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

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000 FXUS64 KMRX 300724 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 324 AM EDT Sun Apr 30 2017 .SHORT TERM (Today through Monday)... Another summer-like day forecast across the area. Temperatures at 3 am are still in the upper 60s to mid 70s across the area. Current water vapor and RAP upper air analysis indicates a closed low spinning across the Southern Plains with a ridge just off the Carolina coast. At the surface, a low pressure center is currently near Tulsa, Oklahoma with a warm front stretch to the east along the Ohio River Valley and a cold front extending southward into S Texas. IR satellite imagery shows a large area of showers and storms ahead of the cold front across Arkansas and stretching southwards into SE Texas. Expect a few areas of patchy fog to start off the day that will quickly mix out shortly after sunrise. Model soundings suggest that the CAP will be stronger today and a bit more elevated in the 750- 650 mb range. Therefore, not expecting any shower or storms outside of the higher elevations. Winds will begin to increase as the pressure gradient tightens from the approaching front. Winds in the mountains late in the day could approach wind advisory criteria but have decided to hold off on an advisory for now. Temperatures will once again top out well above normal for late April with highs in the 80s for most locations. Models have come into pretty good agreement with the timing of the system overnight tonight into Monday morning. Expect the line of shower/storms will be weakening as they move into a more stable and capped environment. Model soundings indicate the atmosphere will saturate late tonight but SBCAPE values are generally less than 500 J/Kg with some weak capping continuing throughout the overnight hours. The low level wind field is very impressive with an 850 mb jet of around 55-60 kts. Expect a couple of storms will be strong enough to transport these winds down to the ground despite the limiting factors. Therefore, the main threat with these storms will be damaging straight line winds. The low-level shear profile is generally uni-directional and the storms will be weakening as they move into the forecast area and think the chance for a tornado is very low. Flooding should not be an issue with the line of showers and storms moving through the area rather quickly. The main timeframe for strong to severe storms will be from around midnight to 8 am Monday morning. Clearing conditions are expected by Monday afternoon with cooler temperatures behind the front. Highs on Monday will be much more pleasant in the upper 60s to mid 70s as cold air advects in behind the departing system. .LONG TERM (Monday Night through Saturday)... A cold front and associated shower and thunderstorm activity will be pulling away from the area Monday night for generally dry conditions. However...850MB winds will remain elevated and breezy...gusty winds will continue over the region through the night. These breezy winds will bring in cooler near normal temperatures. Surface high pressure and zonal flow aloft on Tuesday will provide a quiet and dry weather day. Then...we will quickly move into an active weather pattern Wednesday through the end of the period. Model consistency isn`t great but there is some general agreement. The basic pattern appears to be a weak warm front lifting through around Wednesday... followed quickly by a cold front Thursday and the upper low slowly moving across the area around the Friday/Saturday time frame. This general scenario will keep at least chance pops in place through the end of the extended with the best chance of convection expected on around Thursday. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 86 63 73 53 / 10 100 70 10 Knoxville McGhee Tyson Airport, TN 87 66 73 50 / 10 60 80 10 Oak Ridge, TN 87 64 72 50 / 10 70 80 10 Tri Cities Airport, TN 85 66 73 48 / 10 30 60 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ MA/MJB

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