670 FXUS64 KMRX 052318 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 618 PM EST Mon Dec 5 2022 ...New AVIATION... .SHORT TERM... (This evening through Tuesday) Issued at 312 PM EST Mon Dec 5 2022 Key Messages: 1: Rain showers will continue to move across the area tonight through tomorrow, with a slight chance for a few rumbles of thunder. 2. Low probability of localized flooding across portions of the southern TN valley and southwest NC. If flooding issues arises, it will likely be across low lying and flood prone areas. Discussion: A good slug of precipitation is currently moving across the southern TN valley and southwest NC this afternoon. The HRRR and RAP both show this first wave of moderate precip slowly sliding to our east later this evening. However, additional showers will develop and spread in from southwest to northeast through the night as isentropic lift persists ahead of a warm front to our southwest. Additional QPF overnight ranges from 0.5 to 0.75 inches across the southern TN valley and southwest NC, around 0.5 inches across the central and northern TN valley, and 0.25 inches across northeast TN and southwest VA. If we see any minor flooding issues it will be across the southern areas as mentioned above. Also, low-end, elevated, instability is seen in soundings overnight so will include slight chance for thunder. There is some uncertainty on how POPs play out through the day tomorrow. We remain in a moist environment with elevated PWATS but precip will be determined on where the lift is focused, which will be determined by where the front sets up. The NAM suggests that the higher POPs shift north through the day tomorrow and into KY, leaving much of TN valley on the drier side with only slight chance/chance POPs in place. This idea is currently supported by the NBM as well. This means that after good coverage of morning showers we should start to see more spotty showers during the afternoon hours with much less coverage. Highest POPs for tomorrow will be focused along the TN/KY/VA state lines, where better lift is expected. Temperatures remain well above normal through the period due to the southwest flow and abundant cloud cover. && .LONG TERM... (Tuesday night through next Monday) Issued at 312 PM EST Mon Dec 5 2022 Key Messages: 1. Periods of rain will continue through the week. Some flooding concerns still present for areas that see repeated rounds of moderate to heavy rainfall. Best chance for this is generally north of I-40 mid to late week. 2. Above normal temperatures Wednesday and Thursday will gradually cool into the weekend. Discussion: Tuesday night through most of the rest of the work week will continue to be cloudy, rainy, and pretty warm. Quasi-stationary boundary will remain laid out in the southern Ohio Valley and sometimes dipping into the Tennessee Valley. Continuous moisture will be fed into the region as the low level flow generally remains out of the south/southwest. Models continue the trend of keeping the boundary and axis of heaviest precipitation Tuesday night into Friday to our west and north, along West/Middle TN up into southern KY. This is still close to the eastern Tennessee valley, and therefore we'll still likely see waves of rain throughout the week, but am still expecting QPF amounts to be the highest further west and north. For the middle of the week, areas north of Interstate 40, and the Cumberland Plateau will likely see the highest rainfall totals. Have continued to keep QPF amounts close to NBM/WPC guidance with a slight bump up in totals in areas north of Interstate 40, and a slight decrease in southeast TN into southwest NC. Forecasted amounts generally remain 2-3" for the week with mostly light rain expected, and periods of more moderate rain at times. Model discrepancies crop back up as we move into Friday with regards on how to handle the low moving into the Great Lakes region and finally forcing through the front, and drying out the area. Will continue with PoP chances lingering into Friday afternoon, but as we get closer to the end of the week, hopefully we'll be able to trim back the temporal extent of the PoPs when models come into better agreement on timing. We'll take a break from rain heading into the weekend before another front that is forecasted to quickly sweep through the eastern U.S. during the first part of next week. This system should help to usher in a period of colder weather to start of next week. && .AVIATION... (00Z TAFS) Issued at 614 PM EST Mon Dec 5 2022 Highly variable conditions are expected at the TAF sites as rain spreads across the area tonight and tomorrow. Conditions have been varying from VFR to IFR across the TN Valley, depending on where the heavier rain occurs. CHA is expected to have the best chance of IFR vis and cigs tonight as rain will be heavier there, with TYS expected to have predominantly MVFR conditions with periods of cigs dropping to IFR. At TRI, downslope winds off the mountains have kept cigs VFR, but this should drop to MVFR when rain increases there tomorrow morning. MVFR cigs will likely persist through tomorrow, with IFR cigs possible. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 48 63 59 70 / 90 70 60 60 Knoxville McGhee Tyson Airport, TN 46 63 58 69 / 100 80 70 80 Oak Ridge, TN 44 62 56 67 / 90 80 80 80 Tri Cities Airport, TN 45 61 54 66 / 90 80 70 80 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...SR LONG TERM....ABM AVIATION...DGS