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Area Forecast Discussion (AFD)

Issued by Jackson, KY (JKL)

FXUS63 KJKL 191443 AAA

National Weather Service Jackson KY
1043 AM EDT Thu Sep 19 2019

Issued at 1043 AM EDT THU SEP 19 2019

Made a few adjustments to the forecast. Updated sky cover based on
the latest satellite trends. Now have more cloud cover in our
northeastern and eastern counties, and slightly less cloud cover
in our southwest. Also used the latest obs to trend hourly
forecast elements through early this afternoon. Also removed
mention of fog from the zone forecast text product as any fog has
long since lifted and dissipated across the area. Overall the
forecast has been on track so far this morning, with hourly
temperatures remaining within a degree of forecast values.

UPDATE Issued at 700 AM EDT THU SEP 19 2019

Issued an update to the grids to input the latest observations and
trend them through mid morning. Adjusted the cloud cover a bit to
match the trends this morning. Otherwise, the forecast is on


.SHORT TERM...(Today through Friday)
Issued at 403 AM EDT THU SEP 19 2019

The current surface analysis across the region features again,
high pressure in place with the surface high centered over the NY
and New England region. A ridge axis extends southwest from here
along the the leeward side of the Appalachian chain. This set up
will bring southerly to southwest flow for today. A dry boundary
layer will remain, thus fog will be suppressed this morning with 
any visible, along the river valleys. The southerly flow will be 
present at 850MB and this will show after dawn as some cumulus, 
rather high based at 5 to 6 kft develops from along I-75 and then 
spreading east through the day. This cloud cover will assist in 
keeping temps from reaching 90 across the area and likely the 
upper 80s for that matter. Cloud cover will not be as widespread 
in the far east today and this will show with RH values in the low
30 percent range as highs will get into the upper 80s in some 
spots. While there were a few pop up showers and a storm or two 
yesterday, the lack of instability due to the lack of moisture 
should keep development at bay today especially since the best 
instability will be in the west and will not have the orographic 
support in the east like yesterday's activity did. 

Heading into tonight, the mentioned cumulus will dissipate in the
evening resulting in mostly clear skies again to begin the night
but another weak disturbance in the southerly flow will bring
developing cloud cover again towards dawn. Thus, will again expect
little fog development tonight and any development being sparse
and linked to the deeper river valleys. Mid level ridging
intensifies for Friday as the current pattern still does not
indicate enough moisture advection to impact the continued dry
boundary layer. Highs with the dry conditions will reach into the
middle 80s again with another afternoon of high based cumulus
development. At this point, model soundings show another afternoon
of little to no instability. Thus, will keep a dry forecast.  

.LONG TERM...(Friday night through Wednesday)
Issued at 522 AM EDT THU SEP 19 2019

The period will start with an upper level high over the southeast
CONUS with ridging extending northward over the Great Lakes, and
large, sprawling surface high pressure centered just to our east.
Our low level flow will be originating out of the high, and not 
riding across a moisture source, keeping our weather dry early on.
Meanwhile, the upper level ridging will promote warm 

The northward extent of the upper level ridging will translate
eastward off the coast by late Sunday, as a progressive trough  
moves eastward across the northern tier of states. This will work 
to suppress the center of the upper high southward, and allow a 
cold front to move southeast through the local area Monday and 
Monday night. Flow off the gulf is forecast to transport moisture 
up the Mississippi Valley ahead of and along the front. However, 
the better moisture will probably be pinched off as the front 
arrives here, keeping our rain potential fairly low. Behind this 
cold front, dry weather is expected by Tuesday.

Beyond this time frame, the picture becomes more uncertain as
models solutions show greater differences. Another upper level
trough will move east in the flow, with part of it shown closing
off over the southwest CONUS, and the remainder being progressive
in the flow. The GFS has a piece of this supporting a surface low
making its way east through the mid Mississippi Valley and Ohio
Valley with a potential for rain at mid week, while the ECMWF is 
much more suppressed and has the system fading away before it gets
here. Have carried a minimal 20% POP on Wednesday at this point,
waiting to see how it plays out in future model runs.


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

VFR conditions are expected to prevail through most of the 
period. Cumulus has developed over the western portion of the CWA
and will build into a broken deck by mid morning for most places.
Much of the cumulus development will dissipate a bit heading into
the late afternoon as the layer will become scattered before 
clearing by the evening. Look for variable winds of 5 kts to 
gradually veer around to the southeast and south by the afternoon.
Dry conditions will inhibit fog development again tonight as
another bout of cloud cover will move into the area late tonight
further inhibiting fog development.