Area Forecast Discussion
Issued by NWS Jackson, KY

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997 FXUS63 KJKL 241835 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 235 PM EDT Mon Jul 24 2017 .UPDATE...
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Issued at 235 PM EDT MON JUL 24 2017 Showers and t`storms are developing just about on schedule. Coverage is still fairly limited, and the POP has been left at 20% at this point. UPDATE Issued at 1059 AM EDT MON JUL 24 2017 Have updated POP/wx grids based on latest mesoscale model runs. They all focus the potential for convection this afternoon into tonight along the cold front dropping south through the area. There is uncertainty regarding coverage and how effectively a mid level cap can be broken. MOS POPs from last night`s runs are all sub 20%. Have left the POP low at this point, but if enough development occurs, a revision would be necessary. UPDATE Issued at 645 AM EDT MON JUL 24 2017 Did a quick update to the grids to fine tune the sky cover and tweak the T/Td grids per the latest obs and trends. Patchy fog has developed along the fringes of the clouds currently bisecting the CWA - but any dense fog has so far been fleeting per the obs and web cams. These updated grids have been sent to the NDFD and web servers.
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&& .SHORT TERM...(Today through Tuesday) Issued at 340 AM EDT MON JUL 24 2017 07z sfc analysis shows weak high pressure now settling into Kentucky with a washed out front lying over the southern parts of the state. This boundary is keeping clouds through the southern half of the CWA limiting the fog potential down there despite the minimal dewpoint depression. To the north, a bit more of spread to the temperatures and dewpoints are also serving to keep fog to a minimum ATTM. Readings are fairly uniform through the area - generally in the upper 60s to lower 70s with dewpoints in the upper 60s most places while winds area light, mainly from the southwest. The models are in good agreement aloft in the wake of the stronger shortwave exiting the Ohio Valley to the east early this morning. They all depict northwest flow continuing as low heights curl east through the eastern Great Lakes with ridging found to the southwest. This ridging starts to build back east through Tuesday with heights rising and any energy packets coming through the region weaker and weaker. Given the model agreement will favor a general blend with particular attention to the HRRR and NAM12 solutions in the near term. Sensible weather will feature another warm day, though not quite as humid as heat indices peak in the mid to upper 90s. The weak front nearby will be the potential source for storm development by mid day, but the models are not very impressive so have kept the PoPs in the chance category. Drier air will continue to seep into the area at all levels also limiting the storm potential and certainly concerns for excessive rainfall. This is due to lower PW air for most of the CWA now that the deeper moisture has pushed off to the south. For tonight, will have to be on the lookout for low stratus to develop along with fog, but otherwise it will be a quiet night in a rising heights environment. Similarly, Tuesday looks dry and warm with partly sunny conditions and minimal storm chances as a deep cap develops while the mid level ridge spreads northeast into the region. Again used the CONSShort as the start for the forecast grids with only minor point adjustments to lows and highs. Did adjust PoPs today to better align with the front and HRRR QPF depictions. .LONG TERM...(Tuesday night through Sunday) Issued at 245 AM EDT MON JUL 24 2017 The extended period will start off warm and dry as a ridge of high pressure settles over the region. Normal to slightly above normal temperatures will accompany light and variable winds Tuesday night through Thursday. After that, however, a slow moving frontal boundary will invade the area from the north. This boundary will bring chances for rain to eastern Kentucky from Thursday morning through Saturday. The highest probability for rain will likely occur Thursday night and Friday, as a cold front moves slowly across the area. The rain should taper off during the day on Saturday, as the front begins to exit the area. Isolated to scattered showers and storms are expected to linger across our eastern and southern counties through Sunday evening, as the front stalls out just to the south of the area, and an wave of low pressure aloft moves across the eastern Great Lakes region. Temperatures from Friday onward are expected to be below normal, due to persistent cloud cover and precipitation. Highs from Friday through Sunday will max out in the lower 80s across the area, while max values on Wednesday and Thursday should be in the upper 80s. Nightly low will be in the 60s, with the warmest nights at the start of the period, and the coolest nights from Thursday night onward. && .AVIATION...
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(For the 18Z TAFS through 18Z Tuesday afternoon) ISSUED AT 235 PM EDT MON JUL 24 2017 Isolated showers and t`storms were occurring over the northern half of the forecast area at the start of the period. Outside of the heavier precip, conditions were VFR. The precip was occurring near a cold front. The front and the precip will slowly sink south through the area this afternoon and evening. Precip coverage should remain sparse enough so that nothing more than VCSH or VCTS is warranted in the TAFs. Even though the front will drop to our south tonight, the influx of drier air will be relatively weak. This will make it difficult to scour out our humid air, especially in valleys. The end result will be fog developing in valleys. The issue is how far it spreads in breadth and depth. The current forecast takes most of the area to IFR or lower. The places most likely to avoid it will be on ridges and in the far north. Fog and low clouds will eventually dry up on Tuesday morning, with VFR expected by the end of the period.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...HAL SHORT TERM...GREIF LONG TERM...AR AVIATION...HAL

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