Area Forecast Discussion
Issued by NWS Jackson, KY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KJKL 230303 AAB

National Weather Service Jackson KY
1103 PM EDT Thu Mar 22 2018

Issued at 1055 PM EDT THU MAR 22 2018

Skies remain mostly clear to clear under high pressure with
decoupling in valleys leading to some readings near 30 if not the
upper 20s at this time with mid 30s on the ridges. These readings
indicate that the lower min T updated to this evening appears to
be on target.

Uncertainty remains with the system this weekend as the 0Z
guidance begins to roll in. Further analysis of the previous data
seems to point toward a sharper temperature gradient from north or
northeast to southwest with Fleming, Rowan, and Elliott counties
remaining a category or so lower than blended model guidance and
have followed these trends for temperatures on Saturday. 18Z GFS
guidance and new 0Z NAM sounding point toward the column remaining
the coldest in these counties. Latest trends seem to be toward a
bit more accumulation in those locations and these counties were
highlighted a refreshed SPS. As the remainder of the 0Z guidance
comes in a better determination can be made on what headlines may
be needed for portions of the region.

UPDATE Issued at 845 PM EDT THU MAR 22 2018

Hourly temperatures have been freshened up based on observation
trends. High pressure should bring mostly clear to partly cloudy
skies tonight. MOS guidance points toward colder valley
temperatures in the northeast and east compared to the previous
forecast while LAMP guidance points toward ridgetop locations
also a degree or two colder. At this time, have trended
temperatures down a degree or two across the board with no other
changes at this time.

Lots of uncertainty remain with the system to affect the region
late Friday night into Saturday especially with the thermal
profile in the lowest few thousand feet. Model consensus is for
the coldest profiles near 0C at the sfc and for several thousand
feet aloft over Fleming, Rowan, and Elliott counties. The NAM has
quicker warming aloft associated with the low level jet which
would lead to melting and transfer of warmer air to the surface
quicker. The GFS is colder, especially over northern Fleming
County and this seems to be the most probable location for a
couple of inches of accumulation. Whatever does fall will be
battling rather warm ground and even limited solar insolation from
late March sun should help inch temperatures above freezing in
all locations by Saturday afternoon.


.SHORT TERM...(This evening through Friday night)
Issued at 340 PM EDT THU MAR 22 2018

19z sfc analysis shows high pressure building more effectively
into eastern Kentucky. This is helping to settle the winds some
after a time of gustiness following the breaking of the inversion
early in the afternoon. Additionally, the high is helping to keep
the cu to a minimum out there - mainly found in the far east.
With ample sunshine temperatures have climbed into the low to mid
40s while dewpoints remain in the low to mid 20s. The latest
satellite images shows the substantial erosion of any snow cover
due to the warmer temps and late March sun.

The models are in good agreement aloft through the short term
portion of the forecast. They all depict full-latitude, strong
ridging through the High Plains at the start of the period with
Kentucky in the midst of fast northwest flow. This ridge does
break down quickly as it attempts to come east but runs into a
blocking closed low trough centered over New England. This will
allow more Pacific energy and moisture to stream through the Upper
Midwest and then down southeast into Kentucky for late Friday into
Saturday morning. The core of this energy will be strong enough to
buckle the ridge over the Central Plains Saturday morning - the
NAM is strongest with this and actually starts to close off a mid
level low while the other models maintain open waves. This all
slides southeast into the JKL area on Saturday. Given the model
agreement have favored general model blend with a strong lean
toward the details from the higher resolution NAM12 and HRRR
throughout the period.

Sensible weather will feature high pressure moving over the state
tonight and off to the east on Friday. Expect a ridge to valley
temperature split to develop tonight with widespread frost
through the area and some patchy fog along the river valleys.
High clouds will slowly arrive on Friday from the west as a warm
front starts to take shape to the southwest. This boundary lifts
into eastern Kentucky later Friday night with ample moisture and
lift to generate pcpn through the CWA as it moves from southwest
to northeast with time. The cold air will be tough to shift out of
the way in the northeast parts of the area along with wet bulbing
likely to lower temps further at onset of the pcpn. Accordingly,
expect the pcpn to move in as snow generally north and east of a
line from Irvine to Whitesburg. Gradually this line will shift
northeast through the night with a mix with and switch to rain
anticipated for much of the area by 12z Saturday. Locations
generally along and north of Interstate 64 will likely stay as
snow and an inch or so of accumulation will be possible by sunrise
Saturday. The snow will continue into the morning in our far
northern areas - but likely remain below warning criteria due to
low snow ratios. For that reason will keep Fleming and Rowan out
of the Winter Storm Watches current in effect to the north and
instead issue an SPS highlighting this concern in addition to
mentions in the HWO.

Started with the CONSShort and ShortBlend for the bulk of the
grids in the short term portion of the forecast. Did make some
significant adjustments to temperatures tonight for relative
elevation differences - especially northeast. As for PoPs, beefed
them up in the south quicker Friday night into Saturday morning
closest to the NAM12 scenario.

.LONG TERM...(Saturday through Thursday)
Issued at 325 PM EDT THU MAR 22 2018

The extended will feature a period of colder weather and the
potential for accumulating snowfall to start things off, before
transitioning into a much warmer weather pattern that will feature
chances of rain the first few days of the new work week. An area of
low pressure is forecast to move southeastward and across the Ohio
and eastern Tennessee valley regions Friday night into Saturday.
Rain will quickly transition to a rain snow mix and then to all snow
Friday night. The snow is expected to move across northern portions
of eastern Kentucky through late Saturday morning, before change
back over to all rain by the afternoon. Some accumulations of snow
will be possible, but there is some uncertainty at this time as to
how much snow we will see. The current pattern does suggest that the
bulk of any accumulating snow would occur north of the Hal Rogers
Parkway. As the area of low pressure moves across the area during
the warmer part of the day on Saturday, it may even trigger a few
thunderstorms from the Tennessee border northward to the Hal Rogers
Parkway, where warmer temperatures and a bit of elevated instability
may exist. The rain should finally begin to taper of late Saturday
night, as the low pulls away to the southeast. We will likely see
some snow mixing with the rain Saturday night as well, as colder air
makes a weak southward push. Little if any accumulation is expected
from this second batch of snow. Any remaining precipitation should
move out of eastern Kentucky by early Saturday evening.

Temperatures are expected to be below normal over the weekend as a
trough of low pressure aloft keeps colder air in place over the
region. Once this trough moves away, as a ridge of high pressure
settles over the region. An area of low pressure will also be in
play to during this time, and could bring a few rain showers to the
western portions of our forecast area, but isolated to scattered at
best on Monday and part of Tuesday. Better chances of rain will be
in the offing Wednesday and Wednesday night, as a frontal boundary
moves across the area. This boundary may even stall for a bit,
bringing enhanced rain chances to eastern Kentucky. Southerly flow
associated with this front, and the ridge that will temporarily set
up across the area in the days before the front arrives, will also
bring warm air from the Gulf of Mexico into the region. This will
allow temperatures to warm into the upper 50s to perhaps 60 on
Monday, and into the 60s the rest of the week.


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)

High pressure at the surface and northwest flow aloft is expected
through the period. Some mid level clouds are expected in the
northwest flow tonight with an increase in low and mid level
moisture after 12Z leading to some thickening and lowering cloud
bases ahead of a warm front. Some light rain could reach the Lake
Cumberland region including near KSME by the end of the period.
However, MVFR is expected to prevail throughout the period with
light winds.




AVIATION...JP is the U.S. government's official web portal to all federal, state and local government web resources and services.