Area Forecast Discussion
Issued by NWS Jackson, KY

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103
FXUS63 KJKL 302355 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
755 PM EDT Sun Apr 30 2017

.UPDATE...
Issued at 740 PM EDT SUN APR 30 2017

Did a quick update to the grids to reflect the storms moving in
from the southwest and their gradual dissipation as the move
deeper into the CWA. Also tweaked the near term T and Td per the
latest obs and trends. These have been sent to the NDFD and web
servers.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 440 PM EDT SUN APR 30 2017

19z sfc analysis shows deep low pressure moving through the
Central Plains with a warm front strung out to the east northeast
well north of Kentucky. This places the JKL CWA in a large warm
sector of higher instability. The question is, as it was last
night, will there be enough sfc convergence to generate convection
that can get through a weak cap. So far a couple of showers or
storms have popped up but also faded out. Do expect a few more
through the first part of the evening so will run the zones with a
pre-first period to cover this. Skies are partly sunny with the
thicker clouds noted to the west and thin ones east. The cloud
cover is helping to keep temperatures in check further west with
low to mid 80s common while more sunshine in the east has made for
upper to mid 80s in most places. dewpoints held up in the 60s for
the most part with only some late mixing sending some points to
the upper 50s. This period of drying likely helped to kill the
earlier convection. Winds have been breezy across the area this
afternoon from the south at 10 to 15 mph with gusts to 25 mph at
times, mainly west.

The models are in good agreement aloft through the short term
portion of the forecast. They all depict a very deep closed low
lifting northeast, and deepening further, through the mid
Mississippi Valley to the western Great Lakes by Monday evening.
Mid level energy will precede the height falls into Kentucky this
evening with the main surge arriving towards dawn for the east.
Heights will slowly rebound over the state in the wake of the low
moving into Canada early Tuesday. Given the good agreement aloft,
will favor the consensus blends with a lean in the near term
toward the high resolution HRRR.

Sensible weather will feature a mostly quiet and mild evening
with still a threat for a strong storm to develop in situ while
also the need to watch for outflow boundaries seeping into the
area from the south, particularly with the line moving across
south central Tennessee attm. Have allowed the pre-frontal shower
and storm threat to push deeper into eastern Kentucky this evening
and early overnight before fading out. The main push of the front
will be through during the late night hours with still a chance
for thunder. Winds will be gusty on the ridges in the east
overnight and have highlighted this in the HWO. The front moves
through the rest of the area early Monday with gusty winds along
the boundary and behind it - blowing from the southwest. For
this, have issued a Wind Advisory from 11 am through 8 pm. Colder
air follows behind the front along with sc clouds wrapping down
from the north - also keeping the temps in check late Monday.
Cool conditions follow for Monday night with lows in the upper 40s
and lower 50s.

Again used the CONSShort and ShortBlend as the starting point for
all the grids with some adjustments for ridge to valley T
distinctions tonight and for the CAA pattern Monday night. Also
beefed up PoPs right with the front late tonight into Monday
morning as it looks like most places will see measurable QPF when
the boundary does go through.

.LONG TERM...(Tuesday through Sunday)
Issued at 245 PM EDT SUN APR 30 2017

The models were not in quite as good of agreement with the general
flow pattern across the CONUS in the extended. The GFS was quite a
bit slower than the ECMWF regarding timing of precipitation onset
during the Wednesday and Wednesday night periods. The GFS had the
same general flow pattern as the ECMWF, with similar placement of
high and low pressure centers and boundaries, the GFS was just
slower about bringing precipitation eastward into central and
eastern Kentucky Wednesday and Wednesday. The ECMWF, however, was
consistent with its previous of runs and continues to show
precipitation moving into the forecast area around 18Z Wednesday.
That being said, decided to go pretty close to the national model
blend, with very few tweaks needed. The forecast issue this go round
looks to be the timing and duration of rainfall across eastern
Kentucky from Wednesday afternoon through Saturday night. The
highest precipitation probabilities should occur from Wednesday
night through Friday night, as a frontal boundary gets hung up
across the region, and a series of disturbances move from west to
east along it. Based on the latest model data, instability will be
hard to come by in the extended, as thunderstorm activity was
confined to a short time frame Wednesday afternoon and evening.

Temperatures during the period should generally be below normal,
with daily highs topping around 70 most days, and nightly lows
ranging from the mid to 40s to lower 50s across the area. Daytime
temperatures will likely be held in check by widespread cloud cover
and persistent precipitation from Wednesday onward. We could see
gusty winds again on Tuesday, with sustained southwesterly to
westerly flow between 10 and 15 mph expected and gusts of 20 to 25
mph possible.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 755 PM EDT SUN APR 30 2017

Aside from the storms affecting the southwestern portion of the
Cumberland Valley attm, VFR conditions are expected to hold
through the first part of the night. Gusty south winds ongoing
currently will settle for a time this evening before picking up
as a frontal boundary approaches the area by 06z - also kicking
up some low level wind shear that will last through the rest of
the night. The front will pass late tonight into early Monday
morning with a likely solid band of showers and a few storms
moving on through. We will see winds behind the front midday
Monday through late afternoon even stronger than those of this
afternoon - gusts up to 35 knots possible. Any MVFR cigs and
vsbys associated with the front will break up by mid morning
Monday when post fropa dry air advection kicks in. Look for the
winds to start to settle down toward 00z Tuesday.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 11 AM to 8 PM EDT Monday for KYZ044-050>052-
058>060-068-069-079-080-083>088-104-106>120.

&&

$$

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



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