763 FXUS63 KJKL 261626 AAB AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 1126 AM EST Thu Nov 26 2020 .UPDATE... Issued at 1125 AM EST THU NOV 26 2020 A weak sfc trough and some cooling aloft are likely leading to the upstream echoes from the low cloud deck over portions of central KY. Have mainly updated to allow for these a tier or two of counties further south through the afternoon and account for recent radar trends. The low clouds are expected to be remain most persistent across the western or northwestern half of the area with breaks continuing across the southeastern portions of the area. In the area of most persistent clouds, temperatures should move very little for the remainder of the day. UPDATE Issued at 810 AM EST THU NOV 26 2020 Forecast largely on track. A weak surface trough, along the Ohio River, continues to drift eastward. The latest radar shows a few weak echoes, likely sprinkles, with this feature back over SE Indiana and S Ohio. Some of these sprinkle will probably drift across northern Kentucky later this morning and afternoon. Updated grids to mention sprinkles north I-64 to account for this potential. Otherwise, freshened grids with latest obs. Updates have been sent and published. && .SHORT TERM...(Today through Friday) Issued at 505 AM EST THU NOV 26 2020 A mild and quiet short term period is ahead. At 9z, an upper level low and its ~1007mb surface reflection were situated near/over Lake Erie. This system's decaying cold front extended SE from to the low into western PA then arced S to SW along the spine of the Appalachians. Another weak surface trough, roughly coincident with a subtle upper level shortwave trough, extended SW from the surface low to over the Ohio Valley. To the west, upper level ridging extended from the Ark-La-Tex region N to NE to near Sault Ste. Marie, MI. The resulting ~1019 mb surface high was centered near Jackson, MS with its major ridge axis extending into the Upper Mississippi Valley and Western Great Lakes. A minor surface ridge axis extended NE across the Tennessee Valley into SE Kentucky where it was sandwiched between the cold front to the E and the weak surface trough to the NW. The radar is showing a few weak returns over far east Kentucky behind the front, but most of them appear to be evaporating in the relatively dry low- levels before reaching the surface. However, an isolated sprinkle cannot be entirely ruled out through sunrise. Otherwise, we are seeing varying amounts of cloud cover over eastern Kentucky with temperatures ranging from the upper 40s, north of I-64 and west of I-75, to the mid 50s over southeast Kentucky. Expect that these temperatures will drop a few more degrees through sunrise given some weak CAA at the lowest levels. After a breezy start to the night, winds have diminished to less than 10 mph and are generally from a northwest to southwest direction. As we head through the morning hours, clouds should increase again and persist through much of the afternoon as a broad expanse of low-level moisture wraps around the low to our north. The cloud cover will likely be most extensive for areas north of the Cumberland Valley. Additionally, the subtle surface trough over the lower Ohio valley and a couple of weak mid-level perturbations may produce enough lifting for a stray sprinkle or some patchy drizzle, particularly over the northern half of the forecast area. Otherwise, a relatively mild day is in store with highs ranging from the mid 50s over northern Kentucky to the lower 60s in the deeper valleys near the TN and VA borders. By late in the day, partial clearing should gradually develop from south to north as surface high pressure lifts across TN and KY. However, another mid-level disturbance will brush northern areas tonight which will prevent full clearing and could even cause clouds to increase again over northern areas. Low temperatures are expected to fall back into the mid 30s to mid 40s with the coolest readings in sheltered southern valleys. Some fog formation is probable in the southern main stem river valleys where more clearing prevails. Surface high pressure will slowly weaken over the central Appalachians on Friday as a weak and moisture-starved cold front drops southeastward into the Ohio Valley late in the day. Any morning clouds and valley fog should give way to mostly sunny skies for most locations by midday. This should warm temperatures into the mid 50s to lower 60s, northeast to southwest, during the afternoon. .LONG TERM...(Friday night through Wednesday) Issued at 502 AM EST THU NOV 26 2020 The long term period will be a story of the calm before the storm. A weak cold front will be crossing eastern KY as the period starts, but will have very limited moisture and should not bring anything more than some clouds. The upper level trough supporting the front will leave behind a closed low over the southwest CONUS, and this will be an important player in subsequent weather. Surface high pressure behind the front will pass over the area from west to east during the weekend, providing dry and seasonably mild weather. During the weekend, the aforementioned upper low will move east, and models are consistent in allowing it be pickup/phased with a northern stream trough diving southeast out of Canada. Models continue to come into better agreement on the evolution of this system. It should prompt surface low development over the northwestern Gulf of Mexico late Saturday. The low then rapidly deepens and moves northeast along the Appalachians, reaching our area by Monday morning, and it eventually gets caught up underneath its massive closed upper low in the vicinity of the lower Great Lakes. The system's approach should bring rain Sunday night into Monday, but once it passes, much colder air arrives on its back side. The ongoing scenario in models is for deep moisture wrapping around the system's back side to bring snow for our area from Monday night into Tuesday. It's looking more likely that it could be the first accumulating snow of the season for most of the area. However, still being several days out, confidence in amounts is lacking. By midweek, the giant storm system is past its peak and the low begins to fill. We will still be under its influence, but any precip should be less significant. && .AVIATION...(For the 12Z TAFS through 12Z Friday morning) ISSUED AT 700 AM EST THU NOV 26 2020 At 12z, an extensive MVFR to IFR cloud deck, over the western Great Lakes, mid-Mississippi Valley, and Lower Ohio Valley, continues to wrap around a low pressure system spinning over the eastern Great Lakes. Across eastern Kentucky, a majority of the airfields are experiencing MVFR ceilings and the few sites that have higher ceilings should see them drop to MVFR within the next couple of hours. Ceilings should lift to VFR by late afternoon near and south of a SJS-JKL-SME line and could even become broken or scattered closer to the VA and TN borders. However, they will again lower to MVFR after sunset. Some patchy valley fog is possible tonight at airfields which see partial clearing this afternoon. Westerly winds at 5 knots this morning will diminish to light and variable. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...GEERTSON LONG TERM...HAL AVIATION...GEERTSON