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

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000 FXUS64 KMRX 290655 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 255 AM EDT Sat Apr 29 2017 .SHORT TERM(Today and Tonight)...
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Current IR satellite imagery indicates an elongated E-W area of showers and storms stretching along a stalled frontal boundary from Oklahoma to Maryland. Fortunately this activity is forecast to remain to the north of the area. IR imagery does indicate the cirrus shield is expanding southward from the showers/storms and expect some high clouds to start the day. Current water vapor imagery also notes strong moisture convergence near the Ozarks stretching to the Ohio River Valley. Closer to home, an upper level ridge sits just to the east of the Florida peninsula. This upper level feature will be the main focus throughout the short-term forecast for the Southern Appalachians. This morning should not start out as foggy as yesterday. High clouds and slightly higher winds will hinder fog formation. The main challenge once again will be PoPs. The cap will remain in place around 700-800 mb but is forecast to be a bit weaker today. There is not much to speak of in the way of lift with the ridge being the main weather influence. In addition, the surface front will remain to the north of the forecast area as well. The weaker cap should allow for a few isolated to scattered summer-like afternoon shower/storms with the better chances in the higher elevations. The main story will be the record breaking high temperatures forecast today. The higher heights aloft and insolation will push temperatures up into the upper 80a and low 90s for most valley locations. The record for Knoxville is 88 degrees set back in 1872 during the Grant Administration. The records for CHA and TRI are a bit more recent. See the data below for more information. Knoxville 88 set in 1872 Forecast High 90 Chattanooga 88 set in 1942 Forecast High 90 Tri-Cities 86 set in 1996 Forecast High 90 .LONG TERM (Sunday through Friday)... An upper ridge of high pressure will shift eastward on Sunday...allowing for slightly cooler but still well above normal temperatures. Limited diurnal convection is possible late in the afternoon but this activity should remain confined to higher elevations. Will see a pattern change Sunday night into Monday as a cold front approaches from the west. A line of showers and thunderstorms is expected to develop and move through the region ahead of the front. A strong 60 to 70 KT jet will accompany the front and will provide widespread breezy and gusty conditions...and also may allow for a stray thunderstorms to generate significant winds. By Tuesday...the frontal boundary will be well to our east for a dry day with near normal temperatures. Model consistency becomes poor and confidence is low Wednesday through the end of the extended. Overall...the pattern looks unsettled with an area of low pressure moving through and the approach of an upper trough. The best chance for precip through this period currently looks like Thursday and will keep likely pops in place with decreasing chances into Friday.
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Chattanooga Airport, TN 90 68 87 65 / 20 20 10 70 Knoxville McGhee Tyson Airport, TN 90 68 85 64 / 20 10 10 50 Oak Ridge, TN 91 68 85 63 / 20 10 10 60 Tri Cities Airport, TN 90 64 81 61 / 20 10 10 30
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