Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 170659 AAC AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 159 AM EST Wed Jan 17 2018 .UPDATE...
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Issued at 155 AM EST WED JAN 17 2018 Hourly grids were freshened up based on recent observations and radar trends. This led to some downward adjustments in min T and hourly temperatures for a few locations. GOES 16 night time cloud microphysics indicates a narrow area of clearing running from Elliott County to Wayne County moving to the southeast. Low clouds are occurring outside of this clear slot. Radar appears to indicate some flurries or very light snow showers north of JKL now in addition to the topographically driven bands in the southeast. Flurries or very lights snow showers are anticipated where low clouds exist. UPDATE Issued at 1045 PM EST TUE JAN 16 2018 The latest scans of the WSR-88D radar show much of the moderate to at times heavy snowfall has exited to our east. The 850mb front associated with that is not on the other side of the Appalachians. Therefore, did opt to cancel the winter weather advisory given the bulk of the accumulating snow has exited. The clouds have now become the biggest challenge with some spots seeing clear skies. This has really tanked the temperatures in a few spots, with EKQ seeing -11 and Richmond mesonet seeing -10. There is an area of lower clouds drifting slowly southeast that has already moved into portions of Fleming County. These clouds will slow the temperature drops down in those shelter valley locations. The latest thinking has been added to the grids and will send to NDFD shortly. UPDATE Issued at 754 PM EST TUE JAN 16 2018 The latest WSR-88D scans show the main area of light to moderate snow continues to exit southeast this evening. We did keep Winter Weather Advisory going a little longer at some of the far southeast counties given the radar trends. Otherwise flurries and perhaps a few snow showers were seen in the wake of the main band of precip associated with the 850mb front. The latest GOES-16 water vapor imagery shows a positively tilted trough still extends from the lower Great Lakes into the Central Plains this evening. This trough will slowly progress eastward tonight and some clouds are coming into portions of central and western Kentucky as it moves east. The cloud cover forecast has been tricky this evening, with snow showers and the main cloud deck mentioned above. In contrast, some areas have seen clearing skies and temperatures have consequently plummeted into the single digits or lower in those spots. Overall think the temperatures will level off some eventually, but all spots will see at least single digits overnight. Given this and the potential for snow showers did opt to hoist a SPS for the area to handle these issues. In term of hourly temperatures tried to use obs and slowly blend into the current trend. These will likely have to be further fine tuned in subsequent updates. Grids have been updated with thinking and sent to NDFD.
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&& .SHORT TERM...(This evening through Wednesday night) Issued at 355 PM EST TUE JAN 16 2018 A positively tilted trough is currently aligned from eastern Canada down to northern Mexico. This feature is slowly working its way east. A lingering upper level jet, lending sustained deeper lift, has brought widespread moderate to heavy snow to eastern Kentucky through the day. So far, totals have ranged from about an inch across our far southeast, with 2 to 5 inches elsewhere. The back edge of the snow is moving through the I-64 corridor, and this will gradually work off to the southeast through this evening. Some partial clearing may work in temporarily tonight, before the trough axis moves in, allowing for a return of clouds and a few snow showers. Temperatures will drop into the single digits for lows. On Wednesday, isolated snow showers and flurries will diminish generally from west to east through the day, with highs only at around 20. The center of a surface high pressure will build in closer to us Wednesday night, especially in the southern portion of our area. This will allow for a cold night, with temperatures likely dropping down to near zero or lower in places, given the lingering snow pack and clearing skies. .LONG TERM...(Thursday through Tuesday) Issued at 355 PM EST TUE JAN 16 2018 The overall pattern for the long term shows a distinct separation between the northern stream over the Great Lakes and the southern stream over the Mississippi Valley. This will lead to more zonal flow evolving to ridging for eastern KY through the weekend before a disturbance moves through early next week. The models seem to be in decently good agreement with the overall pattern, but differ in timing and intensity of the cold front next Monday. The ECMWF shows a slightly faster and more intense band of precip as compared with the GFS. Therefore, the uncertainty for precip totals and timing into the CWA is high. Looking closer to the surface, high pressure will set up to the SW of eastern KY for the beginning of the extended period. The high will gradually shift to the east and be to our SE by the weekend. This will bring in SW to S winds, and this combined with minimal cloud cover, will increase the potential for ridge/valley temperature splits Thursday and Friday night. This also means WAA into the region over the weekend leading to warmer high temps in the 50s and 60s. With such high temps, the precip brought in by the cold front Monday will likely be rain showers. The passage of the cold front will usher in cooler temps, with precip possibly ending as a mix of rain/snow on the higher elevations. && .AVIATION...
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(For the 06Z TAFS through 06Z Wednesday night) ISSUED AT 135 AM EST WED JAN 17 2018 A narrow band of clearing is moving southeast across the area with more low clouds upstream of the area in the MVFR range in general. At this time, MVFR is reported across the north and south with a few of the TAF sites in the clear slot for up to 2 or 3 more hours. However, low clouds and MVFR should return with some light snow showers and flurries. These areas of MVFR should persist through the 15Z to 21Z period before drier air moves in and lapse rates become not as steep. Winds will remain 10kt or less out of the west and northwest through the period.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...GEOGERIAN LONG TERM...CGAL AVIATION...JP

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