Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 271043

Area Forecast Discussion
National Weather Service Louisville KY
643 AM EDT WED APR 27 2016

...Updated Aviation Discussion...

...Forecast Update...
Issued at 625 AM EDT Wed Apr 27 2016

Issued a grid update for some patches of fog in our northwest and
west and also to narrow the focus for precip the next couple of
hours. Had one cell pop up and likely become severe, but have not
had any reports from that sparsely populated area.  No other changes
planned beyond those first few hours, and a zone update is not

.SHORT TERM (Now through Thursday)...
Issued at 300 AM EDT Wed Apr 27 2016

Stalled frontal boundary resides just north of the region, whereas a
second boundary is just south of the region, the remnant from the
line of storms that moved through the region last evening. In
between we are seeing some weak isentropic lift that is resulting in
some new shower development across central Kentucky. Model QPF
fields seem overdone in areal coverage of this precip, based on
latest radar, but for the daylight morning hours, the higher-res
versions try and provide more focus on a northwest/southeast-
oriented line. Have gone in line with this thinking and placed a
narrow band of high-likely pops from HNB to AAS with pops tapering
off north and south of that line.

Beyond the morning hours, expect a brief lull in coverage, with the
airmass just juicy enough to squeeze out some scattered showers
perhaps thunder. A PV anomaly will then rotate around a larger upper
low centered over southeast Nebraska. Timing this feature with peak
daytime heating, expect a line of storms to develop across western
TN/KY and head northeastward. The main threat with these storms
again will be damaging winds, with this threat mainly limited to
points west of the I-65 corridor. The storms should weaken with loss
of heating as they continue into the rest of the forecast area.

We dry out some for Thursday, with precipitable waters dropping down
to around an inch. The upper low over the Central Plains this
afternoon should be over the upper Midwest Thursday. The distance
from this feature and lack of a trigger should limit coverage of any
storms to isolated to scattered.

As for temperatures, our string of above normal days will continue,
with highs ranging from the mid 70s to low 80s and lows around 60.

.LONG TERM (Thursday night through Tuesday)...
Issued at 300 AM EDT Wed Apr 27 2016

The drying trend should continue at least through Friday, as ridging
moves over the region. Then Friday night, that ridging will start to
push east of us as another storm system comes out of the Plains.
This system should lift a warm front toward the region, which could
bring some light rain showers west of I-65 by daybreak Saturday.
Deterministic model guidance shows this boundary stalling over our
region for the weekend, meaning another couple of days with good
rain chances. A surface low crossing the region during the day
Sunday could mean some stronger storms, and will be something to
watch for, to see if we can get some instability to go along with
the dynamics of this system.

Latest deterministic models pull this low out of the region by
Monday morning, whereas the GEFS mean has it a little slower, a sign
of timing differences within the ensemble members, as spread also is
high. Thus will keep in a lower-end chance for rain into Monday.
After that Tuesday should have even less chance for rain, as a
narrow shortwave ridge moves into the region. Given how small this
feature is and another wave potentially dropping into the Midwest,
cannot pull rain chances altogether.

As for temperatures in this period, Friday should be one more above
normal day, then we should be closer to normal for the weekend and
possibly below for the start of the next work week.


.AVIATION (12Z TAF Update)...
Updated at 642 AM EDT Wed Apr 27 2016

The main challenge for this TAF period continues to be the timing of
thunderstorms. The line of thunderstorms across central KY looks
like it should stay mainly to the south of SDF, so will keep the
mention of thunder out of the TAF for this morning right now.
However, this line will be monitored over the next few hours.
Otherwise, more showers and storms are expected to develop this
afternoon and continue into the evening hours. Some strong storms
are not out of the question this afternoon and evening, so these
will have to be watched. Precipitation may continue off an on
overnight, but will keep just SHRA for the overnight hours for now.
Winds today will be generally out of a southerly direction and will
increase to 8-12 knots through the morning.


.LMK Watches/Warnings/Advisories...


Short Term.....RJS
Long Term......RJS
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