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Area Forecast Discussion (AFD)

Issued by Jackson, KY (JKL)

                            
135 
FXUS63 KJKL 200228
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1028 PM EDT Wed Sep 19 2018

.UPDATE...
Issued at 1028 PM EDT WED SEP 19 2018

Mostly clear conditions prevail across eastern Kentucky this
evening and will be the general rule through the night. We are
seeing some fog starting to develop and went ahead moved the fog
up a bit sooner in spots. Otherwise the forecast grids are on
track, but did blend in the latest obs to generate a better 
temperature curve.

UPDATE Issued at 745 PM EDT WED SEP 19 2018

The isolated showers that developed this afternoon have dissipated
and we are left with mostly clear skies. This will be the trend
through the night with fog developing tonight. The latest obs and
trends were incorporated into the grids.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 359 PM EDT WED SEP 19 2018

Isolated showers have developed again today after diurnal surface
destabilization occurred. These will affect a very small share of
the forecast area this afternoon, and should then die out this
evening. A 20% POP has been used area wide. This may be generous
in terms of coverage, but some areas are definitely seeing
measurable rain. Forecast soundings suggest the showers will
generally stay capped below 500 mb (where temps are around -4C),
and no thunder is expected.

On the synoptic scale, upper level ridging currently centered over
the lower/mid Mississippi Valley will slowly shift east during the
period. It should crest over our area during the day Thursday, and
then slip to our east Thursday night. This will result in slightly
warmer mid level temps on Thursday, making showers less likely,
and a dry forecast has been used. At the surface, high pressure
over the Tennessee Valley today is expected to be absorbed by 
ridging to our northeast, and slowly move east of our area by 
Thursday. Along with the building upper ridge, the scenario should
result in even warmer temperatures than today, with some places 
possibly seeing 90 degrees.

.LONG TERM...(Friday through Wednesday)
Issued at 506 PM EDT WED SEP 19 2018

The period will start with an upper level high centered over the
Carolinas, and a short wave over the north central CONUS 
progressing through the westerlies over the northern tier of 
CONUS states. The wave will impinge on the high, suppressing it 
and shoving it offshore by the weekend. This will allow a surface 
cold front to approach Friday, and likely move through Friday 
night and Saturday. As the front's upper level support departs and
it becomes strung out parallel to the upper level flow, it should
stall to our south. Although the GFS and ECMWF may not agree on 
the exact position of the stalled front, they agree on the 
general outcome for our area. Deep moisture will accompany the 
front and then persist over our area as the front stalls, 
resulting in a lingering threat of rain. 

A much more potent upper level trough is expected to drop 
southeast to the middle of the CONUS by the end of the period, 
supporting another cold front to approach us from the northwest at
the end of the period. What's left of the first front stalled to 
our south will be drawn back north through the area as a warm 
front early in the week before the next cold front heads in. This 
keeps the mention of rain in the forecast through the end of the 
period.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 729 PM EDT WED SEP 19 2018

An area of weak surface high pressure and upper level ridging 
will keep the weather quiet again tonight. The TAFs will remain 
mostly VFR, but some MVFR fog or perhaps lower at times will be 
possible at a few of the TAF sites. Did add a TEMPO group for JKL 
given the wind direction could bring in some fog from the valley
floor. The valleys is where much of the fog will reside tonight 
and this will dissipate through the mid morning hours Thursday. 
Then VFR conditions dominate to end the TAF period, but we will 
probably see scattered cumulus at around 4 kft in the afternoon 
hours on Thursday. The winds will remain light through the TAF 
period. 

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...DJ
SHORT TERM...HAL
LONG TERM...HAL
AVIATION...DJ