143 FXUS64 KMRX 131107 AFDMRX AREA FORECAST DISCUSSION National Weather Service Morristown TN 707 AM EDT Mon Sep 13 2021 .UPDATE... FOR 12Z AVIATION. && .SHORT TERM...(Today through Tonight)... Key Messages: 1. Dry and mostly sunny, above normal highs. Discussion: A 595dm anticyclone remains centered over the TN valley this morning, extending southward across much of the Deep South, all while a zonally oriented cold front remains well northward across the Great Lakes and TC Nicholas slowly migrates northward through the western GOM. Closer to home, clear skies are allowing for abundant radiational cooling this morning, which combined with slightly higher dewpoints from morning's past has allowed for patchy fog (some dense) development. Moving into/through Monday, the upper ridge will prevail yet again favoring fair wx cu beneath some high cirrus intruding from the south in association with Nicholas. Some higher resolution guidance indicates the potential for weak/iso showers across the southern plateau/mountains this afternoon, however confidence is low at this point thus no pops are noted. Otherwise, dry with light sly/vrb winds with high temperatures topping out in the mid/upr 80s across the lower terrain, upr 70s to lwr 80s in the high terrain. Am expecting continued advection of thin cirrus tonight therefore less efficient radiational cooling is expected. This could impact fog coverage on a wider scale, yet still will note patchy levels in the fcst. CDG .LONG TERM...(Tuesday through Sunday Night)... Key Messages: 1. Very warm and increasingly humid through midweek with the warm, humid conditions lasting through next weekend. 2. Chances for diurnal convection gradually start Tues peaking in coverage Wed through Fri. Discussion: The main story within the extended will be the track and impacts from what is now Tropical Storm Nicholas. By 12Z Tuesday, guidance suggests the remnants of this tropical system will be slowly lifting through eastern Texas with an upper level disturbance extending across the northern plains and back through the Rockies. Broad surface high pressure centered near Bermuda will keep a veered low level flow in place and resultant warm air advection regime into the Tennessee Valley on Tuesday. Increased CAPE values resulting from an increase in low level moisture and surface heating will result in chances of scattered thunderstorms on Tuesday and Tuesday evening. As we head into Wednesday, the forecast becomes very uncertain with the eventual track of Nicholas as the main jet remains well to our north keeping quasi-zonal flow in place across much of the region. With weak steering flow aloft, Nicholas will likely have a slow forward motion with a very uncertain track. With that said, the influx of higher PW and diurnal heating will come together to keep slight chance to chance PoPs in the forecast for Wednesday and Thursday. Temperatures during this period will continue to remain near to above normal with highs in the mid to upper 80's. Mid-upper level disturbance is still progged to brush by to the north Wednesday and Thursday with a weak frontal boundary near or just north of the area. Again confidence is low with this feature as well given the uncertainty of any interaction with the remnants of Nicholas. Subtropical ridging to the southwest will continue to favor a summer like pattern through the end of the period with warm temperatures and daily chances of showers and thunderstorms mainly in the afternoon hours. Diegan && .AVIATION... 12Z TAF DISCUSSION. Mostly VFR through this taf cycle outside of early period patchy MVFR/IFR fog this morning. Otherwise, all fog should erode after sunrise with low VFR cu beneath high cirrus amidst prevailing high pressure for the remainder of the day amidst light sly/vrb winds. CDG && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 89 67 88 68 84 / 10 10 20 10 50 Knoxville McGhee Tyson Airport, TN 88 66 88 68 84 / 0 0 20 10 40 Oak Ridge, TN 88 65 87 66 83 / 0 0 20 10 50 Tri Cities Airport, TN 87 63 87 63 85 / 0 0 10 10 40 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...Dense Fog Advisory until 10 AM EDT this morning for Cherokee- Clay. TN...Dense Fog Advisory until 10 AM EDT /9 AM CDT/ this morning for Anderson-Bledsoe-Blount Smoky Mountains-Bradley-Campbell- Claiborne-Cocke Smoky Mountains-East Polk-Grainger-Hamblen- Hamilton-Hancock-Hawkins-Jefferson-Johnson-Knox-Loudon- Marion-McMinn-Meigs-Morgan-North Sevier-Northwest Blount- Northwest Carter-Northwest Cocke-Northwest Greene-Northwest Monroe-Rhea-Roane-Scott-Sequatchie-Sevier Smoky Mountains- Southeast Carter-Southeast Greene-Southeast Monroe-Sullivan- Unicoi-Union-Washington-West Polk. VA...Dense Fog Advisory until 10 AM EDT this morning for Lee-Russell- Scott-Washington-Wise. && $$