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

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000 FXUS64 KMRX 021508 AFDMRX AREA FORECAST DISCUSSION National Weather Service Morristown TN 1008 AM EST Tue Mar 2 2021 .UPDATE... MORNING UPDATE. && .DISCUSSION... Quite a bit of high clouds around, especially south. These will decrease across the north today. A shower may sneak into southern areas late in the day. Current forecast seems to have a decent handle on all of this, so just some minor tweaks mainly to hourly temps and dew points at this time. && .AVIATION... 12Z TAF DISCUSSION. Confidence of rain and lower flight conditions at TYS have lessen from the previous TAFs. VFR conditions are still expected deteriorate across the southern valley (CHA Terminal) this evening as another system moves across the Gulf Coast states. After 00Z Wednesday, lower ceilings will drop flight conditions to MVFR at CHA. An area of rain will spread northeast at CHA between 00-02Z and possibly TYS 04-06Z. TRI will stay dry with VFR conditions throughout the forecast period. Improving flight conditions are expected at CHA before daybreak Wednesday. && .PREV DISCUSSION... /ISSUED 331 AM EST Tue Mar 2 2021/ SHORT TERM...(Today and Tonight)... Key Messages... 1) A wintry mix is expected to move northeast into the far east Tennessee and southwest North Carolina mountains tonight. Snow accumulations up to 1 inch is possible across the highest elevations, generally above 5kft. For Today, weak ridging aloft will keep conditions dry today with only areas of high level clouds over the region. For Tonight, an upper trough will move across the Gulf Coast states into the southeast. The strong upper jet dynamics will remain south of the southern Appalachians but QG forcing is anticipated generally along and south of interstate 40. Strongest forcing is between 03-07Z. Models are having some disagreements on how far north the precipitation will be able to move. Using GEFS and HREF feel confident that precipitation will move into CHA and TYS, but will likely remain south and east of TRI. Model temperature profile suggest the highest elevations, generally above 4500 feet, will receive a wintry mix with snow accumulations up to 1 inch over the highest peaks. The dynamics will move east of the region by daybreak with precipitation ending. LONG TERM...(Wednesday through Monday night)... Generally quiet weather is expected through the extended period with a near miss from a couple of systems. A closed upper low and upper trough axis will be moving east of the region on Wednesday morning with lingering precip ending quickly from west to east. A light wintry mix is possible across the higher elevations of the southeast TN and southwest NC mountains, but little additional accumulation is expected prior to precip rapidly exiting the area. Shortwave ridging builds in Wednesday afternoon with a pleasant day expected across the area. Max temperatures should be near or just above normal. As we get further into the extended a consistent longwave pattern develops with ridging across the Southern Plains and troughing across the Northeast and Mid-Atlantic. This overall synoptic setup will be the main feature that impacts our weather changes over the extended. With this pattern, locations across NE TN and SW VA may be near or slightly below normal while locations further southwest toward Chattanooga are expected to be slightly above normal. A noticeable temperature gradient will be present across our forecast area from southwest to northeast. With NW flow and subsidence, mostly clear conditions are expected mid to late week. Several shortwaves within the longwave trough will move southeast across the Mid-Atlantic on Wednesday night and Thursday bringing an associated back door cold front across our area from the N/NE. No precipitation is expected with this system, but it will bring some reinforcing cooler, drier air to the area on Thursday night and Friday with a large area of high pressure centered across the Central Appalachians. A closed low is expected to phase with a northern stream vort max and eject eastward from the Southern Plains across the Gulf Coast on Saturday. There are minor differences within the guidance; however, with the strong surface ridging, dry air, and primary jet dynamics located to our south across the Gulf Coast states, little to no precipitation is currently expected with only slight chance PoPs across our southern/southeastern zones on Friday night through early Saturday morning. With enough cold air in place, a slight chance of a wintry mix or light snow would be expected across our higher elevations. Importantly, at this time, little to no impacts are expected with this system forecast to remain mostly south of our forecast area. As this early weekend system tracks southeast of our area, surface and upper ridging builds across the region Sunday through early next week bringing dry weather and expected above normal temperatures. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 55 39 62 37 66 / 20 80 10 0 0 Knoxville McGhee Tyson Airport, TN 53 37 59 35 62 / 0 60 10 0 0 Oak Ridge, TN 53 35 61 35 64 / 0 40 10 0 0 Tri Cities Airport, TN 52 32 58 33 58 / 0 10 10 0 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$

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