Area Forecast Discussion
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855 FXUS62 KTAE 131505 AFDTAE AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 1105 AM EDT Sun Apr 13 2014 .Near Term [Through Today]...
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Very few changes made to the existing forecast for today. As was the case yesterday, the morning has consisted of sunny skies and quickly warming temperatures. The hourly temperature trends have been slightly warmer than the existing forecast, but the high temperature forecast (mid 80s in most areas) still seems on track. Therefore, most of the changes were made to adjust the temperature trends through the afternoon to account for recent observations. A cumulus field should develop by afternoon with partly sunny skies area-wide.
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&& .Prev Discussion [549 AM EDT]...
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.Short Term [Tonight Through Tuesday]... Tonight...the large scale pattern continues to amplify highlighted by positively tilted full latitude trough over Ern Plains with broad cyclonic SWLY steering downstream into the Gulf Region. At the surface...low over Great Lakes with advancing cold front Swd into TX. This will push Wrn Atlc high further into Atlc ocean. As reflected on area soundings...flow sfc-H8 veering to SSW then SWLY to H5 and WNW above. This in turn advects more moisture onshore with PWATs climbing to over 1 inch increasing chances for low clouds and fog developing after midnight. Isolated showers are also possible late across Wrn counties. With local area in warm sector and prevalence of fog or low clouds...mild minimum temps around 60 degrees are expected. Monday...The upstream trough will continue to pivot and deepen Ewd aided by several shortwaves combining with approaching 40+ KT SW low level jet will pull increasing moisture Nwd from Gulf of Mex. Dew points increase to low-mid 60s. Original surface reflection lifted rapidly Newd with models hinting that another wave will develop along front in Nrn AL or Nrn GA bringing cold front to Cntrl AL by sundown. Area soundings show deep SWLY flow as PWATS increase to around 1.4 inches. Will go with 50-20% NW-SE POP gradient. Increasing clouds especially wrn counties will offset some high temps there. Expect highs from upper 70 NW to mid 80s east. Monday Night...Trough continues to deepen Ewd. Above NRN GA sfc low lifts Newd allowing trailing front to move to our Wrn doorstep. This reflected in area soundings with show nearly uni-directional SW flow noticeably increasing with height. PWATs increase to around 1.8 inches. This combination of deep uni-directional flow plus high moisture content should yield heavy rain and...on top of earlier rain... flooding concerns and river rises. 80-30% NW-SE POP gradient. Under cloudy skies...mild lows ranging from upper 50s NW to mid 60s SE with fog a good bet across portions of CWA. Tuesday...Trough deepens over SE states with axis down Gulf of Mex during the morning. Cold front moves across in the morning bringing another round of showers and storms and exasperating flooding/river concerns. In its wake...GFS with H5 trough...then H85 trough...move across in aftn allowing decreasing clouds for all but lowest levels. A surface high will form over NE states and begin to ridge down Ern seaboard. Soundings shows precipitous drop in PWATS with low level flow shifting to NWLY by sundown. Of course if ECMWF verifies... improving conditions will be slower to arrive. Will go with 70% POP gradient with focus in morning and decreasing from NW-SE during aftn. Max temp forecast tricky as dependent on speed of frontal passage. If ECMWF verifies...aftn POPs will be higher. Under extensive cloudiness...will go from near 70 NW to near 80 SE. With high to our NE and low to our NW...expect a tight gradient with breezy/gusty conditions. As far as severe weather and heavy rainfall potential...models in better agreement than previous run but GFS (slightly faster) and ECMWF still differ somewhat on the timing and duration. Strengthening winds aloft plus increasing low level shear and SRH could support a QLCS or supercells with bowing segments beginning Monday late eve over Wrn counties but more likely after midnight. Severe Wx is also possible ahead of advancing cold front after sunrise Tues when relatively strong deep layer shear overlapping with weak to moderate buoyancy could be sufficient for...given uni-directional flow...at least low end severe wind and hail but an isolated tornado cant be ruled out. Local severe Wx tool shows best chances for severe Wx are 06z-12z Tues over FL Panhandle and ...12z-18z Tues over Wrn Big