Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 141755

National Weather Service Jackson KY
1255 PM EST Wed Feb 14 2018

Issued at 954 AM EST WED FEB 14 2018

Latest radar shows an area of showers moving across the far
northern part of the forecast area. Trends indicate this will be
the focus area for rain over the next several hours. Have updated
NDFD to account for latest precipitation trends.

UPDATE Issued at 804 AM EST WED FEB 14 2018

Have updated for the latest precip trends observed on radar, and
inserted the latest observed temps/dew points into the forecast
grids. For the big picture, there is little change.


.SHORT TERM...(Today through Thursday)
Issued at 506 AM EST WED FEB 14 2018

A damp pattern will prevail during the period. An anomalously
strong ridge over the Gulf of Mexico will remain in place, with
our area in the broad anticyclonic flow around the periphery. At
the surface, persistent flow off the Gulf will continue to bring
milder and more humid air northward. The general scenario is
favorable for bouts of wet weather, with precip occurring as weak
waves aloft pass through and act in tandem with the warm air
advection/isentropic lift. One round of precip began to affect
the southern part of the forecast area overnight, with the rest of
the region expected to be affected later today or this evening.
Forecast soundings also show weak elevated instability developing.
There has already been a bit of lightning observed well upstream
from MS and LA northward to southern IL. In light of this, have
included a slight chance of thunder. This system will exit to our
east tonight, but leave us in a mild and moist air mass.

An upper trough will drop south into the CONUS and begin to
impinge on the ridge tonight. It will support a southward moving
surface cold front. Another gush of moisture and warm air
advection is expected ahead of the front on Thursday, leading to
the expectation of more showers.

.LONG TERM...(Thursday night through Tuesday)
Issued at 338 AM EST WED FEB 14 2018

The rain chances continue for this forecast. A seasonally large
ridge will sit over the Gulf of Mexico through much of the week,
finally shifting eastward towards the Atlantic during the weekend,
where it will still remain near the coast through the remainder of
the extended. Meanwhile, a strong arctic low will remain placed
across the Hudson bay, resulting in sharp and very tight pressure
gradients at times between the two systems. It is of happy note that
as of 3am the GFS and ECMWF models are finally in much better
agreement throughout much of the extended, unlike in previous days
and forecasts. Both models depict strong WSW flow aloft across the
Ohio Valley starting 0Z Friday and continuing into the first part of
the weekend. Several smaller disturbances will travel through this
flow and across the region during this time. A broader shortwave
will move through during the weekend, namely Saturday and Saturday
night before quickly exiting to the east. Zonal flow will briefly
take place behind Sunday with gradients slackening a bit as the
strong ridge over the Gulf finally shifts eastward into the
Atlantic. Meanwhile, a open wave will begin digging a fairly strong
trough across the western conus as we head into Monday. This, in
conjunction with the ridge retrograding back to Florida, will lead to
enhanced SW flow across the region to end out the forecast period.

So what does this mean for sensible weather. General WSW to SW flow
across the region for the majority of the forecast period will do
two things. Promote an influx of moisture into the region, as well
as decent warm air advection. Surface systems will play with this
some, but overall this should be the general trend...warmer than
normal and wet. As we start the forecast period Thursday  night, a
cold front will be approaching from the NW following the lowering
heights associated with the upper level shortwave. SW flow will pick
up ahead of this system, with precip expected to commence from NW to
SE throughout the night and continuing through the day Friday as the
front begins to traverse eastern KY. This system will be something
to watch as between half an inch and an inch of precipitation is
still forecast to fall over an already soaked eastern KY. The only
silver lining is that the bulk of the heaviest QPF is forecast
across the less hit northern CWA.

Post cold front, drier northerly flow will take hold of the region
in the llvls as surface high pressure builds in Friday night. The
ECMWF does have some lingering precip across the far southern CWA
through Saturday evening before completely tapering off, but
otherwise the remainder of the CWA should be dry and cooler. Lows
Friday night/Saturday morning will drop to or below freezing in most
locations. Post frontal highs on Saturday will also be on the cool
side, in the 40s across the CWA. This cold snap will be short-lived
however, as the surface high quickly traverses eastward into the day
Saturday and return flow takes back a hold across the JKL CWA, in
line with the ongoing mid and upper level flow. Highs by Sunday will
be back into the low 50s, several degrees above seasonal normals. A
surface low will be moving NE across the deep South during the day
Saturday into Saturday evening. This will bring yet another
epicenter for moisture into the state Saturday afternoon and
evening, quickly clearing out for Sunday. Surface winds will
become southerly again by Sunday night into Monday, correlating
with the more southerly flow in the mid and upper levels, bringing
yet another opportunity for warm moist air to advect into the
region. Further chances of rain are expected through the rest of
the extended period. Highs on Sunday will be in the upper 40s and
low 50s, several degrees above seasonal normals, but Monday into
Tuesday could see mid and upper 60s despite rain chances.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)

Extensive low clouds covered the forecast area early this
afternoon, and there will be little change over the next 24 hours
with IFR to very low MVFR ceilings continuing. Showers are
forecast to become more numerous late this afternoon and into the
evening, which will also result in some temporary visibility
restrictions as well. While thunder cannot be totally ruled out
late this afternoon and evening, the chances are very low so have
left any mention of thunder out of the TAFS for now.




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