Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 241539 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1139 AM EDT Fri Mar 24 2017 .UPDATE...
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Issued at 1139 AM EDT FRI MAR 24 2017 Satellite and surface observations show quite variable sky conditions across the area late this morning with some spots broken to overcast and others clear. The overall trend though has been for a little less cloud than earlier forecast, though clouds are expected to increase later this afternoon. With more sunshine temperatures have surged upward in some areas with it already 71 at 1135 EDT here at the NWS office in Jackson. With all this in mind have made forecast updates based on latest observational trends, with the main changes to decrease clouds and increase afternoon maximum temperatures. Pushed maximums into the mid 70s in the areas experiencing more sun, but if the clouds do not become more widespread this afternoon, this may not even be high enough. UPDATE Issued at 645 AM EDT FRI MAR 24 2017 IR SAT this morning showing an area of lower clouds likely due to isentropic lift continuing to expend north out of Middle Tennessee. While initial expansion into the greater Tennessee Valley was blocked by the Cumberland Plateau the next surge will not be blocked as much. Therefore, did opt to increase cloud cover particularly across the western portion of the CWA. Temperatures have been a bit of a challenge, and continue to be with cooler spots being the deeper valleys that have been able to decouple. Updates sent to NDFD and Web.
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&& .SHORT TERM...(Today through Saturday) Issued at 357 AM EDT FRI MAR 24 2017 Morning surface analysis indicates surface high pressure centered off the coast of VA/NC. A weak warm front is progressing NE and while there is a slight kink in isobars the front is tough to define. Winds have already switched to a more southeast to south direction around the surface high this morning. Therefore temperatures are mild at the more mixed sites. The exception to the rule are the deeper valley locales where decoupling is leading to lower 40s. First forecast challenge of the day will be cloud cover. We have seen clouds streaming out of the TN Valley and southward likely associated with isentropic ascent ahead of the approaching system in the Front Range. Most of the model soundings indicate some lower clouds are not out of the question as we move through the day. Right now keeping the better coverage across the western and northern portions of the CWA and seems reasonable right now based on the SAT trends. The next challenge will be how much moisture recovery do we get particularly in the far east toward the Big Sandy. There will be decent afternoon mixing and given the strengthening LLJ would lead to 15 to 20 mph gusts particularly in the Lake Cumberland and Bluegrass. Overall think recovery should be enough to lead to higher RH than yesterday, but even so far east could be looking at lower 30 RH values. All of this will play a crucial role in temperatures and did lean up a bit given SUPERBLEND was higher than previous forecast. Tonight the cloud challenge will continue as the lower deck is expected to dissipate. However, we will keep a higher deck at minimum, but the deeper valleys could see a decent split once again. Think this will be more confined to the far eastern valleys given the better LLJ to the west. Moving into Saturday the clouds will continue to be on the increase through the day and more a top down saturation seen in the model sounding data. The one caveat to the increased cloud cover will be the backed flow by Saturday afternoon which could promote downslope flow in the far east. That said, did opt to keep lesser coverage as you move east. Also think most will remain dry on Saturday given upper level trough will negatively tilt across the Midwest and slow surface features down. However, did opt to bring slight POPs in the Lake Cumberland region by late Saturday given some CAMs support the possibility. .LONG TERM...(Saturday night through Thursday) Issued at 357 AM EDT FRI MAR 24 2017 A stacked low pressure system over MO at the start of the period will be weakening as it slowly moves northeast, reaching the Great Lakes Sunday night. A stream of moisture off the Gulf of Mexico coupled with the approaching upper level system will bring showers to most places Saturday night and Sunday. Weak instability should also be present, and justifies including a mention of thunderstorms. As the disintegrating system passes to our north, its cold front is expected to dissolve and leave us without a change in air mass. Models show another weakening low pressure system coming out of the southern plains early in the work week and moving up the Ohio Valley. This time around, cold frontal passage is expected to occur, accompanied by an increase in the POP for Monday night into Tuesday. The GFS and ECMWF are in a little bit better agreement now, as compared to 24 hours ago, and are both showing the front settling far enough to our south to allow a period of mainly dry weather from Tuesday night into Thursday. Yet another in a parade of systems is expected to track from the southern plains to the Ohio Valley at the end of the week. While precip from this system can`t be ruled out on Thursday, it`s more likely to hold off just a bit longer. && .AVIATION...(For the 12Z TAFS through 12Z Saturday morning) ISSUED AT 652 AM EDT FRI MAR 24 2017 IR SAT coupled with obs are showing an area of lower clouds moving northeast out of Middle Tennessee. However, this deck is expected to remain VFR at or around 5 KFT through the day. Then by this evening expect this lower deck to dissipate and we will be left with high clouds. Low level jet will continue to increase leading to gustier winds in the Lake Cumberland and Bluegrass around 15 to 20 knots at times. Overall winds will be out of the southwest through the day, but are expected to back some out of the south and southeast tonight as they decrease. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...SBH SHORT TERM...DJ LONG TERM...HAL AVIATION...DJ is the U.S. government's official web portal to all federal, state and local government web resources and services.