Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 190544
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
144 AM EDT Tue Mar 19 2024

...Updated Aviation Discussion...

.KEY MESSAGES...

* Unseasonably cool through Tuesday morning, with subfreezing
  temperatures likely again tonight.

* Dry and breezy on Tuesday and Wednesday, resulting in increased
  fire danger.

* Next chance for precipitation Thursday night or Friday.

&&

.UPDATE...
Issued at 858 PM EDT Mon Mar 18 2024

A 5 kft cloud deck is slowly clearing across the southwestern CWA,
with the clearing line near Bowling Green. Clouds will linger a few
more hours as they gradually scatter out from SW to NE. Temperatures
have dipped into the low/mid 30s this evening, but the temperature
drop will accelerate as skies clear and winds diminish a bit. Still
looking at a hard freeze early Tuesday with lows in the 20s.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 144 AM EDT Tue Mar 19 2024

A shortwave trough axis is rotating into the region at this hour,
bringing a nearly solid overcast mid level cloud deck, and even
spitting out a few flurries across the area. Given the dry air in
place at the surface, wouldn`t expect anything more than that, so
won`t actually carry any measurable pops. Given the extensive cloud
cover and steady cold advection component, temperatures are
struggling today as expected. As a result, only expecting highs to
peak in the upper 30s and low 40s.

Another cold night expected as temperatures fall off well into the
20s for lows. Very dry air in place would allow for even colder
temperatures, however surface winds are expected to stay up between
5 and 10 mph overnight, and switch to a SW component toward dawn. In
addition, some high clouds may help keep temps from completely
bottoming out. Still, the hard freeze could damage any sensitive
early vegetation blooms. Given the growing season hasn`t officially
commenced, (per collaboration with ag partners) plan to mention this
threat again in an SPS.

Dry NW flow aloft takes hold over our area behind the departing
trough axis for tomorrow. At the surface, strong Canadian high
pressure settles over the western Gulf Coast states, with a tight
pressure gradient over our region between the surface high, and an
eastern Canada surface low. Looks like the BL will mix fairly well
into a 30-35 knot layer around 925-850 mb. As a result expect 30 to
40 mph winds to accompany sustained winds in the 20-25 mph range. In
addition, mixing into a very dry low level atmosphere will likely
allow for relative humidity values to bottom out. Given the gusty SW
winds and very low RH values, there are some fire weather concerns.
The Wind/RH values would meet Red Flag Warning criteria pretty
easily, however smaller fuels and fairly cool high temperatures are
the sticking point for going as far as Red Flag Headlines. Talks
with area forestry partners yielded that fuels weren`t quite ready
enough for a full headline, but that messaging an elevated fire
danger would be welcome. So, will mention this threat as well in the
SPS in collaboration with surrounding offices. The gusty gradient
winds will also get a mention in the SPS as a stand alone threat.
Went above guidance for highs tomorrow given full sun, mixy SW flow,
and the tendency for these types of events to overachieve.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 304 PM EDT Mon Mar 18 2024

Rex Block pattern over the western CONUS will begin breaking down by
midweek as an upper level low over the Desert SW transitions into a
shortwave trough embedded within stronger flow aloft. Locally, dry
conditions will continue Wednesday into Thursday before the trough
arrives late Thursday night into Friday. Isentropic lift begins to
ramp up Thursday night as deeper moisture is drawn into the region.
Models indicate widespread showers developing overnight Thursday and
continuing into Friday.

A weak cold front will drag drier air into the region Friday night
into Saturday. Much of the weekend is looking to stay dry as high
pressure drifts from the Northern Plains into the eastern CONUS.
Next chances of rain could arrive late Sunday into early next week
as a trough digs into the western CONUS and ridging begins to
amplify over the eastern CONUS, resulting in southwesterly flow
aloft with embedded weak waves. The trough will eventually swing
into the Plains and Ohio/Tennessee Valleys by next Tuesday and
Wednesday, likely bring widespread rain showers and some storms.

&&

.AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 144 AM EDT Tue Mar 19 2024

Impacts/Confidence:
- High confidence in gusty SW winds of +25 knots today
- High confidence in LLWS tonight

Discussion...VFR conditions continue through this TAF period given
the influence of high pressure and dry airmass. Winds have started
to shift from the northwest to the southwest while decreasing in
magnitude. However, tightening pressure gradient ahead of a +40-knot
LLJ dropping from the Midwest/Great Lakes will ensue gusty SW winds
starting this morning with gusts of 25 knots or more during the
afternoon. For tonight, the presence of the LLJ over the region will
account for LLWS at all terminals with surface gusts likely in the
15-20 knot range.

&&

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

&&

$$

UPDATE...EBW
SHORT TERM...BJS
LONG TERM...DM
AVIATION...ALL


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