Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 201216 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 816 AM EDT Sun May 20 2018 .UPDATE... Issued at 816 AM EDT SUN MAY 20 2018 Opaque clouds appear less extensive on early morning satellite imagery than what was forecast at this point, and the forecast has been updated to include more sun. && .SHORT TERM...(Today through Monday) Issued at 524 AM EDT SUN MAY 20 2018 The night started off with moist rain cooled air at the surface, and clouds were sparse enough and winds light enough for most of the night to allow radiation fog to develop, mainly in valleys. The fog will dissipate as warming occurs this morning. The upper level trough which brought showers and thunderstorms on Saturday is well to our east now, and ridging over the southeast CONUS is expanding its influence northward over our area. Even though there has been no change in air mass and significant instability will develop today, the ridging will result in less favorable conditions aloft for deep convection, and coverage of showers and thunderstorms should be much more limited. A weak shortwave trough rippling around the northern periphery of the ridge tonight will begin to flatten it already. At the same time, a weak surface low associated with it will move east northeast from MO to OH, bringing a return of warm/moist advection for our area. The weakening upper level ridge and return of warm/moist low level inflow will result in an increasing POP late tonight, and especially on Monday with the addition of heating. .LONG TERM...(Monday night through Saturday) Issued at 402 AM EDT SUN MAY 20 2018 The extended portion of the forecast begins on Monday night with a return flow pattern still in place across the southeastern CONUS. Both the GFS and Euro indicate at this pattern continuing through Tuesday before the pattern breaks down a bit. For Monday night into Tuesday, a weakened shortwave will be tracking along the northern stream into the upper OH Valley. This is combined with a slowly becoming washed out boundary along the OH river and southerly flow bringing in warm and moist air into the region. It is also possible of a dying MCS moving through the previous night and interfering with development the next day. Thus with a few features and sufficient instability in place, showers and thunderstorms will be possible Monday night and possibly continuing through the day on Tuesday and a peak of activity in the afternoon. The presence of synoptic features in place may allow convection to continue on a limited basis into Tuesday night. Some storms may be strong through this period but most of them will be capable of heavy rainfall due to the saturated airmass and plethora of instability. By Wednesday, the mentioned boundary finally pushes south as the upper level pattern switches due to northwest flow and a shortwave ridge pushing southeast. This will set up the boundary along the TN and VA border. Thus this will be the focus for convection for Wednesday afternoon. The mentioned northwest flow will bring a bout of high pressure and dry weather to the region for Wednesday night through Friday morning. Slightly cooler temps and dew points back into the lower 60s and upper 50s will lead to more comfortable conditions across the area. As the ridge of high pressure passes to the east it will slide down the east coast setting up just southeast off the coast. This will allow the pattern to revert back to a return flow situation for Friday and Saturday. This will bring chances for showers and thunderstorms back into the forecast. Models hint at a frontal system moving into the area Saturday night but model agreement is low on timing and strength. Overall, despite a break in the pattern midweek, temperatures still remain above normal. && .AVIATION...(For the 12Z TAFS through 12Z Monday morning) ISSUED AT 816 AM EDT SUN MAY 20 2018 Fog is in the process of lifting and dissipating and will be gone shortly. The improvement to VFR should last into tonight for the most part. There is a very small potential for a few thunderstorms to develop this afternoon, but the effects would likely be very limited in terms of duration and coverage. Valley fog is expected again late tonight, but probably more limited than last night. Most TAF sites will probably be affected by IFR for a time overnight. A few more showers or storms can`t be ruled out by dawn on Monday as well, but the probability is low. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...HAL SHORT TERM...HAL LONG TERM...SHALLENBERGER AVIATION...HAL is the U.S. government's official web portal to all federal, state and local government web resources and services.