Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 301813 AAC AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 113 PM EST Wed Nov 30 2016 .UPDATE... Issued at 113 PM EST WED NOV 30 2016 Hourly grids have been freshened up based on recent observations and radar trends. We still expect some additional isolated to scattered showers to develop or linger behind the main band gradually shifting into WV and VA as the cold front now over Central KY nears and temperatures cool aloft. UPDATE Issued at 1007 AM EST WED NOV 30 2016 Hourly grids have been freshened up based on upstream radar trends as well as current observations and satellite data in combination with near term model trends. This led to lower pops over the next few hours in the Eastern Bluegrass counties and higher pops along the VA border. Showers should slowly taper off from west to east through early to mid afternoon. However, chances will remain this afternoon and into the evening as the cold front works into the area this afternoon and colder air moves in aloft increasing lapse rates. UPDATE Issued at 800 AM EST WED NOV 30 2016 Precip has tapered off in the far NW part of the forecast area a little faster than was originally forecast, and POPs have been lowered there. Also, lightning has diminished and shifted well southeast of KY, so have removed it from our forecast. && .SHORT TERM...(Today through Thursday) Issued at 424 AM EST WED NOV 30 2016 Showers are ongoing across the area early this morning, but lightning has been sparse, with most of it occurring to our south. There are some thunderstorms again making their way to our southern border, moving quickly northeast. The back edge of the precip was advancing southeast across central KY. This back edge will be about ready to move into the NW part of the JKL forecast area around 12z. Have used likely to categorical POP as 1st period starts, but the precip will taper off from NW to SE during the day. Have included a slight chance of thunder during the period of highest POP, timing its dissipation with the exiting of elevated instability in the models. The precip is due to an upper level impulse rotating around a large stacked low over the north central CONUS, and an associated surface cold front moving in from the west. Gulf of mexico moisture was quickly drawn northward ahead of the front. Much of the feed of warm/moist air appears to have been intercepted by the convection which developed to our south, which limited our thunderstorms further north. However, moisture still streamed north, especially in the mid/upper levels. This moisture and convection will leave today, but models show the potential for additional shower development as the upper level impulse and actual cold front progress through the area this afternoon. This will exit to the east during the late afternoon and early evening, and drier and much cooler air will begin to make its way in. The large parent storm system will slowly move eastward, reaching Quebec by late Thursday. Flow around it will keep cold air advection in place locally. Deep moisture associated with the system should stay to our north tonight and Thursday, with only stratocumulus expected for our area. .LONG TERM...(Thursday night through Tuesday) Issued at 424 AM EST WED NOV 30 2016 While forecast confidence remains high through Saturday, still a large amount of uncertainty from Sunday through the first half of next week. High pressure will bring dry weather from Thursday night through Saturday. The weather will remain on the cool side into Saturday with broad mid level troughing remaining over the region. By Sunday night, our next storm system taking shape upstream will start to move towards the region. Models seem in reasonable agreement on bringing some light precipitation into the area by daybreak Sunday. At this point, it doesn`t look like enough warm air will work back north, so we may see some light snow at the onset of the precipitation. After it seemed models might be converging on a solution for Sunday into early next week, they have again went opposite directions with the 00z runs. The ECMWF is back to a stronger low, tracking it virtually right across eastern Kentucky Sunday into Sunday night. GFS remains much weaker with the system as it has all along. While the GFS limits precipitation to mainly Sunday with precipitation totals under a quarter of an inch, the ECMWF solution brings 1 to 3 inches of rain across eastern Kentucky and has rain lingering into Monday (which the GFS is currently dry for Monday). The GFS is then quicker to bring another system back across the area by Tuesday, while the ECMWF is drier. Thus, with none of the dry and wet periods lining up in the models, going to have to carry climatological normal values for rain chances from Monday into the middle of next week. We certainly will be able to squeeze out a dry period somewhere in that time frame, but right now, difficult to discern where that will be. It does look like that after the snow chance early Sunday, all remaining precipitation will be rain into the middle of next week. One last interesting note, the models have been persistent on a surge of more arctic air for the end of next week with 850mb temperatures plummeting to -14C. This would certainly be the coldest air we have seen since last winter if it holds. Right now, snow chances look low despite the surge of arctic air. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) ISSUED AT 110 PM EST WED NOV 30 2016 The main band of rain continues to shift into WV and VA with isolated showers behind it. Initial CIGS varied widely, from IFR to VFR, with the worst conditions generally in the southern and southeast part of the area. Between 18Z and 0Z most locations should experience improvement to VFR. However, cigs and or vis may still drop to MVFR at times as additional isolated to scattered showers are expected through 3Z behind the main band. Low level moisture is projected to linger so some 5 KFT or lower VFR or MVFR CIGS are expected from then through the end of the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...HAL LONG TERM...KAS AVIATION...JP

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