Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 271040
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
640 AM EDT Mon Apr 27 2015

...Updated Aviation Discussion...

.SHORT TERM (Now through Tuesday)...
Issued at 245 AM EDT Mon Apr 27 2015

Cool and dry weather will continue through Tuesday in the Ohio
Valley, as the NW flow on the backside of an eastern CONUS trof
gives way to upper ridging building in from the Plains and the Upper
Midwest. Low-level air mass is of Canadian origin, so our temps will
run below normal. Only real challenge is whether we`ll be cold
enough for any patchy frost tonight. Expect most locations to bottom
out in the lower 40s Tuesday morning, in fairly similar fashion to
this morning. Mid/upper 30s not out of the question in the sheltered
valleys, and frost formation should be limited to these locations.

.LONG TERM (Tuesday Night through Sunday)...
Issued at 310 AM EDT Mon Apr 27 2015

A couple of upper lows will affect the region for the second half of
the work week. The first will cross the Tennessee Valley and help to
spawn a surface low across the southeast U.S. Our region will be on
the far northern extent of the rain shield for this system, likely
with a sharp gradient in where the rain actually falls over KY. The
00Z GEM continues to confine this precip well south of our region,
whereas the GFS have a more realistic deformation band forming
precip into southern KY. Will continue to trend pops up some in that
region.

The second upper low will dive south out of Ontario on its way to or
east of the I-65 corridor in KY during the day Thursday. Model
guidance is in reasonable agreement on this scenario. We may have
just enough moisture to eek our some rain showers east of the I-65
as this system passes through the region. Low-level thicknesses are
fairly small with this system, so expect below normal temperatures
to continue.

Friday should be one more day with at or just below normal
temperatures, as ridging tries to build in from the west and push
the cooler surface high east as well. The GEM is a little more pushy
with the high, getting it well east of the region for the weekend
(and thus providing a nice warm up). The GFS is slower and keeps
some cooler thicknesses over us until Sunday, and with that some
possible warm-air advection showers. The 12Z Euro was somewhat of a
blend between these two solutions, whereas the new run coming in
leans a little more toward the GEM. Will hold off on slight chance
pops until Sunday, though would not be surprised to see future
shifts get them in either Saturday or Saturday night.

&&

.AVIATION (12Z TAF Update)...
Updated at 630 AM EDT Mon Apr 27 2015

VFR conditions will continue for the valid TAF period. Diurnal cu
around 5-6K feet will be enough for a ceiling in LEX this afternoon,
but just few/sct at BWG and SDF. North winds today will veer NE this
evening, but speeds will remain below 10 kt.

&&

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

$$

Short Term........RAS
Long Term.........RJS
Aviation..........RAS





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