Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 260640
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
240 AM EDT Fri May 26 2017

.Short Term...(Today through Saturday)
Issued at 230 AM EDT Fri May 26 2017

High pressure ridging across the Appalachians at this time will
weaken as our next low pressure system moves out of the Central
Plains. This low will be filling though as it moves into the Midwest
this evening. Shower/storm activity associated with this system
should stay northwest of the region through this afternoon. Forecast
soundings indicate a fairly stout cap around 700 mb that should keep
us dry for the day. With more sunshine today as well as southerly
winds, we should warm up into the upper 70s to lower 80s, roughly
near normal.

Tonight, a warm front will trail southeast from the surface low
moving toward southern Lake Michigan late tonight. This front will
be near CVG and should serve as a focus for overnight storms along
our northern border counties. Cannot rule out a few showers
developing as well, in an area of weak convergence along a 30-40
knot low-level jet along the Ohio River.

Saturday is a bit of a complicated forecast, as model guidance keep
light QPF area-wide but also pull in contradictory CAPEs around 5000
J/kg (NAM!) by the end of the day. Based on forecast soundings,
would not be surprised to see some lower clouds/light precip through
the morning hours, possibly the remnant of any boundaries dropping
in from the storms across the north Friday night. Then for the
afternoon, expect a cap should be enough to keep most of the area
dry. Based on model QPF fields, have to keep in some scattered pops,
but again would not be surprised to see Saturday afternoon dry out
some in model trends.

&&

.Long Term...(Saturday night through Thursday)
Issued at 230 AM EDT Fri May 26 2017

...Organized Severe Weather Possible Late Saturday and Sunday of
the Holiday Weekend...

The bigger threat will come from storms initiating well west of the
region during the day Saturday. Back-tracking the latest NAM Nest
solution has a squall line moving across our area Sat. night coming
from a set of snow showers over southeast Idaho early this morning.
By 00Z Sunday, that NAM has a line of storms around St. Louis. The
GFS is a little faster and the 12Z Euro was a little slower. The
latest ARW instead develops new storms over southeast Missouri, as
well as showers across the Commonwealth. Would believe more of the
MO storms than that over KY, given the cap mentioned above.

Given above model discrepancy, there is still some uncertainty in
where storms will occur Saturday night, but the most reasonable
solution would have be something moving from the west rapidly across
either the Ohio or Tennessee Valleys, and given plenty of elevated
CAPE, the storms should at least maintain themselves well into our
latitude through midnight before starting to fade some farther east.

Sunday`s forecast will depend greatly on what happens Sat. night,
and any boundaries left in the area as well as a cold front moving
slowly in from the west. Soundings argue for damaging wind potential
in the stronger cells that could develop that day, but again it`s a
little early to get into severe particulars just yet. One thing that
could pose a problem though is flooding, with any areas that see
storms both Sat. night and Sunday afternoon/evening.

Sunday night, the front should be clearing our region, with Monday
being a dry day. That drying may be short-lived however, as the
various deterministic and ensemble guidance again bring us light
rain chances in vortmaxes rounding the base of a large upper low Tue-
Thu.

&&

.Aviation...(06Z TAF Issuance)
Issued at 132 AM EDT Fri May 26 2017

VFR conditions are forecast at all TAF sites through the valid TAF
period as progressive upper level ridging moves into the Ohio
Valley. Other than SDF potentially dropping down around 6SM for a
period pre-dawn, expect light SW winds with a few upper level
clouds. After sunrise, expect a steady SSW wind between 10 and 15
mph with a few-sct mid and upper clouds. SDF could contend with a
few showers or storms toward dawn on Saturday, but will leave
mention out until confidence is higher.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&

$$

Short Term...RJS
Long Term...RJS
Aviation...BJS


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