. In fact, this progression now appears to be rapid enough to allow plenty of the cooler and drier air to become quickly established over much of the CWA by Wednesday morning, with the majority of the numerical and raw model guidance now showing low temperatures dipping down into the mid to upper 30s across the western half of the region. A mostly sunny and unseasonably cool day will follow on Wednesday, with a gradual warming trend expected for the end of the week and into next weekend. As for rain chances by the latter part of the period, the models have begun to diverge significantly once again, with the GFS still indicating the potential for a possible two-pronged rainfall event, while the ECMWF shows a split in the jet stream flow, which would allow one shortwave to pass to our north and another to pass to our south. This would leave most of the CWA protected with fair and seasonable conditions, but it is clearly too far in advance to buy solely into one of these solutions. Therefore, will plan on a compromised resultant for the end of the period, using our statistically verified blend of GFS/ECMWF/HPC guidance which has shown to be quite difficult to beat over the long haul. .Marine... Winds and seas will begin to gradually increase out of the south then southwest ahead of the approaching cold front on Monday night into Tuesday reaching cautionary levels. After the cold front passes through later from west to east on Tuesday, winds will quickly increase out of the northwest to Small Craft Advisory levels over the waters, with headline conditions lingering into Wednesday morning. Furthermore, only a brief respite in the elevated winds and seas is expected, as a tight pressure pattern is expected to keep conditions fairly difficult for small craft for much of the week. .Fire Weather... Relative humidity levels will remain above critical thresholds for the next several afternoons. The next wetting rains should arrive Monday Night and Tuesday. .Hydrology... While a few of our area rivers remain in minor flood stage (except for the Choctawhatchee river near Bruce which is at moderate flood levels and will likely remain quite elevated for several days), most have crested and begun to slowly recede. However, yet another batch of rainfall on Monday night into Tuesday may cause some of these rivers to return to minor flood stage. The good news is that the models continue to come into better agreement that the low pressure system which will be responsible for the coming rains will be very progressive. Therefore, with the rain expected to come to an end by late Tuesday afternoon or evening, now expect lower storm total rainfall amounts across the CWA. These should generally range from 0.75" over the SE FL Big Bend to generally 1.0" to 1.5" elsewhere. A few locations over SE AL could still see closer to 2.0" before all is said and done, so expect any concerns caused by this system to be minor. The most up to date, specific river forecast information can be found on the AHPS page at http:/water.weather.gov/ahps2/index.php?wfo=tae.
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&& .Preliminary Point Temps/PoPs... Tallahassee 63 82 62 73 39 / 10 20 50 70 10 Panama City 65 77 62 65 44 / 10 30 70 70 10 Dothan 62 82 57 65 36 / 10 40 90 60 10 Albany 63 82 62 66 38 / 10 30 70 70 10 Valdosta 63 85 63 73 40 / 10 20 50 70 20 Cross City 63 85 63 76 42 / 10 20 30 70 30 Apalachicola 66 77 65 69 46 / 10 20 50 70 10 && .TAE Watches/Warnings/Advisories... FL...None. GA...None. AL...None. GM...None. && $$ NEAR TERM...MCDERMOTT SHORT TERM...GOULD LONG TERM...GOULD AVIATION...FOURNIER MARINE...GOULD FIRE WEATHER...LAMERS HYDROLOGY...GOULD

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