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

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948 FXUS64 KMRX 190749 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 249 AM EST Sun Feb 19 2017 .SHORT TERM (Today and Tonight)...
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A mild start to the day currently with temperatures in the mid 40s to low 50s. Seeing some patchy fog on the observations but not expecting anything to get down low enough for a dense fog advisory this morning. Current water vapor imagery and RAP upper air analysis indicates a closed low spinning overhead. At the surface, there is a trough to the east of the Appalachian Mountains. For today, the closed low will transition to an open wave and will be located just off the South Carolina coast by the end of the day. Expect fog and light drizzle will continue this morning with a small chance of a shower across the higher elevations. The main challenge will be how long do the clouds hold in across the area. Low level isentropic lift looks to come to an end by early this afternoon with clearing skies from southwest to northeast. A ridge will quickly move in behind the departing low with 500 mb heights of 580-583 dm building in by the end of the day. These higher heights aloft will produce much warmer than normal temperatures across the area with highs today generally in the mid to upper 60s. If clouds clear out sooner could see temperatures warm into the low 70s in a few locations. Drier air will settle into the area tonight with PW values in the 0.3-0.5 inch range. Warmer than average lows will continue tonight with temperatures generally in the upper 30s to mid 40s. .LONG TERM (Monday through Saturday)... A strong ridge of high pressure will remain positioned over the eastern U.S. on Monday for a seasonally warm and dry day. On Tuesday...will see a cold front approach the region. Models have struggled with the timing and strength of this system. The current trend is towards a slower approach...so have pushed low pops to late in the day Tuesday with the main band of showers and highest pops expected late Tuesday night and Wednesday. There continues to be questions as to strength and amount of moisture associated with the boundary. This is due mainly to the effect of another low moving through along the gulf. As such...have kept pops in chance category for now. For the rest of the extended...there continues to be poor agreement with models. Overall...it looks to be a rather unsettle period. A weak short wave is expected to move through the region around Thursday but strength and track remain a question and have kept pops around 20 to 30. Then...another frontal boundary is expected to move in around the Friday/Saturday time frame. With warm...moisture air moving in ahead of the system...could see weak instability develop over southern areas for a chance of thunder. As for timing...have trended highest pops for Friday/Friday night. Temperatures will be well above normal for much of the period.
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&& .PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN 69 45 72 52 / 10 0 0 0 Knoxville McGhee Tyson Airport, TN 66 42 71 50 / 10 0 0 0 Oak Ridge, TN 68 42 71 50 / 10 0 0 0 Tri Cities Airport, TN 63 39 69 46 / 20 0 0 0
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&& .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ MA/MJB

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