Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 270733
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
333 AM EDT Wed Mar 27 2024

.KEY MESSAGES...

* Dry and mild rest of the work week. Warmer temperatures and
  increasing shower and storm chances later this weekend.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 333 AM EDT Wed Mar 27 2024

Quiet stretch of weather expected through the short term as surface
high pressure slowly builds into the area beneath unremarkable upper
troughing aloft. Looking for steady cool and dry advection today,
and this combined with some early cloud cover will help to keep
temperatures around 5 degrees below normal for this time of year.
Calling for highs mostly in the mid to upper 50s as the more
probable scenario, however if sky cover ends up being less
pronounced, could see us getting up into the upper 50s to around 60.

The clouds are the only real forecast challenge for the day, as they
could keep temps below what is currently forecast just as easily,
especially across the northern half of the CWA. Current Nighttime
Microphysics satellite imagery shows an expansive area of stratus
off to our NW, and a 925-850mb analysis of RH/Temp/Wind shows good
initial capturing, as well as some clues for maintenance and
advection of this cloud deck through the morning and early
afternoon. Have high confidence that the stratus deck will maintain
through the morning given thermal troughing in that 925-850mb layer,
and advection eastward is expected over the next several hours as
west winds average around 20 knots in that layer. The cloud shield
is expected to be along and north of the Ohio River by 9 or 10 AM
EDT, and then expect slower eastward progression and some erosion as
areas downstream begin to heat up a bit. From that point forward,
expect steady erosion of the cloud shield as it moves slowly
eastward through the late morning into the early afternoon. Some
late temp recovery is then expect through the mid to late afternoon
as skies clear out.

Surface winds drop off to light and somewhat variable tonight as
surface high pressure centers over the mid Mississippi River Valley.
Expecting mostly clear skies and light winds, so should be a pretty
good radiational cooling night. This should yield lows mostly in the
30 to 35 degree range.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 333 AM EDT Wed Mar 27 2024

Synopsis...The mid-level height pattern late on the workweek will
feature East CONUS longwave trough moving offshore into the Atlantic
while ridging starts building over the Central US and prominent low-
to mid-level vorticity energy crosses the Rockies. At the surface,
high pressure will quickly track north to south across the Plains to
finally settle in the Southeast US with weak are of low pressure
forming in the Mid Mississippi. Further pattern amplification is
anticipated during the weekend as a strong upper low digs across
California`s coast and subtropical upper anticyclone reinforces the
ridge over the Central and Eastern US. Rain chances will increase
during the weekend as the vorticity energy and associated weak
surface low ejects to the east, setting a frontal zone close enough
to the region to serve as a focus for convective development. For
next week, the West Coast upper low will move inland into the
Southwest and Plains while the ridge is pushed to the south and
east, but there is still fair amount of uncertainty in the exact
evolution to commit to a certain scenario.

Model Confidence/Evaluation...Confidence in the large-scale features
through Sunday remains relatively high, although some variations
with the weak surface low track and intensity on Saturday morning
are observed during the last 48 hours worth of model outputs.
Overall, deterministic guidance is showing a slightly stronger and
farther northward surface low which might influence the timing and
coverage of precipitation, so medium confidence is assigned to the
those forecast elements during the weekend. Otherwise, confidence
remains low for early next week as model guidance keeps exhibiting a
high degree of variability from run to run. The GFS has gone back to
show a Canadian wave dropping across the Great Lakes, although this
time is not as strong as a couple of days ago, while a weaker wave
ejects out of the Southwest US. This is somewhat similar to what the
CMC has been hinting at, but the latter is much more detached as the
upper low remains stronger and slower. Lastly, the ECWMF has trended
towards a phased solution with greater contribution from Canadian
wave energy.

Thursday - Friday...Position of the surface high pressure will favor
winds slowly shifting to a southerly component which in combination
with mostly sunny skies will account for a gradual warming trend.
Light breeze with gusts around 15 mph at times will be present
Friday afternoon as the pressure gradient strengthens.

Weekend...Even though changes in the low track and intensity could
impact precipitation potential, still expecting increasing rain and
storm chances with gusty non-thunderstorm winds of 20 to 30 mph,
especially on Saturday. Highs during the weekend has also trended
upwards as the lower Ohio Valley remains under warm air advection
regime for a longer period. As for convective potential and storm
coverage, recent trends might argue for a diminished potential on
Saturday as forecast region is displaced from the focus of
convective initiation while Sunday could still a conditional setup
for strong to severe storms as shear profile improves and there
could be higher theta-e recovery. On the other hand, previous day
and/or downstream convection will also play an important role
defining the position of the effective boundary that ignite storms.

Next Week...Forecast confidence remains low on best timing and
coverage of heavy showers and storms with a more phased solution
probably favoring heavy rain versus strong to severe storms.

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 155 AM EDT Wed Mar 27 2024

The cold front has pushed to the east of all TAF sites at this hour,
and expect a steady W wind to prevail through the overnight. Seeing
some mid level cloud cover ranging from Sct to Bkn 5-6 K feet across
the area for the moment, and the expectation is that these ceilings
will lower through the early morning hours, however confidence is
pretty low as to whether we will end up with MVFR ceilings as dry
air advection and the steady surface winds could mitigate that
toward dawn. Stayed fairly optimistic for the prevailing forecast
but will acknowledge that MVFR is possible. Outside of the morning
concerns, would expect any lingering cloud cover to lift and scatter
into the afternoon, with surface winds veering to a more WNW and NW
component through the late afternoon/evening. A light N wind with
clear skies is then expected overnight.

&&

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

&&

$$

SHORT TERM...BJS
LONG TERM...ALL
AVIATION...BJS


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