421 FXUS64 KMRX 110737 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 337 AM EDT Fri Apr 11 2025 ...New SHORT TERM, LONG TERM... .SHORT TERM... (Today and tonight) Issued at 305 AM EDT Fri Apr 11 2025 Key Messages: 1. Patchy dense fog this morning, primarily for south of I-40 and near I-75. 2. Light rain showers continue today with isolated thunderstorms. 3. Cooler behind the cold front today and tonight. Frost possible for the plateau and higher elevations into southwest VA Saturday morning. Discussion: Conditions have rapidly cleared across the south within the past hour or so, resulting in dense fog developing. Currently, Chattanooga, Athens, and Cleveland are under a quarter mile of visibility. Will issue an SPS for the morning hours to message the possibility of dense fog elsewhere. This will primarily be for everywhere EXCEPT the far northeastern part of the forecast area currently under light showers and cloud cover. Be cautious driving this morning, as we have not had a nearly moist and foggy morning in quite some time. The area is situated under an upper level trough and weak surface low. The trough will slowly slide eastward with time today with its axis over the Atlantic Coast by this time tomorrow. The weak surface low will follow the same track. Northerly flow behind the exit of the trough and low, will aid showers and possibly some thunderstorms into the late afternoon and early evening today. Best chances for greater than a quarter inch or so of rainfall will be across the higher terrain and parts of the valley north of I-40/81. Otherwise, it will be a mostly gloomy day with temperatures in the 40s (higher elevations) and 50s. Some low 60s possible for the southern valley where they may get more sun poking through the clouds. We dry pretty quickly than previously forecast tonight as high pressure sags down from the NW and clouds begin to break further away from the far eastern parts of the CWA. This paired with some light winds or calm conditions overnight, and another cold night on tap with lows in the 30s, frost will be possible especially where the aforementioned area overlaps; almost everywhere except the far southern valley, parts of the Southern Appalachians, and parts of southwest VA. With that being said, the thinking of light snowfall the past couple of days across the higher terrain tonight will pretty much be null. There could still be a dusting to a tenth somewhere across the highest peaks of the Smokies though. && .LONG TERM... (Saturday through Thursday) Issued at 305 AM EDT Fri Apr 11 2025 Key Messages: 1. Possible widespread frost Sunday morning with freeze across parts of southwest Virginia, southwest North Carolina, and far east Tennessee mountains. 2. Trending dry for the weekend with temperatures increasing into the beginning of next week. 3. Cold front Monday night and Tuesday brings next chances of showers. 4. Frost possible again Tuesday night and Wednesday night. Discussion: Temperature Rollercoaster is the main theme for the extended. As usual for spring, a good deal of pattern change. Current deep upper trough will move east of the southern Appalachians Saturday with ridging building into the Tennessee valley and southern Appalachians for this weekend. Due to the surface ridging, good radiational cooling conditions are expected Saturday night. Freeze is possible across the far east Tennessee mountains, southwest Virginia, and southwest North Carolina with a frost elsewhere. For Sunday and Monday, developing upper ridge will produce mostly dry conditions and warmer temperatures. For Monday night, another deep upper trough becomes established over the Great Lakes and eventually into the eastern United States for Tuesday. A cold front will sweep southeast across the Tennessee valley and southern Appalachians. NBM probabilities of a quarter inch or more of QPF is low with this frontal passage. This is due to limited Gulf moisture return and best dynamics from upper trough well north of the region. For Tuesday night and northern sections Wednesday night, surface ridging and cooler airmass will produce area of frost. For Thursday, another quick moving short-wave/jet streak in northwest flow will move across the Tennessee valley into the southern Appalachians. NBM CAPE ensembles show instability moving back into the area with another round of convection. Confidence is low on the development of this system but there is a potential of strong to severe storms. && .AVIATION... (06Z TAFS) Issued at 147 AM EDT Fri Apr 11 2025 A cold front and thus, wind shift is expected to move through sometime during the overnight or very early hours this morning. Winds will primarily be out of the north from then onward until the end of the TAF period. A stacked upper level low and surface low will provide showers mainly for TYS and TRI today. CIG are expected to fall to MVFR in the next couple of hours, with TRI approaching IFR by mid-morning. TYS and TRI may keep MVFR entire TAF period, meanwhile CHA will improve to VFR by this evening. Not expecting much thunder, so will continue to leave that out of the TAF. Near 00z and after, rain expected to be east of the area. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 62 41 63 39 / 50 20 0 0 Knoxville McGhee Tyson Airport, TN 58 40 59 36 / 50 20 0 0 Oak Ridge, TN 59 39 60 36 / 50 10 0 0 Tri Cities Airport, TN 54 38 54 34 / 50 20 0 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...KS LONG TERM....DH AVIATION...KS