Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 151925

National Weather Service Jackson KY
325 PM EDT Thu Mar 15 2018

.SHORT TERM...(This evening through Friday night)
Issued at 325 PM EDT THU MAR 15 2018

A cold front over the northern part of the forecast area will
work its way south across the forecast area tonight. The front
will stall over TN on Friday. The front will then serve as a
focus for precipitation as it gradually lifts north Friday night
in response to low pressure moving east from the plains into the
Mississippi Valley.

The model trend has been for a slower onset of precipitation, and
also warmer temperatures Friday night. At this time any freezing
rain Friday night looks to occur north and northeast of the
forecast area.

Some mid level clouds, associated with a jet streak, have
lingered across the center part of the forecast area through much
of the day. These should gradually shift south overnight. Despite
a gradual increase in clouds in the south and eventually the
central part of the forecast area late tonight, there should still
be enough radiational cooling in the valleys for at least a small
ridge valley temperature difference to develop tonight.

.LONG TERM...(Friday night through Wednesday)
Issued at 505 AM EDT THU MAR 15 2018

The models remain in only fair agreement aloft through the long
term portion of the forecast during this busy and progressive,
transition season, pattern. Some agreement at the largest scale
breaks down and become more disjointed at smaller scales through
the forecast period. This results in lower confidence in any
specific model solution and favors an ensemble and blended
solution as a starting point. The models depict 3 separate and
significant impulses to move through the region over the next
week. The first of these comes out of the Central Plains as a
closed low but dampens quickly as it slides east Friday night
into Saturday. The GFS is quicker and weaker than the ECMWF and
CMC with this feature. Fairly flat ridging follows for the area
into Sunday with still plenty of energy packets moving through the
swift mid level flow. For Monday, the next impulse will be
inbound with the GFS again fastest, but with similar strength. The
core of this dampening, but still distinct and healthy, wave
rides over eastern Kentucky early Tuesday morning. The pattern
then becomes more convoluted by mid week as more energy passes
through the Midwest and into the Ohio Valley with heights
falling and a full latitude trough taking shape over the region
into Wednesday - quicker, further south, and not quite as strong
in the GFS than the ECMWF - but similar enough to make for a clear
trend toward continued active and changeable weather. Despite the
larger than desired spread to the models it is clear that near
normal to mild regional temperatures early on will turn colder
toward the end of the period while damp conditions look to remain
in place or worsen with time.

Sensible weather will be quite active through the period with
several sfc lows passing through the Ohio Valley from Friday night
through Wednesday. The first of these will lift a warm front
through eastern Kentucky Friday night into Saturday morning. The
leading edge of this will push into cold and dry air in place over
the northeast parts of the JKL CWA and the pcpn may catch up to
this air to result in a brief period of mixed weather towards
dawn, though the amount of warming aloft should mitigate this
threat. In fact, the sfc low may also take advantage of its warm
surge on Saturday to kick off a few thunderstorms, but model
uncertainty precludes adding any TRW to the grids, at this time.
Cooler and mainly dry weather follows into Sunday before the next
warm front lifts into Kentucky early Monday with this later sfc
low passing right through the state with showers and potential
thunderstorms that afternoon followed by colder temperatures into
Tuesday. Some snow may start to mix in later Tuesday and into
Wednesday as the larger trough aloft takes shape and lowers sfc
pressure throughout the region - though significant uncertainty
remains at these later time steps.

Made only minor adjustment to most of the temperature grids
through the period, but did nudge them strongly toward the
CONSRaw blend Friday night into Saturday (along with dewpoints).
As for PoPs, again tried to limit them bulk of them to the sfc
features - focused on each successive wave passage.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)

Mixing has allowed some stronger winds aloft to make their way
down to the surface. As a result west winds will gust to between
20 and 30 knots this afternoon. The winds will diminish quickly
this evening and become variable and light in most areas by Friday
morning. VFR conditions will prevail through the TAF forecast
period, with mid level clouds gradually increasing over southern
and central parts of the forecast area tonight.




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