Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 011810 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 210 PM EDT Sat Oct 1 2016 .UPDATE...
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Issued at 145 PM EDT SAT OCT 1 2016 Did a quick update to fine tune the PoPs/Sprinkles through the rest of the afternoon. Also adjusted the T/Td grids per the latest obs and trends. UPDATE Issued at 1105 AM EDT SAT OCT 1 2016 14z sfc analysis shows that the center of low pressure has backed off to the northwest of the area, though relative low pressure remains over eastern Kentucky. This, and the upper low not far away, will continue a threat of light pcpn through the area today, but mainly for the Bluegrass region of Kentucky per the latest HRRR and NAM12 model guidance. The morning fog has cleared out so have removed that from the Wx grids and zones. Temperatures currently in the upper 50s to low 60s will be capped today by the clouds and sprinkles/showers. Dewpoints are generally in the low to mid 50s through the area with light and variable winds. This update included the latest CONSShort and ShortBlend guidance as well as the current obs and trends. These have been sent to the NDFD and web servers along with an updated set of zones. UPDATE Issued at 744 AM EDT SAT OCT 1 2016 Light showers/virga continue to develop across central Kentucky, but tend to be diminishing in intensity as they move into eastern Kentucky when farther displaced from forcing aloft. Still possible to see some of these across the Bluegrass region through the Interstate 75 corridor later today with diurnal heating.
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&& .SHORT TERM...(Today through Sunday) Issued at 346 AM EDT SAT OCT 1 2016 Upper low continues to slowly propagate north, now located just about directly over Cincinnati. This will keep isolated shower chances confined to the Bluegrass region down toward Lake Cumberland as upper forcing continues to depart off toward the lower Great Lakes today. Thunder chances still looking anemic with surface-based instability of perhaps a couple hundred J/kg complete with a stout temperature inversion near 700 mb. Increasing heights/thicknesses and warmer air advecting in on southwesterly flow will be somewhat offset by increasing cloud cover rotating into the region this morning and afternoon, keeping high temperatures in the mid 60s to low 70s. Weak surface ridging will build north tonight across southeastern Kentucky, allowing for another appreciable ridge/valley split as valley temperatures dip into the upper 40s with ridgetops remaining in the low-mid 50s. Shower chances will continue as energy skirts around the southern flank of the upper low riding through the southern Great Lakes. Valley fog will also be in the offing, especially across southeastern Kentucky where quicker clearing will take place. Sunday will offer up one final day of isolated showers, mainly north of Hal Rogers Parkway/Highway 80 in closer vicinity to any impulses which may clip eastern Kentucky. Cloud cover will slowly diminish from south to north through the day with warmer air once again kicking in aloft, allowing for high temperatures to reach normal values in the low-mid 70s. .LONG TERM...(Sunday night through Friday) Issued at 404 AM EDT SAT OCT 1 2016 Strong upper level low will continue to exit to the northeast during the extended portion of the forecast. This will leave general ridging across the Ohio River Valley, with surface high pressure expected to be in control for Kentucky and points northward from Monday through midweek. Winds will shift from a northerly direction to more southerly flow by Tuesday as we find ourselves on the southwest flank of the center of high pressure. This will allow for better WAA and temperature modification. While highs on Monday will stay with in the mid 70s, temperatures by Tuesday will increase to the upper 70s to around 80 degrees, with a slight uptick in humidity expected as well. Given the strong southerly pull generated from the soundings, in addition to good mixing this day, went ahead and nudged temperatures up a degree or two higher in some locations compared to the Superblend. Similar conditions will be in place on Wednesday as well with southerly flow still in place. Meanwhile, a strong upper level low, which will be located across the far western conus during the day Monday, will continue on a northeast track, reaching the Canada/North Dakota border by 0Z Wednesday. This will result in deep upper level troughing across much of the western and central conus, and decreasing heights across the Ohio River Valley. The closed low will lose some momentum and strength, but should continue to push northeastward through the rest of the work week, with the axis of the trough moving across Kentucky Thursday night into Friday (given some slight model discrepancies this far out in the forecast). At the surface, a low pressure system will follow in the tracks of the upper level low. It should lag slightly behind the upper level feature, moving into the northern Dakotas/Canadian border throughout the day Wednesday. The cold front produced from this system will extend southward the length of the conus, and should be located across the central plains and into Texas by Wednesday afternoon. This will be yet another contributor to the increasing southerly flow across the Ohio River Valley as this frontal zone approaches. The cold front should arrive and traverse the state sometime during the day Friday (once again this differs slightly given the lack of forecast agreement this far out). However, continuing to note some large discrepancies in the extent of precipitation associated with this frontal passage. As the low continues to pull north while the front pushes eastward, we stray farther and farther away from the best forcing. GFS run 24 hours ago showed no precip across the region as the front passed. However latest 00Z run shows a skinny but defined line along the frontal axis traversing western KY during the day Friday, but still loses coverage as it makes it into eastern KY Friday evening/night. Meanwhile, the ECWMF is much faster and continues to bring a line of precipitation across the entire state Thursday night through Friday morning, exiting east of the state by 18z Friday. Which model is right is yet to be discovered, however given the strong uncertainty, did not feel confident enough to lean towards one or the other. Kept with the blend, which resulted in slight chance pops closer to the ECMWF timeline. Given the weakening boundary and the lack of any instability in the forecast soundings, chose to remove thunder wording with the precipitation chances. Temperatures will be on a decline after the frontal passage, with mid 70s expected for highs on Friday, but only upper 60s on Saturday. During the extended portion of the forecast, we also continue to track Hurricane Matthew as it approaches the southeast Atlantic Coast. The GFS is much more progressive in its movement toward the conus, showing Matthew reaching eastern FL by Thursday and then riding northward along the coastline through Saturday, before merging into the upper level trough system Sunday. The ECMWF is a bit slower and keeps the system well off the Atlantic coast. the ECMWF actually seems a bit more realistic in its timing/velocity of movement northward through the weekend. But once again, given the lack of agreement this far out in the forecast, it is yet to be seen which solution will be closer to the truth. Either way, this system and its influence on the weather, should remain east of the state during the extended portion of the forecast. && .AVIATION...
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(For the 18Z TAFS through 18Z Sunday afternoon) ISSUED AT 210 PM EDT SAT OCT 1 2016 The upper level low continues to meander across the Ohio Valley. This will lead to bands of clouds through the period and the threat of isolated showers/sprinkles, although the more substantive of these should remain west and north of all TAF sites. VFR to high MVFR conditions will be the rule through the afternoon with southwest winds of to 5-10 knots. Winds will diminish this evening as low stratus potentially develops near the Bluegrass region and down towards Lake Cumberland. With the main concentration of this and any visibility reductions again likely centered north and west of all TAF sites so left mention out for now, but did allow for some MVFR vis for a time at SME/LOZ and SYM. VFR conditions should return by mid morning on Sunday with light and variable winds.
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&& .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.