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

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000 FXUS64 KMRX 220729 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 329 AM EDT Sat Jul 22 2017 .SHORT TERM...
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Today and tonight)...Another very hot day for today. Low amplitude mid level ridge will remain centered just to our west but its influence over our area will begin to weaken a bit. Significant convective energy again today but model soundings continue to show weak capping and there is again little forcing evident, so convection likely to be diurnally and terrain driven again. Will keep PoPs on the low side. Will mention possibility of strong to severe storms in HWO, as any convection that does form may be able to produce some strong gusty winds. Dewpoints may run a bit higher than yesterday given a bit more low level flow from the southwest. However, heat index values still look to top out near to a bit above 100 in the southern and central valley areas, so no heat advisory at this time. .LONG TERM...(Sunday through Friday)...At the beginning of this period (Sunday morning), the upper ridge is receding back to the west and the westerly upper flow to our north is sagging more into our area. A cold front will be north of the area Sunday that will be sagging southward as well. Low level moisture will be plentiful in the area and MLCAPE values will likely rise above 2000 J/kg . Sunday afternoon. The model blend has been initializing with surface dew points too high in the afternoon hours, when mixing has been lowering the dew points, so I`ve trimmed back the afternoon dew points on Sunday by about 3-4 degrees. This will also keep the Heat Index values from being as high as well. Late Sunday and into Sunday evening, an upper level disturbance will be moving into the area. Storms will likely develop north of the area and move into the northern counties. With CAPES high, storms will likely be strong. As the storms move southward nighttime cooling will start to lower the CAPE values, so the storms will lose some of their intensity farther south. The SPC Day 2 threat areas reflect this scenario. Models diverge on how things play out for the rest of the week, whether the front moves through as well as timing and strength of upper level disturbances. However, there is agreement that we will stay in this pattern, with the upper ridge staying to the west and our area being under an unsettled upper northwest flow. So, POPs will be in the forecast for most periods.
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Chattanooga Airport, TN 96 76 92 74 / 20 20 40 50 Knoxville McGhee Tyson Airport, TN 95 75 90 72 / 20 20 40 60 Oak Ridge, TN 95 76 91 73 / 20 20 50 60 Tri Cities Airport, TN 92 70 89 70 / 30 20 50 60
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