Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

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000 FXUS64 KMRX 251900 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 300 PM EDT MON JUL 25 2016 .SHORT TERM...
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(Tonight and Tomorrow)... Isolated-to-scattered convection will be ongoing to begin the tonight period. Coverage should wane through the night compared to this afternoon but will still keep slight chance and low-end chance pops in place due to the proximity of the approaching front. Mild overnight lows expected with temps near 70 north and lower 70s south. A few of these overnight showers/storms will still have the potential to produce locally heavy rainfall due to elevated PWS. Tomorrow, showers and storms should start earlier due to the nearby front with development possible by late morning. High-end chance pops in place during the afternoon hours as we destabilize. NAM soundings showing MLCAPE values anywhere from 1500 to 2000 J/KG by the afternoon. No shear to be found as we will be in a weak zonal flow so this should greatly dampen any severe threat. The big thing to keep an eye on will be for heavy rainfall potential as PWS are on the high side for this time of year. This combined with slow storm motions could produce localized flooding. Expecting more cloud cover tomorrow so highs will be a few degrees cooler, in the upper 80s-to-low-90s. .LONG TERM...(Tuesday night through Monday)... The high pressure ridge that has been over the Southeast will be retreating eastward off the Atlantic coast to start the period. Precip should be focused on the periphery of the ridge near the MS Valley and western portions of the TN Valley on Wednesday. Will lower pops Wednesday from likely to a chance as forcing is lacking and convection should be scattered and mainly diurnal. Rain chances will generally be rising as the ridge continues its retreat, and a southern stream low over LA/MS gets picked up by a shortwave trough crossing the lower Great Lakes and Ohio Valley. The NAM, GFS, and ECMWF differ on the timing of the trough progression and best rain chances, with the ECMWF being the slower model and the NAM being the fastest. Will lean toward the GFS Ensemble mean and have likely pops for the western half on Thursday and for the entire area on Friday. A broad trough remains over the region through the weekend, which should result in a fairly wet period for East TN as the feed of moisture from the Gulf will remain open in the low-to-midlevel SW flow. With the finer details still uncertain, will keep pops in the chance range for Saturday through Monday, and lean toward a diurnal trend for the highest pops each day with near normal temperatures.
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&& .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 74 94 75 93 / 30 40 30 40 Knoxville McGhee Tyson Airport, TN 73 92 74 92 / 30 40 30 40 Oak Ridge, TN 74 92 74 92 / 30 40 30 40 Tri Cities Airport, TN 70 89 70 91 / 30 50 30 40 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ SR/DGS is the U.S. government's official web portal to all federal, state and local government web resources and services.