Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 131056 AAC AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 656 AM EDT Fri Oct 13 2017 .UPDATE...
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Issued at 645 AM EDT FRI OCT 13 2017 Expanded the fog advisory to include the remainder of the area. Valleys across the remainder of the area experiencing dense fog in many locations per reports and what can be inferred from GOES imagery. UPDATE Issued at 503 AM EDT FRI OCT 13 2017 GOES nighttime cloud microphysics RGB and observations continue to to indicate that the dense fog is widespread in portions of the Cumberland Valley. A dense fog advisory has been issued for that area until 10 AM EDT.
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&& .SHORT TERM...
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(Today through Saturday) Issued at 410 AM EDT FRI OCT 13 2017 Early this morning, surface high pressure was centered to the northeast of the area though the ridge extended back into the Ohio Valley region. Meanwhile an upper level ridge was centered over the Lower MS Valley region and extended across the eastern Conus. Low level moisture remains below about 5000 feet despite the clearing that occurred on Thursday afternoon and evening. This has given way to what appears to be extensive valley fog on GOES 16 imagery such as the nighttime cloud microphysics RGB and GOES as it is likely rather16 10.3-3.9 fog product. Patchy stratus and stratocu is also present. The upper level ridge is expected to flatten a bit through the period and become aligned from GA/Carolinas across the southeast through the end of the short term period. At the same time, the surface high will shift to the east and lead to increasingly southerly flow today and on Saturday as a low pressure system begins to approach. The main forecast concern early this morning is the extent of mainly valley fog through mid morning as well as stratus. For now have continued with the SPS and highlighted the threat on social media though the threat will continue to be monitored for a dense fog advisory for portions of the area. The fog should gradually lift through the morning into at least some brief cumulus. With more sunshine compared to Thursday and the model consensus of temperatures reaching the 70s to around 80, a mild day is in store. Low level moisture should increase starting today with dewpoints climbing through the 50s. The depth of the low level moisture should increase tonight per both the NAM and GFS and more in the way of stratus and or stratocu formation is possible along with some valley fog as well. If the moisture were to deepen sufficiently, some drizzle could even fall from any potential stratus particularly in the southwest part of the area. At this point, drizzle was not included, but it is likely sky cover may need to be increased for Saturday night and drizzle potential will be monitored. The low clouds and status should gradually lift into a cumulus deck on Saturday. Saturday will again be mild with rather moist dewpoints for mid October. .LONG TERM...(Saturday night through Thursday) Issued at 325 AM EDT FRI OCT 13 2017 Clouds will be on the increase Saturday night ahead of an approaching cold front. The clouds and increasing gradient ahead of the front will keep fog from forming overnight. The cold front will slide southeast across eastern Kentucky during the day Sunday. Models continue to trend towards a faster frontal passage, and it now looks like the front will be through the area by early Sunday evening. With increasing confidence on rain chances with good GFS ensemble support, will go categorical with the rain chances on Sunday. Plan to maintain the slight chance of thunder as we can`t rule out some isolated storms. Should be a rather gusty day for eastern Kentucky with some wind gusts up to 15 or 20 mph. A few high gusts would be possible on ridgetops and in the Bluegrass region. Rain chances will diminish from northwest to southeast Sunday evening with drier and much cooler weather settling into the area to start the new work week. Highs on Monday will only reach into the low 60s. Strong upper level ridging will develop and maintain itself over the region through the remainder of the week. As the ridge axis slowly shifts east, heights will rebound allowing for a nice recovery in temperatures as we head through the week. The airmass will also feature very dry conditions. This will support undercutting guidance dewpoints by a good 5 to 10 degrees each afternoon, putting relative humidities down between 20 and 30 percent each afternoon. While the extended stretch of dry afternoons is expected, winds should be fairly light through the week, so wildfire concerns should remain somewhat low. We will see areas of dense valley fog each morning through the week. Some widely isolated instances of frost may be possible Tuesday and Wednesday morning, although conditions continue to favor more of a fog threat as cross over temperatures will remain somewhat elevated.
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&& .AVIATION...
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(For the 12Z TAFS through 12Z Friday night) ISSUED AT 700 AM EDT FRI OCT 13 2017 Areas of dense valley fog have developed overnight and has affected the TAF sites per obs and GOES 16 Nighttime Microphysics RGB. Initial IFR conditions, possibly below airport min, will improve through around 14Z to 15Z. A brief period of stratocu in the MVFR range is possible as the fog lifts before all locations improve to VFR. Valley fog could again form tonight, with MVFR status or stratocu possibly being more favored in the west as southerly flow lead to increasing low level moisture.
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&& .JKL WATCHES/WARNINGS/ADVISORIES...
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Dense Fog Advisory until 10 AM EDT this morning for KYZ044- 050>052-058>060-068-069-079-080-083>088-104-106>120.
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&& $$ UPDATE...JP SHORT TERM...JP LONG TERM...KAS AVIATION...JP

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