Area Forecast Discussion
Issued by NWS Jackson, KY

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249 FXUS63 KJKL 192355 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 755 PM EDT Wed Jul 19 2017 .UPDATE... Issued at 735 PM EDT WED JUL 19 2017 23z sfc analysis shows high pressure (and heights aloft) in control of the weather through eastern Kentucky. This has kept the majority of clouds and any convection at bay through the afternoon and into the evening - even over the higher eastern terrain in contrast to yesterday. Nevertheless the heat and humidity laid into the area today with readings just now starting to settle back down into the lower and middle 80s while dewpoints are generally in the mid and upper 60s - along with light winds. Persistence conditions will continue this night with low temps expected close to last night`s values along with a similar pattern to the fog formation. This all is well handled in the forecast zones and grids so just a touch up to the T/Td/Sky grids was performed based on current observations and trends. These updates have been sent to the NDFD and web servers. && .SHORT TERM...(This evening through Thursday night) Issued at 355 PM EDT WED JUL 19 2017 As of mid afternoon, the region remains under the influence of mid and upper level ridging while surface high pressure is in place across the southeastern Conus. Outside of very isolated showers that developed west of JKL and near Dewey Lake that formed and dissipated over the past couple of hours, cu has generally remained shallow. Recently, cu is a bit more robust near the escarpment/Daniel Boone Forest where a surface trough/wind shift is present and evident on radar. A dampening shortwave is moving across western and central KY with some shower activity associated with it. Through this evening and tonight, the dampening shortwave moving around the center of the ridge will drop into the TN Valley region and stay south and southwest of the area while the axis of the upper ridge remains in place across the region. Surface high pressure is expected to remain in place across the Southeastern Conus. This should lead to similar conditions than last night. Current dewpoints/crossover temperatures are mainly in the mid 60s to around 70 degree range and with high pressure in place, temperatures should drop to this range with river valley fog and fog along the larger creeks likely to develop. Some of this could become dense late tonight in a few spots right along the rivers. Thursday and Thursday night, the center of the mid and upper level ridge will remain west of the area over the Plains to MS Valley region. Meanwhile, an upper level low is expected to generally move east from the western portion of Hudson Bay and into northern Quebec while a shortwave trough moves into and across the Great Lakes and into St Lawrence Valley and the Northeast Conus. At the surface and area of low pressure will move across the Great Lakes and into the Northeast with a cold front dropping south of the Great Lakes toward the Ohio River. However, convection associated with this should remain north of the area through the period with high pressure dominating. At this point, the mid and upper level ridge should keep the atmosphere capped with only shallow to moderate cu expected to remain develop on Thursday. An increase in clouds should lead to less in the way of fog on Thursday night. Temperatures will remain mild through the period with lows tonight and highs on Thursday similar to, if a degree or two warmer than last night and today. Dewpoints should creep up a couple of degrees tomorrow afternoon compared to today with the higher dewpoints persisting in the warm sector ahead of the front to the north that will begin to stall. This should lead to milder overnight lows from near 70 or the lower 70s on Thursday night. .LONG TERM...(Friday through Wednesday) Issued at 255 PM EDT WED JUL 19 2017 We will remain under the influence of mid/upper level ridge through Saturday which means more of the same with heat and humidity staying around. A stray afternoon shower or storm is possible, but coverage will likely remain at or under 5 percent areawide. Better rain chances look to return on Sunday as a weak cold front inches southward across the area during the day. Still some question as to the aerial extent of the showers and storms as forcing will remain weak. Shortwave trough will then swing east across the great lakes early next week, but the better forcing with that trough will remain to our north. However, it could help to refocus convection along the slowly moving front as it slow pushes southward. Thus, it looks like rain chances will continue through Monday. Tuesday and Wednesday will see a return to slightly cooler weather behind the exiting front. However, depending on where the front dissolves, some moisture could linger to provide a lingering shower into the midweek period, especially in the south or southeast. Still lots of uncertainty on this potential. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) ISSUED AT 755 PM EDT WED JUL 19 2017 Surface high pressure and an upper level ridge building into the area will continue the rather stagnant weather pattern, with VFR conditions and light winds prevailing through the period. Mainly just diurnally driven cu is expected. Fog will develop in the river valleys once again late tonight and could affect SME or other sites if the conditions are just right, but more likely the TAF sites will all stay unrestricted owing to another dry day, though, river valley locations will likely experience MVFR or IFR reductions. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...JP LONG TERM...KAS AVIATION...JP/GREIF

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