Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 080600 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 100 AM EST Thu Dec 8 2016 .UPDATE...
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Issued at 100 AM EST THU DEC 8 2016 The forecast remains on track. Did freshen up the hourly temperatures and dew points, as temperatures have warmed up in the eastern valleys, where decoupling had taken place earlier. There are some weaker returns starting to show up on radar; however, there are still no reports of flurries thus far. Will continue to leave the mention in for now. UPDATE Issued at 912 PM EST WED DEC 7 2016 High and mid level clouds moving across the area so far have been too sparse to keep the southeastern Valley locations from decoupling and dropping to around 30 degrees. The top of Black Mtn around 4000 feet MSL has experienced an increase in dewpoints from the single digits above zero to around 20 during the past hour, however, model data and 0Z ILN and BNA RAOB suggests there is still a dry layer between that level and about 7 to 10kft. Models continue to suggest some moistening up of this dry layer as a shortwave approaches overnight, possibly enough to support a few flurries prior to dawn or around dawn falling from this mid deck or high low cloud deck. Upstream over parts of central MO a few flurry or very light snow observations have been noted over the past hour. HRRR and short term models generally keep any very light activity south of the I 64 or the Mtn Parkway and have it diminishing as moisture again 850 to 700 mb moisture decreases after dawn on Thursday. Hourly grids have been freshened up based on recent observations and short term model trends. UPDATE Issued at 730 PM EST WED DEC 7 2016 Some mid and high clouds continue to drift overhead with light generally northwest winds across the area as sfc high pressure begins to build into the region. At upper levels, a closed low was located over Ontario and the Northern Great Lakes region with a couple of shortwaves in west to southwest flow approaching the Lower OH Valley region. As the strongest of these shortwaves nears, models do have an increase in moisture near and below the dendritic growth zone and some omega in that layer later tonight into early on Thursday although the air from about 850 mb to the sfc is progged to remain rather dry. This scenario will be favorable for lowering of the mid clouds toward the 5kft mark at least briefly around sunrise and perhaps a few flurries. This is in line with the previous forecast. Hourly grids have been freshened up based on recent observations and trends with little change overall being necessary at this time.
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&& .SHORT TERM...(This evening through Thursday night) Issued at 245 PM EST WED DEC 7 2016 Upper low north of Lake Superior will continue to move east across Ontario, with trailing upper trough axis over the plains shifting east. At the surface, cold high pressure will continue to nose east into the Ohio Valley. The upper troughing and surface ridging results in colder air working its way into KY, with lows tonight mostly in the upper 20s and highs on Thursday from the mid 30s to around 40, about 10 degrees cooler than today. Even with the trough shifting east, and the surge of colder air, there will be very little moisture available. The outside chance for a few flurries remains in the forecast for late tonight and early Thursday. Thursday night will be even colder than tonight, with lows in the upper teens to lower 20s. Some clouds will affect the northeastern part of the forecast area as a short wave trough swings by to our northeast. The clouds are not expected until late in the night, so temperatures should still fall off quickly in the northeast Thursday evening. If the clouds move in earlier than expected overnight lows would be warmer than current forecast in the northeast. There is still an outside chance for a few flurries in the northeastern part of the forecast area late Thursday night. .LONG TERM...(Friday through Wednesday) Issued at 318 PM EST WED DEC 7 2016 Models struggle right out the gate trying to capture strength and timing of progressive features in a broad mean trough, or nearly zonal flow pattern across the CONUS. First main shortwave disturbance to deal with will track quickly out of the Pacific NW and through the Plains, bearing down on the Ohio Valley region by sometime Sunday, or possibly Sunday night into Monday. The 12Z ECMWF is roughly 18 to 24 hours slower than the 12Z GFS with this first system. The 12Z Canadian keeps the middle ground, showing similar timing to the ECMWF while at the same time finding a way to support the GFS by picking up on some energy into the area a bit earlier on Sunday proper. The second main shortwave system to affect our area, similar to the first with respect to its track will drop into the region at the end of the extended window. The ECMWF is considerably weaker with this shortwave than the GFS but is similar in timing. For sensible weather, temperatures remain seasonably cold to below normal through the entire period. Models are still having difficulty with the details of Sunday`s system and forecaster confidence is low. This system appears to be trending slower overall. As such that may provide enough time for the column to warm so that the bulk of precipitation falls as rain. However, we still can not rule out a little wintry mix at the onset of precipitation. For our second system at the very end of the extended window, there is reasonable agreement that this next system will be colder. Still way too far out to say for sure, but this system may present our first real chance at some accumulating snowfall. Time will tell. && .AVIATION...
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(For the 06Z TAFS through 06Z Thursday night) ISSUED AT 100 AM EST THU DEC 8 2016 VFR conditions look to hold on through the period. Clouds will lower to the 6-8k feet agl range through 15z, before thinning out through the rest of the day. Northwest winds of around 5 kts will become west to northwest at around 10 kts by noon, with gusts of around 15 kts at times. Winds will then diminish to around 5 kts by dusk.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GEOGERIAN SHORT TERM...SBH LONG TERM...RAY AVIATION...GEOGERIAN

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