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

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000 FXUS64 KMRX 240741 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 341 AM EDT Tue Apr 24 2018 .SHORT TERM...(Today and Tonight)...An area of low pressure will be rotating through the region today and will begin to exit east tonight. Through the first half of the day the best chances of rain will be across the central valley/northern valley as well as the central/northern plateau as this is where the strongest lift will be. The lift is in response to the leading edge of a strong vort max associated with the upper low, along with a strong 850 jet directly underneath. Northeast TN and southwest VA will stay drier as downsloping continues into the early afternoon hours. As the center of the low slowly pushes eastward these downsloping winds will diminish by mid/late afternoon and precip chances will increases across these areas. Also, soundings show some instability developing this afteroon as we have steep lapse rates in place due to the low overhead. So have slight chance for a few thunderstorms in for the afternoon. Small hail is possible with any of these storms due to the steep lapse rates in place. Temperatures will be 5 to 10 degrees below normal with highs in the low to mid 60s. Tonight, valley locations will see precip chances drop as the low pushes east and the deeper moisture exits. However, as the low moves east, winds will shift and be out of the northwest. This will cause the orographic lift to kick in. Though moisture is shallow the upslope flow will keep precip chances likely/categorical across the favored upslope areas through the night but the precip will be light. Lows tonight will be mild with temps in the lower 50s. .LONG TERM...(Wednesday through Monday)...At the beginning of this period the first upper low has exited the area into the Carolinas, while our next upper low heading toward us is in the Central Plains heading southeast. The surface low will be in the Carolinas as well with the northerly wind component continuing. So, this next short wave and upper low will pass through the area around Thursday, then a final weak clipper shortwave will race through on Saturday (looking mostly dry). During this whole time we will generally have a northerly component to the surface wind and the warm-up will be very slow. Finally, after this final shortwave passes, an upper ridge starts to build in by Sunday, and the winds finally get a south component, and by Monday we should definitely get some bona fide warming. For precip, Wednesday looks wet north tapering off to low POPs in the southern valley, then all precip moves out Wed night, only to return Thursday with the upper low/trough moving through. Precip for most of the area should be moving out on Friday and continue dry through the weekend, although keeping some minimal POPs in the mountains Friday night and Saturday. The airmass looks too stable for thunder in any of these periods. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 67 53 67 52 / 50 40 10 10 Knoxville McGhee Tyson Airport, TN 65 54 66 50 / 90 50 40 20 Oak Ridge, TN 66 53 67 49 / 90 50 40 10 Tri Cities Airport, TN 66 51 63 46 / 60 60 60 30 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ SR/GM

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