Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 211515

National Weather Service Jackson KY
1115 AM EDT Fri Jul 21 2017

Issued at 1115 AM EDT FRI JUL 21 2017

Convection weakened and scattered out quicker than expected so
have updated NDFD to account for this. Looks like coverage this
afternoon will be isolated to scattered at best.

UPDATE Issued at 1015 AM EDT FRI JUL 21 2017

Showers and thunderstorms have moved into Fleming County but
overall the convection is weakening as it continues to move
southeast. Despite this there will be numerous showers and
thunderstorms across the northern part of the forecast area for
the next few hours. Have increased the shower and thunderstorm
chances in the north and central part of the forecast area with
the latest NDFD update. Have also adjusted temperatures. With
precipitation and then lingering clouds temperatures in the north
and central part of the area may struggle to reach the original
forecast highs. The HRRR did not catch on to the current
convective trends until the 10Z run, but seems to be handling
things better now. Have trended towards the latest HRRR for the
updated forecast.

UPDATE Issued at 832 AM EDT FRI JUL 21 2017

MCS dropping into KY from the Cincinnati area should affect our
northern counties late this morning. POPs have been raised to
likely category for this. It is unclear how well it will hold
together. Movement has been extrapolated to the southeast, with a
fading of the high POP with time. If it does not weaken, higher
POPs will need to be extended further southeast.


.SHORT TERM...(Today through Saturday)
Issued at 500 AM EDT FRI JUL 21 2017

The main concerns during the period are the levels of heat and
humidity, and the extent of convective precip. A slow moving cold
front was dropping south through Indiana and Ohio early this
morning. An MCS was over northwest Indiana, with isolated showers
stretching east into West Virginia. The coverage of precip
through 06z was less than forecast by the models, which calls into
question how well models will perform.

The cold front is expected to make it to near the Ohio River this
evening, before stalling and heading to the northeast as a warm
front tonight and Saturday. The highest probability of precip
will be in our northern counties closest to the front, with some
POP enhancement also in our southeast counties due to terrain.
Will hold all POP values to slight chance and chance categories.

Max temps will be influenced by the extent of clouds and precip,
and have some uncertainty. At this point, it appears that the
temperature and dew point combinations will lead to heat indices
generally shy of the advisory criterion, and will hold off on use
of a NPW.

.LONG TERM...(Saturday night through Thursday)
Issued at 403 AM EDT FRI JUL 21 2017

Based on the latest model data, the extended will be active and will
feature periods of showers and storms and cooler weather. It appears
that a frontal boundary will meander about the lower Ohio Valley and
Upper Tennessee valley during the extended. There should be rain
chances each day, except Wednesday, as the front meanders about the
area. The front may move far enough south on Wednesday, to keep
precipitation out of eastern Kentucky. A second weather system
moving from the south may bring showers and storms back to the area
from Thursday onward, after only a brief respite. The best chances
for showers and storms will be the afternoon and evening hours, with
little if any thunder expected during the night time periods.
Temperatures during the period should be around normal, or even
slightly below normal at times, due to persistent cloud cover and
repeated episodes of showers and storms. Daily highs are expected to
average in the low to mid 80s most days for most locations. Nightly
lows will start out in the lower 70s, but should generally be in the
60s for most of of the period.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)

Morning fog is thinning out, and VFR conditions are expected
shortly after the period begins. However, an area of
thunderstorms entering northern KY at the start of the period will
probably affect the far northern and northeastern portions of the
forecast area late this morning. It is unclear how long the
storms will hold together and what the southern extent will be.
VCTS was used late this morning at KSYM, but TAF amendments may be
needed for late this morning to cover the convective system if it
does not weaken. Once the morning thunderstorms are gone, there
will still be a potential for more development later in the day,
but there is not enough confidence to include it in the TAFS.




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