National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KLMK 131912
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
312 PM EDT Thu Mar 13 2014

.SHORT TERM (Now through Friday Night)...
Issued at 311 PM EDT Thu Mar 13 2014

The synoptic pattern this afternoon features a longwave upper trough
pushing off the East Coast, with another shortwave trough moving
through the northwest flow aloft.  This secondary trough will help
to induce a surface cyclone across the northern Great Lakes, which
will help drag a weak cold front towards the region Friday night.

Surface high pressure continues to slowly drift east across the
region this afternoon.  In its wake, winds will become southerly
this evening into tonight.  Therefore, expect temperatures to drop
off slightly this evening after sunset, before leveling off and even
rising a bit towards dawn Friday morning.  Overnight lows will be in
the mid to upper 30s.

The main story on Friday will be the increasing warmth due to the
increasing winds.  The aforementioned surface high will slide
southeast into the western Atlantic, while a strong area of low
pressure gets organized across the northern Great Lakes.  This will
place the Ohio Valley within a strong surface pressure gradient,
making for rather windy conditions.  Forecast soundings depict deep
mixing potential tomorrow, perhaps all the way up to around 850mb.
Winds at the top of this mixed layer will be around 40-45+ knots.
Highly considered issuing a Wind Advisory for tomorrow, but after
collaborating with neighboring offices, decided to hold off for
now.  The main limiting factors will be the tendency for gustiness
to underachieve a bit in warm air advection regimes, along with
increasing mid/high level clouds which may hinder the expected
mixing a bit.  Will pass these concerns on to the midnight shift,
but a Wind Advisory may be needed for tomorrow for 40+ mph wind
gusts.

Another concern tomorrow will be an elevated fire danger.  However,
there are a few things working against the issuance of any fire
weather headlines.  The first is rather marginal RH values, as a
conservative dewpoint forecast only puts minimum RH values in the
30-40% range.  Additionally, area fuels are still rather moist,
which overall should work to limit the potential.

Otherwise, given the deep mixing and rather dry low-level airmass,
have continued to go on the warm end of guidance for temperatures
tomorrow.  This puts highs in the middle 60s for most locations.

The aforementioned surface low will drag a cold front toward the
region Friday night.  Some guidance is suggesting some light showers
working into the Northern Bluegrass with this front, but think the
dry air will win out.  With the front beginning to stall as it heads
into the region, overnight lows will vary across the region.  They
will bottom out in the upper 30s across southern IN, while southern
KY will remain in the mid 40s.

.LONG TERM (Saturday through Thursday)...
Issued at 307 PM EDT Thu Mar 13 2014

The ECMWF has been the most consistent model recently and is also
favored by WPC so we will lean toward that solution for this
forecast.  having said that, a quick glance at this morning`s EC
reveals that it has trended slightly toward the latest operational
GFS.

An upper trof will be approaching from the west this weekend and
move overhead Monday.  Associated surface low pressure will develop
over the Plains Saturday, drop southeast, and move along the Gulf
Coast Sunday.  Deep moisture will stream northward Saturday night
through Sunday night before moving off to the east Monday morning.
Precipitation type is a big question with this system.  We should be
all rain Saturday night into at least Sunday afternoon.  By Sunday
evening into Sunday night, however, surface temperatures fall below
freezing while warm air remains in place around 850hPa.  Soundings
suggest a wintry mix may be possible.  At this time it does appear
that amounts would be light...especially on the EC.  The GFS paints
a bit grimmer of a picture.  For now in the forecast will simply go
with a basic rain/snow mix, with future edits to be made as the time
approaches.

The next upper system will dig into the Plains right behind the
departing weekend system, pushing a cold front through here
probably sometime on Wednesday.  The front will be accompanied by
showers, with not much thunder indicated at this time.

Temperatures will ride the springtime roller coaster as these
systems move through.  The warmest day looks to be Saturday with
highs ranging from the mid 50s to lower 60s.  The coldest night will
be Sunday night with that potential wintry mix, with temperatures
dropping into the mid 20s to lower 30s north to south.

&&

.AVIATION (18Z TAF Update)...
Updated at 105 PM EDT Thu Mar 13 2014

VFR conditions will prevail through the period, although LLWS will
be a concern tonight.  Surface high pressure continues to push to
the east across all terminals early this afternoon.  After a period
of light and variable winds, winds will slightly increase to around
5-9 knots out of the SSW later this afternoon.  Mainly clear skies
will prevail, although a SCT to BKN deck of mid-level clouds could
affect KSDF and KLEX a bit later this afternoon/evening.

A low-level jet will ramp up tonight just above the surface, setting
the stage for a period of LLWS at all sites.  This jet could be on
the order of 40-45+ knots late tonight into Friday morning, with the
highest values expected at KLEX and KSDF.  Otherwise, skies should
be mainly clear, although some high clouds will increase towards
Friday morning.

The main story during the day on Friday will be surface winds.
Southwesterly winds will increase to 20 to 25 knots, with gusts of
30 to 35 knots possible.  Mid and high clouds will slowly increase
through the day.

&&

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

$$

Short Term........KJD
Long Term.........13
Aviation..........KJD