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421
FXUS63 KJKL 220037 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
837 PM EDT Sun May 21 2017

.UPDATE...
Issued at 825 PM EDT SUN MAY 21 2017

Showers and a few thunderstorms along and in advance of a cold
front continue to move across parts of central and eastern KY.
Most of these, however, appear to generally be weakening as
sunset approaches. Wind gusts of 20 to 30 mph and possibly pea
size hail will be possible over the next hour or two with the
strongest cells. The rather narrow bands or areas of showers and
some thunderstorms should bring measurable rain to much of the
area tonight. Hourly pops have been adjusted accordingly in line
with recent radar trends and short term model trends. The showers
are still expected to end late this evening into the overnight
from west to east, ending by sunrise even in the far southeast.


&&

.SHORT TERM...(This evening through Monday night)
Issued at 425 PM EDT SUN MAY 21 2017

19z sfc analysis shows a cold front approaching central Kentucky
with new convection developing along it and east into the
Cumberland Valley. Far eastern Kentucky is still seeing light
showers tracking north out of southwestern Virginia. Even on
satellite, the clouds are more cumuliform over the western parts
of the CWA with breaks opening up. These should help to send
temperatures up into the middle to upper 70s in those locations
allowing for more instability to full the development of
thunderstorms. Will continue the mention of heavy rain potential
in the HWO as the PWs remain high and we have a few spots of low
FFG due to the storms of the past couple of days. Currently,
temperatures vary from the low 70s in the northeast where the rain
has been steadiest to the mid 70s elsewhere while dewpoints are
generally in the mid to upper 60s. Winds have been mainly light
and out of the south, but with some breaks for sunshine in the
west they have picked up to between 10 to 15 mph from the
southwest.

The models are in better agreement aloft through the short term
portion of the forecast as they all similarly depict the
evolution of the nearby and rather large mid level trough. This
low lies to the north of Kentucky tonight with nearly zonal flow
across the state along with the passing of a relatively minor
short wave by 12z Monday. Further amplification of the nearby
pattern then takes place into Monday night as the western portion
of the trough deepens over the Upper Midwest and starts to dig
south with more energy setting up to pass through the southern
Ohio Valley late in the period. Given the models` consistency and
agreement have favored a blend with a lean toward the latest high
resolution CAMS for details through the night.

Sensible weather will feature another round of showers and storms
for the forecast area before an eastward moving cold front shuts
down activity toward midnight from west to east. High pressure
follows briefly allowing the area to dry out through Monday
evening before more moisture is lured up from the south and may
return showers to the area by dawn Tuesday. Temperatures will be
near normal through the period with highs in the mid 70s and lows
in the mid 50s to lower 60s - though do anticipate a ridge to
valley split developing in the lows for Tuesday morning - not so
much tonight with the moisture and late CAA.

Used the CONSShort and ShortBlend as the grids` starting point
with some adjustments to lows Monday night owing to a ridge to
valley split developing. As for PoPs, have tightened them up in
the near term for radar and HRRR trends while also knocking them
down into Monday night.

.LONG TERM...(Tuesday through Sunday)
Issued at 300 PM EDT SUN MAY 21 2017

The extended portion of the forecast begins on Tuesday with an
amplified upper level pattern in place featuring strong ridging in
the west with a longwave trough digging into the Midwest and into
the OH Valley. This transitions to a more active and progressive
pattern and less amplified through the coming week. The passing
open low in the east swings through and into the New England states
by Friday. The ridging mentioned in the west will slide east as well
providing a break in the weather for Friday and Saturday, the last 2
days in the extended. The GFS and Euro show some disagreement on
this solution but overall, there is agreement on at least Friday
being dry.

Closer to the surface, with broad closed low overhead and developing
cold front over the southeast. In southerly flow, this will bring
ample moisture northeast into the Appalachians and a good chance for
showers and thunderstorms across the area. The upper low and remnant
surface boundaries coupled with any leftover mesoscale boundaries
will make for convection to initiate each day from Tuesday through
Thursday. Maximum occurrence will be associated with the diurnal
trend with cells peaking just after max heating and dissipating
after sunset. The main threat will tend to remain heavy rain as
instability and shear at this this point appear to be supportive of
a strong storm or two at most. Thus will stick close to the Super
Blend and may adjust dry according to the new Euro and neighbor
consensus for Day 6 and 7.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 820 PM EDT SUN MAY 21 2017

Showers and a few thunderstorms along and in advance of a cold
front will affect the TAF sites mainly during the first 2 to 6
hours of the period. MVFR and even brief IFR vis or ceilings are
expected with the stronger showers and any thunderstorms with a
lowering in the ceilings areawide to MVFR along and for a couple
of hours behind the cold front. As drier air moves in, the MVFR
ceilings should scatter out from northwest to southwest during
the 7Z to 13Z period, with VFR then developing. Outside of any
thunderstorms, winds should average 10KT or less shifting from
the south to southwest winds to west northwest during the 5Z to
9Z timeframe.

&&

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

$$

UPDATE...KAS
SHORT TERM...GREIF
LONG TERM...SHALLENBERGER
AVIATION...JP