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

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000 FXUS64 KMRX 132026 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 326 PM EST Tue Feb 13 2018 .SHORT TERM...
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(Today through Wednesday)... Showers have cleared out of the area, but some mid/low level clouds are still sticking around this afternoon. Still seeing downsloping flow along the mountains and that has allowed more sun to shine in the foothills today. Quiet weather will continue into tonight before rain chances ramp back up again. Low level winds will get wetter as they turn more southerly allowing gulf moisture to move in. Decent isentropic lift will allow for widespread rain over the area, through the daylight hours. There is a possibility to see some lightning tomorrow, but CAPE values are pretty low, so the vast majority of people will likely just see rain. .LONG TERM (Wednesday Night through Tuesday)... The long-term forecast will continue to feature a wet, mild, and active pattern. Additional rainfall could lead to further flooding issues especially on Friday. Wednesday night will see continued southwesterly flow in the low levels with warm advection and isentropic ascent. Model soundings indicate deep saturation especially early in the overnight period with PW values in the 1.1-1.3 inch range. The higher end of this range is near the maximum observed for mid-February and have continued with elevated PoPs during this timeframe. Further into the overnight period and into the day on Thursday, these higher moisture values shift to the north along a boundary that stretches E-W near the Ohio River. Due to this, have decreased PoPs from south to north during this timeframe. Expect clouds will linger throughout much of the day on Thursday but there could be a brief break in the precipitation during this timeframe. The upper level ridge across the Gulf of Mexico will expand a bit northward during this timeframe as well. With increasing upper level heights, temperatures will top out in the mid 60s to low 70s on Thursday afternoon. Thursday night into Friday a NE-SW oriented front will sweep southward across the Central Plains and Mid-Mississippi River Valley. Moisture convergence along this boundary will lead to PW values near maximum observed once again on Friday. The models are coming into a bit better agreement in regards to timing with the front moving through during the day on Friday. There may be some weak instability ahead of the boundary across the southern tier of counties or so but there is not enough confidence to add thunder to the forecast just yet. Rainfall amount will be light and generally range from half an inch to an inch but any additional rainfall will lead to rises along already elevated rivers and streams. The GFS and ECMWF begin to diverge over the weekend with the front to the south. The ECMWF indicates the front will surge back to the north on Saturday with continued lift along the northern side of the boundary. This will keep precipitation continuing into the day Saturday. The GFS indicates the front will make it all the way to the Gulf Coast and that most of the day Saturday will be dry. For now have sided more towards the ECMWF with the current wet and active pattern. Both models support dry conditions on Sunday as surface high pressure passes to the north. Southwesterly flow throughout the atmosphere will develop early next week with elevated rain chances continuing into the next work week. Temperatures throughout the forecast period will be mild with the warmest day on Thursday with highs into the mid 60s to low 70s. The coldest morning will be Sunday with lows in the mid 30s to low 40s.
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Chattanooga Airport, TN 47 59 56 71 / 40 90 90 60 Knoxville McGhee Tyson Airport, TN 47 60 54 70 / 40 90 80 70 Oak Ridge, TN 47 57 54 70 / 50 100 90 80 Tri Cities Airport, TN 43 59 51 69 / 40 100 100 80
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