Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
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408 FXUS64 KMRX 151329 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 929 AM EDT Mon Jul 15 2024 ...New UPDATE... .UPDATE... Issued at 927 AM EDT Mon Jul 15 2024 Forecast is on track this morning with temperatures slightly cooler than previous days due to the mid-level cloud deck. However, moisture is on the increase, especially across southern areas of the forecast area, which will lead to higher heat index values this afternoon. Isolated diurnal convection continue to be expected across the plateau and southern counties of the forecast area this afternoon. && .SHORT TERM... (Today and tonight) Issued at 342 AM EDT Mon Jul 15 2024 Key Messages: 1. Hot again today. Heat Indices will range from the mid/upper 90s north of I-40 and near 100 south of I-40. 2. Better coverage of showers and storms today, but still isolated to scattered. Discussion: A weak, mid-level, shortwave still resides just to our southwest. Conditions look more favorable today to see isolated to scattered showers and storms this afternoon. This is mainly due to better moisture today due to the southerly flow at 850mb. Weak mid-level vorticity and upper divergence continue to remain in place. Greatest coverage will be during peak heating and generally south of I-40. However, even with the increased coverage, many places will still remain dry today. Not expecting any severe weather today. Due to the increase in moisture today, I expect greater cloud cover. This will mainly be in the form of a mid/high cloud deck. The uncertainty though is how much coverage as models are in very poor agreement. Best guess as of now is a SCT mid/high deck for much of the area with some areas seeing BKN. If this plays out, this will dampen our temperatures by a few degrees compared to yesterday. By how much depends on the extent of cloud cover. Generally have the central and southern TN valley a few degrees cooler. While northeast TN and southwest VA will see similar temps due to lesser cloud cover that far north. Heat Indices will still range from the mid/upper 90s to near 100 for this afternoon which is similar to yesterday, due to the increasing dew points. Convection peters out this evening with loss of heating. Above normal temps expected overnight with lows in the lower 70s for most places. && .LONG TERM... (Tuesday through Sunday) Issued at 342 AM EDT Mon Jul 15 2024 Key Messages: 1. Unseasonably hot conditions are expected Tuesday and Wednesday. Heat indices will range from the upper 90s to lower 100s each afternoon. 2. Scattered storms are expected on Tuesday with more numerous coverage Wednesday and Thursday. Lower chances continue into this weekend with relief from the heat expected Thursday onward. Discussion: Overall, there remains pretty minimal change in the messaging and key points from previous forecast issuance. Increasing moisture advection and weak disturbances aloft will lead to scattered chances for showers and storms Tuesday, although, latest hi-resolution guidance generally highlights areas along and south of I-40 with the greatest chances for precipitation. While temperatures relative to the previous days are expected to ever so slightly cool, increasing humidity will still allow for heat indices to approach the lower 100s across portions of the central and southern valley. There is potential that a heat advisory may be needed in future forecast packages but there is a conditional aspect to reaching criteria revolving around how exactly storm coverage and their timing pans out. Humid and muggy conditions will persist into Wednesday as a surface boundary encroaches on the region, bringing increased chances of scattered to widespread showers and storms. While temperatures will be cooler, continuance of favorable moisture advection will promote heat indices in the lower 100s across portions of the central and southern valley once more. Advisory criteria currently looks unlikely this day. H5 heights fall to ~586-584dam as greater influence from troughing and persistent clouds bring relief from the heat Thursday into the weekend. The chance for precipitation will linger each day, however, there is some uncertainty in the best timing/coverage based on potential shortwaves and how exactly a surface boundary lingers across the region. For the Tuesday through Thursday timeframe, there looks to be pretty minimal threat for any strong to severe concerns but as is typical of any summertime activity, locally gusty winds are possible with the tallest storms. We are highlighted by WPC for a marginal risk in excessive rainfall for Wednesday and Thursday due to PWAT values around 1.9-2.1 inches and tall/skinny CAPE profiles. However, the lack of recent rainfall should really limit any flood threat. && .AVIATION... (12Z TAFS) Issued at 709 AM EDT Mon Jul 15 2024 VFR conditions through the period at TYS and TRI with light southwest winds. Mostly VFR at CHA but a PROB30 MVFR during the afternoon for thunderstorms. Isolated showers and storms may be near TYS and TRI this afternoon but not enough confidence to include VCTS. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 95 74 95 75 / 40 30 50 30 Knoxville McGhee Tyson Airport, TN 95 74 95 75 / 30 10 40 30 Oak Ridge, TN 95 72 95 74 / 30 10 40 30 Tri Cities Airport, TN 94 70 93 72 / 20 10 40 30 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM... LONG TERM....KRS AVIATION...