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

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000 FXUS64 KMRX 202032 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 332 PM EST Fri Jan 20 2017 .SHORT TERM (Tonight and Tomorrow)...
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Visible satellite imagery indicating more breaks in cloud cover this afternoon as the deep moisture has exited NE of the area. With these breaks, temperatures have been able to climb into the upper 60`s over southern two-thirds of the area, with Chattanooga currently at 70 degrees and within a degree of tying a record of 71 set in 1929. We will continue to experience a break in pcpn overnight tonight ahead of the next active weather period. Given residual low level moisture, we may see some localized areas of patchy fog by late tonight into the morning hours. Otherwise, overnight lows from the upper 40`s to middle 50`s will be about 15-20 degrees F above late January normals. For tomorrow, middle level ridge axis extends N to S along the east coast. A shortwave trough will ride NE along the western periphery of this ridge across our area during the day. This coupled with increasing instability and the return of significant moisture to the lowest 300 mb of the atmosphere will help to generate shower activity that is expected to push from SW to NE across the area through the day. Overall rainfall amounts with this round of pcpn do not look to be that impressive given continued middle level dry air holding on for most of the day. Would expect most areas to see less than 0.25 inches in shower activity. However, the combination of increasing instability coupled with the shortwave energy and favorable 0-3 km directional shear fcst for the latter portion of the period, strong to possibly severe convection could develop and would produce locally higher rainfall amounts. Threat for strong to possible severe looks to be mainly over the southern third of the area during the afternoon and evening hours with greatest threat expected to be wind, hail, and possible localized flooding. .LONG TERM (Tomorrow Night through Friday)... The active weather pattern continues through the long term with a strong short wave driving northeast across the Southern Appalachians Saturday night into Sunday, followed by a deep upper level low Sunday into Monday. Probability will be in the categorical range for much of the area during this period for showers. However, strong dynamics and instability with this system will require thunderstorms to be included in the forecast. Some of the storms may be rather strong late Saturday night into Sunday. The main threat with the storms will be strong and gusty winds. The showers will taper off from slowly from west to east Monday night into Tuesday as the deep upper low shifts northeast into the Northeastern U.S. Some colder air will build in behind this system and the precip may end as brief period of light snow across the highest terrain in the Smoky Mountains. Due to the broadbrushed nature of the superblend protocol, the only period in the remainder of the long term with no pops will be Tuesday night as drier air and ridging build into the region. The next upper trough and surface cold frontal system will move across the area Wednesday into Wednesday night in the form of rain showers. However, it will be turning colder as a deepening upper trough develops over much of the nation and there may be opportunities for orographically driven snowfall as perhaps as many as three shorter wavelength features build across the Southern Appalachians in this predominant northwest flow regime. $$
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Chattanooga Airport, TN 54 67 54 64 / 20 70 90 80 Knoxville McGhee Tyson Airport, TN 53 67 53 64 / 10 50 80 90 Oak Ridge, TN 52 66 53 63 / 10 50 80 80 Tri Cities Airport, TN 47 65 50 62 / 10 40 70 80
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.