Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 211807 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 207 PM EDT Wed Jun 21 2017 .UPDATE...
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Issued at 207 PM EDT WED JUN 21 2017 The forecast remains on track. Once again, just freshened up the hourly temperatures and dew points through the rest of the afternoon. Updates have been sent. UPDATE Issued at 1132 AM EDT WED JUN 21 2017 Mainly just freshened up the hourly temperatures and dew points through this afternoon. Forecast highs mainly in the mid 80s, with a few upper 80s, look on target. Updates have been sent. UPDATE Issued at 805 AM EDT WED JUN 21 2017 Hourly grids were freshened up based on recent observations and trends. This led to no substantial changes at this time.
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&& .SHORT TERM...(Today through Thursday) Issued at 425 AM EDT WED JUN 21 2017 Early this morning, surface high pressure was located over the Appalachians. Thicker cirrus is streaming from West Tn east northeast to the KY/VA border region into the Central Appalachians. The region is in a seasonably moist airmass between weak cold front or outflow boundary north of the Ohio River and nearly stationary boundary from east TX east northeast to the Delmarva which is the leading edge of the much deeper tropical moisture to the south. This moisture is being transported into the Gulf states around Tropical Storm Cindy. Aloft, an upper level trough extended south from Ontario and Quebec and Ontario into the Great Lakes and parts of the OH Valley with a ridge centered southwest of Bermuda and another ridge centered over the Desert Southwest. In between was weakness with the center of Tropical Storm Cindy over the Gulf of Mexico. Observations indicate generally less in the way of valley fog compared to recent mornings. Through this morning, a general decrease in the thickness of the cirrus is expected for most locations through some debris mid and high clouds could affect northern portions of the area. The axis of the trough to the north and northeast of the area will shift to the north and east today with an increase in mid level heights. Some diurnally driven cu may form but should be rather shallow or capped by some subsidence. Temperatures should moderate further from readings over the past couple of days with surface and upper level high pressure dominating. Highs should average above normal, generally in the mid 80s with a few upper 80s across the area with slightly warmer readings in the north with a bit less in the way of clouds. Through today and into tonight, the center of tropical storm Cindy should continue moving across the northern Gulf of Mexico and associated upper low should move toward the upper TX coast with the southwest US ridge and ridge near Bermuda remaining in generally the same location and strength. Disturbances will pass by to the north in rather quick westerly flow. East KY will dominated by surface and upper level ridge through the night, but moisture will begin to increase especially in the southwest. PW will also begin to increase today and especially tonight form values currently near 1 inch to an inch to an inch and a third by sunset. The more dramatic increase will occur tonight and into Thursday with values reaching in excess of 1.5 inches toward sunrise on Thursday. As the center of Cindy moves into the upper TX coast or western LA as well as an upper low moisture will continue increasing form the southwest with some isentropic lift across the area. PW should climb above 1.5 inches in the far north and east by the end of the period with PW nearing or exceeding 2 inches in the far southwest at that time. A shortwave should also approach in the westerlies at the time. This and some solar insolation will lead to increasing chances for showers and a few thunderstorms through the day though the west moisture and lift will be in the southwest where chances and qpf are expected to be the greatest through 0Z Friday. However, the heaviest rainfall should off until the long term period. .LONG TERM...(Thursday night through Tuesday) Issued at 319 AM EDT WED JUN 21 2017 The primary concern in the extended will be the potential for heavy rainfall associated with the remnants of tropical storm Cindy Friday night and Saturday. At this time the latest model data has several rounds of moderate to heavy rainfall occurring across the Ohio and Tennessee valleys at the end of the week and into the upcoming weekend. Whatever is left of Cindy will likely interact and merge with a cold front that is forecast to approach from the north. There is still a considerable amount of uncertainty as to what the exact track of the two weather systems will be, and therefore the amount of rainfall that will fall across the area. The model data has several rounds of moderate to heavy rain occurring across the region, with bulls eyes of maximum rainfall amounts randomly appearing across the area. Because of this, the forecast will need to be refined a number of times over the next couple of days as the models hone in on a more common and consolidated solution. In general, it does appear that 2.5 to 4.25 inches of rainfall will be possible across the area during the duration of the event, the bulk of which should fall Friday night and Saturday. After a brief break in the rain Saturday night through Sunday morning, a fast moving and weak area of low pressure is forecast to bring isolated to scattered showers and storms to the area Sunday afternoon through early Monday afternoon. Temperatures for most of the period are forecast to be below normal, due to extensive cloud cover, multiple rounds of rainfall, and the invasion of cooler air into the region after a couple of weather systems move east of the area. Friday night and Saturday should have close to normal temperatures, with lows in the upper 60s and highs in the lower 80s expected respectively. Once this initial system moves east of the area, our first round of cooler air will spread across the area. A second shot of cool air is expected to filter into the region behind a second weather system after it departs the area on Monday, thereby reinforcing the cooler air that will already be in place. This will be the primary reason whey we see below normal temperatures through the middle of next week. From Sunday onward, daytime highs are forecast to top out mostly in the mid to upper 70s across the area. Nightly lows are expected to average in the mid to upper 50s for most locations. && .AVIATION...
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(For the 18Z TAFS through 18Z Thursday afternoon) ISSUED AT 207 PM EDT WED JUN 21 2017 High pressure will maintain control through late this evening, with afternoon cumulus dissipating by dusk. A low level jet will then increase from the south and southwest towards dawn Thursday, bringing lowering ceilings and eventually showers and a few thunderstorms to the area during the day on Thursday. West southwest winds at 5 to 10 kts, will gradually back to the south southwest later in the period.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GEOGERIAN SHORT TERM...JP LONG TERM...AR AVIATION...GEOGERIAN is the U.S. government's official web portal to all federal, state and local government web resources and services.