LMK issues Area Forecast Discussion (AFD) at Sep 29, 9:37 PM EDT187
FXUS63 KLMK 300137
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
937 PM EDT Sun Sep 29 2024
.KEY MESSAGES...
* Light rain showers will diminish by this evening.
* Widespread fog development is likely tonight and Monday night.
Locally dense fog will be possible.
* Dry weather and seasonal temperatures to come by mid next week.
&&
.UPDATE...
Issued at 936 PM EDT Sun Sep 29 2024
Isolated light rain is diminishing this evening, and should see a
drier trend as we head later into the night. Main challenge
continues to be the dense fog potential for overnight. Hi-res
guidance continues to have a very strong signal for low stratus and
dense fog, mainly after 06z. Forecast lows in the lower 60s will
also be 2-3 degrees below crossover temps, which adds to the
potential for dense fog. However, lingering cloud cover remains the
primary concern to any fog limitation. Discussed with neighboring
WFOs about hoisting a Dense Fog Advisory, but consensus was to hold
off until confidence in the cloud cover increased. So, will hold
onto the SPS we have, and continue to monitor sfc obs into the
overnight. Otherwise, the forecast remains in good shape and no
major changes are planned.
&&
.SHORT TERM /THROUGH MONDAY/...
Issued at 255 PM EDT Sun Sep 29 2024
Afternoon satellite imagery shows the remnant circulation of Helene
along with a large upper level low spinning across the southern Ohio
Valley. We've seen some breaks in the clouds, especially across
areas west of I-65. Temperatures have warmed into the upper 60s and
lower 70s. The heating has allowed some shallow convection to
develop across the region. This activity will continue to move west
and west-southwest through the afternoon hours before diminishing
toward sunset with the loss of heating.
For tonight, combination of thinning cloud cover, light winds,
abundant low-level moisture, and wet ground will set the stage for
fog and low stratus development. There remains some uncertainty on
how much cloud cover we'll have and whether we'll just see low
stratus build downward with low ceilings or the eventual development
of widespread ground fog. The mesoscale models (HRRR/NAM3K/RRFS)
are in pretty good agreement with visibilities dropping
significantly across much of KY in areas south of I-64. This is
likely due to the models having a bit thicker cloud cover over
southern Indiana and southern Ohio. Given the strong signal, will
hoist a Special Weather Statement to highlight the fog and low
visibility threat. If fog develops rapidly late this evening, a
Dense Fog Advisory will be need over portions of the area. Overnight
lows will average in the upper 50s to the lower 60s.
For Monday, we'll start off the morning with low clouds and fog, but
that should mix out by mid-late morning. Skies may break up a bit
more with some patchy sunshine during the afternoon. With some
heating, still can not rule out some scattered showers in the
afternoon, mainly east of I-65. Highs on the day should be a bit
warmer with most places in the 70-75 degree range.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Issued at 255 PM EDT Sun Sep 29 2024
A few features of note in the long term:
* Departing upper low carrying the remnant moisture from Helene away
Monday night
* Weak cold front moving through the area Tuesday
* Quiet seasonal weather Wed through at least Saturday
* A little uncertainty on if deepening trough over the NE US will be
strong enough to bring some rain chances to our region Sunday
The remaining increased soil moisture combined with better sky cover
conditions could result in another round of fog or low stratus
development Tuesday morning.
The departing atmospheric moisture combined with the weak cold front
will bring one more round of isolated (20% chance) to scattered (30-
50% chance) showers to the region Tuesday afternoon, with the better
chances the farther east of the I-65 corridor you get. Temperatures
behind that front will get closer to where we should be this time of
year (and break us from the small diurnal ranges we've had with
Helene's presence in our area).
Next up for the weekend will be to see how some waves dropping down
in broad troughiness in the NE US flow will impact us. Current grand
ensemble and NBM forecasts both keep rain chances at less than 20
percent, so will keep the forecast Sunday dry for now. Fairly wide
uncertainty in temperatures for both weekend days, with the grand
ensemble showing ~10 degree spreads for the 25th-75th percentiles.
Previous forecast leaned towards the higher side of that box. Given
better chances for dry conditions, will continue leaning in that
direction as well.
&&
.AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 736 PM EDT Sun Sep 29 2024
Terminals are mostly VFR this evening, with just some spotty showers
circling around the low to our south. These radar echoes are fairly
light, and any precip at a terminal will be very light and brief.
Expect this precip activity to diminish in coverage shortly with
sunset.
For tonight, guidance continues a very strong signal for fog, so
this TAF package will again hit the vis/cig impacts hard at all
terminal sites. LIFR or VLIFR conditions are expected mainly between
08-14z Monday morning. Vis improvements will be possible after 14z,
but could have some lingering IFR cigs until the early afternoon
hours. We should eventually return to VFR tomorrow afternoon.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
UPDATE...CJP
SHORT TERM...MJ
LONG TERM...RJS
AVIATION...CJP
Source:
LMK issues Area Forecast Discussion (AFD) at Sep 29, 9:37 PM EDT---------------
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