319 FXUS63 KJKL 051738 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1238 PM EST Fri Jan 5 2024 .UPDATE... Issued at 1238 PM EST FRI JAN 5 2024 Have been using the latest obs to freshen up the hourly grids over the past several hours and to establish new trends. Some spots have been a bit slower to warm up than the inherited forecast indicated, but it does appear that forecast highs around the area will be realized today, considering how thin/sparse incoming cloud cover continues to be. UPDATE Issued at 655 AM EST FRI JAN 5 2024 Hourly grids for this morning have been freshened up based on recent observation and satellite trends. This led to no substantial changes at this point. Sheltered eastern valley locations are starting the day well down into the teens but all locations should moderate to near normal levels this afternoon with highs expected to range through the 40s. && .SHORT TERM...(Today through Saturday) Issued at 525 AM EST FRI JAN 5 2024 Key Messages: - An area of low pressure tracking across the Gulf Coast states and the Southeastern U.S. and a couple of associated upper level disturbances will lead to mixed wintery precipitation at onset late tonight to early on Saturday morning. - Locations near and north of the Mountain Parkway and also above 2500 feet elevation near the Virginia border have the highest chances for picking up light wet snow accumulations late tonight to early on Saturday. - A few of the more sheltered eastern valley locations could experience a brief glaze of ice accumulation near precipitation onset before melting as precipitation transitions to rain. Analysis and Discussion: Early this morning the axis of an upper level ridge extended from the eastern Gulf of Mexico northwest to the TN and OH Valleys to portions of the MS Valley region. Meanwhile, an upper level trough extended from eastern MT into portions of the Plains with a closed low was centered in the vicinity of the OK and TX panhandles. A series of upper level shortwaves were moving from the Northwest Conus across portions of the western Conus in northwest flow from between the troughing over the Plains and portions of the Central Conus and an upper level ridge over the Pacific. To the east and southeast of the upper level low in the OK and TX panhandle vicinity was a shortwave trough extending from OK to eastern portions of TX with another rotating through the southern Rockies. At the sfc, a ridge of high pressure extended from the mid to upper OH Valley region into the Southeastern Conus while a sfc low was over the TX panhandle vicinity with a frontal zone extending through central portions of TX. Meanwhile another sfc low was beginning to take shape in the northwest Gulf of Mexico coastal region along a frontal zone that extended from southern and eastern portions of the Gulf of Mexico to the TX Gulf coastal region. Locally a few cirrus were passing across eastern KY with a ridge/valley temperature split in place with temperatures in deeper more sheltered valley locations in the mid to upper teens with readings generally in the low to mid 20s elsewhere. A dry airmass is in place at present associated with the ridging with the subsidence inversion air having lowered to near the top of Black Mtn where dewpoints have been -10F or lower during the overnight hours. The upper level ridge axis is expected to shift east and northeast today and extend from the vicinity of the Bahamas northeast into the Central Appalachians to Great Lakes early this evening. Further west, the upper level low is expected to meander to the SE NE/SW IA/NE KS and NW MO vicinity this evening while the initial shortwave trough nears the mid to Lower MS Valley region and approaches the Southeast Conus. At the same time, shortwaves moving across western portions of the Conus should move toward central portions of the Rockies and approach the Four Corners region. As tonight progresses, a more broad trough should is expected over the Central Conus while the initial shortwave trough nears the Lower OH Valley and works into the TN Valley and into the Southeast Conus. At the same time, the sfc low initially over the Northwest Gulf of Mexico vicinity should become dominant and track to AL by dawn on Saturday with an inverted trough extending into eastern KY at that point. The axis of this shortwave trough is expected to track across central and eastern KY from Saturday morning into the early after with the axis moving northeast of eastern KY Saturday afternoon as the upper level low works into the western Great Lakes region and weakens. Further west, the upper level trough is expected to sharpen on Saturday as additional shortwaves move into it with the axis of the 500 mb trough approaching the MS Valley late on Saturday. Once the axis of the upper level ridge works northeast of eastern KY later this afternoon to early this evening, moisture is expected to increase through the column with some general moistening from the top down also anticipated this evening and through tonight into early on Saturday. PW should climb from values in the 0.15 to 0.25 inch range in place through late this afternoon to about 0.4 to 0.7 inches near 6Z (1 AM on Saturday morning) to about 0.75 inches areawide near dawn on Saturday. However, as the shortwave trough axis passes across eastern KY on Saturday, PW will decrease from west to east as the day progresses as fall back to back to around the 0.4 to 0.5 inch range to end the period in an area of dry slotting between the initial shortwave and the 500 mb trough axis to the west. As the column saturates tonight, there should be a period where the column develops an isothermal layer near the 0C isotherm and slight variations of the thermal profile of only 0.5C could make a difference in whether liquid or snow reaches the surface at onset. Also, if hydrometeors are melted before reaching the surface, some locations particularly deeper sheltered valley locations may drop off to the freezing mark if not below during the evening when clouds should initially in the high cloud range or mostly in the high cloud range. Thus a brief period where some freezing rain could occur is not completely out of the question. The marginal or near marginal thermal profiles will transition to one supporting just rain in all areas as Saturday morning progresses. By the afternoon, with deeper moisture moving east and northeast along with the passage of the shortwave trough, chances for rain will diminish. The consensus of guidance is that areas near or generally north of the Mtn Parkway and above about 2500 feet elevation will have the best chances for some wet snow accumulations near onset as the column saturates late tonight to around dawn on Saturday. Some of the most recent convective allowing models including 06Z HRRR and 06Z NAM p type analysis suggest a bit longer period where the precipitation could be snow across the north than currently forecast though the top down approach on forecast soundings suggest the southern extent of that may be overdone at the very least. These trends will continue to be monitored. 