Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 240044 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 744 PM EST Thu Nov 23 2017 .UPDATE... Issued at 735 PM EST THU NOV 23 2017 High pressure remains in control across the region with mostly clear skies. Upstream satellite imagery and model guidance suggests this will continue. With the center of the high expected to settle east of the Appalachians a steeper nocturnal inversion is expected to develop across the far eastern and southeastern counties with valleys several degrees colder than the ridges. The previous Min T was overall in good shape. A couple of slight adjustments were made based on recent trends. However, the main changes so far this evening were to update hourly temperatures and dewpoints based on recent observations and trends. && .SHORT TERM...(This evening through Friday night) Issued at 259 PM EST THU NOV 23 2017 High pressure will dominate the weather through Friday. As the airmass continues to moderate with time over the region, highs here today reached the low 50s in some locations, and are expected to be even warmer in the upper 50s by Friday. This will be aided by southerly return flow as the area of high pressure starts to shift east of the region. Overnight lows tonight will remain on the cold side (below freezing) with light winds and clear skies allowing for good radiational cooling. Kept a strong ridge-valley split in the grids, with some of the sheltered valleys reading some 10 degrees below the neighboring ridges. An approaching cold front will lead to an increase in clouds Friday night into Saturday morning. Expect the night to start off clear with clouds moving in generally after 6Z, which should keep temps from dropping as low. Low 40s are forecast for most locations. There is some concern with mid/upper level moisture making it through the surface dry layer and producing some sprinkles as the front nears, though no other moisture is expected in connection with this system. Used 75 percent sky cover as a threshold for mentioning isolated sprinkles. .LONG TERM...(Saturday through Thursday) Issued at 305 PM EST THU NOV 23 2017 Extended begins with models in good agreement but continue to diverge by early next week, lowering confidence in the forecast. Overall the pattern aloft is amplified and progressive. Main feature of interest will be a center of low pressure, or trough that will move into the lower 48 by early next week. This system then splits into northern and southern stream components. Models are having a considerable time with the timing and strength of energy as it crosses the CONUS, particularly with the southern stream. The GFS has been typically too fast, opposite of much slower ECMWF solutions. The Canadian has turned out to be a fairly reasonable compromise. Unfortunately there has been no tangible or consistent trend to pick up on as solutions have been all over the place. Consequently the blended solution is the best option at this time, though PoPs were reduced just a bit for overall uncertainties, resulting in a more consistent forecast with neighboring offices. Sensible weather features a roller coaster of sorts with respect to temperatures, fluctuating between brief periods of cooler and warmer weather. Overall temperatures will likely average out to near normal, possibly a little above. After an extended period of dry weather we will see the threat of rain increasing at the very end of the period. However, would not be surprised if future cycles see that threat trend a little slower with time, in line with more of a compromise of the ECMWF and GFS solutions. Made minor adjustments to the temperature grids each night anticipating a small to moderate ridge to valley split during those times when high pressure is centered more directly over our forecast area. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) ISSUED AT 735 PM EST THU NOV 23 2017 With high pressure to dominate at the sfc and aloft, VFR conditions and light winds will prevail through the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...JMW LONG TERM...RAY AVIATION...JP

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