Area Forecast Discussion
Issued by NWS Jackson, KY

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388 FXUS63 KJKL 161150 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 750 AM EDT Wed Aug 16 2017 .UPDATE...
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Issued at 730 AM EDT WED AUG 16 2017 Did a quick update to touch up the Sky, PoP, T, and Td grids per the current conditions and trends as well as latest guidance from the HRRR. Areas of dense fog persist, especially in the valleys. These grids have been sent to the NDFD and web servers.
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&& .SHORT TERM...(Today through Thursday) Issued at 415 AM EDT WED AUG 16 2017 07z sfc analysis shows a broad area of low pressure over the region. Earlier in the night scattered showers faded out through eastern Kentucky while the skies cleared. This has allowed for areas of fog to develop throughout the CWA with some locally dense patches found in the valleys. Currently, temperatures are running in the low 70s on ridges to the upper 60s in the valleys while dewpoints generally within a degree or two of the dry bulb with the winds light to calm throughout the area. The models are in good agreement aloft through the short term portion of the forecast. They depict a building ridge over the southeast portion of the nation while zonal to southwest flow is found through the Ohio Valley north of this ridge. Within this flow some weak packets of energy will pass through Kentucky today before attention turns to a stronger shortwave trough moving into the Upper Midwest by Thursday morning and then lifting northeast into the Great Lakes by evening with height falls spreading through the area late in the short term. Given the model similarities have favored a general blend with wx specifics derived mainly from the higher resolution HRRR and NAM12. Sensible weather will feature fog burning off this morning with partly sunny skies and warm conditions leading to scattered showers and thunderstorms developing by early afternoon. Again, any storms this afternoon could be prolific rain producers given the high PW air. The convection will die off in the evening setting the stage for a similar night of fog formation and ridge to valley temperature differences. For Thursday, showers and thunderstorms are again expected to develop this time out ahead of an approaching cold front. A few of these storms could be strong and potentially organized owing to good instability developing as the day wears on, along with favorable mid and upper level winds. Currently a good portion of our CWA is outlined for a marginal risk of severe thunderstorms from SPC. Additionally, the storms on Thursday should be more progressive and limit our concerns for excessive rainfall, despite the still high PW air. Again used the CONSShort as the starting point for the grids through the short term portion of the forecast with some adjustments to temperatures each night for terrain differences. As for PoPs, did again enhance them diurnally and also broaden the area of best chances on Thursday given some uncertainly remains. .LONG TERM...(Thursday night through Tuesday) Issued at 322 AM EDT WED AUG 16 2017 The extended portion of the forecast begins on Thursday night with an active upper level pattern continuing. During the beginning of the extended, a strong upper level low will be passing through the OH Valley Thursday night as a surface cold front passes through. Lingering convection will keep showers and thunderstorms over the area through the night and into the day on Friday. Forcing and instability in place should be enough to keep the chance for precip through the night. Models suggest the front moving through by Friday afternoon with precip coming to an end. Surface high pressure moving in behind the front should keep mainly dry conditions through the weekend. A weak disturbance passing by to the north on Saturday evening may be enough to kick off a few showers or storms north of the Mountain Parkway. Otherwise, a dry weekend will be on tap. By Monday, the mid level ridge over the southeast CONUS will reengage the return flow into the southern and central Appalachian with plenty or moisture brought into place. This setup with another strong wave moving into the OH Valley by Monday afternoon will set the stage for another bout of showers and thunderstorms. Tuesday then follows with a continued active pattern as another front shifts into the region with renewed convection lasting through the end of the extended. The super blend adds some confidence to this assessment as well. Overall, an active and wet extended pattern will be in place. && .AVIATION...
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(For the 12Z TAFS through 12Z Thursday morning) ISSUED AT 750 AM EDT WED AUG 16 2017 The main concern for the next couple of hours remains the IFR to VLIFR fog currently affecting the TAF sites. The fog will slowly dissipate through the morning as temperatures warm and mixing commences for the boundary layer. Scattered showers and thunderstorms will return for the afternoon and have maintained VCTS for this at all locations. Winds will be light and variable, outside of any storms, through the period across all the TAF sites.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...GREIF LONG TERM...SHALLENBERGER AVIATION...GREIF is the U.S. government's official web portal to all federal, state and local government web resources and services.