322 FXUS64 KMRX 190152 AAA AFDMRX AREA FORECAST DISCUSSION...UPDATED National Weather Service Morristown TN 952 PM EDT Mon Oct 18 2021 .UPDATE... EVENING UPDATE. && .DISCUSSION... Potential for fog development appears favorable tonight, especially near bodies of water. Dewpoints are higher at this time than they were 24 hours ago, and winds have become calm earlier. So the forecast update will expand the areas of fog and lower visbilities. Confidence is lower away from rivers and lakes, so an Dense Fog Advisory will not be issued at this time. DGS && .AVIATION... 00Z TAF DISCUSSION. Fog will be a possibility at TRI late tonight/tomorrow morning, and if it does form it will likely be dense with vis of a half mile or less. Expect similar timing to last night, between 10-13Z. Otherwise, clear and VFR conditions are forecast. DGS && .PREV DISCUSSION... /ISSUED 333 PM EDT Mon Oct 18 2021/ SHORT TERM...(Tonight and Tuesday)... Key Messages: 1. Continued quiet weather through the short term period with increasing temperatures into Tuesday. Discussion: The short term period will begin with an upper level ridge axis extending up through the Mississippi river valley and into southern portions of central Canada. Additionally, over the eastern and western portions of the CONUS, troughing will act to create an omega- like upper level pattern over the CONUS as a whole. Closer to home, upper level flow will be from the northwest as eastern TN will be located near the transition zone of the trough/ridge pattern. The northwesterly flow will result in plenty of dry air aloft and can be seen in model derived soundings and observed on satellite imagery as well. This will lead to continued clear skies this evening and into Tuesday. That being said, the clear skies will allow for ample radiational cooling with overnight lows below seasonal normal values. Some patchy frost cannot be ruled in Clay/Cherokee counties of NC or extreme NE TN and SW VA, however, it currently does not warrant an advisory as it would be very spotty. Heading into Tuesday, the aforementioned upper level futures along with surface high pressure will continue to meander eastwards. H5 height rises and low level flow transitioning to a southerly component will promote a warming trend as high temperatures will increase back to seasonal normals. The continued lack of moisture availability and overall subsidence will keep conditions dry again Tuesday. KS LONG TERM (Tuesday Night through Monday)... Key Messages: 1. Dry weather Wednesday and Wednesday night. An increase in showers and possibly thunderstorms Thursday and Thursday night ahead of a front. 2. Towards next weekend, drier weather is expected, but models are struggling to thoroughly dry us out. Discussion: We begin the extended Tuesday night underneath h5 ridging while an upper level closed low moves off the Rockies and lifts into the northern plains. Surface high pressure continues to anchor itself across the Appalachians Tuesday night and Wednesday promoting tranquil weather conditions. An h85 ridge axis shifting east will continue to promote southerly low level flow aiding in weak warm air advection and a moderation in temperatures (back to near or only slightly above seasonal levels). Wednesday night and Thursday, the upper low begins to transition to an open wave as it phases with the northern branch of the westerlies across the Great Lakes. A surface cyclone will lift NE from the Midwest and into the Great Lakes with a trailing cold front extending from the parent low southward into the Ohio and Tennessee Valley. Isentropic ascent on the 295 and 300K surface suggests an increase in showers as early as 12Z Thursday across northern Alabama/southern Tennessee while a the cold front begins to move into western Tennessee. The front enters the Cumberland Plateau in the afternoon hours Thursday. Weak frontal convergence supports scattered showers or thunderstorms along the front with its passage. Friday and into the weekend, we will remain underneath generally lower heights with with a deep closed low across southern Canada. Several shortwaves are progged to drop from the northwest which could promote chances of showers Sunday night. Otherwise, dry weather is expected during the weekend. Temperatures will fall again during this time with highs in the 60's and lows in the 40's. Diegan && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 45 74 49 76 59 / 0 0 0 0 20 Knoxville McGhee Tyson Airport, TN 42 73 47 74 55 / 0 0 0 0 10 Oak Ridge, TN 43 73 47 73 54 / 0 0 0 0 20 Tri Cities Airport, TN 39 72 43 72 48 / 0 0 0 0 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$