138 
FXUS63 KLMK 140125
AFDLMK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
924 PM EDT WED MAR 13 2013

.Forecast Update...
Issued at 924 PM EDT Wed Mar 13 2013

Made a quick update this evening to lower minimum temperatures
tonight.  Current observations are running 2-3 degrees below the
going forecast, despite the lingering cloud cover.  Once skies clear
out and the winds die down, radiational cooling effects will allow
temperatures to dip into the lower 20s and even upper teens in some
of the cold spots.  The remainder of the forecast looks well on
track.

&&

.Short Term (Tonight through Thursday night)...
Issued at 325 PM EDT Wed Mar 13 2013

Strong surface high pressure over the Plains is helping to draw
unseasonably cold air into the Ohio Valley. Dry weather will be
short-lived as fast NW flow aloft continues, and the next
disturbance is just emerging from the Canadian Rockies.
Low-confidence forecast hinges on the timing and exact path of this
disturbance, and precip type and chances as it crosses the Ohio
Valley.

This afternoon's gusty winds will diminish around sunset, and the
residual strato-cu should clear quickly, giving way to a cold night.
Most locations will be in the lower/mid 20s, but can't rule out some
of the typical cold spots dipping into the the teens. Will start off
mostly clear Thursday morning, but mid-level clouds will stream in
from the NW ahead of the Clipper. This makes the temp forecast
rather tricky, and it is likely that we will see a sharp SW-NE
gradient somewhere across Kentucky. Have opened a range from lower
40s across the Bluegrass to around 50 near Bowling Green, but the
actual spread could be even larger, and quite sharp somewhere in
between.

Precip arrives late in the afternoon across southern Indiana, and by
early evening over central Kentucky. Still some model discrepancies
as the NAM and GEM keep most of the precip over the Bluegrass, while
ECMWF and GFS spread it farther west. Expect that the precip will be
mostly rain, as most of the ice aloft will be lost before the
boundary layer can saturate. However, there will be a narrow window
for precip to fall as snow, so this forecast will show a rain/snow
mix where low-level temps get cold enough.

This will be a quick-hitting system with most, if not all the precip
exiting around midnight Thursday night. Fri morning lows will
generally be near freezing or just above, mitigating most
re-freezing concerns.

.Long Term (Friday through Wednesday)...
Issued at 300 PM EDT Wed Mar 13 2013

A fast moving shortwave in northwest flow aloft should be exiting
the southeast forecast area by about daybreak Friday, with dry
conditions expected through the day. Temperatures ranging from the
mid 50s in the northeast to low 60s in the southwest appear on track
Friday, with southwesterly low-level winds expected. Low-level
clouds will exit, while higher clouds move in through the day as our
next system approaches for Friday night.

The next shortwave will arrive late Friday night and last through
Saturday afternoon, as the surface boundary sliding south.
Temperatures will only fall into the upper 40s and low 50s Friday
night, with temps Saturday being highly dependent on the frontal
boundary placement. Warmer temps, perhaps in the 60s will be across
the south, with lower 50s across the north on Saturday. The bulk of
this precip Friday night into Saturday morning appears to favor our
northeastern half of the CWA, with continued or new development
along the front across south-central Kentucky during the late
morning and afternoon hours. Expecting all rain with this event and
could have some rumbles of thunder, as soundings indicate some
elevated instability. This frontal boundary will become
quasi-stationary across the Ohio and Tennessee Valleys Sunday
through Tuesday, as more zonal flow aloft becomes established. This
will provide a chance of rain Sunday through early morning Tuesday
as several waves pass across the area. There should be brief breaks
in precip between the waves, but a little too difficult to time this
far out with noticeable ensemble spread.

The next shortwave arrives Sunday, but we should start to see rain
Saturday night with rain dissipating sometime Monday morning. The
location of the quasi-stationary boundary remains a fairly big
difference amongst models, but an ensemble approach would place it
directly west-east across the CWA. Temperatures could have quite a
gradient from north to south if this occurs. For now, mid and upper
40s across our far north to low 60s across our far south for Sunday
seem reasonable. Temperatures should warm more for Monday as the
boundary lifts north with our next weather system quickly moving in.
So, while precip diminishes Monday morning from the Sunday system,
rain will quickly overspread the region during the day Monday and
last through early Tuesday morning.

For our final system Monday, two broad areas of low pressure appear
to form and sweep across the Ohio Valley. The trailing front will
push all activity to the eastern CONUS Tuesday, with dry high
pressure settling across the area Tuesday through Wednesday. Cannot
rule out some upslope development in our east during the late
morning and afternoon hours Tuesday, but chances seem small at this
time. With the boundary setting up across the CWA and several waves
of precip expected, rainfall totals from Sunday through early
morning Tuesday of up to two inches are possible. However, the key
factor will be the exact placement of the quasi-stationary boundary.
High temperatures generally in the 40s, maybe low 50s in the south
are on tap Tuesday. Will see several degrees of warming Wednesday,
with mid and upper 50s anticipated.

&&

.Aviation (00Z TAF Issuance)...
Issued at 725 PM EDT Wed Mar 13 2013

VFR stratocumulus deck will continue to drift off to the east as it
dissipates with the loss of daytime heating.  Therefore, expect all
terminals to go SKC by late this evening, which will last through
the overnight hours.  NW winds will also die down in the next hour
or two as mixing wanes.

VFR conditions will continue through the majority of Thursday.  The
next upper-level system will first spread a mid-level deck across
all sites through the day on Thursday.  By late in the afternoon, a
few showers (mostly rain with perhaps some snow mixed in) and a
lowering VFR ceiling (FL040-FL060) will spread across mainly KSDF
and KLEX.  The bulk of the precipitation looks to remain north of
KBWG at this time, so will leave VCSH wording out.  This system will
be quick-moving, clearing out of KSDF by the end of the planning
period.

&&

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


Update...........KD
Short Term.......RAS
Long Term........MJP
Aviation.........KD