LMK issues Area Forecast Discussion (AFD) at Oct 14, 6:12 AM EDT ...Updated Aviation Discussion...011
FXUS63 KLMK 141012
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
612 AM EDT Mon Oct 14 2024
...Updated Aviation Discussion...
.KEY MESSAGES...
* Breezy and much cooler today.
* A few light rain showers possible Tuesday, particularly in the
Bluegrass region.
* Widespread frost likely Thursday morning. There is an increasing
probability of sub-freezing temperatures in typical cool spots.
&&
.SHORT TERM /THROUGH TUESDAY/...
Issued at 259 AM EDT Mon Oct 14 2024
Low pressure across the northeast and high pressure moving into the
forecast area from the west has the area positioned in between
a pressure gradient that will drive breezy conditions again
today. While most model data has wind gusts between 20 and 25
mph today, there's about a 25% chance that wind gusts could
reach over 25 mph or higher at times this morning into the early
afternoon.
Through the day the pressure gradient is expected to lax as the
surface high pressure system moves closer to the forecast area. The
upper level trough of low pressure rotates through the area later
this afternoon and evening, which will bring enough uplift to create
some noticeable mostly cloudy to cloudy skies into the
overnight. Some locations may even see some light rain (trace to
0.01"), mainly northeast of a line from Winchester to
Georgetown, toward Tuesday morning's sunrise.
High temperatures today will be between 17 and 22 degrees cooler
than yesterday in the upper 50s to mid 60s, which is roughly 10
degrees below average temperatures for mid October. Cloud cover will
keep low temperatures closer to 13 degrees below normal in the low
to mid 40s.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 259 AM EDT Mon Oct 14 2024
Synopsis...
At the beginning of the extended forecast period Tuesday morning, a
broad upper level trough will be in place across the eastern half of
North America, with upper ridging expected over the intermountain
west. During the day on Tuesday, a shortwave embedded within the
larger trough will swing from NW to SE across the Ohio Valley and
into the southern Appalachians. As this upper disturbance clears the
region Tuesday night, 1030+ mb Canadian high pressure will begin to
descend into the upper Midwest and mid-Mississippi Valley, with a
renewed shot of lower troposphere cold advection via northerly flow
expected Tuesday afternoon into Wednesday morning.
From Wednesday through the end of the week, the overall pattern will
translate eastward, with upper ridging setup over the eastern CONUS
by Friday. At the surface, the center of high pressure is progged to
slide across the Ohio and Tennessee valleys Wednesday night into
Thursday before setting up over the Mid-Atlantic region for Friday
into next weekend. While another upper level trough will enter the
western half of North America by late in the week, the majority of
ensemble guidance now has this disturbance slowing and eventually
becoming cut off over the Mojave Desert early next weekend, while
upper ridging and sfc high pressure continues to build over the
eastern half of the CONUS. While the upper closed low will
eventually eject eastward, there is increased support in ensemble
guidance that this transition will be delayed into early next week.
Tuesday Rain Chances...
The only significant chance for rain in the long term forecast
period is on Tuesday as the above-mentioned upper shortwave swings
through the region. Model soundings show most of the moisture being
confined to the 850-700 mb layer, and moisture will likely be the
limiting factor on precipitation coverage. On the other hand, broad
rising motion thanks to differential CVA and some instability from
steep low-level lapse rates supports the potential for isolated to
scattered rain showers, especially across the Bluegrass region. Any
chance for rain will dissipate quickly Tuesday evening.
Midweek Frost/Freeze Potential and Gradual Late Week Warmup...
With the reinforcing shot of cold advection arriving on Tuesday, the
coolest temperatures of the season so far are expected Tuesday
through Thursday morning. With extra clouds/showers and a persistent
NW wind present, Tuesday has the appearance of a fairly raw day, and
most locations will struggle to make it out of the 50s.
While the 850 mb thermal trough will be overhead Tuesday night into
Wednesday morning, there are potential limiting factors which may
slow the rate of cooling and limit frost potential. With the center
of sfc high pressure still NW of the region, a persistent light NW
wind may carry over into Tuesday night. Additionally, model time
height plots show some lingering low-level moisture, with scattered
stratus clouds potentially limiting radiational cooling. Still,
widespread 30s are expected Wednesday morning, with NBM
probabilities of lows in the 30s near 100% except in the middle of
the Louisville heat island.
It continues to look like the higher confidence in frost and even
freeze conditions will be Wednesday night into Thursday morning, as
the sfc high will be over the region. Less concern exists in winds
and sky cover, allowing for prime radiational cooling conditions.
NBM probabilities of sub-freezing lows Thursday morning exceed 80%
across large swaths of the Bluegrass and Hoosier National Forest,
with frost appearing almost certain across the area.
With upper ridging moving overhead by late week and increasing
amounts of sunshine expected, a slow warming trend in daytime
temperatures is expected from Wednesday into Friday. With the western
CONUS trough not in a hurry to move east, only weak warm return flow
is expected by Friday into next weekend. Another frosty morning will
be possible across portions of the area Friday morning, though the
extent should be limited relative to previous mornings.
Next Weekend...
With increasing support in medium-range guidance for the upper
disturbance over the western CONUS becoming cut off late this week,
it looks increasingly likely that we will remain dry across the Ohio
Valley through next weekend. Temperatures should be near, to
slightly above, climatological norms, with highs in the low-to-mid
70s and lows in the upper 30s and 40s.
&&
.AVIATION /12Z TAFS THROUGH 18Z TUESDAY/...
Issued at 611 AM EDT Mon Oct 14 2024
VFR for the next 24-30 hours. High pressure continues to progress
into the region, but until the complete air mass transition occurs
wind gusts from the northwest will continue today up to 20 kts at
times. Wind gusts will diminish by the late afternoon to early
evening and overnight hours with a west wind between 5 and 10 kts.
Some BKN to OVC ceilings are possible across several terminals,
mainly high deck but a few at low to mid deck are also possible.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
SHORT TERM...MK
LONG TERM...CSG
AVIATION...MK
Source:
LMK issues Area Forecast Discussion (AFD) at Oct 14, 6:12 AM EDT ...Updated Aviation Discussion...---------------
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