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

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000 FXUS64 KMRX 280722 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 322 AM EDT SUN AUG 28 2016 .SHORT TERM (Today and Tonight)...
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Not much change with the 595 dm ridge holding strong centered just to the NW across the Mid-Atlantic. Current radar imagery is not showing any precipitation in the area with showers/storms coming to an end earlier this evening after the loss of daytime heating. The boundary layer remains moist with light winds and mostly clear skies, therefore, there could be a few areas of patchy fog near sunrise but not expecting any dense fog. For today, the mid-level ridge will show some signs of slight weakening as an easterly wave moves closer to the GA/SC coast. In the upper levels, models actually show some cyclonic flow across the area entering into a weak 30-35 kt jet streak. Models also depict low level cyclonic flow and convergence. PW values will range from 1.6-1.9 inches this afternoon with the higher values being near the 90th percentile for late August. Models differ a good bit on the amount of instability later this afternoon. The NAM is the most aggressive with steep low-level lapse rates and SBCAPE values of 2000-3000 J/Kg. The GFS is not nearly as impressive with values in the 750-1500 J/Kg range. All models soundings indicate a mixed layer up to about 750-800 mb with DCAPE values around 800-1200 J/Kg. These sounding profiles would support some stronger downdrafts in some storms later this afternoon with marginally severe wind gusts possible. The upper level flow is weak and do not expect any organized convection later this afternoon but a strong to marginally severe storm cannot be ruled out. The main threat would be marginally severe damaging winds. With the low-level convergence and high PW values, expect coverage will be a bit more widespread than yesterday afternoon and increased PoPs. Convection should come to an end shortly after sunset due to the loss of daytime heating. Models indicate that a moisture gradient will move in from the NE tonight along an old frontal boundary. Dewpoints in SW VA and NE TN will drop down into the upper 50s and lower 60s. This will also lead to low temperatures falling off into the low to mid 60s. .LONG TERM (Monday through Saturday)... The high pressure ridge that has dominated area weather recently may shift a bit over the region and strengthen and dampen a bit across the area but overall will continue to be the main influence of our weather through the extended. This will provide continued above normal temperatures and the strong daytime heating will continue to provide isolated to scattered convection each afternoon...at least over higher elevations. A couple of weak impulses tracking through the upper flow will occasionally add to the convection development and provide a better chance of thunderstorms. Model consistency has been poor on details...but current runs bring the strongest of these disturbances in around the Friday/Saturday time frame.
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&& .PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN 92 72 93 70 / 50 40 20 10 Knoxville McGhee Tyson Airport, TN 92 70 91 69 / 30 30 20 10 Oak Ridge, TN 93 71 91 69 / 40 30 20 10 Tri Cities Airport, TN 91 64 90 66 / 20 20 20 10
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ MA/MJB

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