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Area Forecast Discussion (AFD)

Issued by Jackson, KY (JKL)

                            
000
FXUS63 KJKL 180552
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1252 AM EST Fri Jan 18 2019

.UPDATE...
Issued at 1115 PM EST THU JAN 17 2019

Showers continue to move across southeastern KY, while drizzle 
has been observed in the northwest and hinted at by the lighter 
returns there. Hourly grids have been updated based on recent 
observations and radar trends. For now carried slight chance to 
chance pops for the drizzle potential behind the showers. Overall,
no substantial changes were needed at this time.

UPDATE Issued at 755 PM EST THU JAN 17 2019

A cold front continues to approach the region as a shortwave also
is moving across the area. This is leading to scattered to
numerous showers working across the area at this time. Some
drizzle or more isolated showers are being reported or indicated
on radar upstream over central KY. These should continue to slowly
become less widespread from northwest to southeast through late
evening and into the overnight as the mid level wave moves east 
and moisture depth/mid level moisture decrease. Low clouds and 
some lower visibilities are also being reported upstream of the 
area. Model guidance suggests at least some transient patchy fog 
overnight, especially along and just behind the cold front as it 
works south and east late this evening and overnight. Ridgetops 
would likely be most susceptible to this. Also, the low level 
flow will become more upslope late, with low level moisture 
remaining. With the low level moisture and clouds persisting, 
chances for light rain showers or possibly drizzle will remain 
most of the night, especially in the far southeast. 

Some adjustments were made to mainly hourly pop and temperature grids
based on recent observations and radar and short term model
trends.

&&

.SHORT TERM...(This evening through Friday night)
Issued at 315 PM EST THU JAN 17 2019

The short term portion of the forecast will feature a couple of
bouts of rain across eastern Kentucky to end out the week. The
first round of rain will gradually taper off this evening and
tonight, as a trough of low pressure moves quickly across the Ohio
Valley region. The last of the rain should be exiting the area by
early Friday morning. Temperatures should remain above freezing
for all but our highest elevation locations along the Virginia
border, so rain will be the predominate precipitation type through
tomorrow morning. We should see a brief reprieve from the rain
Friday and Friday night, as we will be between storm systems
during that time. The next round of rain should arrive early
Saturday morning, as another, but much stronger, area of low
pressure moves towards us out of the southern Plains. This system
could bring locally rainfall and accumulating snow to the area
over the weekend. Any rainfall we receive the through late tonight
should be light in nature and should not cause any problems.

Temperatures through the end of the week should be normal during 
the day on Friday, highs in the lower 40s, and well above normal 
the next two nights, with lows in the mid to upper 30s on tap. The
stubborn widespread cloud cover we've been experiencing the past 
several days will not be going anywhere anytime soon. In fact, we 
will be seeing overcast skies across the area through out the 
period and over the weekend. Winds will continue to blow from the 
south or southwest through tonight, before shifting to the west 
and northwest after the trough moves past us tonight. We should 
then see the winds shift to a general easterly direction across 
the area, as the next storms system approaches from the 
southwest.

.LONG TERM...(Saturday through Thursday)
Issued at 335 PM EST THU JAN 17 2019

The models, aloft, continue to struggle to resolve a couple of major 
weather systems to affect the region through the extended portion of 
the forecast. The first of these sweep through Saturday and Sunday 
as a full latitude trough with the GFS and CMC quicker than the 
slightly stronger ECMWF. The main energy band from this system looks 
to crash through eastern Kentucky late Saturday with a 5h trough 
axis to follow by Sunday morning. Northwest flow then commences 
briefly through the start of the new work week before a temporary 
rebound in heights spread east through the state. Upstream, the next 
major weather system takes shape through the Great Basin - digging 
into the Four Corners Region by Tuesday morning - the ECMWF and CMC 
are deepest with this while the GFS is weaker and quicker. Look for 
southwest flow for Kentucky ahead of this next trough's approach 
into mid week. By Wednesday morning the CMC really starts to lag the 
other models with the ECMWF the fastest and the GFS offering a 
reasonable compromise solution. Going with the latter's idea, the 
trough will pass through Kentucky later Wednesday into Thursday 
morning with the lowest heights moving overhead for the JKL CWA on 
Thursday. Given the uncertainty that remains with both these major 
winter weather troughs have favored a blended solution throughout 
the extended portion of the forecast with some WPC based adjustments 
applied to QPF and snow specifics with the weekend storm. 

Sensible weather will feature one last mild day on Saturday before 
winter makes a strong push back into the region later that night. 
With the track of this potent and deepening sfc low moving east 
right through the state a good slug of moisture will precede the 
cold air and bring soaking rains along with a potential for 
convection across the area on Saturday. Localized high water may 
be an issue from this later Saturday and Saturday night - likely
affecting the rivers by the start of the new work week.

The low track also keeps the cold air north of the CWA sparing 
eastern Kentucky some of the heaviest snow amounts of the storm. 
However, the cold air that pours into the state on brisk northwest
winds will quickly change the liquid pcpn over to snow, with 
perhaps a brief period of freezing rain or sleet at the transition
onset from west to east Saturday night. A couple of inches of 
snow may be possible just in the wake of the cold front into 
Sunday morning with upslope to follow, continuing light snow 
showers, but not much additional accumulation after mid morning. 

Cold temperatures will be the rule on Sunday with highs likely set 
in the morning and readings falling for much of the day. Brisk 
winds will contribute to the cold with single digit wind chills 
possible by evening. CAA continues in the night as air
temperatures bottom out in the single digits for most on Monday 
morning. Some sunshine should make an appearance on Monday while
high pressure is overhead but readings will likely not get above 
freezing for most. 

There will be a brief warmup ahead of the next system on Tuesday 
thanks to some southerly winds and a retreat of the Arctic high to 
the east. With this, though, another round of rain late Tuesday 
will precede a renewed shot of winter's air for Wednesday with 
some light snow accumulation possible mid week as it departs. 
Again temperatures will be down into the low 20s and possibly 
the teens for Thursday morning then struggle to climb into the mid
and upper 30s later that day thanks to system's trailing high 
pressure. Plenty of uncertainty remains with both these systems 
and the potential for further southern development - particularly 
the Wednesday one - that could slow its passage and result in 
more snow. Needless to say, winter is roaring back (or just 
arriving for many) for the extended portion of the forecast and 
beyond.

For temperatures in the extended, did not deviate far from the Blend 
except to lower them across the board later in the week with the
potential for additional intrusions of modified arctic air. As 
for PoPs, lingered them longer than the guidance into Sunday
evening for upslope and also tweaked them down to the west late in
the period - favoring the southeast development with the latter
system as it departs Wednesday into Thursday. 

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
ISSUED AT 1252 AM EST FRI JAN 18 2019

We are beginning the period in a mix of LIFR and IFR tonight, 
with most location experiencing some fog or drizzle. The 
soundings are indicating that the low level moisture remains in 
place through the period even with the front progressing across 
the area. Given this have kept the CIGs in the IFR or lower range
through a good portion of the period, with perhaps some
improvements to MVFR by this afternoon or evening timeframe. 
Overall the rain showers have ended minus a few left over rain 
showers in far southeast and some drizzle at times. The winds will
remain light through the TAF period, with some shifts in 
direction related to the cold front.

&&

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

$$

UPDATE...JP
SHORT TERM...AR
LONG TERM...GREIF
AVIATION...DJ