Area Forecast Discussion
Issued by NWS Jackson, KY

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801 FXUS63 KJKL 182037 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 337 PM EST Wed Jan 18 2017 .UPDATE... Issued at 1259 PM EST WED JAN 18 2017 Clearing has occurred over parts of Eastern TN and Southwest VA and some of this has spread into some of the higher terrain near the VA and TN borders over much of Harlan County and the Log Mtns in Bell Co. Meanwhile breaks in the low clouds are occurring across other portions of the Cumberland Valley Region and the Lake Cumberland Region as sfc and upper ridging continue to build in. However, deep enough moisture and an uslope low level component is still leading to a few patches of drizzle east of JKL that are diminishing. A gradual mixing out of low clouds should continue throughout the afternoon and into the evening. The clouds should linger longest in the central and norther part of the area where temperatures may average near normal for highs, but locations in the central to south that receive sun should climb above average. UPDATE Issued at 1005 AM EST WED JAN 18 2017 Low level moisture remains across the region with weak upslope flow. Radar indicates drizzle still lingering across the northern and eastern counties. This moisture should become more shallow by midday into early afternoon as sfc and upper level ridging build into the area. However, the it appears that the drizzle should linger a bit longer than the previous forecast and has been extended in the weather grids by about 2 hours. Otherwise, no changes were needed at this time. UPDATE Issued at 620 AM EST WED JAN 18 2017 Did a quick update to the grids to account for the latest obs and trends - keeping the patchy drizzle and sprinkles in there for a couple of more hours. These have been sent to the NDFD and web servers. && .SHORT TERM...
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(Today through Thursday) Issued at 355 AM EST WED JAN 18 2017 08z sfc analysis shows a cold front departing to the east while high pressure builds in from the west. However, plenty of low level moisture remains in place and, along with the passage of a compact upper trough to the northeast early this morning, this is keeping the cigs low and a potential for drizzle or sprinkles in the forecast through dawn. Temperatures remain mild overnight for this time of year with readings varying from the low 40s northwest to the lower 50s in the southeast. Dewpoints are not far off from the dry bulb temperatures - just a few degrees lower in most places. Meanwhile, winds are from the northwest to west at 5 to 10 mph with occasional gusts to 15 mph. Patchy fog also is found through the area early this morning. The models are in better agreement aloft than last night as they all depict a sharp trough - with minimal spread - diving into the Central Appalachians from the northwest early this morning. This is followed by a quick shot of ridging today and renewed deep layer southwest flow later tonight and Thursday in the face of a deep and broad closed low over the High Plains. In this flow, a lead batch of energy will lift into the Tennessee Valley early Thursday with more support and height falls arriving by evening. Given the better model agreement will favor a blend, though with a strong lean toward the HRRR in the near term. Sensible weather will feature patches of sprinkles and drizzle around this morning before a lull for drying sets up later today and tonight as high pressure passes quickly over the area. The next system then approaches from the southwest late tonight pressing into the Cumberland Valley on Thursday. All the while warm weather continues so that all pcpn will continue to be only in the form of rain across eastern Kentucky through the short term and well beyond. Again started with the CONSShort and ShortBlend for most elements through the short term portion of the forecast - making only minor adjustments to the low temps tonight. Also, adjusted PoPs to spread the next round of pcpn in a bit quicker and slightly more extensively on Thursday than suggested by the CONSShort. .LONG TERM...(Friday through Wednesday) Issued at 337 PM EST WED JAN 18 2017 The extended forecast period begins on Friday with an active and progressive pattern in place. A short wave will track northeast through the Midwest and Middle Atlantic states on Friday. The general progression of this feature seems to push through rather quickly and the Euro and GFS agree on this. Precip will be brief as it will exit the area by Friday night. In this active pattern and on the heels of Fridays system another wave develops in the lower MS River Valley and tracks northeast into the central Appalachians by Saturday afternoon bringing another shot of rainfall to the area. Isentropic ascent with this next feature will pose the possibility for thunder but being well capped at onset will hinder this possibility so will leave out of the forecast for now. The active pattern continues into the beginning of next week as a secondary upper low dives into the lower MS Valley and lifts northeast again through the area late Sunday and into Monday. This shot of rainfall will appear to be the most out of the series as the GFS and Euro agree with up to an additional 3 quarters of an inch QPF expected in far eastern Kentucky by Tuesday. Most of this rainfall appears to fall in the headwaters of Eastern Kentucky. Total rainfall for this period looks to be up to 2 inches over a 48 hour period. At this time, its nothing to be too concerned about with rainfall but will put a mention in the HWO. Through the extended forecast, the warm trend continues with temperatures in some days nearly 20 degrees above normal. So, will not expect any frozen precip through the extended.
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&& .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) ISSUED AT 105 PM EST WED JAN 18 2017 Low clouds leading to MVFR should gradually decrease through the first 9 to 11 hours of the period as surface and upper ridging build in. Meanwhile, clouds will begin to increase and lower ahead of a warm front beginning first in the southwest between 6Z and 9Z and then shifting to the northeast through the end of the period. However, VFR is expected with this through the end of the period. Light winds are expected through the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...GREIF LONG TERM...SHALLENBERGER AVIATION...JP

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