Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
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730 FXUS64 KMRX 040737 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 337 AM EDT Tue Jun 4 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (Today and tonight) Issued at 309 AM EDT Tue Jun 4 2024 Key Messages: 1. Scattered to numerous showers and storms are expected to traverse the forecast area this afternoon and through the early evening. Cannot rule out a few strong storms with locally gusty winds or heavy downpours but overall, general thunderstorm activity will be predominant. Discussion: Recent SPC Mesoanalysis page depicts weak vort maxima`s swinging through the region. Combined with lingering outflow boundaries, a few weak showers continue to briefly sprout across southern Tennessee and southwest North Carolina. This is expected to remain light with a very low chance of a lightning strike or two through the morning. Upper level clouds advecting ahead of a MCV over the lower Mississippi River Valley will help limit fog this morning, however, some patchy fog will be possible in typical sheltered valleys and along rivers and bodies of water. The aforementioned activity is expected to continue an eastward track over the next 24 or so hours, with scattered to numerous showers and thunderstorms expected to approach the Cumberland Plateau around noon to shortly after. SPC HREF depicts MUCAPE will generally increase to around or just slightly above 1000J/kg with the return of afternoon heat. Thankfully, little to no synoptic support means effective shear should remain less than 10kts and really hinder the chances of any strong to severe organized activity. A few stronger storms with gusty winds and locally heavy downpours may occur but the overall severe threat is very low. Hi-res models are in pretty decent agreement that coverage of showers and storms will trend downward by the early evening hours, though the overnight may not stay totally dry. Generally expect temperatures to remain near normal for early June but the exact timing & coverage of showers and storms could perhaps swing things slightly cooler than forecast. && .LONG TERM... (Wednesday through Monday) Issued at 309 AM EDT Tue Jun 4 2024 Key Message: 1) Highest POPs of the long term are on Wednesday, as widespread showers and scattered storms move across the area. A strong storm or two is possible, but most likely non-severe. Primary threats with any stronger storm is damaging winds. Isolated flash flooding is also possible, but low probability. 2) Drier and cooler Friday through Saturday. 3) Poor agreement in models from Sunday onward, but NBM has POPs back in the forecast through the end of the extended. Discussion: Wednesday morning, a weak shortwave is moving across middle TN and into our area. This means showers and a few storms will be around to start the day. This wave is out ahead of an unphased trough (low to our southwest and low to our northeast) moving in from the Mississippi River Valley. The morning showers and storms should produce enough cloud cover to limit instability through the day. HREF probs of 1000 J/Kg SBCAPE during the afternoon hours are pretty low and generally range from 20 to 30% chance. Because of this, I am not too excited about any stronger storms, especially with the weak mid to upper level flow across our area. However, if we do see some clearing and can generate some instability, then a few strong storms will be possible. The primary threat will be damaging winds. NAM soundings show PWATS of 1.6 to 1.8 inches, which is around the 90 percentile based on BNA sounding climatology. So some areas may see some heavy rainfall, which may lead to isolated flash flooding. This corresponds with WPC`s ERO of Marginal across our area for Wednesday. Showers and storms continue Wednesday night into Thursday morning as the aforementioned unphased trough swings through. LLJ increases to around 30kts during this time, so breezy winds are expected across our highest terrain areas (above 5000 feet) with wind gusts up to 30 mph. Drier air begins to build into the region by late Thursday morning with sunshine for most by mid afternoon. Deep mixing is expected during the afternoon hours with the drier air moving in and wind gusts up to 20 mph expected for all locations. Similar wind gusts expected on Friday afternoon for the same reason. Northwest flow will be in place behind the trough, leading to cooler and drier conditions through Saturday. Highs and lows will be around 5 degrees below normal. With dewpoints in the 50s, it will be quite pleasant. Beyond Saturday, models are in poor agreement on the large scale pattern but NBM POPs return Sunday and remain through the end of the period. && .AVIATION... (06Z TAFS) Issued at 132 AM EDT Tue Jun 4 2024 TRI still looks to have best chance for fog impacts this morning as high clouds continue to stream in from the west. Will definitely need to monitor obs around TYS as they will be on the edge of these clouds, and have a more uncertain potential for fog as a result. Showers and thunderstorm will move west to east across the area tomorrow afternoon and through the evening hours. Reduced vis and cigs possible with any heavier downpours but predominant MVFR conditions are not expected at this time. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 84 69 86 69 / 70 40 80 60 Knoxville McGhee Tyson Airport, TN 84 67 83 68 / 70 50 90 80 Oak Ridge, TN 83 66 82 66 / 70 60 90 70 Tri Cities Airport, TN 84 63 81 66 / 60 40 90 80 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...KRS AVIATION...KRS