Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 210233
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1033 PM EDT Mon Mar 20 2017

.UPDATE...
Issued at 1033 PM EDT MON MAR 20 2017

Last of the thunderstorm activity just about to depart Pike
county. Instability will be greatly diminished through the
remainder of the night, so will leave out any mention through the
remainder of the night. The cold front will slip south overnight
and will bring a continued threat for a few showers as it pushes
southward. Most of the shower activity should be fairly light and
sporadic. In fact, still some pretty good dry air in the low
levels over the area, so it may take a little time to saturate up
to see showers in some places. Activity will depart by daybreak
with a mainly dry Tuesday on tap. Models continue to shift
everything southward towards the frontal boundary on Tuesday, so
have continued moving the rain chances southward. We may not see
anything reach far southern Kentucky until closer to 00z tomorrow
evening. Updated grids to reflect these latest changes.

UPDATE Issued at 754 PM EDT MON MAR 20 2017

Showers and storms are feeding on some elevated instability (above
10kft). Latest satellite imagery shows stable low level clouds in
place across central Kentucky. This would indicate a surface layer
very stable despite the elevated instability. Thus, no real
concern of winds mixing down to the ground. Thunderstorms are now
bearing down on areas just north of I-64 in northeast Kentucky.
Still looks like this activity will stay on our fringe counties in
northeast Kentucky. Rest of the area looks to stay dry through the
evening. Still watching the cold front approaching from the
northwest and will still be the focus for a few showers or storms
as it sinks southward later tonight. Updated grids to increase
rain chances in northeast Kentucky.

UPDATE Issued at 620 PM EDT MON MAR 20 2017

Complex of showers and storms continues to skirt into far northern
Kentucky this evening. A few isolated/scattered showers have
popped up ahead of this activity and drifting across Fleming, Rowan
and Bath counties. On the current trajectory, the complex of
showers/storms will just skirt our northeast counties as it drops
southeast. Should see a weakening trend as instability is much
less to the southeast of this system. However, a period of rain
will be possible in northeast Kentucky. Elsewhere, looks like a
dry evening for the rest of the area as dewpoints remain quite low
in the wake of the earlier day activity. As the front pushes on
through overnight, we may see moisture push back across the area
ahead of the front and could trigger some showers/storms as it
passes through the area overnight. Enough moisture may linger
behind the front to yield a bit of drizzle late tonight/Tuesday
morning. Tuesday is looking drier and drier as models continue to
back off on precipitation chances. Thus, removed most of the pops
through mid afternoon. May go further with this pending the 00z
hi-res model runs.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 359 PM EDT MON MAR 20 2017

The latest surface map features broad low pressure sprawled from
the southern Plains into Ohio Valley, with high pressure having
retreated to the Gulf Coast. Aloft, fairly zonal flow exists
across the heart of the CONUS, with several embedded weaker short
wave troughs. A more vigorous short wave trough is rotating
through south central Canada.

Convection has been dominating the synoptics thus far over the
past 24 hours, with a decaying MCS exiting eastern Kentucky.
This left an impressive differential heating boundary across the
Commonwealth, with a nearly 40 degree gradient in place at one
point earlier this afternoon. Temperatures are now rebounding in
our area, as clouds have thinned, and better low level warm air
advection has engaged. Meanwhile, upstream convection is growing
across Indiana and into western Ohio, closer to the surface low
and surface boundary, along with a secondary line of activity
forming along a leftover outflow boundary.

There is general model agreement with modest short wave energy
helping to bring the surface front southeast into our area
overnight, with convection likely recycling or sustaining
itself. Have maintained categorical POPs to the northeast, and
chance POPs west of I-75. Lows tonight will be much milder
compared to previous nights, with readings generally ranging from
the upper 40s to lower 50s.

Convection will be exiting to our east Tuesday morning, before
refiring along the surface cold front during the afternoon and
early evening. Highs will range from around 60 north, to the upper
60s south. The models have trended further south with the
boundary position, and the best POPs for the afternoon will be
along the Cumberland Valley. Convection will gradually wind down
through Tuesday night, as high pressure builds in from the north.
Lows Tuesday night will range from the lower 30s north of I-64, to
the lower 40s bordering Tennessee and Virginia.

.LONG TERM...(Wednesday through Monday)
Issued at 330 PM EDT MON MAR 20 2017

Rain will push south of eastern Kentucky Wednesday morning as an
upper low across the Northwestern Passages and Hudson Bay dislodges
east, sending a trailing trough axis through the Great Lakes and
upper Ohio Valley. Surface ridging will follow a similar trajectory
along the southeastern Great Lakes, ushering a cooler airmass into
the Commonwealth in wake of a cold front. High temperatures look to
largely drop into the mid 40s to low 50s, prior to lows Wednesday
night dipping into the upper 20s to low 30s. Valley locales across
far eastern Kentucky may even drop into the mid 20s, promoting frost
formation by daybreak Thursday. Will have to monitor exactly how far
aforementioned surface ridging pushes south, as the possibility may
exist for a stray shower or two to develop into south central
Kentucky through Wednesday evening as energy moves through in a
northwest flow regime aloft. Not currently expecting anything
measurable out of this given overall subsidence in place, but
again will have to see if a clean frontal passage can occur
earlier in the day to completely scour out available moisture.

A warming trend will take place Thursday into the weekend as upper
ridging slides in aloft with winds veering southerly at the surface.
This will be in response to surface high pressure moving into the
Atlantic while lee cyclogenesis materializes in the southern to
central Great Plains downstream of a digging upper low east of the
Four Corners Region. Dry conditions look to remain in place through
the end of the week, as precipitation stays shunted off farther
north across the Ohio Valley and upper Midwest into the Great Lakes
nearer greater forcing from another Hudson Bay upper low. Greater
moisture will also reside at farther north latitudes along a cold
front extending south off of this feature, as well as along a warm
front passing north of eastern Kentucky Thursday into Friday.

Rain chances will increase into the weekend as the stacked low
pressure system plows east, bringing both an increase in forcing and
moisture out of the Gulf of Mexico. Thunderstorms will also be
possible by Saturday afternoon as temperatures warm to near 70
degrees. Will have to continue monitoring synoptic/mesoscale details
later in the week regarding strong to severe thunderstorm potential
for the weekend. A brief dry period looks to ensue by late weekend
into early next week, before cyclonic flow loads up once again off
to the southwest. This should preclude much in the way of any
significant cooldown in wake of the weekend system.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
ISSUED AT 754 PM EDT MON MAR 20 2017

VFR conditions will last through the evening hours. A cold front
will push on through overnight with ceilings lowering through the
second half of the night. Latest model guidance is struggling with
the low clouds early tomorrow morning. Its possible we stay in the
MVFR category tomorrow morning, although GFS LAMP guidance
continues to support some IFR. For now, going to stay with the
MVFR as it matches model soundings better. MVFR may linger through
much of tomorrow as we stay just north of the cold front as it
stalls to our south.

&&

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

$$

UPDATE...KAS
SHORT TERM...GEOGERIAN
LONG TERM...GUSEMAN
AVIATION...KAS



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