Area Forecast Discussion
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516 FXUS62 KTAE 240827 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 327 AM EST Mon Nov 24 2014 ...Unsettled Weather to Continue with Much Cooler Air Arriving on Tuesday... .Near Term [Through Today]...
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As of 06Z, the synoptic cold front associated with the deepening Great Lakes cyclone had not yet reached the Mississippi River. This front will likely arrive late this morning or in the afternoon. In the meantime, objective MSAS analysis places a local theta-e minimum right over our forecast area, likely related to the convective overturning from yesterday afternoon`s squall line. The 00Z TAE sounding showed an inversion layer below 900mb, with lingering moderate mid-level lapse rates around 6 C/km providing some CAPE for parcels elevated around 900-800mb. With the surface front and low-mid level trough axis still situated west of our area, southerly flow in the lower levels has been maintained. This pattern is aiding air mass recovery across our area, and also creating some isentropic ascent. Therefore, we expect surface dew points and temperatures to continue to slowly rise before sunrise. Additionally, we are already seeing evidence of the increasing ascent in the form of scattered showers beginning to develop near the north/west periphery of the MUCAPE gradient. The showers should become more numerous as the surface front approaches and northward moisture flux continues into the morning hours. Additionally, gradual destabilization is likely to occur, and most models indicate 500-1000 J/kg of MLCAPE by 15-18Z over the southeastern half of our forecast area. Therefore some thunderstorms will certainly be possible, and if some cells can root near the surface, isolated severe weather is not out of the question given about 50 knots of effective deep layer shear. For the PoP forecast, we followed a consensus of convection-allowing models (CAM) which shows showers becoming likely along a Panama City to Tifton axis by 09-12Z, and then gradually shifting southeast to an Apalachicola to Valdosta axis by 18Z. Given the likelihood of an abundance of cloud cover and occasional rain showers, we trended high temperatures a bit lower than guidance in between the two aforementioned lines. If breaks in the cloud cover do not develop, this temperature forecast may need to be trended down further. .Short Term [Tonight Through Wednesday]... The active and unsettled weather pattern will continue through this period. There will be sufficient instability for some evening thunderstorms ahead of the advancing cold front. The front will eventually stall over or near our eastern zones overnight. Cyclogenesis will then occur over the south central Gulf of Mexico north of the Yucatan Peninsula as another short waves works its way into the base of the Great Plains upper trough over Texas. This low will track rapidly northeast across FL Tuesday night before passing near Cape Hatteras, NC on Wednesday. Isolated thunderstorms will be ongoing across the eastern FL Big Bend zones at the start of the period and could persist until after midnight around Dixie County. Isentropic ascent and DPVA will then increase across the area with forcing for ascent peaking from Tuesday afternoon into the overnight hours. PoPs will peak in the categorical range during this time with 1-2 inches of rain common over the southeast half of the forecast area. Lower levels will be cool and stable. However, we may see strong enough ascent aloft to see some elevated thunderstorms Tuesday evening. As the low pulls away from NC, drier air will final make some quick eastward progress across the local forecast area on Wednesday and we have trimmed PoPs back for the afternoon period. All of the clouds and rain will keep daytime temps much lower than what we will see today, mainly in the mid 50s to lower 60s. Overnight lows will be in the 40s. .Long Term [Wednesday Night Through Monday]... This period will be dry with surface high pressure in control. Heights will also rise with zonal flow in place from Friday into the weekend. A chilly air mass will be in place for a couple of more days with Thursday and Friday feeling more like January than late November. Temperatures will moderate over the weekend with some areas seeing 70 degrees by Sunday.
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&& .Aviation...
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[Through 06Z Tuesday] A variety of flight categories have been observed across the region early this morning, but in general the trend has been for IFR or LIFR CIGS to settle in. These should persist through the mid-morning hours (around 15-16Z) at most terminals, with conditions gradually improving to VFR in the afternoon. There will be a good chance of showers at all terminals at some point this morning, with chances decreasing in the afternoon. Some thunderstorms are also possible.
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&& .Marine...
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Seas should drop below advisory levels this morning. However, winds will return to cautionary levels for much of this morning before falling off this afternoon. Winds will shift to offshore overnight and increase to cautionary to marginal advisory levels. By Tuesday afternoon, we should see solid advisory criteria with winds speeds peaking Tuesday night. Some gale-force gusts will be possible during this time. Winds and seas will then fall off quickly on Wednesday as low pressure accelerates northeastward off the U.S. East Coast. High pressure will build in north of the Gulf of Mexico for the latter part of the week, but winds should stay just below headline criteria in the offshore flow.
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&& .Fire Weather...
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There is no chance of red flag conditions over the next few days as high RH and periodic rain are expected.
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&& .Hydrology...
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Recent rains are causing rises on most area rivers. Before the approaching frontal system clears the area, and additional 1-2 inches of rainfall are expected over the southeastern 2/3 of the forecast area, possibly a bit more over the Lower Suwannee Valley. These rains will once again be mostly beneficial with no riverine flooding anticipated at this time.
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&& .Preliminary Point Temps/PoPs...
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Tallahassee 75 53 57 43 60 / 60 40 70 80 30 Panama City 71 53 57 43 61 / 50 30 60 80 20 Dothan 75 48 57 40 59 / 20 10 50 80 20 Albany 76 50 57 41 58 / 50 20 60 80 30 Valdosta 77 54 58 44 59 / 60 40 70 80 40 Cross City 78 59 64 48 61 / 50 40 80 80 50 Apalachicola 72 55 59 44 61 / 50 40 70 80 20
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&& .TAE Watches/Warnings/Advisories...
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FL...High Rip Current Risk through late tonight for Coastal Bay- Coastal Franklin-Coastal Gulf-South Walton. GA...None. AL...None. GM...Small Craft Advisory until 7 AM EST this morning for Coastal waters from Apalachicola to Destin FL out 20 NM-Waters from Apalachicola to Destin FL from 20 to 60 NM.
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&& $$ NEAR TERM...LAMERS SHORT TERM...WOOL LONG TERM...WOOL AVIATION...LAMERS MARINE...WOOL FIRE WEATHER...LAMERS HYDROLOGY...WOOL

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