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

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000 FXUS64 KMRX 230655 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 255 AM EDT Sat Sep 23 2017 .SHORT TERM (Today through tonight)...
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The upper level flow should be different today, changing from a NE flow down the spine of the Appalachians, veering today to more of an easterly flow off the mountains. This flow along with some weak lift will favor better chances of storms across the central and southern valley this afternoon. Will keep the northern half of the valley dry for now, as the storm threat tapers off farther north where the lower levels are drier. Southern valley will likely have CAPE values over 1000 J/kg, and with dry air aloft, there could be some locally gusty outflow winds, but not expecting any severe storms. Valley fog and lake fog are a little slower to get going this morning--temps are generally 1-2 degrees warmer, thereby taking longer to cool down and saturate. Think fog will go ahead and continue to form this morning and again late tonight, so will include some localized fog again tonight. .LONG TERM (Sunday through Friday)...Pretty much a persistence forecast through the majority of the long term with high pressure dominating the region but there is a change a coming...coming round the bend. High pressure over the Great Lakes leaves us warm and dry Sunday through Wednesday. No precip chances in the forecast during this time. Highs will be in the mid to upper 80s with lows in the low to mid 60s, which is above normal for this time of year. The only thing of interest during this period is latest model runs bring Hurricane Maria closer to the Outer Banks. If this plays out, we could see some of Maria`s outer cirrus bands Tuesday afternoon/evening but that`s about it. On Wednesday high pressure begins to break down as an upper level trough swings down through the Great Lakes but we remain warm and dry. Thursday afternoon slight chance for showers and storms in for all areas as associated frontal boundary approaches our area. The frontal passage doesn`t look to occur until Thursday night. Moisture is weak with this boundary so very little QPF anticipated at this time. Stronger shortwave drops down into the backside of the trough on Friday and digs the trough further south into our area. This wave will bring much cooler and drier air into the region, making it feel like fall again with highs in the low to mid 70s and lows in the upper 40s to mid 50s. As of now, looks like this second wave only brings cold and dry air, still not much moisture to work with. Only a slight chance POP in for NETN and SWVA.
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Chattanooga Airport, TN 87 65 87 66 / 30 20 0 0 Knoxville McGhee Tyson Airport, TN 87 63 87 63 / 20 10 0 0 Oak Ridge, TN 88 64 86 64 / 10 10 0 0 Tri Cities Airport, TN 86 56 85 59 / 10 0 0 0
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