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

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000 FXUS64 KMRX 230725 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 325 AM EDT SAT JUL 23 2016 .SHORT TERM (Today and Tonight)...
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A strong upper level ridge continues across the Central U.S. with 500 mb heights in the 596-598 dm range in the center. Closer to home, water vapor imagery and RAP upper air analysis indicates a weak shortwave trough across the Tennessee Valley rotating around the periphery of the upper level ridge. Radar imagery shows a couple of isolated showers continuing early this morning as this wave rotates through. For today, the shortwave trough will continue to slowly rotate through the area with weak cyclonic flow aloft for much of the day. Models indicate that PW values will increase across the region with values ranging from 1.6-2.0 inches with lower values across SW VA and the higher values across the Souther Valley. The upper end of these values are up into the 90th percentile for mid-July. The latest suite of models have also increased the coverage of showers and storms this afternoon, especially over the Southern Valley. Therefore, increased PoPs in the forecast for today and lowered high temperatures some due to the increased coverage of showers and storms. It will still be a hot and humid day across the area with most locations experiencing low 90s for highs with dewpoints in the upper 60s and low 70s. SBCAPE values will range from around 750-1500 J/Kg with even the more aggressive models keeping values under 2000 J/Kg. The 0-6 km deep layer shear is a minuscule 10-15 kts, therefore, not expecting any strong to severe storms. Convection will decrease near sunset due to the loss of daytime heating and as the weak shortwave through pushes off to the southwest. .LONG TERM (Sunday through Friday)... High pressure in control early in the period...keeping hot and humid conditions in place through at least Monday. Strong diurnal heating and a couple of weak impulses moving through the upper flow will allow scattered shower/thunderstorm development both Sunday and Monday...centered mainly around the afternoon hours. Models trending slower with the high dampening over the area...and it now looks like it will be Tuesday before the flow aloft becoming more zonal as a weak boundary approaches from the north. The boundary will become broad and diffuse as it settles over the area and temperatures should cool slightly by mid week. The boundary will stall over the region and act as a focus for scattered convection each day through the rest of the extended period.
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Chattanooga Airport, TN 93 74 96 75 / 50 30 20 20 Knoxville McGhee Tyson Airport, TN 93 74 93 72 / 20 20 20 20 Oak Ridge, TN 93 73 93 72 / 20 20 20 20 Tri Cities Airport, TN 92 69 92 69 / 20 10 30 30
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