Area Forecast Discussion
Issued by NWS Louisville, KY

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633
FXUS63 KLMK 261830
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
230 PM EDT Wed Apr 26 2017

.Short Term...(This evening through Thursday night)
Issued at 230 PM EDT Wed Apr 26 2017

...Becoming Breezy Late Tonight...

Surface low pressure forming across Arkansas this afternoon, and
models prog that low to move to the Bootheel. As it does so, it
should force a line of showers and storms slowly eastward tonight.
The trough looks to become negative-tilt tonight, and as it does so
we will see an increase in winds above the surface, with the latest
hi-res guidance showing a 60- to 70-knot 850 mb jet by 6Z in a
narrow north/south axis across the region. So will have to watch as
the line of decaying showers/storms move through tonight to see if
any of these stronger winds can mix down late tonight.

Those showers should end during the morning hours as the front
pushes east of the region and a narrow bubble of high pressure
builds over the Ohio Valley by the end of the day Thursday. Clouds
should stick around most of the day and keep our temperatures down,
but not too far below normal for late April.

&&

.Long Term...(Friday through Wednesday)
Issued at 230 PM EDT Wed Apr 26 2017

Winds will pick up out of the south Friday, as a dry warm front
lifts northward over the Ohio Valley region. Temperatures Friday
should end up ~10 degrees warmer than Thursday. That front should
serve as the focus for storm development just west and north of the
region, while capping in place over our part of the warm sector
should keep this area dry. There is some elevated instability above
this cap, so any good cold pool from the storms to our north that
can push into our region could be able to get to this level and
maintain themselves as they head eastward Friday night.

Models struggle a bit in how far north the front gets and stalls for
the weekend, but should it stall over one place for long, the amount
of moisture moving in along it will be well above normal for this
time of year, and could lead to some flood potential. Ensemble
guidance in this forecast suite tends to agree with the operational
NAM in keeping most of that moisture just north of the area, but we
will need to monitor the forecast over the next couple of days for
any southward push there, especially as we could get some severe
storms depending on that location and available instability later in
the day Saturday.

Saturday night and Sunday, a stronger upper low will move out of the
Central Plains and finally force this slug of moisture eastward.
Given extent of time out in the model world, there still is some
uncertainty factored in here to the exact timing, but a push that
comes through during the day Sunday would take advantage of good
heating that could cause severe weather. Again, something to watch
for over the several model runs.

Monday should turn breezy and cooler as that front pushes east. We
moderate a little on Tuesday before the GFS/Euro bring back a shot
at rains along a slowly lifting warm front.

&&

.Aviation...(18Z TAF Issuance)
Issued at 143 PM EDT Wed Apr 26 2017

We`ll be VFR for the remainder of today and much of the overnight as
we sit in the warm sector between a warm front to our north and a
cold front poised to move into the region Thursday morning. Main
concern for this afternoon will be gusty south winds between 20 and
25 mph. As we move past sunset, a 40-50 knot low level jet at and
just below 2 k feet will overspread the region. Seeing just enough
speed shear along with an inversion to warrant a narrow window for
LLWS mention mainly between 03-09z at the TAF sites. As we near the
daylight hours, winds will become more mixy/gusty and the LLJ core
will move off, ending the threat. Showers and a few embedded
thunderstorms arrive for the hours around dawn. In addition,
ceilings down into the MVFR range and even below fuel-alternate are
possible.

As we get into the mid to late morning time frame, SDF/BWG should
become dry with gradually improving ceilings and veering winds as
the cold front passes. Will keep MVFR ceilings and shower mention at
LEX through the end of the cycle.

&&

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

$$

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



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