Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 200028
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
828 PM EDT Fri May 19 2017

.UPDATE...
Issued at 828 PM EDT FRI MAY 19 2017

Convection has spread across areas along and just north of I-64.
Outside of the brief rotation on radar, things look to be calming
down with storms showing a slow weakening trend. This could
continue as instability wanes and storms move into an environment
with much less shear. Updated to trim back pops to just the north.

&&

.SHORT TERM...(This evening through Saturday night)
Issued at 356 PM EDT FRI MAY 19 2017

After a wet Friday morning across eastern Kentucky, a dry afternoon
has materialized. That being said, a broken line of storms has
developed from the Indiana/Ohio line south to western Tennessee
along a cold front, with additional development across central Ohio
where surface convergence exists. Not expecting much of this
activity to propagate southeastward into eastern Kentucky given the
worked over airmass in place, although temperatures have warmed into
the upper 70s while dewpoints reside in the upper 60s. This may
allow for a few storms to stream in and develop, most notably across
the Bluegrass region nearer the greater forcing and ongoing
convection.

The aforementioned cold front will remain well north and west of the
Bluegrass region as an upper low ejects out of the Front Range of
the Rockies into the central Plains, keeping eastern Kentucky firmly
in the warm sector as a surface low moves through the Missouri
Valley toward the Corn Belt Saturday. This should keep coverage
isolated to scattered at best through Saturday, with mostly dry
conditions expected tonight. Further hindering greater storm chances
Saturday will be rising heights aloft as shortwave ridging
strengthens from the southeastern U.S. to Hudson Bay. A period of
backing southeasterly surface winds would also keep conditions drier
as downsloping takes place. Given the relatively drier conditions
Saturday, high temperatures should warm into the mid-upper 80s,
flirting with record territory. Much better shower and thunderstorm
chances will materialize Saturday night into Sunday as height falls
occur with an approaching cold front. Heavy rainfall looks to be the
primary threat with this round of showers and storms given the deep
rich moisture in place and lack of dry air to support downburst
winds or lowering freezing levels and hail.

.LONG TERM...(Sunday through Friday)
Issued at 410 PM EDT FRI MAY 19 2017

A deep upper level low will continue to push northeast from the
Upper Midwest into Ontario from Sunday morning through Monday
morning, where it will pivot and transition eastward into Quebec by
Tuesday. This will result in lowering heights across Kentucky
through this time. A shortwave will develop in the troughing Monday
morning across the Northern Plains, shifting southeast towards the
Ohio Valley through midweek, with the axis pivoting across eastern
Kentucky Thursday morning. Models are in fairly good agreement
during this time, however, start to diverge after Wednesday night in
their solutions. The latest ECMWF will keep zonal flow across the
region to finish out the forecast period, while the GFS will keep
troughing in place. Given uncertainty, did not waiver much from the
blended solutions.

At the surface, a low pressure system will accompany the upper level
low, moving into the Upper Great Lakes during the day Sunday,
reaching central Ontario by Sunday night, before shifting eastward
during the day Monday and continuing into Quebec Tuesday. A cold
front will extend southward from this low, dragging eastward across
KY during the day Sunday, reaching eastern KY Sunday night. As the
low continues to move farther northward, the frontal zone will begin
to shear out a bit by the time it reaches our region. Nevertheless,
this will be the focus for widespread showers and thunderstorms
ahead of and along the frontal passage during the day Sunday and
into Sunday evening. Strong high pressure will move in just behind
the frontal passage, with a sharp drop in temperatures expected as
well as a quick cut off in moisture as drier air moves into place.
This will effectively cut off any remaining convection behind the
frontal passage, as well as rainfall Monday morning. Held on to pops
slightly longer than yesterdays forecast given the latest model
agreement/trends.

High pressure will remain in place for about a day across the
Commonwealth, before the secondary shortwave produces another
surface low pressure system and resulting cold front, which will
shift southeast towards the region on Tuesday. This will be a very
fast moving system, with the frontal boundary expected to pass
through eastern KY Tuesday evening/night. Warm southerly flow ahead
of this next frontal passage will once again allow for showers and
thunderstorm chances across the CWA starting Tuesday afternoon.
Another surface low pressure system is expected to develop to our SW
and move NE into the state according to the latest ECMWF. Confidence
is still a bit low on the intensity of this system, as well as the
timing, but if it materializes, we could expect precip chances
across much of the CWA from Wednesday and throughout the day
Thursday, finally tapering off for Friday.

Temperatures will be at or just below seasonable normals during this
period, with the combination of clouds/precip and upper level
troughing helping to play a role.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 828 PM EDT FRI MAY 19 2017

Mainly VFR conditions will be seen through Saturday evening for
most areas. However, a brief thunderstorm will move through over
the next hour providing a brief period of MVFR at KSYM. Then some
valley fog will likely develop tonight with the recent rainfall
impacting KSME and KLOZ.

&&

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

$$

UPDATE...KAS
SHORT TERM...GUSEMAN
LONG TERM...JMW
AVIATION...KAS



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