Area Forecast Discussion
Issued by NWS Jackson, KY
Issued by NWS Jackson, KY
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187 FXUS63 KJKL 171043 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 643 AM EDT Fri May 17 2024 .KEY MESSAGES... - Shower and thunderstorms are expected today through Saturday evening before tapering off Sunday. - High pressure brings dry weather back to the area Sunday night through Tuesday. A couple areas of low pressure will bring rain back to the area Tuesday night through Thursday. - Near normal to slightly above normal temperatures are expected to continue into the weekend. A further warm up is then expected into the first part of next week. && .UPDATE... Issued at 643 AM EDT FRI MAY 17 2024 Just sent out a quick update to expand 15 (i.e., slight chance) PoPs quicker across the area this morning as light rain begins to move into areas west of Interstate 75. The forecast looks good otherwise. && .SHORT TERM...(Today through Saturday) Issued at 320 AM EDT FRI MAY 17 2024 A large-scale positively-tilted pair of northern stream and southern stream upper troughs will bring unsettled weather to the region for the short-term (through early Saturday evening), with much of the jet energy ahead of the southern stream system moving across the Gulf Coast states and Tennessee Valley. With the region on the cold side of the jet stream, instability will be modest by mid-May standards. Nevertheless, showers and a few thunderstorms will move into the region by early Friday afternoon and persist into Friday overnight and early Saturday morning, before high pressure ridging aloft builds over the Midwest Saturday, causing the upper trough to pinch off over the Southeast US. Thus, another round of showers and thunderstorms is expected to develop Saturday afternoon within a weakly unstable and modestly moist environment. With modest shear and instability, no severe weather is expected, with showers more likely to be the prevailing precipitation rather than thunderstorms today and tonight. Instability increases a bit Saturday but within an environment with practically no wind shear. The main concern especially today and tonight is the potential for locally heavy rain causing minor flooding concerns, but even this concern is very low. With thickening cloud cover and precipitation concerns, temperatures will be limited to near normal with 70s for highs, cooler in the west where precipitation will arrive earlier in the day and a bit warmer in the east where precipitation may not arrive in some locations until late afternoon or early evening. Lows tonight will return to the upper 50s and lower 60s with precipitation chances continuing, with mid-50s in the deeper sheltered valleys, especially where any partial clearing can occur. A more uniform distribution of mid-70s can be expected Saturday given expected redevelopment of showers and thunderstorms by early afternoon and continuing into the evening. .LONG TERM...(Saturday night through Thursday) Issued at 404 AM EDT FRI MAY 17 2024 The 17/00z model suite upper level analysis is in fair agreement at the start of the long-term forecast period on Saturday evening. A very weak upper level low, embedded within a split flow pattern, will be found over the Ohio and Tennessee valleys. This system drifts southeastward on Sunday, through there is disagreement as to how rapidly, and thus there is uncertainty as to how widespread shower and thunderstorm activity might actually be on Sunday. Presently, forecast retains a 30 to 60 PoP on Sunday afternoon with lower values northwest of I-64 and highest values near the Virginia border. However, some solutions are quite dry. Additional refinements in the forecast will likely be needed as Sunday comes into the range of the full CAM suite. Once that upper level trough/low drifts southeast of area, ridging will build in at the surface and aloft Sunday night and persist into Tuesday. Cannot rule out a stray instance of deep convection on Tuesday afternoon, but the lack of forcing is evident from neutral to weak height rises. The ridging will finally break down Tuesday night and Wednesday as a complex upper low potentially coalesces and passes over/just north of the Great Lakes -- the system appears to be the end result of interactions/phasing between a stronger upper low initially over the Canadian Prairies, a shortwave trough over the Pacific Northwest and another weak low over the East Pacific. The models are clearly still trying to resolve how this system will evolve. In general, there seems to be a trend towards a weaker and less phased solution at this point. This would support the slower arrival of a cold front (associated with the upper low) across the Ohio Valley late Wednesday or Thursday. While the parameter space certainly appears favorable for severe weather with the front, there are scenarios in which organized convection splits as it approaches eastern Kentucky as suggested by the 00z deterministic GFS and GDPS. It is not difficult to imagine the northern convection becoming more tied with the better forcing to our north while the southern convection drops into the Tennessee Valley toward better instability. In more sensible terms, look for showers and storms to wane going into Saturday night. Any clearing should promote fog formation, especially in the valleys. Temperatures should remain mild, with lows in the mid 50s to lower 60s. An uptick in the shower and thunderstorms is possible on Sunday, best chances adjacent to the Virginia border. Forecast temperatures are seasonable, topping out in the mid 70s to lower 80s. For Monday night into Tuesday, fair and mainly dry conditions can be expected with just a stray chance for a shower or storm late Tuesday. Low temperatures in the mid 50s to lower 60s should be common while highs warm into the lower to middle 80s on Monday and well into the mid 80s on Tuesday. Nighttime/early morning valley fog is also likely through Tuesday morning in the favored locales. Forecaster confidence then lowers from Tuesday onward as the timing of the next cold front remains uncertain due to model-to-model and run- to-run inconsistency. In general, a cold front is likely to pass sometimes Wednesday or Thursday and is favored to be attended by showers and thunderstorms. Temperatures then trend back closer to the seasonal norms behind the front late in the week. && .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) ISSUED AT 142 PM EDT THU MAY 16 2024 Based on current trends, the TAF sites will continue to experience BKN low level cover through around 0Z this evening, before the clouds begin to scatter out a bit. VFR should be the rule at JKL, LOZ, and SME, but SJS and SYM will continue to see MVFR CIGs of around 2K this afternoon, before the clouds scatter and lift a bit this evening. Winds should be generally light and variable through out the period, but especially tonight. Clouds will be on the increase late tonight, as an area of low pressure moves in from the west, leading to periods of BKN clouds. A few showers and storms could begin moving into the I-64 corridor in our northwestern counties late this evening. The rain will continue to advance slowly eastward overnight into early Friday, and could begin to affect JKL, LOZ ,SME, and SYM toward the end of the forecast period. MVFR fog will be possible again tonight as moisture advects in ahead of the incoming storm system. LOZ and SME might even see brief periods of IFR fog between 10 and 12Z on Friday. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...CMC SHORT TERM...CMC LONG TERM...GEERTSON AVIATION...JP