Bend with small chances of a tornado there into GA counties. SPC has placed our Panhandle and SE AL counties in a slight risk for day 2 and our Ern areas in a see text for Tues. While both model solutions also favor an active event including several rounds of rain during that time...the slower ECMWF leaning towards a more aggressive solution regarding flooding and likely these concerns continue beyond Tuesday. Total QPF ranging from about 2.3 inches NW to 1.4 inches SE CWA. Inserted Isold T+ in Panhandle and heavy rain in adjacent marine area for 06z-12z Tues Grids. .Long Term [Tuesday Night Through Saturday]... After our reasonably long respite from the unsettled weather (given the nature of the extremely progressive and active upper level pattern this spring) which has lasted from last Wednesday through the first half of this weekend, signs of yet another developing shortwave to our west are already taking shape to impact our weather early next week. As was the case on Friday, the Global models are still in reasonable agreement of a steep upper level trof carving its way down to the northern Gulf coast Tuesday into Wednesday before gradually pulling away to our NE. The main differences between the GFS and ECMWF are the timing and duration of this potential severe weather and likely heavy rainfall maker, with the ECMWF leaning towards a more bleak solution, with the possibility of a very heavy round or two of precip both over our CWA and upstream, which would exacerbate the flooding on many of our rivers and streams which are still quite high and recovering from the last flooding event. For now, the GFS is significantly faster, and while both models could still pose a severe weather threat (which we will be examining more closely over the next couple of days), the overall flooding impacts would be lower given the GFS solution with any significant impacts likely over by the end of the day on Tuesday. Thereafter, fair and near seasonable conditions should return for the balance of the week, with the next chance for inclement weather returning on Friday into Saturday. .Aviation... [Through 06Z Monday] Occasionally dense fog is likely to continue to affect KECP through sunrise. Elsewhere, tempo MVFR visibility is expected with patchy shallow fog. All fog will dissipate rapidly after sunrise with VFR conditions prevailing through the day and southeast winds around 10 knots. .Marine... Southeast winds are expected to increase to moderate with well offshore winds approaching cautionary levels through tonight. Then, onshore winds and seas will remain light to moderate through Monday before increasing to at least cautionary levels out of the southwest on Monday night out ahead of the next low pressure system and cold frontal boundary. In its wake, cautionary to possibly advisory level offshore winds and seas are expected to move into the marine area Tuesday through Tuesday night before decreasing again. .Fire Weather... Relative humidity levels will remain above critical thresholds for the next several afternoons. A seabreeze is expected near the coast both today and Monday. The next wetting rainfall should arrive late Monday and Tuesday. .Hydrology... Most rivers have reached their peak and are generally falling. The only exceptions are the Choctawhatchee River at Bruce and Ochlockonee River at Havana. The Ochlockonee River at Concord is continuing a broad crest. The next chance of rainfall is Monday through Tuesday night. At this time the system looks progressive enough to keep rainfall totals around 1.5"-2.5", with higher rainfall totals north and west of the line from Apalachicola to Tallahassee to Fitzgerald. These totals will be too low for flash flooding to be a main concern...however, this may slow the decreases on already swollen rivers and may even cause a few to return to bankfull or minor flood stage by later in the week. 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...
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Tallahassee 85 62 82 64 75 / 0 10 20 40 70 Panama City 78 65 77 63 70 / 0 10 30 60 70 Dothan 83 61 80 59 70 / 0 10 40 70 60 Albany 84 60 81 62 72 / 0 10 30 60 70 Valdosta 88 61 83 64 76 / 10 10 20 40 70 Cross City 85 61 84 64 77 / 10 10 20 30 60 Apalachicola 76 66 77 65 72 / 0 10 20 50 70
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&& .TAE Watches/Warnings/Advisories...
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FL...None. GA...None. AL...None. GM...None.
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&& $$ NEAR TERM...LAMERS SHORT TERM...BLOCK LONG TERM...GOULD AVIATION...DVD MARINE...BLOCK FIRE WEATHER...DVD HYDROLOGY...BLOCK

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