Area Forecast Discussion
Issued by NWS Jackson, KY

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946
FXUS63 KJKL 261031
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
531 AM EST Sun Feb 26 2017

.SHORT TERM...(Today through Monday)
Issued at 410 AM EST SUN FEB 26 2017

As of early this morning, the region was under westerly flow
aloft within a broad trough extended from the Rockies east into
the eastern Conus. 500 mid level heights are not all that high,
but surface high pressure has built into the Lower OH and TN
Valley region south into the southeastern Conus. A mid and upper
level low was centered in the vicinity of the Hudson Bay Region
with a shortwave trough rotating around it that is currently
approaching the upper MS Valley and western Great Lakes regions.
Another shortwave is moving across the Central Plains while a
series of shortwaves are moving across the southern and central
Rockies with the main mid and upper level shortwave trough nearing
the southwestern Conus. The airmass in place across the region is
dry with dewpoints on the ridges generally in the teens though
some decoupled valleys have dewpoints in the 20s.

The surface high will begin to depart to the east today before
settling off the Mid Atlantic coast late tonight. Mid level
heights are also expected to increase today across the
southeastern Conus as ridging builds across the Caribbean. The
northernmost shortwave will rotate through the Great Lakes today
and then into Ontario and Quebec and St Lawrence Valley while the
one now over the Central Plains region merges with it. These
should bring an increase in cirrus to the area late today. Warm
advection will begin today and high temperatures should fall only
a couple of degrees below normals for late February.

Tonight, a couple of lead shortwaves eject toward the Oh Valley
while the main mid and upper level trough moves into the southern
Plains. Another shortwave trough will move across the Plains and
approach from the west. An area of low pressure should develop
over the Plains while return flow and isentropic lift should bring
increasing initially mainly mid and high level moisture to the
region tonight and into the day on Monday with the atmosphere
moistening up from the top down as a lingering result from the
ridging that will be departing. Valley locations should decouple
Winchell and with the dry air in place some locations in the far
east may fall to near 30 degrees before mid level clouds increase
and temperatures warm by the overnight hours. In addition, there
will be downslope flow in the southeast.

At this time, it appears the best chance precipitation late
tonight and early on Monday will be across the western and
northern fringes of the area as a shortwave moves passes through
the OH Valley. After this shortwave passes there may be a relative
lull in the precipitation chances with warm air advection and
isentropic precipitation beginning to increase mainly south of
the area late on Monday as warm front starts to lift toward the
area. Higher chances for more substantial precipitation will come
during the long term period.

.LONG TERM...(Monday night through Saturday)
Issued at 330 AM EST SUN FEB 26 2017

The period will be met with broad southwesterly flow with surface
high pressure parked off to the east. Meanwhile quasi-zonal flow
aloft with perturbations riding through the flow will keep the
period active Monday night into Tuesday night. There is some
instability Tuesday into Tuesday night that will lead to slight
chances of thunder. That said there will be a period of transition
Tuesday night that will lead to little to no POPs particularly in
the southeast. This period of transition will occur, as an upper
level wave moves into the central plains and low pressure deepens
across the Great Lakes.

A trailing cold front and height falls, as upper wave progresses
east will lead to best chances of POPs late Tuesday into
Wednesday. There are some timing differences, with GFS being the
faster solution and digs the trough a bit more than other
solutions. The ensemble mean seems to better align with slower
solutions seen in the long term guidance, and therefore think the
overall model blend POPs look good at this point. Given the
reasonable consistency did go ahead and keep the model blends CAT
POPs. We stand to get a good soaking rain, but still a bit
uncertain on exact axis of heavier precipitation. Right now total
amounts of 1 to 1.5 inches would be quite possible throughout the
region Tuesday night into Wednesday evening. The severe chances
look relatively low with SPC MARS and CIPS analog keeping better
chances to the west and southwest. This lines up better with the
SPC climatology as well. However given deep layer shear and at
least some meager instability some of these storms could be
strong.

Cold air mass will arrive Wednesday night into Thursday,
but this will primarily bring us back closer to normal values for
this time of year. These near to a little below normal
temperatures will remain through Friday. A clipper does drop into
the Ohio Valley Thursday night into Friday and perhaps a few
sprinkles/flurries or rain/snow showers pass across NE portions of
the CWA. Right now feel the better forcing will reside NE of the
CWA and therefore low confidence on any measurable precip in KY.
Canadian high pressure quickly pushes southeast late Friday into
Friday night leading to a decent night for ridge/valley splits.
Right now with some uncertainty will go 5 degrees, but the COOP
MOSGUIDE suggests possibility of a larger split. Temperatures are
set to warm some as high shifts east Saturday, but air mass will
still keep low to mid 50s in place. Given upper level ridging we
should also remain dry to round out the long term period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
ISSUED AT 109 AM EST SUN FEB 26 2017

Calm winds are initially observed at LOZ and SME and light west
southwest winds at JKL, SJS, and SYM. Stratocu has built back
into areas from near SYM to just south of IOB and then southeast
to near JKL to PBX. This is leading to BKN to OVC VFR Cigs in the
4 to 5KFT AGL range at SYM, SJS, and JKL to begin the period. As
the sfc ridge center nears in the first 6 hours of the period,
this stratocu should scatter out with just some high clouds
passing by from time to time well into Sun. Overall, VFR is
expected through the period, though high clouds will increase
from 21Z on and mid level clouds near 10KFT AGL should move into
the area by the end of the period. Winds will remain light through
the period with high pressure dominating.

&&

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

$$

SHORT TERM...JP
LONG TERM...DJ
AVIATION...JP



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