Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
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219 FXUS64 KMRX 160725 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 325 AM EDT Thu May 16 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (Today and tonight) Issued at 300 AM EDT Thu May 16 2024 Key Messages: 1. Warming trend today with mostly dry conditions across the forecast area, save some isolated showers in our Virginia counties and the Tri Cities area of Tennessee. 2. Dry overnight, but showers will be quickly approaching the southern areas towards the end of the period. Discussion: The gist of the short term...An upper trough/low will continue to pull away to the northeast today, moving off the mid-Atlantic and New England coast by shortly after daybreak. Upper ridging will build in across the region today in the wake of this feature, leading to mostly dry conditions across the CWA along with warming temperatures. The only caveat would be the potential for a handful of showers over the far northeast parts of the CWA this afternoon. Otherwise, dry conditions last late into the night before rain chances increase as we head into the long term period with the next system approaching. Going into a bit more detail...Satellite imagery shows plenty of low clouds across the CWA, especially in the northern parts covering VA and far northeast TN. As mentioned above, I expect mostly dry conditions across most all of the forecast area today. However, model soundings do show some weak instability below 700 mb today. If warming is as forecast, then LFC and LCL heights will be equal and there`s enough low level moisture and surface-based instability to support some shallow showers and perhaps even a rumble of thunder in the northeast. Model guidance supports this thinking. Did limit PoPs to slight chance values however, and went with a blend to get the areal coverage where I wanted it, which was basically along/east of a line from Wise to Unicoi counties. The cloud layer in place seems to be somewhat thin vertically, and there are plenty of breaks per satellite imagery early this morning, so it seems reasonable to expect the mixing/warming forecast by guidance and subsequent shower possibilities. Otherwise, upper heights build in by mid to late afternoon and shut off whatever shower activity there is rather quickly late this afternoon. Tonight could see some dense fog potential depending on how quickly high clouds increase ahead of the system moving in tomorrow. Have some patchy fog in the forecast, but if the high clouds remain thin enough, light winds and a moisture rich surface layer will promote fairly widespread fog development. Time will tell in that regard. Kept the forecast dry overnight, but showers will be quickly approaching by daybreak or shortly thereafter into the long term period. && .LONG TERM... (Friday through Wednesday) Issued at 300 AM EDT Thu May 16 2024 .LONG TERM... (Friday through Wednesday) Key Messages: 1. Wet pattern setting up for Friday through Saturday. 2. Drier and warmer Monday and Tuesday. 3. Cold front and storms move into the area around next Wednesday. A disorganized but wet pattern will be setting up for Friday and Saturday. On Friday an upper level low pressure center will be located to our west in the Southern Plains. It looks like a weak upper shortwave, connected to this low, will move through the area from southwest to northeast spreading rains into the area. There may be a lull behind this shortwave in the southern parts of the area Friday for at least part of the afternoon. Then in the late afternoon, but especially in the evening a 50 knot low level jet is expected to surge into the area bringing elevated instability into the area overnight. As the overall pattern shifts east, this jet will slide east of the area, probably before Noon on Saturday. So it looks like the best chances for stronger storms will be Friday night. The SPC Marginal Risk fits this pretty well, with low-end severe wind and hail threats. It looks like the heaviest rain rates will likely be during the Friday night early Saturday morning timeframe as well. For Saturday, the main axis of deep moisture moves into the area from the west, but instability and especially shear look very unimpressive. So for Saturday, there may be widespread rains, but the rain rates will not be as intense as Friday night`s. For Saturday night through Sunday, we will be slowly getting rid of the upper low and associated spokes of lift that are swirling around it. Left some thunder in for Saturday evening, then just rain showers afterwards. Western and southern parts of the forecast area will be farther away from all this disturbed weather on Sunday and may start the more favorable trend that the whole forecast area will see by Monday. Monday and Tuesday look dry as an upper ridge builds into the area. Afternoon Max Temperatures should warm up as well. By Tuesday night and certainly by Wednesday the next weather system will be approaching from the west. This system looks a lot more organized, with a stronger cold front moving into the area around Wednesday. && .AVIATION... (06Z TAFS) Issued at 136 AM EDT Thu May 16 2024 Satellite imagery shows a fairly expansive area of low clouds forming across the region over the last hour or two, with a mix of low-end VFR and MVFR CIGS mixed in. Low cloud cover is highest around and north of KTYS, with significant breaks in cloud cover south towards KCHA. Suspect that low CIGS will be the predominant flight category concern through mid morning, with broken decks ranging from 700-1500 FT AGL being the most likely to occur. That said, the low levels are saturated, so some fog could be a concern too. Have higher confidence in that at KTRI than anywhere else. Expect all sites to lift back to VFR levels by 16z this morning, remaining there through the end of the 06z period. Fog may make a reappearance at KTRI before the end, but high clouds will be increasing ahead of the next system so will hold off on including that for now. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 85 64 75 66 / 0 10 80 80 Knoxville McGhee Tyson Airport, TN 80 61 75 64 / 0 10 80 90 Oak Ridge, TN 81 61 75 63 / 0 10 80 90 Tri Cities Airport, TN 76 56 77 61 / 20 10 70 80 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...CD LONG TERM...GM AVIATION...CD