0Z HREF PMM snowfall was generally under one inch across eastern KY with a max from the members near or just over 1 inch for areas near and north of the I-64 corridor. .LONG TERM...(Saturday night through Thursday) Issued at 328 AM EST FRI JAN 5 2024 Key Messages: * Generally rain, though some rain/snow mix possible late Saturday night, before showers taper off from west to east through Sunday. * A potent low pressure system will approach into Tuesday, bringing windy conditions and widespread rainfall to the area. Gusts exceeding 40 mph increasingly likely for the high SE terrain. * Overriding moisture behind a passing cold front could allow a brief window of wintry mix or snow Wednesday, but no accumulations are expected at this time. An unsettled weather pattern can be expected throughout the extended, as a series of disturbances look to press through the eastern half of the CONUS. At the start of the period, Eastern Kentucky will be in the midst of a passing secondary mid-level impulse. This will ripple through the parent trough, centered just east of the Ohio Valley. At the surface, low pressure will be exiting the Currituck Sound, while a cold front associated with a Canadian low, will be aligned upstream through the Midwest. With the upper shortwave propagating through the Ohio Valley, likely to widespread (50-80%) PoPs are forecast. Near-surface temperatures will be the deciding factor in p-type, but soundings largely favor rain across the bulk of the area. That said, locations north of I-64 with a better tap of cooler air and the higher southeast terrain could see a brief rain/wet snow mix near dawn Sunday. No accumulations are expected Saturday night into Sunday morning, with all precipitation turning to rain with warming temperatures into the day Sunday. Thereafter, heights will recover with a passing ridge. High pressure will meander through the Ohio Valley and into the Mid Atlantic, allowing for precipitation-free weather Monday and highs warmer in the mid 40s near I-64 to around 50 for locations near the Tennessee border. This will be short-lived though, as a very anomalously strong low pressure system and attendant cold front take shape across the Southern Plains and take aim at the Tennessee and Ohio Valleys into Tuesday. In terms of climatological norms, the low will be near seasonal maximums, with sub 980 mb possible as it progresses north of the area- through the Great Lakes. Deep moisture advection, squarely in the warm sector of the system, will allow for widespread showers and possibly a thunderstorm on Tuesday. Have not included the mention of thunder within the gridded forecast, but near 100 J/kg of MUCAPE in soundings across the Cumberland Basin could warrant the inclusion of a low-end probability in future packages. The biggest threat associated with this midweek system will be winds/gusts. The strong pressure gradient will allow for increasing southeasterly winds, where a developing 55-70 kt LLJ will build in overnight Monday into Tuesday before shifting east of the Appalachians into the day. Nonetheless, gusty winds of 40 to 50 mph will be possible for the high southeast terrain (bordering VA/WV) into Tuesday. Elsewhere, a stable layer could limit this mixing down to the surface, particularly for valleys, with gusts to around 30 mph more reasonable. Ensembles largely agree the high southeast terrain will pose the highest risk, with the EFI depicting a high likelihood for very unusual wind gusts compared to norms and a SoT of +1: an indication of higher agreement within ensemble members for an extreme event. Likewise, the ensemble probability for wind gusts near the border of VA/WV exceeding 40 mph is near 100%. The associated cold front is expected to progress through into Wednesday morning, where steeper lapse rates within CAA could induce better mixing area-wide once more, and thus, gusty winds for a stint the first half of the day Wednesday. Ensembles are not as bullish through Wednesday morning, but still suggest low to medium confidence in westerly wind gusts of 35 mph or greater for at least the northeastern half of the CWA. Overriding moisture within much cooler air advecting in could allow for a period of rain/snow mix for Eastern Kentucky Wednesday. With moisture becoming more limited as the day carries on and warm surface temperatures leading in (highs well above normal Tuesday), no snow accumulations are expected outside of low-end chances atop Black Mountain. Precipitation should taper off by Wednesday evening, where shortwave ridging fills in across the area. Another late period wave could then swing east out of the Northern Plains bringing increasing PoPs through Friday. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) ISSUED AT 1238 PM EST FRI JAN 5 2024 SCT high clouds will continue to stream over eastern KY through out the day today. The clouds will eventually lower and thicken to BKN by around 3Z this evening across the area. Clouds will lower to MVFR levels between 4 and 8Z, as an area of low pressure moves by to our south and southeast. Precipitation will make its way into our southwestern counties by 5 or 6Z tonight, affecting SME and LOZ first, with JKL, SYM, and SJS seeing precip by 7 or 8Z. The forecast challenge will be how quickly precip transitions from rain to rain/snow mix and/or all snow early Saturday morning. Alot of uncertainty exists in the forecast models to this point, but there are indications that more snow may occur along and north of I-64 early Saturday, with SYM perhaps seeing snow shower activity for a few hours Saturday morning. LOZ and SME should see mostly rain, with JKL and SJS seeing rain transitioning to a rain snow mix early Saturday. MVFR conditions, especially CIGS, should begin to occur at the airports by 9Z Saturday due to incoming precipitation, with IFR conditions possible at times from 10Z onward. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AR SHORT TERM...JP LONG TERM...BB AVIATION...AR