Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 260516
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1216 AM EST Mon Jan 26 2015
...Updated Aviation Discussion...
Issued at 855 PM EST Sun Jan 25 2015
The surface low pressure center now is east of Louisville, with the
airport going over to northerly winds. Those winds will pick up from
the northwest the rest of the night as the gradient tightens up.
Precipitation across our region still is all rain, though just north
of us in IND`s area, seeing some snow reports from a few of the
bordering AWOS`s. HRRR still gives a brief shot at a deformation
band taking a swipe at our counties northeast of Louisville over the
next few hours, but otherwise the precip looks to be rather light,
save for the moderate rain showers along the KY/TN border right now.
Precipitation totals for the day so far are in the 1-2 tenths of an
inch range. This bodes a little better against their being lots of
black ice in the morning, as winds behind the low pressure will act
to dry out the roadways some. However we still have the chance for
freezing drizzle, according to forecast soundings, and this could
create a glaze on its own. Will keep the SPS going and let the mid
shift decide, as road reports are coming in, if an upgrade to a
Traveler`s Advisory is needed before the morning rush hour Monday.
Did another grid update, but forecast still looks on track, so no
need for a zone update.
Issued at 625 PM EST Sun Jan 25 2015
Looked through the forecast grids and tweaked toward current
conditions. After leaning towards the high-res consensus models for
the various parameters, ended up coming up with similar numbers for
QPF and snow totals as ongoing forecast. Still more concerned about
the threat for wet roads freezing than snow accumulations,
especially in the area already highlighted by the previous
forecaster. The possible saving grace here will be gusty northwest
winds that may help to dry off some of the roads before they get a
chance to freeze. Will be issuing updates through the evening and
overnight, so stay tuned.
.SHORT TERM (Now through Monday Night)...
Issued at 310 PM EST Sun Jan 25 2015
...Light wintry precipitation could cause slick spots overnight into
The surface low associated with a strong PV anomaly is now working
across southern Illinois, and will continue to slide ESE across our
area this evening. Light to occasionally moderate rainfall will
continue late this afternoon and evening ahead of this feature. Most
spots should see around a quarter of an inch of rainfall, with
locaized spots up to a half an inch.
As the system departs to our east tonight, a sharp cold front will
slide NW to SE across our area with rapidly dropping temperatures
into the mid 20s. Enough low level moisture looks to linger during
this time to support a change over to light snow. Can`t rule out
some freezing drizzle as well as saturation only goes up to around
-7 or -8 C, bringing the availability of ice crystals into question.
Either way, the combination of wet roads (from recent heavier
rainfall), and potential for a light snow dusting, or a very thin
glaze of ice could lead to some travel problems ahead of and into
the morning commute. Confidence isn`t overly high in widespread
travel problems, but enough that special mention should be given.
Issued a Special Weather Statement to highlight concerns. If
confidence does become higher, then can`t rule out an upgraded
product with future updates. Overall, kept light snow as the
predominant p-type as we head toward dawn, with generally a half an
inch or less of snow accumulation. Most likely area to see more
problems with slick roads should be east of I-65 and along and north
Expect lingering light snow/flurries/or freezing drizzle along and
east of I-75 through the first part of Monday. Temperatures will
struggle for much of the day under steady cold advection and only
expect highs in the low and mid 30s. Skies should stay mostly cloudy
to cloudy under lingering low clouds.
As we move into Monday evening/Monday night, we`ll watch as the left
exit region of an upper jet dives sharply south southeastward
overnight. As it does so, 1000-700 mb moisture will pool underneath
and should result in some light precipitation across the area,
mostly in the form of light snow. Best location for this looks to be
along and west of I-65 Monday evening, moving to along and east of
I-65 late Monday night.
.LONG TERM (Tuesday through Sunday)...
Issued at 250 PM EST Sun Jan 25 2015
Several light precipitation chances still remain the long term
period as we remain in an unsettled weather pattern.
Tues small vort waves on the back side of a broad upper trough will
create snow shower chances during the morning hours and then
possibly changing over to a rain/snow mix west of I-65/remaining
snow east of I-65 during the afternoon hours. A light snow
accumulation may result from this snow shower activity on Tuesday.
Flurries will likely last into the evening hours.
The next precip chances will come Wed night into Thurs as a clipper
system moves east across the upper Midwest. At this time, the low
associated with this clipper looks to pass to our north and actually
pull up a decent amount of warm air on Wed night. Precip may start
as a brief wintry mix Wed night and then transition to plain rain as
upper 30s and lower 40s temps get pulled into our area. Southerly
winds and a noticeably warmer airmass will result in rain on Thurs
with high temps reaching the upper 40s to around 50. Precipitation
will likely end Thurs night as light snow or a rain/snow mix.
Temps will run slightly below normal Tues/Wed, then a warm day
expected for Thurs, and back to slightly below normal for the end of
The weekend forecast is much less certain with models backing off of
any major weather systems to bring us notable precip. Have
scaled back POPs to 20% for Sat night/Sun night with snow or
rain/snow being the p-type.
.AVIATION (06Z TAF Update)...
Issued at 1215 AM EST Mon Jan 26 2015
Low-end MVFR and IFR conditions continue early this morning, but
there should be a slow improvement through the TAF period. A cold
front has just pushed through KSDF, and will slide through KBWG and
KLEX in the next couple of hours. This front will bring gusty
northwesterly winds, likely pushing 20-25 knots at times. In
addition, the passage of this front may bring a brief period of
snow, but it does not appear as if it will amount to much more than
a dusting. Clouds have been bouncing around high-end IFR and
fuel-alternate MVFR, but should slowly improve to fuel-alternate
MVFR later this morning at all sites, as drier low-level air works
in behind the front. This MVFR deck will slowly lift through the
day today, with northwesterly winds decreasing through the afternoon
as the low pressure system pushes to the east.