Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 301810 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 210 PM EDT Fri Sep 30 2016 .UPDATE... Issued at 145 PM EDT FRI SEP 30 2016 A quick update to the public grids to fine tune sky cover and the T/Td grids per the latest obs and trends. These have been sent to the NDFD and web servers. UPDATE Issued at 1135 AM EDT FRI SEP 30 2016 14z sfc analysis shows the reflection of the stacked low just to the west and north of eastern Kentucky. This slow moving system is responsible for the clouds today along with the some sprinkles for the majority of the CWA and better shower chances in our western and eastern fringes. Just to the north of the forecast area thunderstorms will be possible with the stronger ones likely contained to places closer to the Ohio River. Areas of dense fog, mainly affecting the ridges, will continue to break up over the next hour or so. However, the fog and clouds have managed to slow the diurnal rise through eastern Kentucky area with readings not far from the low to mid 50s. Once the low clouds and fog lift temperatures should be able to rebound toward forecast highs this afternoon. Meanwhile, dewpoints are in the low to mid 50s across the area with light and variable winds. Have updated the Sky, PoPs, and Wx grids along with T and Td ones for the latest obs and trends. These have been sent to the NDFD and web servers. An updated ZFP was also sent - mainly to remove the fog wording. UPDATE Issued at 750 AM EDT FRI SEP 30 2016 Patchy dense fog continues across portions of eastern Kentucky with low stratus plaguing the region. Will see this fog mix out and stratus begin to lift with sunrise and subsequent turbulent mixing. && .SHORT TERM...(Today through Saturday) Issued at 357 AM EDT FRI SEP 30 2016 The well advertised upper low continues to spin over Lexington this morning, bringing isolated shower activity to far eastern Kentucky toward the Ohio Valley. Dry slotting has wrapped into much of the rest of eastern Kentucky on the northwestern flank of a surface low positioned across western North Carolina. Will continue to see the main precipitation shield move northward through the day today as the upper low slowly wobbles toward the Ohio River, thus keeping much of eastern Kentucky dry. For those areas in the Bluegrass region and near the West Virginia border who do see rain today, capping aloft should negate any chances for thunder with cloud tops struggling to punch above 10k feet. Nonetheless, will still hang on to a good deal of cloud cover through the day under the presence of cyclonic flow. A meager intrusion of warmer air aloft as the low meanders northwestward will help warm temperatures a few degrees from Thursday`s readings, with highs topping out in the mid-upper 60s. The Bluegrass region through portions of the Interstate 75 corridor will see a slight bump in precipitation chances this evening into tonight as an upper impulse looks to round the southern periphery of the parent upper low. This will help to reintroduce cloud cover from west to east as warm air advection ensues aloft. Overnight lows still look to drop into the mid-upper 40s in valleys and low 50s on ridges as this warmer air will be confined to above the nocturnal boundary layer. Will begin to tap into some of this warmer air aloft Saturday morning as turbulent mixing occurs with deep layer southwest flow remaining in place. This will send temperatures back to near normal values, with highs in the upper 60s to mid 70s. Shower chances will be greatest in the Bluegrass region nearer the best pool of moisture and forcing for ascent. Will again see decent low level lapse rates, but quicker warming aloft near the 700 mb level will promote strong enough capping again to keep any mention of thunder out of the forecast. .LONG TERM...(Saturday night through Thursday) Issued at 415 AM EDT FRI SEP 30 2016 The strong closed low that has been rotating over top of KY during the short term will finally begin to shift to the NE, reaching northern IN and OH by 0z Sunday. The low will become less wrapped up as it continues into the lower Great Lakes by 0z Monday, allowing weakening gradients of isobars aloft. Upper level ridging will begin working in to start off the workweek and should remain in place through midweek. Meanwhile, a strong upper level low in place across northern CA and Washington Monday will continue its path westward, with deep troughing resulting across much of the western conus. The ECMWF and GFS agree quite well on the general pattern, however are struggling just a bit with placement and strength through Wednesday. However, by Thursday both models come back into better agreement as the low continues to move northeast and into MN/ND/south-central Canadian border. The associated trough is expected to start pushing into Kentucky during the day Thursday and continue through the end of the forecast period. Also during this time period, models are continuing to come into better agreement about the tropical system in the Atlantic approaching the southeast coastal states and then riding up along the east coast by next weekend. Overall, at this point, it does not look to affect our weather here in KY during the forecast period. With the exiting upper level wave in place, the associated surface low will also begin exiting to the north. This will leave high pressure in place across the region with winds shifting from SW to N from 0z Sunday through 0z Monday. Some slight chance rain showers will still be possible to start the period before the system fully exits far enough north. But by Sunday evening, high pressure will be fully in control with northerly winds preventing any further moisture from entering into the region. High pressure is expected to remain in place through at least mid week. By Thursday, a strong surface low pressure system, associated with the upper level closed low, will move across northern MN and toward Lake Superior, dragging with it a cold front. This cold front will extend from north to south across the entire conus, and is expected to reach the Mississippi River Valley just after 12Z Thursday. Winds ahead of this system will begin shifting to the SE and then eventually to the S across our CWA during the day Thursday. This will begin pulling moisture into the region which could result in precip chances ahead of the approaching front. There is quite a bit of disagreement among the GFS and ECMWF models however, as the GFS keeps much drier air across the region during this time, preventing any precip from reaching the CWA. Meanwhile the ECMWF shows more moisture advection and a defined swath of precip through the Ohio River Valley and points southward. Given the uncertainty and the fact it is so late in the forecast period, stuck with only slight chances of precip at this time, undercutting the model blend a bit. Temperatures will start off near seasonable normals for Sunday and Monday. However, airmass modification under mostly sunny skies will help temperatures to increase a few degrees for Tuesday afternoon. Then WAA will take hold for the remainder of the forecast period ahead of the approaching system, with highs reaching the upper 70s and low 80s. Overnight lows should remain in the low to mid 50s generally throughout the period. && .AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon) ISSUED AT 210 PM EDT FRI SEP 30 2016 The lower cigs and last of the fog are clearing out of the TAF sites ATTM. Expect most locations will go VFR for a time into the early evening hours. However, we will see a round of shower activity move toward eastern Kentucky from the west this evening into tonight, but too much uncertainty remains in timing/spatial extent of this activity to warrant mention for the TAFs at this time. Cloud cover will remain variable through the forecast period with some lowering of cigs anticipated overnight, but still plenty of questions concerning the timing and occurrences of sub- VFR conditions. Fog, locally dense, looks to be a good bet in valleys tonight, but TAF sites will likely be limited to mainly MVFR vis restrictions, at worst, through 13z Saturday. Following this, anticipate improving conditions into Saturday afternoon with mostly VFR cig and vis values. Winds will remain light and variable through the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...GUSEMAN LONG TERM...JMW AVIATION...GREIF is the U.S. government's official web portal to all federal, state and local government web resources and services.