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Area Forecast Discussion
Issued by NWS Jackson, KY
Issued by NWS Jackson, KY
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035 FXUS63 KJKL 161956 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 356 PM EDT Fri Aug 16 2024 .KEY MESSAGES... - Humidity, along with the possibility of showers and thunderstorms, will increase today and last into Saturday night. - Below normal temperatures are expected Sunday through Wednesday behind a cold front passage late Saturday night. - Showers and thunderstorms will remain possible Sunday and Monday, especially in the afternoon and early evening, with a drying trend for Tuesday into Wednesday. && .UPDATE... Issued at 1233 PM EDT FRI AUG 16 2024 Made some updates to the forecast for the rest of today. Based on current radar trends and model data, precipitation probabilities for the rest of today were overdone by quite a bit. Therefore, decreased precip chances across the area through 23Z today per current trends. Also lower todays hourly and max temperatures for a large part of the area per the latest trends in surface obs. An updated zone forecast product has been sent and any updated grids were saved, published, and sent to the remote web servers. UPDATE Issued at 710 AM EDT FRI AUG 16 2024 Convection has begun to increase in coverage just a bit across the area, especially over our west central zones, and to some extent our eastern zones. Radar is showing newly developed convection taking aim at our Bluegrass counties as well, which will be moving into those areas over the next hour or so. In addition, we are seeing the second round of convection developing upstream over central Kentucky. This upstream convection will be expanding and moving into our forecast area a bit later this morning. Overall the forecast appears on track at this time and only minor adjustments were required to bring grids in line with current hourly observations and trends in radar. && .SHORT TERM...(Today through Saturday) Issued at 450 AM EDT FRI AUG 16 2024 A slow moving mid/upper level low will move from the Upper Midwest into the heart of the Great Lakes through the short term. Pockets of short wave energy will round the bottom of the low as it drifts eastward. Eastern Kentucky will reside in the left exit region of a 40-50 kt mid-level jet today, with a 30-40 kt H850 LLJ jet nosing into the area by this afternoon. This will help with lift across the forecast area today. However, extensive cloud cover will tend to keep instability generally below 1000 J/kg through the bulk of the day. Shear will be marginal as well at 25-35 kts. All said the severe threat looks marginal and as expected SPC keeps eastern kentucky within a marginal risk for severe weather. Consequently, the area could experience a few strong storms and an isolated severe storm or two could not be ruled out should any convection find itself residing within a locally, more favorable storm environment. PWATs are reasonably high, climbing to near 2 inches over much of the area and freezing levels are relatively high at around 14 kft. But storm motions are 20-25 kts or greater on average. Thus overall any hydro threats look marginal and localized...and would more likely have to be associated with training or repeated rounds of thunderstorms should that occur. But even this type of scenario does not appear particularly favorable at this time. With the expected timing of convection and cloud debris post convection, muted afternoon high temperatures across our east and southeast as compared to model guidance. However, there could be some late afternoon partial clearing and the chance for a substantial recovery of temperatures does exist for the late afternoon time frame. For the remainder of the short term, additional short wave energy rotating around the upper low will pass through the Ohio Valley tonight and then into the region again by late Saturday. Thus after a lull in activity across eastern Kentucky through the late this afternoon and early evening, convection may show a breif period of enhancement late in the evening or overnight. It is more likely that showers and thunderstorms redevelop late Saturday with the help of late day heating as a more organized short wave lobe tracks through the region. The surface front will be closer to the area as well which will provide a better focus for convection to fire. Instability and shear will be more favorable for storms by late Saturday. However, lapse rates aloft are weak and wind fields aloft are not as favorable for the lifting needed for severe storms. Consequently, the severe threat will remain marginal for late Saturday as well. .LONG TERM...(Sunday through Friday) Issued at 356 PM EDT FRI AUG 16 2024 There remains a good amount of agreement on the overall pattern in the various ensembles and deterministic model guidance for the long term period. An upper level low will continue to work across the Great Lakes and eventually into the Northeast to begin the period. The associated trough axis will swing through the Ohio Valley and will keep the weather active through Monday. The main cold front will push through Sunday and this coupled with the trough axis will keep around a 60 to 90 percent chance of rain across eastern Kentucky. By Monday, the chance of rain decrease with most in the 50 to 80 percent range and the better forcing begins to move eastward and PWAT values decrease in the 1.2 to 1.4 range. Tuesday, there is good agreement on an area of surface high pressure pushing into the Great Lakes. This will help to usher in a much drier airmass under northerly flow at the surface. This northerly flow will also help to provide a fall like feel to the area, with afternoon highs in the mid to upper 70s. This surface high will eventually pull east through the remainder of the long term forecast. However, before it does it will provide several cool crisp mornings, with lows in the 50s and even upper 40s in some cases. The coldest mornings will be Wednesday and Thursday and those days you could see valleys make it into the upper 40s. Given this needed to adjust toward the NBM 10th percentile in the valleys to provide better temperature splits. As mentioned, the surface high will push east and this will eventually lead to some return flow and highs will creep back up toward normal with low to mid 80s being the story to end the period. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) ISSUED AT 127 PM EDT FRI AUG 16 2024 The TAFs will be challenging today and tonight, as showers and storms continue moving through the area ahead of an approaching surface cold front and disturbance aloft. Conditions at any give TAF airport will vary from MVFR to LIFR due to heavy rain and fog as showers and especially storms move through. In the meantime, VFR should be the norm. Winds will be generally light and variable except in thunderstorms, where winds should increase a bit and become gusty. The rain should gradually taper off overnight, due to loss of daytime heating. We will then see another uptick in shower and storm activity during the day on Sunday, as moist air continues streaming into the area ahead of the oncoming cold front. The front should be moving through area by the end of the day on Saturday. As before, conditions at any TAF airport could deteriorate quickly from VFR to MVFR, IFR, or worse, in any thunderstorm. Sky cover should be mostly BKN, but there could be a few instances from time to time, especially north of I-64, where we could see SCT cloud cover at times. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AR SHORT TERM...RAY LONG TERM...DJ AVIATION...AR