Area Forecast Discussion
Issued by NWS Jackson, KY

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453 FXUS63 KJKL 151725 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 125 PM EDT Sun Oct 15 2017 .UPDATE... Issued at 1146 AM EDT SUN OCT 15 2017 A few isolated showers have developed ahead of the original leading line of showers, while the original line has diminished on the northern end. Main area of showers remains back across IN and western KY closer to the cold front. Currently no lightning is being detected with the convection, but a few lightning strikes remain possible. Have updated NDFD and associated products mainly to refine timing of showers and isolated thunderstorms. UPDATE Issued at 947 AM EDT SUN OCT 15 2017 Low clouds are moving quickly into the eastern part of the forecast area, and have updated NDFD to increase sky cover at a faster pace. Timing the line of showers currently moving across IN brings the first chance of rain to the northwest part of the forecast area around 1PM. This is a about an hour faster than the latest runs of the HRRR, but overall there is good agreement in timing based on short range guidance, extrapolation and current hourly NDFD. The leading edge of the showers have shown a decreasing intensity trend, and with more extensive low level cloud cover ahead of the convection limiting the chance for increasing low level stability it may be hard to generate convection that would produce thunder this afternoon. UPDATE Issued at 745 AM EDT SUN OCT 15 2017 Low clouds continue to expand to the west and south of the area early this morning as low level moisture increases in advance of an approaching cold front. Meanwhile, fog lingers in some valley locations, mainly in the Big Sandy Valley, but this should continue to dissipate over the next hour or two. Hourly sky, temperature and dewpoint grids have been updated accordingly. && .SHORT TERM...(Today through Monday) Issued at 358 AM EDT SUN OCT 15 2017 Early this morning, an upper level ridge was in place across the southeast Conus with a trough moving through the Central Conus and another ridge in place across the southwest Conus. At the surface, an area of low pressure was moving into the Great Lakes region with a cold front trailing south into the southern Plains. High pressure was centered to the east and northeast of the area and extended into the Southeastern Conus. Despite the increasing pressure gradient between the approaching front and high, several valley locations south of the Mountain Parkway corridor remain decoupled per observations with GOES 16 satellite imagery indicating generally less extensive valley fog compared to 24 hours ago. Models remain in good agreement with the timing of the cold front into the region today arriving during the afternoon as the surface low tracks by well to the north of the region in advance of the eastward moving upper trough. Low level moisture will increase this morning as the front approaches and winds should also increase in the morning as the pressure gradient tightens. Mixing prior to the arrival of the front during the morning could yield some wind gusts in the 20 to 30 mph range. A relatively narrow band of showers and perhaps some thunderstorms should accompany the front as it moves east. Instability is expected to be limited as the front passes, but have continued with a slight chance of thunderstorms. Some heating of the airmass should occur ahead of the front so thunderstorms cannot be ruled out, especially in the southeast half of the area per recent HRRR runs. High temperatures should be reached around the arrival time of the precipitation with a mixture of cold air advection and wetbulbing leading to falling temperatures by mid afternoon into the evening. As the front pushes southeast, the threat for showers will end from northwest to southeast during the evening. Models continue to have the highest qpf in the southeastern counties or in the area where convection could be a bit stronger due to potentially greater instability. High temperatures should be reached around the arrival time of the precipitation with a mixture of cold air advection and wetbulbing leading to falling temperatures by mid afternoon into the evening. Cold advection will continue on Sunday night with temperatures dropping into the 40s or noticeably colder than recent days. Behind the front on Monday, sfc high pressure will begin to build into the area from the west. Lingering low clouds should lift and decrease in coverage during the morning, eventually lifting into a cumulus field and mixing out through late afternoon. High temperatures will be considerably lower than recent days reaching near the 60 degree mark, or about 8 to 10 degrees below normal for mid October. .LONG TERM...(Monday night through Saturday) Issued at 235 AM EDT SUN OCT 15 2017 Models in good agreement on persistent upper level ridging to hold over the region through the remaining portion of the week and through next weekend. As the surface ridge slides east through the week, the boundary layer will warm allowing for a nice recovery in temperatures as we head through the middle to latter half of the week. We could be approaching some record highs by late in the week or next weekend. Continued to the trend of going on the high end of guidance with temperatures for highs and colder at night. This is in line with the very dry airmass over the region this week. We will also contend with some valley fog each morning through the week. Also, given the dry airmass, models are way too aggressive in moisture recovery through the week, and continued to go well under guidance for dewpoints through next Saturday. This puts afternoon RH`s between 20 and 30 percent. Fortunately for wildfire concerns, there should be almost no wind through the week. Cross over temperatures heading into Monday night look to be around 40, which is a tad high to support frost formation. Thus, looking more like we should see primarily fog. However, better mixing on Tuesday will bring the cross over temperatures down into the low to mid 30s, setting the stage for slightly better frost potential for Tuesday night, but confined to the coldest sheltered eastern valleys. For the most part, this does not look like a robust frost event for the area. && .AVIATION...
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(For the 18Z TAFS through 18Z Monday afternoon) ISSUED AT 125 PM EDT SUN OCT 15 2017 A broken cloud deck from 2500 to 3500 feet will remain across the area for the remainder of the afternoon. A cold front, which extends from southeast MI to western KY will advance southeast and move southeast of KY shortly after 00Z. A few isolated showers are possible through mid afternoon, then a narrow band of showers is expected to move across eastern KY in association with the cold front. Thunderstorm chances are decreasing but an isolated storm is still possible and will carry VCTS for a few hours at the TAF sites this afternoon. With the passage of the cold front a more solid deck of clouds will bring MVFR ceilings for the beginning of the overnight period. The clouds will scatter our late tonight or early Monday morning. Ahead of the cold front southwest to west winds will gust to 15 to 25 knots this afternoon, then turn to the northwest with the passage of the front late this afternoon and early evening.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...SBH SHORT TERM...JP LONG TERM...KAS AVIATION...SBH

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