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

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000 FXUS64 KMRX 271911 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 311 PM EDT WED JUL 27 2016 .SHORT TERM...(Tonight and Tomorrow)... Isolated-to-scattered convection will continue during the overnight hours as an upper level disturbance approaches our area from out of the southwest out ahead of an incoming trough. Some of these showers and storms will still pose the risk of localized heavy rainfall due to the high PWS that are in place. Overnight lows will be mild with near 70 north and low-to-mid 70s south. Tomorrow will feature the best rain chances we`ve had in quite some time as an upper level disturbance gets absorbed into an incoming trough and swings across the area through the day. This upper level disturbance originated in the Gulf of Mexico and brings with it near record PWS for this time of year. Soundings PWS top out around the 2 inch mark for most areas. Very high PWS combined with long skinny CAPE profiles, 15 to 16k foot freezing levels, and a southwesterly mean flow will lead to the threat of heavy rainfall. Models in fairly good agreement that the main precip axis will stay off to our north. Having said that, our northern most areas from the Northern Plateau and up through Southwest Virginia will be closest to the main axis and will therefore have the best chances of seeing heavier rains. All other locations could still see periods of localized heavy rain throughout the day. We will continue to monitor trends to see if there is any southward shift in the main QPF axis. Increased clouds and precip will allow for temps in the mid to upper 80s by tomorrow afternoon. Incoming trough will also make for a breezy day across the valley with sustained winds from 10 to 15 kts with occasional gusts up to 20kts. .LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)... Low to our southwest that has been riding around the ridge will likely move just north of our area as we head into the end of the work week. This will help to bring a breakdown in the ridge and bring in increased moisture that is wrapped up with this system. Precipitable water values will increase to around or above 2 inches on Thursday leading to chances to see heavy rainfall with storms in the area. Highest PW values and best lift associated with this system looks to be closer to Eastern Kentucky into the Virginias, but that doesn`t rule out the possibility of some of our counties receiving heavy rain Thursday into Friday. In addition to heavy rainfall in some locations, enough CAPE/shear could combine with the impulse moving through to provide an environment where strong to severe storms might be possible. If strong storms do form, the biggest threats would be locally heavy rainfall and strong winds. One thing to watch, in regards to storm strength, will be cloud coverage during the daytime, as increased cloud coverage would likely inhibit daytime destabilization of the atmosphere. After this system moves through we will be under a broad upper level trough that will help keep temperatures near normal and allow for several weaker impulses to move through the region and bring continuous chances for showers and thunderstorms in the afternoon/evenings. Ridge begins to move in from the west towards the end of the forecast leading to increasing temperatures and decreasing rain chances. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 75 89 73 88 / 40 60 50 50 Knoxville McGhee Tyson Airport, TN 74 88 71 86 / 50 60 60 50 Oak Ridge, TN 74 86 71 86 / 50 70 60 50 Tri Cities Airport, TN 70 87 69 84 / 50 70 60 50 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ SR/ABM is the U.S. government's official web portal to all federal, state and local government web resources and services.