Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 291212 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
812 AM EDT Mon May 29 2017

.UPDATE...
Issued at 804 AM EDT MON MAY 29 2017

Hourly grids were updated based on recent observations. This led
to no substantial changes at this time. Low clouds linger across
parts of the area, but with daytime heating these should slowly
mix out.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 420 AM EDT MON MAY 29 2017

The period begins with a closed low over the Northern Great Lakes
and Ontario with an associated trough south into the MS Valley
region. Upper level ridges were in place across the Western Conus
and Gulf of Mexico and Caribbean. At the surface, low pressure
was over Ontario with an occluded front to a triple point low
over the eastern Great Lakes with a cold front trailing south and
then southwest into the OH Valley to the Southern Plains. A
secondary front extended from the low into the WI and then west
across parts of the MO Valley.

Today and tonight, the first cold front will depart into VA and TN
early and begin to stall south of the area with high pressure
nosing northeast into the region from the Southern Plains. Mid
level heights should rise some and then remain steady this
afternoon capping off any cu development. Mid level clouds should
depart early with areas of stratocu or stratus mixing into rather
shallow cu through the morning and into the afternoon. There
should be a period with mostly clear skies from near sunset into
very early on Tuesday morning and this may allow for a small
ridge/valley temperature split to develop with a nocturnal
inversion setting up in the valleys. The secondary cold front
should increase late with an associated increase in low and mid
level clouds. Highs today should be near to slightly above normal
for the end of May with lows tonight near to slightly above
normals as well.

On Tuesday, the secondary cold front will cross the region with
limited moisture. Moisture should be a bit more substantial
across the southern and southeastern counties closer to the
stalled frontal zone and somewhat higher dewpoints. The bulk of
the model guidance suggests isolated to scattered coverage of
showers and perhaps a few thunderstorms near the VA border. The
past two NAM runs appear overdone with moisture and instability
and thus coverage of convection and were weighted very little for
this forecast. GFS forecast soundings across the north indicate
less instability and perhaps a bit of capping so thus thunder
chances were confined to one to two counties nearer to the VA and
TN border where CAPE could reach near 500 J/kg and LI on the order
of
-2C. With more cloud cover, highs on Tuesday should be slightly
lower as compared to today.

.LONG TERM...(Tuesday night through Sunday)
Issued at 345 AM EDT MON MAY 29 2017

A weak cold front will slip south across the area late Tuesday
night and Wednesday. Forcing with the front will be quite weak,
but instability may build south of the front on Wednesday and
spark a few showers and thunderstorms, especially across the
southern half of our forecast area. Looking at 00z model forecast
soundings, there would be some potential for a few strong or
damaging wind gusts as we have modest speed shear from the surface
to 500mb. We also have a pocket of mid level dry air that may aid
in the potential for some downburst winds. The best threat for
the stronger storms would be in southeast Kentucky at this time.

Front will push south Wednesday evening, with showers and storms
exiting south. As high pressure builds south across the region,
this will provide dry weather Wednesday night through Thursday
night. As the high shifts east Friday, moisture will start to
stream back to the north from the Gulf region. A mid level trough
will push north and could spark some showers and storms during the
day Friday. In the wake of this system, looks like plenty of
moisture will reside over the region through the weekend. It
looks like a zone of active convection will develop and align east
to west again through the weekend. PW values will climb back to
around 1.50 to 1.60 inches over the weekend. With the mean
steering flow aligned with the east to west front to our north,
we could be looking at more potential for flash flooding. Models
are in good enough agreement to at least mention the potential in
the HWO. Looks like front will finally push south Monday night,
ending the threat of heavy rain. With the active weather over the
weekend, will maintain the likely rain chances from Saturday
through Sunday. Taking a very early look at severe potential, it
appears shear will be too weak to support much of a severe risk.
Thus, this time around, we could be more focused on hydro
concerns.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
ISSUED AT 750 AM EDT MON MAY 29 2017

Some stratocu or stratus lingers across much of the area with a
mix of MVFR and IFR occurring. The IFR was more prevalent across
the north. This should lift into MVFR during the first 2 to 3
hours of the period with MVFR improving to VFR areawide by 15Z to
16Z. VFR should then prevail through the end of the period with a
weak ridge of high pressure dominating. Winds should generally
remain at 10KT or less through the period.

&&

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

$$

UPDATE...JP
SHORT TERM...JP
LONG TERM...KAS
AVIATION...JP



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