038 FXUS63 KJKL 160408 AAB AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 1108 PM EST Sun Dec 15 2024 .KEY MESSAGES... - Above normal temperatures persist through Wednesday. - Periods of rain are forecast to impact the area at times through Wednesday night. && .UPDATE... Issued at 1108 PM EST SUN DEC 15 2024 Recent radar imagery with light returns in the JKL vicinity suggest spotty drizzle in at least the middle of the CWA and some drizzle could be outside of this area and under the radar beam. Also, KY Mesonet and other area webcams suggest fog in some of the eastern valley locations. With this in mind, more drizzle was added to the grids over the next few hours and more fog was added to the grids, especially in deeper valleys well into the overnight hours. UPDATE Issued at 745 PM EST SUN DEC 15 2024 Minor adjustments were made to hourly grids based on observation trends. This led to no substantial changes at this point. Some web cameras have intermittently been showing rather substantial valley fog. The fog threat for valleys will continue to be monitored for possible adjustments to hourly weather. && .SHORT TERM...(This evening through Monday night) Issued at 347 PM EST SUN DEC 15 2024 Damp conditions linger as showers slowly diminish from west to east late this afternoon. Temperatures are seasonably mild, ranging from the upper 40s in portions of the Licking and Big Sandy River basin up to the mid 50s in the vicinity of Lake Cumberland. The surface analysis shows a warm front draped from the Southern Appalachians northwestward roughly along US-421 across eastern Kentucky and further northwest to a dissipating occluded low over southern Wisconsin. The system's cold front extends southward through the Mid-Mississippi Valley and then turns westward into the Red River Valley of the South where it becomes a warm front. Looking aloft, an ~558 dam closed low is moving toward Lake Erie, leaving the remnant occluded surface low be smothered by a shortwave ridge building along and west of the Mississippi River. The next 500H trough (of Pacific origin) is crossing the Northern/Central High Plains. As the aforementioned cold front moves into the Lower Ohio Valley this evening, it will stall and become more east-west oriented. The 500H shortwave ridging passes over our region tonight. Meanwhile, a new low pressure system will organize along the North Dakota/Canadian border this evening. This new system's 30+ knot warm conveyor belt jet will shift east and overspread eastern Kentucky late tonight. The resulting warm air advection and isentropic upglide will cause shower coverage to increase again toward sunrise Monday. The showers will tend to most persistent toward the Ohio River during the day on Monday where there will be a lingering baroclinic zone from the former cold front. As the new surface low tracks into northern Ontario and becomes increasingly occluded on Tuesday evening, a cold front extending south from this low, will drop through the Commonwealth and bring a round of widespread rain showers, sinking from northwest to southeast. Sensibly, the showers continue to dry up this evening and exit Pike County by or before 9 PM EST. Low clouds, patchy fog, and spotty drizzle and the possibility of a light shower then linger for most of tonight. Temperatures will be mild by December standards only settling back into the middle and upper 40s. Showers redevelop from the west toward sunrise, with likely PoPs reaching the I-75 corridor around 4 to 5 AM and spreading eastward into Pike County by 8 to 9 AM EST. After the initial surge in shower activity, the steadier shower activity is expected to become more confined to near and north of the Mountain Parkway during the midday hours. In fact, locations near and south of the Hal Rogers/KY-80 corridor should be mainly dry for 3 or 4 hours during the midday to mid afternoon. Shower coverage should then increase again from the northwest from mid-afternoon onward as the next cold front approaches from the northwest and crosses the area during the evening hours. Showers taper from northwest to southeast Monday night behind the front. Temperatures remain very mild reaching into the upper 50s to lower 60s on Monday afternoon before falling back into the 40s for most locales on Monday night. Rainfall amounts of 0.5 to 1.0 inch are forecast through Tuesday morning, highest amounts northwest. .LONG TERM...(Tuesday through Sunday) Issued at 447 PM EST Sun Dec 15 2024 At the start of the long term forecast on Tuesday morning, the cold front responsible for Monday's active weather will have lost its upper level support. While said front and its associated cloud cover/precipitation chances are likely to clear the entirety of our forecast area by Tuesday afternoon, it will stall out to our south somewhere in the Tennessee Valley. In its wake, a surface high pressure system will build into the area and foster clearing. Quasi- zonal flow aloft and the return of sunshine will allow for temperatures to recover into the mid/upper 50s across much of the area on Tuesday. However, this reprieve from the rain will not last long, and the progressive nature of the synoptic pattern aloft means that a trough will begin to dig into the greater Mississippi River Valley on Tuesday night into Wednesday. At the surface, this will be represented as a deepening surface low pressure system, which is expected to quickly eject northeast out of ArkLaTex and into Kentucky by Wednesday morning. The stalled boundary will then lift northeast across the Commonwealth as a warm front, with cloud coverage and rain chances increasing accordingly. Temperatures may not follow a traditional diurnal curve overnight into Wednesday morning, with temperatures beginning to rise area-wide after 06z. Together, these synoptics will shift flow throughout the column to a more southwesterly orientation, and the resultant warm air advection and moisture return looks seasonably potent. While this set up does not look particularly concerning from an organized severe weather standpoint, a rumble of thunder cannot be ruled out on Wednesday afternoon/evening. Afternoon highs could top out near 60 across our southern counties, and the last few cycles of long-range probabilistic guidance has been highlighting the potential for some marginal instability down there. The parent upper level trough will progress eastward into Thursday, leading to FROPA late Wednesday night. Cold air advection kicks in behind it, and a very brief changeover to a rain-snow mix is possible before precipitation quickly tapers off on Thursday morning. The rest of Thursday's sensible weather looks dry, but it marks the beginning of a cooler pattern. Deeper, longwave upper level troughing emerges over the eastern half of the CONUS by next weekend, with more amplified ridging out west. High temperatures will drop down into the 40s on Thursday and Friday, with overnight lows dipping near/below freezing again. A clipper-type system embedded in the NW flow around this longwave troughing will approach the area on Friday, and with the colder airmass in place, some light snow could materialize, especially across the higher terrain in our eastern counties. However, there remains some uncertainty in the exact timing of these features and the amount of moisture available to them, so confidence in accumulating snow is low. Confidence is higher that this system will reinforce the cold air headed into the weekend, with forecast highs in the mid/low 30s on Saturday and Sunday and overnight lows in the 20s/teens. Some guidance resolves an embedded upper level shortwave disturbance approaching the area on Saturday, which could once again lead to precipitation chances in areas prone to upslope flow. With the colder air in place, it could fall as snow, but it is far too early to provide any details regarding impacts. Therefore, interests with pre-holiday travel concerns should continue to monitor the forecast in the coming days. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) ISSUED AT 735 PM EST SUN DEC 15 2024 MVFR was reported at the TAF sites near issuance time, though some IFR was observed at a few other sites across the region. An area of showers was diminishing from west to east and these should move east of the area within the first hour or so of the period. Guidance continues to suggest this will give way to patches of drizzle or spotty light showers and given recent webcam imagery and small dewpoint depression patchy fog as well. The next surge of shower activity arrives from the southwest 9Z-12Z for KSME, KLOZ, and KSYM, and KSJS by 14Z. Winds will average south at 10KT or less through 15Z, and then south to southwest to end the period at up to 15KT. Some higher gusts of 20 to 25KT are anticipated generally after 15Z. In the 12Z to 18Z period and before surface winds increase as do gusts, LLWS will be a threat. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...GEERTSON LONG TERM...MARCUS AVIATION...JP