Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 211557
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1157 AM EDT Tue Mar 21 2017

.UPDATE...
Issued at 1157 AM EDT TUE MAR 21 2017

Temperatures have warmed into the mid 60s across far southern
Kentucky to about 30-40 miles north of the Tennessee state line.
Farther north into northeast Kentucky, a stratus deck has kept
temperatures in the low 50s with no signs of this mixing out
anytime soon. Have accordingly lowered high temperatures for this
afternoon north of Mountain Parkway. May very well need to bump
them near the Tennessee border given approaching mid-high clouds
and stratus remain north/west through peak heating. As mixing
continues across south central to southeastern Kentucky, at least
up through about 2500 feet, frontal boundary and subsequent
surface undulations should remain confined to the Volunteer state
as high pressure builds into the Ohio Valley. Have therefore
lowered PoPs to only maintain slight chance mention across
southern Wayne to Bell Counties late this afternoon through this
evening as elevated convection works southeast out of the Midwest
and across the Tennessee Valley. Trends continue to point to
showers/storms remaining south of the Commonwealth, so outside of
any outflow boundaries from preexisting convection working into
eastern Kentucky, mainly dry conditions should remain in play
through the day.

&&

.SHORT TERM...(Today through Wednesday)
Issued at 435 AM EDT TUE MAR 21 2017

Convection near the cold front continues to move east southeast to
southeast from near Manchester southeast into southwest Virginia.
After a lull in lighting activity cloud top temps from GOES 16
test not yet operational imagery were near -51C with multiple
cloud to ground lighting strikes in the southeast Leslie, southern
Perry extreme western Letcher County and on into Harlan County
near Cumberland and Black Mountain. These will probably exit into
VA a bit earlier than the initial forecast grids per cloud top
temp and radar trends.

The cold front will continue to sag southeast before slowing down
or stalling out over the TN Valley. The boundary should reside
approximately near the I 40 corridor by midday. North of the
boundary, a considerable amount clouds are expected, but very
little if any convection is expected today. Convective allowing
models which did not handle overnight convection well, develop
convection near the vicinity of the confluence of the OH and TN
Rivers and then track it along the boundary generally south of the
area as a couple of surface waves of low pressure move along the
boundary. There is some uncertainty as to how far the boundary
will get before height falls associated with a shortwave trough to
move across the OH Valley region this evening. Also, recent GFS
and ECMWF have some weaker convection near the TN border during
the evening. Locations further to the north should only experience
an increase in clouds especially at mid and high levels as the
shortwave moves through. Showers and possibly a couple of
thunderstorms could affect parts of the Lake Cumberland region and
the TN border during the evening and some slight chance to chance
pops have been used during that time period in that area.

Otherwise as one of the surface waves of low pressure reach the
Carolinas and high pressure builds south from Ontario, the
boundary will sag further south of the area with cold air
advection in its wake anticipated along with a gradual decrease
in clouds from north to south. Temperatures generally along and
north of the I 64 corridor could fall to the freezing mark or just
below tonight with lows mainly ranging through the 30s elsewhere.
Locations along the TN border may not fall below 40 however. The
high will bring colder and drier air into the region overnight and
on Wednesday and below normal high temperatures are expected with
the far north probably not reaching 45 and the far south climbing
to about 55. This high and airmass will set the stage for a
rather cold late March night to start the long term period.

.LONG TERM...(Wednesday night through Monday)
Issued at 401 AM EDT TUE MAR 21 2017

Fairly meridional pattern setting up through the long term period
that will lead to multiple chances of precip. The period does
begin with high pressure east of the region along the Mid Atlantic
coast Wednesday night. There will be a period where decoupling and
radiational cooling can occur early on before some mid to high
clouds stream into the region. After this high pushes east as an
upper level ridge will build across the region. This ridging the
return flow around the surface high will put us securely in the
warm sector by Thursday. This will lead spring like temperatures
through most of the period.

Then we focus attention on vertically stacked system ejecting out
of the Front Range Friday and moving into the Ohio and Tennessee
Valleys Saturday into Sunday. There remains some timing
differences and therefore kept close to the blended guidance.
However did opt to cap POPs at likely given the timing uncertainty
at this point. Also in terms of storms it does look like we get
cutoff from better instability by convection along and near the
Gulf coast. This seems reasonable given this lines up well with
SPC severe probability climatology for this time of year. Overall
looks like QPE of around 0.75 inches is possible Saturday into
Sunday night. There could be a few showers Monday wrapping around
surface low, but ridging will build east ahead of next upper level
trough.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
ISSUED AT 800 AM EDT TUE MAR 21 2017

A cold front continues to sag south toward the TN Valley. Low
level moisture and low clouds just north and northeast of the area
should drop into the northern and eastern portions of the area
behind the front from 12Z to 18Z, but improvement back to The
MVFR in all locations by 21Z. This will occur as high pressure
begins to builds into the area. VFR should then prevail through
the remainder of the period. The only caveat will be near the TN
border generally south of LOZ and SME where scattered showers and
perhaps a thunderstorm will be possible during the 21Z to 5Z.
Winds will average 10KT or less through the period.

&&

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

$$

UPDATE...GUSEMAN
SHORT TERM...JP
LONG TERM...DJ
AVIATION...JP


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