Area Forecast Discussion
Issued by NWS Jackson, KY
Issued by NWS Jackson, KY
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
579 FXUS63 KJKL 181839 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 239 PM EDT Sat May 18 2024 .KEY MESSAGES... - An upper level trough advancing slowly toward us from the west will continue to support showers and thunderstorms into Sunday, with the focus shifting southeastward in our area with time. - Upper level ridging moves into the area from the northwest tonight and Sunday bringing drying, with dry weather expected area wide from Sunday night through Tuesday night. - The upper level ridge shifts to our southeast by Wednesday. A series of upper level waves and an approaching cold front will bring the potential for rain back Wednesday into Friday. - The upper level ridge passing over will result in warmer weather, with above to well above normal temperatures forecast Sunday through Wednesday. && .UPDATE... Issued at 117 PM EDT SAT MAY 18 2024 Renewed surfaced based deep convection is trying to get started, but is still very small and sparse. Today`s model runs have backed off on it once again. Have adjusted the POP downward a bit. Will wait to see what`s going on right before the afternoon package goes out to see if further adjustments are needed. Have also lowered max temps slightly, mainly in southeast KY where persistent clouds have slowed the rise. UPDATE Issued at 925 AM EDT SAT MAY 18 2024 Fog is lifting and dissipating, and the Dense Fog Advisory which was in place in the northern part of the forecast area has been allowed to expire. However, have raised sky cover this morning, with satellite showing most places currently overcast. UPDATE Issued at 651 AM EDT SAT MAY 18 2024 Given radar and observed trends, we expanded at least 15 PoPs through the forecast area this morning, though activity for the next several hours should stay primarily south of the Mountain Parkway. Also raised PoPs for this afternoon, especially across the north, using a blend of the NBM, CONShort, and GFS1hr models. && .SHORT TERM...(Today through Sunday) Issued at 349 AM EDT SAT MAY 18 2024 Fog has developed and become quite dense this morning especially from Interstate 64 north, so have issued a Dense Fog Advisory there. Cloud cover and shower activity has made detecting fog of Interstate 64 more difficult. It appears the presence of these clouds and precipitation are providing just enough insolation so far to keep widespread dense fog from developing. However, if observations show an increasing trend of lower visibilities more consistently below one-half mile, a Special Weather Statement or Dense Fog Advisory could be issued. Otherwise, a slow-moving upper trough is poised to cross the region today with light winds aloft becoming more northerly tonight. This northerly flow will help shunt the deeper moisture toward the southeastern Kentucky, with decreasing moisture toward the Bluegrass region. The result will be shower and thunderstorm chances today favoring southeastern Kentucky where there will be categorical (75+%) PoPs, trailing off to chance (40-54%) PoPs along and north of Interstate 64. Drier air will slowly work south through tonight and help to diminish precipitation from northwest to southeast. Fog and low ceilings this morning will give way to sun breaks and thus destabilization by midday into the afternoon, and with little in the way of any capping mechanism, showers and thunderstorms should quickly develop by early afternoon and persist into the evening. As skies begin to clear tonight, expect widespread fog formation, with potentially dense fog in the deeper sheltered valleys especially if there is any substantial clearing. A much drier air mass builds into the area from the north and northeast Sunday, but there will be modest moisture and destabilization remaining especially over the higher terrain along the Virginia border, which warrants at least slight chance PoPs to low-end chance PoPs for those areas. The high temperature forecast for today continues to trend slowly upward into the mid to upper 70s, capped by extensive low cloud cover in the morning and then expected shower and thunderstorm development early to mid-afternoon. Lows tonight will fall into the upper 50s to near 60 degrees as cooler air advects into the region, with widespread fog formation preventing temperatures in the valleys from falling more than about 5 degrees below the ridgetops in the mid 50s. Despite the light northerly flow Sunday will feature a lot more sun than in previous days, with highs thus warming into the lower 80s. .LONG TERM...(Sunday night through Friday) Issued at 402 AM EDT SAT MAY 18 2024 The 18/00z model suite analysis beginning Sunday evening shows a positively-tilted 500H ridge axis oriented southwest-to-northeast from the Ark-La-Tex across the Ohio Valley, Eastern Great Lakes and Northern New England. This ridge is mirrored at the surface by high pressure ridging extending from the Canadian Maritimes down through the Mid-Atlantic to across the Tennessee Valley/Lower Mississippi Valley. Northwest of this ridging, an ~547 dam low resides over Saskatchewan with a a shortwave trough tracking over the Northern Rockies/Pacific Northwest while another weak closed ~575 dam low rotates off the Southern California Coast. The deep layer ridging will remain firmly in place over eastern Kentucky on Monday and Tuesday with abundant sunshine each day and mostly clear skies each night. Fog formation is likely in the typical valley locales late each night. Daytime temperatures will be warm, soaring into the mid to upper 80s both afternoons while nighttime temperatures retreat into the mid 50s to lower 60s for most locations. The ridging becomes suppressed southeast of the Ohio Valley by Tuesday night as the upper level low over the Canadian Prairies, the shortwave trough over the Northwestern US, and the weak Pacific low all translate eastward and interact/partially phase/consolidate into a deeper closed low over the Upper/Northern Great Lakes by late Wednesday. This stronger low then quickly pinwheels northeastward into northern Quebec, taking the best forcing with it. In the process, the system is expected to bring slight height falls to eastern Kentucky as an associated cold front settles south of the Ohio River and stalls. Guidance increasingly favors this boundary stalling right over eastern Kentucky on Thursday and becoming the favored corridor for a passing Pacific disturbance to track along on Friday. Sensibly- speaking, the cold front will bring the renewed threat for showers and thunderstorms beginning on Wednesday and lingering into Thursday. Any lull in the activity Thursday night will likely yield to another round of showery weather on Friday as that Pacific disturbance passes. Some concern for strong to severe storms lingers, primarily on Wednesday; however, with the better forcing remaining to our north and the better instability to our south, there could be a relative minima in convective intensity over eastern Kentucky. Flooding is not currently a concern. Temperatures will trend cooler as clouds and showers arrive. Still expect highs into the 80s on Wednesday ahead of any showers and thunderstorms, cooling back into the 70s to around 80 for Thursday and Friday. Nighttime lows retreat from the 60s to right around 60. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) ISSUED AT 238 PM EDT SAT MAY 18 2024 A mix of VFR and MVFR conditions (due mainly to ceilings) were present at the start of the period. While most showers present during the morning had dissipated, renewed development with daytime heating/destabilization was starting. A general improvement to VFR is expected by late afternoon as ceilings continue to rise. However, additional development of showers and possibly thunderstorms will lead to localized sub-VFR conditions in the heavier precipitation. The showers and thunderstorms will die out this evening and most clouds will dry up. Good radiating conditions will lead to development of valley fog late tonight. It will grow in breadth and depth through dawn, but exactly how widespread it becomes is uncertain. At this point, the best estimate is that TAF sites will be IFR at least at times. The fog will dissipate early Sunday morning, leaving VFR conditions through the end of the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...HAL/CMC SHORT TERM...CMC LONG TERM...GEERTSON AVIATION...HAL