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

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000 FXUS64 KMRX 230736 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 336 AM EDT Mon Apr 23 2018 .SHORT TERM...
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(Today and Tonight)... The main story for the short term period continues to be the rain chances, and also the expected high winds over the mountainous areas. Mid and upper level GOES16 water vapor imagery show a fairly well defined dry slot working east through northern MS/AL and central TN this morning. The eastern edge of this dry slot is situated along the GA/AL border north into central TN, which lines up very well with the precip shield to the east of that line and very limited and light precipitation back to the west. As such, expect the PoP forecast to be somewhat complicated today as the forecast area is likely to see a few distinct waves of rainfall associated with vort lobes that rotate around the parent upper low and through eastern Tennessee. The first will move through much of the area before dawn, or by the time most folks read this discussion, with another wave developing by early afternoon and rotating through the forecast area this afternoon/evening. The complicated part is really in regards to nailing down any of the waves of rainfall to a 3-6hr block of time for the forecast. Regardless, expect most people across eastern Tennessee, southwest Virginia, and far southwest North Carolina to see rainfall at various times today. With regards to amounts, the plateau and Tennessee mountains should get somewhere around an inch when all is said and done (which would cover a time frame extending into the long term period) with notably lighter amounts in the valley where downslope effects will negatively impact rainfall amounts. Speaking of downsloping winds, have left the wind advisory and high wind warnings as is. Winds have been a little sluggish to respond thus far, which concerns me a little bit. But the tightest pressure gradients are yet to come, and the pattern is that of a high wind event. Guidance is still insistent on these high winds developing, and some mountain locations are gusting into the +30mph range. Will leave those headlines as is for the time being and continue to monitor the situation. .LONG TERM...(Tuesday through Sunday)... The pesky upper low will be centered near Nashville at the start of this period. It will be slow to move across East Tennessee and weaken through Tuesday night. Expect showers and a few isolated thunderstorms to occur Tuesday. Rain chances should diminish later Tuesday night as the trough translates into North Carolina and Virginia. A shortwave ridge follows in its wake on Wednesday which would normally bring drier weather, however, models are producing low end PoPs and minimal QPF coinciding with the northwest flow. Confidence is rather low for any measurable rainfall during the Wednesday time period. The next shortwave trough appears to dig farther south Thursday and Thursday night. The southern Tennessee Valley and extreme eastern portions of the forecast will have the better chances of measurable rainfall - at least with the 00Z runs of ECMWF/GFS. Obviously this will become better defined in the upcoming days and newer runs. The ECMWF and GFS begin to diverge in their solutions toward the end of the week. They do agree on the deep trough over the eastern U.S. which will bring cooler than normal temperatures to the region for the weekend.
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Chattanooga Airport, TN 68 55 70 54 / 70 70 60 20 Knoxville McGhee Tyson Airport, TN 67 54 67 53 / 80 80 70 30 Oak Ridge, TN 65 54 68 52 / 80 80 70 30 Tri Cities Airport, TN 62 51 67 50 / 80 70 70 60
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...Wind Advisory until 7 AM EDT this morning for Cherokee-Clay. TN...Wind Advisory until 2 AM EDT Tuesday for Jefferson-NW Blount- North Sevier-Northwest Carter-Northwest Cocke-Northwest Greene-Northwest Monroe-Sullivan-Washington TN. High Wind Warning until 2 AM EDT Tuesday for Blount Smoky Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky Mountains-Southeast Carter-Southeast Greene-Southeast Monroe-Unicoi. Wind Advisory until 7 AM EDT /6 AM CDT/ this morning for Bledsoe- Bradley-East Polk-Hamilton-Marion-McMinn-Meigs-Rhea- Sequatchie-West Polk. VA...Wind Advisory until 2 AM EDT Tuesday for Russell-Washington. && $$ CD/AC is the U.S. government's official web portal to all federal, state and local government web resources and services.