Expires:No;;345138 FXUS63 KJKL 251121 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 721 AM EDT Thu Apr 25 2024 .KEY MESSAGES... - Below normal temperatures persist through tonight, with a bit of frost in some valleys each night. - A warming trend begins on Friday, with well above normal temperatures then expected through next week. - Thunderstorms are possible Friday afternoon and evening to the west of a Middlesboro to Flemingsburg line. Thunderstorms are then possible areawide from late Monday afternoon through Tuesday, and again Wednesday afternoon. && .UPDATE... Issued at 721 AM EDT THU APR 25 2024 Areas of low stratus continues to move southwest into the region from the Ohio Valley and West Virginia, which necessitates some increases to Sky grids for the next few hours. These low clouds will burn off as the morning progresses, though they may be pesky and persistent through mid-morning. Otherwise, the forecast is largely on track with the latest observed trends blended into the forecast. && .SHORT TERM...(Today through Friday) Issued at 314 AM EDT THU APR 25 2024 Surface high pressure continues to nose into the area from the northwest and north under the negative vorticity advection region between upper ridging over the Central US and downstream troughing over the East Coast. This will support mostly sunny skies and light north winds today, though some brief low stratus is possible in some areas in the morning before burning off by midday. With the weak cool advection from the north, highs will be slightly below normal in the lower 60s north to lower 70s south. Winds veer to easterly and then southeasterly overnight as surface high pressure wedges down the eastern slopes of the Appalachians while a surface low and attendant cold front move out onto the Central Plains. With warm advection beginning in the southwest while the surface high remains influencing the northeastern half of the CWA, expect a wide range of temperature and sky cover, with warmer temperatures in the 40s with increasing clouds over the southwestern counties, while good radiational cooling in the sheltered valleys will mean lows in the mid 30s and possibly cooler with some patchy frost possible. A warm front aloft moves across the area Friday and brings an increase in cloud cover and moisture, though that will be mitigated somewhat in our eastern counties directly downwind from the taller mountains. Given the best dynamics and thermodynamics remaining west of the area, and the mitigating influence of downslope drying in the eastern counties, will only be carrying 20 PoPs or less, with the best chance of a thunderstorm or two mainly along and west of I-75 Friday afternoon, but even this is not high confidence given the lack of instability indicated by most modeling. Nevertheless, even with the increased cloud cover, the increasing warm advection and southerly flow temperatures will return to the 70s to near 80 degrees, with warmest temperatures in our eastern counties where the better downslope warming and drying will occur. .LONG TERM...(Friday night through Wednesday) Issued at 350 AM EDT THU APR 25 2024 SW flow will be the story for the majority of the period. This will keep WAA across the region and lead to above average temperatures throughout the period, with a handful of days likely topping 80 degrees for highs. So what is driving this and what impacts can we expect other than heat? By the start of the extended period, we will have transitioned to a upper level ridging pattern across the Ohio Valley and points north and south. This will become amplified as two very strong upper level low pressure systems develop across the Plains and farther to the west, and then travel northeastward through the weekend and into Monday. As this occurs, pressure gradients will tighten along the SW flow side of the ridge, amplifying the amount of WAA and increasing the winds. Much of the weekend, and even into Monday, could see some breezy conditions as a result. The interesting part of this is that, despite being in a somewhat higher instability pattern, most of the energy will be confined to areas closer to the closed lows, which are forecast to stay well west of the Commonwealth. It's one of those rare times where you get strong SW flow and don't have to pay the consequences in the form of unsettled weather. The CWA should remain dry all weekend, from Saturday through Monday morning. These are also 2 of the days that we should top the 80 degree mark for highs (Sunday being the warmest). For Saturday and Sunday night, did go ahead and include some ridge/valley differences in winds and temps since we will be under mostly clear skies. However, given the mixing ongoing even into the overnight, didn't go too crazy on lowering the temps in the deeper valleys. There is a bit of a shift in the pattern during the day Monday. The second of the closed lows will move north of Lake Superior by Monday afternoon. The attached cold front will be oriented almost due north to southward. As this system continues to push NE into Tuesday, the cold front will slowly push eastward towards the Ohio Valley, traversing the state from west to east. This will bring a line of showers and thunderstorms to the region during this time, with the main line/front moving through Tuesday morning based on latest model runs. Would like to note that Tuesday is currently Day 6 of the forecast, so this timing is subject to change a bit - but overall models are in very good agreement considering how far out it is in the forecast! Once this system exits, the overall flow will begin to balance itself back out, with no additional upper level lows expected to producing troughing to our west. Flow will become more zonal across the Ohio Valley for Tuesday and Wednesday. However, zonal flow doesn't induce a large airmass change for the region. For instance, the high on Monday ahead of this cold front will be in the low to mid 80s. Post frontal temperatures Tuesday will only be several degrees cooler, in the upper 70s - still WELL above normal for this time of year. Without a switch to NW to N flow, and a colder airmass moving in, we should stay more moderate with our temperatures. As we head into Wednesday and Thursday, the model agreement starts to quickly deteriorate. Both the GFS and ECMWF point at a potential system impacting portions of the Ohio Valley during this time, but the exact impacts are still very low confidence. The NBM went with isolated to scattered showers and thunderstorms during this period, with convection mainly isolated to the afternoon peak heating. Given the uncertainty, didn't have any reason to change it at this point, but expect it to evolve over the coming days. && .AVIATION...(For the 12Z TAFS through 12Z Friday morning) ISSUED AT 712 AM EDT THU APR 25 2024 A thin MVFR stratus layer of clouds is moving southwest into far northern and eastern parts of the forecast area, and will primarily impact KSJS for the next few hours. However, this stratus layer will burn off by late morning. Otherwise, high pressure brings VFR conditions and north to northwest winds of generally less than 10 kts becoming northeasterly after 00z Friday. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...CMC SHORT TERM...CMC LONG TERM...JMW AVIATION...CMC