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

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411 FXUS64 KMRX 200759 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 259 AM EST Mon Feb 20 2017 .SHORT TERM (Today and Tonight)...
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Mostly clear skies and light winds have lead to ideal radiational cooling conditions this morning with patchy fog being reported. Above average temperatures continue this morning with lows in the upper 30s and 40s. Current water vapor imagery and RAP upper air analysis indicates the closed low is now out over the Atlantic with a strong upper level ridge building into the region. The ridge will lead to subsidence and dry conditions throughout the short-term forecast. Models indicate that 500 dm heights are already in excess of 580 dm, therefore, expect well above normal highs for today. It does not look like it will be the warmest day of the year (temperatures on February 12th were in the mid 70s for all climate sites). Forecast highs are also still a couple of degrees below records for the day. The record for today are 78 for Chattanooga in 1986, 75 for Knoxville in 1986, and 75 for the Tri-Cities in 2014. Current forecast highs are 74, 72, 72 for Chattanooga, Knoxville, and the Tri-Cities respectively. Much above normal temperatures will continue into the overnight hours as the ridge axis passes just to the east. Overnight lows are forecast to be in the mid 40s to low 50s. .LONG TERM (Tuesday through Sunday... The extended will begin with unseasonably warm temperatures and the approach of a weakening cold front. Models have had a difficult time with the front in regards to timing...strength and amount of moisture available. While there continues to be some discrepancy in the details...the overall trend is for increasing clouds Tuesday with a few possible isolated showers beginning to push in late in the afternoon. The main band of showers should move through Tuesday night. Available moisture and strength now look sufficient enough for widespread showers across the area and have increased pops to likely category. The showers should slowly exit the area on Wednesday. Models have also had problems resolving the weather pattern for Thursday...current thinking brings in a weak short wave for a slight chance of showers and even a possible rumble of thunder. Another cold front is progged into the the region on Friday/Friday night. Timing has been an issue with this feature as well. Current model runs are trending towards a Friday night frontal passage. Warm...moist air will be in place ahead of the system and should allow the atmosphere to become at least weakly unstable. Could see a some scattered convection develop well ahead of the front for Friday afternoon. However...the main activity currently looks to occur Friday night. Overnight ...the stability should be limited...but still expect to see some thunderstorm activity. Behind the front for Saturday and Sunday... temperatures will fall to near normal levels. A few scattered showers may linger into Saturday morning but otherwise...high pressure will build in for dry conditions.
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Chattanooga Airport, TN 74 52 70 53 / 0 0 30 60 Knoxville McGhee Tyson Airport, TN 72 49 68 51 / 0 0 20 60 Oak Ridge, TN 74 48 68 51 / 0 0 20 60 Tri Cities Airport, TN 72 46 66 49 / 0 0 10 60
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