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

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000 FXUS64 KMRX 270816 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 416 AM EDT Sun May 27 2018 .SHORT TERM...
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(Today and Tonight)... The main concern for the short term (and long term for that matter) is the possibility of heavy rains associated with moisture from Alberto. The main threat of for heavy/flooding rains is still during the long term period, however there is cause for concern late tonight and into early Monday morning. Convection has been ongoing throughout the Tennessee Valley overnight, with anywhere from half an inch to an inch of rain being fairly common place to the southwest of roughly Knoxville. Suspect half an inch totals to the northeast will be possible by daybreak. The 00z Atlanta sounding from last evening measured 1.75" PWAT values. Based on their observed sounding, and model progs, suspect that locally precipitable water values were somewhere around 1.5" overnight. The significance of this is that models show an area of 1.75 to +2 inch PWAT values rotating north around the eastern periphery of Alberto during the day today, and into the western Carolinas and perhaps the far southern Tennessee mountains late tonight and into Monday. This could lead to some flash flooding concerns as today is expected to be essentially a repeat of recent days, with convection firing during the afternoon and lasting into the overnight hours. For this reason, have gone ahead and hoisted a Flash Flood Watch for southwest NC, and essentially the southern half of our Tennessee mountain zones. With time, this watch will almost certainly need to be expanded to cover more of the forecast area. However, a CWA wide watch doesn`t seem to be appropriate just yet so decided to just highlight the areas of more immediate concern. .LONG TERM...(Monday through Saturday)... It will be a wet week across the Southern Appalachian Region. On Monday...low level moisture will continue to surge into the area and with a weak...diffuse boundary over the region and diurnal heating...will see another day of scattered/likely convection. The main concern through the period continues to be the approach of the remnants of Alberto. Models continue to show some differences in timing and track but the overall general trend will bring the subtropical system through the area during the Tuesday through early Thursday time frame. As the system approaches...low level moisture will continue to push into the area and widespread convection is expected through mid week. These showers and storms will be capable of brief heavy rainfall and localized flooding will continue to be a threat through this period. Additionally...with the heavy rains...area rivers and creeks will rise...adding to the potential flooding problems. What`s left of Alberto should be exiting the region and its affect will be diminished for Friday and Saturday. However...some lingering convection...possibly aided by diurnal heating...can be expected.
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&& .PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN 85 69 82 69 / 50 60 60 70 Knoxville McGhee Tyson Airport, TN 84 68 81 68 / 60 50 60 50 Oak Ridge, TN 85 69 81 68 / 60 40 50 50 Tri Cities Airport, TN 82 65 80 65 / 60 40 50 50
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ CD/MJB

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