Area forecast discussion...updated National Weather Service Jackson Kentucky 941 PM EDT Wednesday Jun 19 2013 Update... issued at 940 PM EDT Wednesday Jun 19 2013 Fes showers in eastern tenn but they are staying there as the front that they are forming on has become stationary down there. In fact we are hard pressed to even find a couple wisps of cirrus over eastern Kentucky. Temperatures are running about a degree above forecast with dewpoints on track. Feel the temperatures will catch up to forecast within the next hour and then the fall should slow down to match the forecast. Grids have been updated with the latest observation but the zones have not changed enough to warrant new issue. Update issued at 613 PM EDT Wednesday Jun 19 2013 Sky is clearing quickly with the loss of day time heating. Dewpoints are running in the lower 60s which is the same as the expected lows. Cold pooling in the valleys should see the highest relative humidity in the valleys with a thermal ridge and drier air on the ridges. Valley fog expected towards dawn. All this handled well in te zone forecast. Updated grids to input latest observation. && Short term...(this evening through Thursday night) issued at 323 PM EDT Wednesday Jun 19 2013 The boundary that dropped into Kentucky on Tuesday evening and Tuesday night is now located near the Tennessee border and is continuing to sag south. To our north and northeast surface high pressure was located over Ontario. At middle and upper levels a ridge of high pressure was centered over northern Mexico and extending north through the plains with general ridging also extending east across the Gulf of Mexico with an upper low over the Pacific northwest. Height rises are generally expected through tonight...but at the same time some weak troughing or a weakness in the ridge is prognosticated over the lower Ohio Valley and Tennessee Valley regions. The center of the surface high will gradually shift east to off the eastern Seaboard with ridging back into the central appalachian and lower Ohio Valley region. The boundary will drop further into the Tennessee Valley and become ill defined and will essentially dissolve. After some drier dewpoints advect in around the surface high through this evening...low level moisture and surface dewpoint should rise slightly on Thursday. With the weak upper trough prognosticated to be to our west on Friday...and a slight increase in moisture...quite a bit of cumulus should develop and some of the model guidance develops some convection near the Tennessee and Virginia borders during peak heating. The previous forecast had a slight chance on Friday evening and we opted to extend this back into Friday afternoon near the Tennessee and Virginia borders. The airmass should moderate a bit on Thursday...with widespread middle 80s anticipated. Each night valley fog should develop though it may become more widespread and reduce visibilities more tonight and possibly lift up to midslope and some Ridgetop locations by dawn on Thursday. With the surface high pressure center exiting to our northeast tonight...there should be a small Ridge/Valley split tonight that will be more pronounced earlier than become smaller as the inversion lifts. Overnight lows should moderate slightly for Thursday night with increased low level moisture. Long term...(friday through wednesday) issued at 349 PM EDT Wednesday Jun 19 2013 A rather stagnant pattern looks to be in place for most of the long term portion of the forecast. Subtropical upper ridge will be in place across the south central United States to start the period...with the ridge eventually retrograding and building over the western part of the country by the end of the period. Surface high pressure off the southeast coast will keep a warm moist low level flow across the area through the upcoming weekend and into early next week. With this type of pattern in place there is little to focus precipitation chances but models are hinting there will be at least a slight chance of convection each day. There are indications that chances for convection will increase by the middle of next week as ridge builds in the western United States and we are in a position on the northeast periphery of the ridge thus be more susceptible to short wave troughs affecting the area. The Standard blended Load showed this with the highest probabilities for precipitation being next Tuesday and Wednesday. Temperatures will be warming at the beginning of the long term portion of the forecast with above normal temperatures expected into the middle of next week. && Aviation...(for the 00z tafs through 00z Thursday evening) issued at 616 PM EDT Wednesday Jun 19 2013 Mainly VFR is expected through the period as a cold front has slid into the Tennessee Valley. Valley fog is expected to develop overnight and possibly affect both loz and sme with IFR or lower conditions between about 8z and 13z. Other valley locations may fall to LIFR. The fog should lift and dissipate by 14z with VFR anticipated at the end of the period. && Jkl watches/warnings/advisories... none. && $$ Update...dusty short term...jp long term...sbh aviation...dusty