324 FXUS63 KJKL 080000 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 800 PM EDT Thu Oct 7 2021 .UPDATE... Issued at 740 PM EDT THU OCT 7 2021 Updated the grids to fine tune the PoPs and thunder chances through the rest of the evening per radar and CAMs - still favoring our western counties then a diurnal fade is anticipated. Did also add in the current obs and trends for the T/Td grids. These updates have been sent to the NDFD and web servers along with fresh issuances of the zones and SAFs. && .SHORT TERM...(This evening through Friday night) Issued at 425 PM EDT THU OCT 7 2021 19Z sfc analysis shows a rather weak area of low pressure to the west of the area while a relatively stronger high is found to the east of the state. This maintains eastern Kentucky's placement in a soupy airmass of high moisture content and some building instability, especially in the southwest. Accordingly, scattered to numerous showers have broken out over the area with a few thunderstorms not far off - in fact, some cloud pulses have been detected in the convection just west of the CWA. Mostly clear skies for a good chunk of the area allowed temperatures to spike into the low 80s in some places - helping to drive the instability a notch higher late this afternoon. Temperatures are currently in the mid to upper 70s most places with those 80s in the southwest. Dewpoints, meanwhile, are in the sticky mid to upper 60s. One thing that continues to be a factor in limiting the convection, for at least the eastern parts of the area, appears to be southeast, downslope, winds of 5 to 10 mph today. The models are in broad general agreement aloft through the short term portion of the forecast. They all depict the opening and northward drift of the closed low to our west from tonight into Friday. The GFS is a bit further north with this low's center by Saturday morning compared to the ECMWF and weakest NAM. As a result, it also brings the follow up ridge into the area a tad quicker than the others for the start of the weekend. All models track more energy across the area this evening and again for Friday afternoon - associated with the passing trough to the north. The still rather small 5h differences are not all that material for the forecast, though, so that the blended solution of the NBM looked to be a reasonable starting point for the grids with no adjustments needed beyond the near term convective specifics - augmented with the radar/CAMs. Sensible weather will feature convection around into the evening with some storms and localized heavy rain possible. The high moisture will likely result in areas of fog later tonight as the showers start to wane. Another mild night follows with the dewpoints providing a floor for the lows and minimal terrain distinctions. We will see similar conditions on Friday though with greater emphasis on the west to east movement of the best PoPs into the evening in conjunction with the deeper moisture shifting off to the east. Some thinner or broken clouds on Friday night will open the door up to more in the way of valley fog and terrain differences in the lows by Saturday morning - though still limited by the seasonably high dewpoints. Mainly just made adjustments to the temperatures from the NBM for Friday night - for those terrain distinctions. As for PoPs, did not keep them as low as the NBM across the area on Friday instead giving some consideration to the deterministic NAM12's pattern of light QPF printouts. .LONG TERM...(Saturday through Thursday) Issued at 252 PM EDT THU OCT 7 2021 Model are in reasonably good agreement, only with the typical biases showing up in the operational solutions, and in particular the GFS. Ridging will build into the Ohio Valley through the first half of the extended as what's left of an exiting trough continues to fill as it shifts eastward and another upstream shortwave trough begins to track into the Upper Midwest by Monday. This trough continues to push through the Great Lakes mid-week next, with some energy brushing our area as it passes Tuesday night into early Wednesday, ~Dy6. Operational models handle this trough differently, with the GFS displaying its usual fast bias in timing the system eastward through the Ohio Valley. In addition the GFS appears too strong (amplified) with the strength of the trough. The Canadian and ECMWF are slower and weaker with this feature. At this time the H500 ensemble cluster prototype tool supports the slower and weaker solutions, without question. This suggests weaker surface features and less influence on sensible weather. Speaking of the surface, a surface cold front appears to make it just into eastern Kentucky before stalling out Tuesday night or Wednesday. With little if any upper level support (most of the energy with this system remains to our north), this cold appears to remain dry as it slides into eastern Kentucky, at least with current runs. Sensible weather features a most likely dry extended, with well above normal temperatures. Daily highs will generally peak out in the upper 70s and overnight lows will drop to around 60 through the bulk of the period, or some 5 to 10 degrees above normal. Some locations will likely flirt with the 80 degree mark on any given day. Other than possibly some extra cloud cover and a short window of time where winds shift, all signs point to the weather remaining dry with this surface front. Most recent run of the NBM has come in with some minor PoPs (15%) for late Monday afternoon, and then again for Tuesday. However, at this time believe the PoP for Monday is overdone based on the ensemble clustering and is the result of the GFS's faster solution. May leave the minor 15 PoP in place for Tuesday as that would correspond to the ECMWF's slower timing of the surface boundary into the area. Another system approaches the area at the very end of the period. NBM advertises additional PoPs for Dy7, Thursday, but expect this will change, once again as a result of the GFS's tendency to bring systems eastward too quickly. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) ISSUED AT 800 PM EDT THU OCT 7 2021 Most sites are VFR at 00Z, though some scattered convection is moving through the CWA and may yet impact a couple of them with MVFR or lower conditions. Low stratus and patchy fog are then expected to set in overnight into Friday morning which is likely to result in MVFR and worse conditions. While a return to MVFR or better restrictions will likely occur by midday Friday there will also be scattered storms around potentially impacting the terminals through the afternoon. Southeast winds of 5 to 8 kts will continue for most of the evening before becoming light and variable later tonight into Friday and staying that way - away from any convection - into the afternoon. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...GREIF LONG TERM...RAY AVIATION...GREIF