Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 210557 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1257 AM EST Sat Jan 21 2017 .UPDATE...
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Issued at 1257 AM EST SAT JAN 21 2017 All is well with the forecast so far tonight. Middle and high level cloud cover will continue to stream over the area ahead of an approaching weather system. Temperatures and winds were still on track based on the latest obs. The most recent obs were ingested into the hourly forecast grids to establish new trends. UPDATE Issued at 655 PM EST FRI JAN 20 2017 Temperatures will fall into the 50s this evening as mid-high clouds move into eastern Kentucky. Although on a decreasing trend, low clouds will be tough to shake in a warm sector airmass characterized by Gulf moisture advecting northeastward.
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&& .SHORT TERM...(This evening through Saturday night) Issued at 401 PM EST FRI JAN 20 2017 A very un-January like warm short term period is in store-- benign to start, but ending with showers and possible thunderstorms. Transitory upper level ridging will pass over the area tonight, while a large longwave trough is positioned over the east Pacific and western 2/3 of the CONUS. A potent shortwave trough moving through the large scale system will come onshore on the west coast tonight, and form a closed low by the time it reaches the lower Mississippi Valley by Sunday morning. A large and deep surface low will also develop coincident with the upper low. It will tap into Gulf of Mexico moisture and a large swath of warm/moist advection will develop east of the system. Convection is expected in the deep south and should intercept some of the flow. The question is to what extent. With such a large and deep synoptic scale system at all levels, it would seem that there would be at least enough moisture for showers further north. The ECMWF is the most restrictive with the northward extent of precip, and the GFS the most expansive. Both MET and MAV MOS POPs were generally high end categorical for the JKL forecast area. Have gone between the MOS POPs and the lower Superblend POPs, using 70% in the northeast part of the forecast area Saturday night to 80% in the south. Weak instability is also present, but lapse rate are not impressive. Have included a slight chance of thunder on Saturday night. .LONG TERM...(Sunday through Friday) Issued at 347 PM EST FRI JAN 20 2017 The extended forecast period begins on Sunday with a continued active pattern in place across the CONUS. On Sunday, a strong upper low crosses into the lower MS valley as it travels along the Gulf Coast before lifting NE into the Appalachians. Current track takes the heaviest precip along the spine of the Appalachians and into the headwaters of eastern Kentucky. Models have been pretty consistent on this track for the past few runs. In fact, as this feature develops and lifts north, instability will still be present continuing to support convection, mainly slight chance, through the day on Sunday. As this feature exits Tuesday morning and colder air filters in behind it, some of the exiting showers will change to a rain and snow mix Tuesday morning on top of the higher elevations but with very little accumulation expected. Heading into midweek next week, the next wave tracks across the central Plains and into the Midwest bringing a round of light showers into eastern Kentucky. Both the GFS and Euro agree with a drying trend to this feature as QPF amounts will likely be less than a tenth of rainfall for Wednesday and Wednesday night. However, following this feature will be a more seasonal airmass filtering into the area by Thursday and Friday. This will lead to a return of northwest flow and a period of snow showers possible Thursday afternoon and Thursday night. Overall, a trend to more normal temperatures is expected towards the end of next week if not cooler than normal. && .AVIATION...
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(For the 06Z TAFS through 06Z Saturday night) ISSUED AT 1257 AM EST SAT JAN 21 2017 VFR conditions are expected to prevail during most of the upcoming TAF period. Middle and high level cloud cover will continue to overspread the area tonight and most of Saturday, as a weather system approaches from the southwest. Visibilities should also remain largely unhindered as winds back south/southeasterly and the mid and high clouds keep radiational cooling at bay. Winds look to remain near or below 5 knots as clouds increase and lower Saturday ahead of the next round of rainfall, likely arriving later Saturday into Sunday.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AR SHORT TERM...HAL LONG TERM...SHALLENBERGER AVIATION...AR

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