Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 070236
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
936 PM EST Thu Mar 6 2014
Issued 932 PM EST Thu Mar 6 2014
Latest IR imagery showing partly cloudy skies across the eastern
sections of the forecast area. Upstream skies are generally clear
with the exception of a thin band of clouds associated with an upper
wave. This feature will pass through overnight without much
sensible weather. Overall, it appears that we`ll be a bit more
clear overnight and we have adjusted cloud cover downward.
With the clear skies, light winds, sub-freezing temperatures, and
adequate soil moisture, probably are going to see some freezing fog
develop across the region. Overall, we believe the fog will be
patchy in nature across the north with a bit better coverage across
south-central Kentucky. The freezing fog may result in some slick
spots developing on area roadways overnight. Have addressed these
concerns in the Hazardous Weather Outlook product. Overnight lows
look to drop into the middle to upper 20s in most areas.
.SHORT TERM (Now through Friday Night)...
Issued at 310 PM EST Thu Mar 6 2014
The primary weather concern for this time period is the potential
for fog to develop across central Kentucky and perhaps into portions
of southern Indiana overnight tonight. The limiting factor on how
widespread it becomes is dependent on the clouds currently streaming
across the region, associated with a low pressure system currently
spinning off of the west coast of Florida, and progged to track
northeastward into the Atlantic. These clouds are anticipated to
move off with the low but the question is will they exit the region
with enough time left in the overnight period for the fog to
develop. High-res short-term models generally support this, with the
Bluegrass region likely being the last to see the clouds move off.
As such, this forecast update depicts the patchy to areas of fog
across much of central Kentucky, but limits the fog mention in the
far NE sections of the forecast area. With high pressure building in
behind the low, winds will calm, decoupling will occur, and with
enough lingering low-level moisture in place, along with residual
ground moisture, the ingredients are lining up for fog formation.
As high pressure continues to temporarily overtake the area, the
weather for the remainder of the short-term period will be benign.
The only question is how long the forecast area will remain locked
under a low stratus deck through early Friday, which could also
wreck havoc on the current projected high temperatures for tomorrow.
However, once the clouds clear out, skies will be mostly clear until
they once again mosey on in from the NW out ahead of the next
Lows tonight are expected to be slight below normal, ranging from
the upper 20s in the north to the lower 30s near Lake Cumberland.
Highs on Friday should be returning to near normal, reaching the mid
to upper 50s, with the aforementioned cloud situation potentially
limiting the temps from reaching quite that high. Overnight Friday
lows will also be near normal, generally in the mid 30s as southerly
to westerly flow returns.
.LONG TERM (Saturday through Thursday)...
Issued at 305 PM EST Thu Mar 6 2014
The main forecast challenge for this weekend will be timing light
precip and temps Sat/Sun. A weak cold front and upper trough look
to move through the area bringing light precip mainly Sat night.
According to temp profiles, looks like the precip will be located in
an airmass mainly above freezing in the lower portion of the
atmosphere so will continue light rain chances. Agree with the
previous forecaster that some light freezing drizzle may be possible
on the back side. However, it looks like this should be a fairly
quick hitting light rainer. There could be some slick spots Sun
morning especially over southern Indiana which will probably fall
into the upper 20s near sunrise.
The next weather system looks to arrive in the Tues night-Wed night
time frame as a potent upper trough dives into the central CONUS
resulting in sfc cyclogenesis east of the Rockies. The low will
then track eastward through the Ohio Valley some time mid week next
week. There are several model solns in regards to the strength and
position of this low pressure system so won`t get too fancy with
timing or p-type at this point. Do think that a good warm surge
ahead of the low will allow ptype to mainly be rain with the chance
for a rain/snow mix on the back side.
As far as temperatures go, we`ll be mild Sat/Mon/Tues in the 50s and
lower 60s for highs and mid 30s to 40s for lows. Sunday we`ll see a
brief, weak cool down behind the fropa Sat night. Highs Sun should
be in the mid 40s to lower 50s with lows in the upper 20s to 30s.
Then the trough for mid week next week has the potential to cool
things down well below normal back into the 30s for highs next Thurs
with lows dropping back into the 20s.
.AVIATION (00Z TAF Update)...
Updated at 609 PM EST Thu Mar 6 2014
VFR conditions are expected at the terminals this evening...with
only some mid-high level clouds passing through the region. Overall
forecast thinking has not changed much from this afternoon. Think
that we`ll see the upper level clouds clearing out with surface
winds going light and variable. This...combined with residual
snowpack on the ground may result in fog to form across central
Kentucky. For now have maintained MVFR conditions developing later
tonight at KBWG and KLEX after 07/05Z. Some IFR reductions in
visibility will be possible between 07/09-13Z. Lower visibilities
are certainly possible if clouds completely shift out of the area
and we develop good radiational cooling. Conditions should return
to VFR after 07/14Z with winds shifting back to the southwest.