Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 200212 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1012 PM EDT Mon Sep 19 2016 .UPDATE...
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Issued at 1012 PM EDT MON SEP 19 2016 Quick update mainly for overnight lows. With strong radiative cooling, hourly temps are running slightly lower than expected so adjusted overnight lows down a degree or two. Only minor tweaks to other grid elements. Updated grids and zones have been issued. UPDATE Issued at 808 PM EDT MON SEP 19 2016 Forecast is on track this evening. Drier air has mixed down over portions of the area, especially in our west. Consequently crossover temps will be lower over those areas through the overnight. On the other hand there will be better subsidence aloft tonight as compared to last night, providing a relatively dry layer that will allow better radiative cooling from within the boundary layer below. Thoughts are this will be a night where we will see the most dense fog within the river valleys and near bodies of water where a source of moisture is present. Updated grids to bring them in line with hourly trends, which resulted in minor changes. May also beef up the wording within the HWO to highlight the more dense areas of valley fog expected tomorrow morning. No updates to the zone package ATTM.
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&& .SHORT TERM...(This evening through Tuesday night) Issued at 321 PM EDT MON SEP 19 2016 Weak surface ridging continues to build into the Ohio Valley in wake of an elongated upper trough crossing the Appalachians and moving toward the Atlantic. A flat cumulus field will slowly erode by late afternoon into this evening with the loss of daytime heating and as slightly drier air slowly advects south. Clear skies and light winds combined with overnight low temperatures reaching and likely falling below crossover temperatures will spell another night of fog across eastern Kentucky. This should not be as widespread and dense as that seen last night and this morning given the lack of any rainfall today. Visibilities may very well drop to 1/4 mile or below in deeper river valleys as temperatures cool into the upper 50s, with restrictions not as prevalent elsewhere with readings in the low- mid 60s. Fog will lift by mid Tuesday morning as high pressure is reinforced following a trailing wave riding through the Great Lakes tonight. Southern extent of today`s departing upper trough will cutoff and lift through a portion of the Appalachians, attempting to usher in some enhanced moisture across southeast Kentucky. Conditions will remain dry locally as eastern Kentucky stays on the northwestern flank of this system, in the subsiding region. Upper ridging spilling into the region from the southwest will bring warmer temperatures aloft, bumping highs into the mid 80s. A similar night will be in store Tuesday night with less fog development following another dry day. .LONG TERM...(Wednesday through Monday) Issued at 300 PM EDT MON SEP 19 2016 A stubborn upper level ridge will remain the dominant influence on our weather during the long term period. A closed low will be parked to the east of the Apps at the start of the period. While this may throw back some mid and high clouds from time to time, I do not anticipate any precip to make it this far to the west. In fact, we should see plenty of sunshine with highs well up in the 80s each day through Saturday. Based on recent trends, and the fact we will be drying out again, I continued to bump up daytime highs a degree or two from the Super Blend guidance. A longwave trough will drop into New England over the weekend as an upper low closes off over the Southwest CONUS. This pinches off the upper ridge to our west and allows a backdoor cold front to drop southward across our region Saturday night or Sunday. The front should pass through dry while bringing a modified Canadian airmass featuring cooler, closer to normal, temperatures and much lower dewpoints Sunday and Monday. The Super Blend guidance offered a small PoP on Monday as the next front plunges into the scene from the west. With the dry airmass in place behind our weekend front, and timing differences shown in the modeling, decided to keep the forecast dry on Monday in general agreement with offices to my east. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) ISSUED AT 808 PM EDT MON SEP 19 2016 Skies are clearing this evening with a light north/northeast wind being realized at the terminals more responsive to winds from that direction, KSME and KLOZ. Drier air has mixed down over portions of the area, especially in our west. Consequently crossover temps will be lower over those areas through the overnight. On the other hand there will be better subsidence aloft tonight as compared to last night, providing a relatively dry layer that will allow better radiative cooling from within the boundary layer below. Thoughts are this will be a night where we will see the most dense fog within the river valleys and near bodies of water where a source of moisture is present. Terminals with some elevation will probably see some brief periods of fog right around sunrise as the valley fog begins to lift and mix out. However, overall did not drop VSBYS as low as guidance would suggest since we did get some mixing down of drier air through the afternoon. Should see fog dissipate by mid morning with light north/northeast winds and mostly sunny skies prevailing for the remainder of the day Tuesday. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...RAY SHORT TERM...GUSEMAN LONG TERM...ABE AVIATION...RAY

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