LMK issues Area Forecast Discussion (AFD) at Feb 2, 6:45 PM EST ...Updated Aviation Discussion...594
FXUS63 KLMK 022345
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
645 PM EST Sun Feb 2 2025
...Updated Aviation Discussion...
.KEY MESSAGES...
* Breezy and unseasonably warm on Monday.
* Showers and thunderstorms are likely Wednesday into Thursday.
Severe and flooding risks cannot be ruled out, but forecast
confidence remains low.
* Another chance of rain, and possibly storms, is expected next
weekend.
&&
.SHORT TERM /THROUGH MONDAY/...
Issued at 255 PM EST Sun Feb 2 2025
Low-level moisture continues to mix out thanks to increasing
southwesterly flow and WAA. SCT low clouds linger in the Bluegrass
Region, but partly to mostly sunny skies are expected the remainder
of the day. A sfc warm front has lifted north of the region, with
temperatures near 60 F and dewpoints in the mid 40s across central
KY and southern IN this afternoon. Deeper low-level mixing is
producing 20-30 mph gusts at the surface. Expect breezy SW winds
through early evening, with gusts diminishing after 5-6 pm.
Tonight, a wave of low pressure is forecast to move east across
Ontario with a cold front extending SW through the Great Lakes and
back into the central Plains. In the Ohio Valley, flow aloft will be
zonal with weak height rises. In the lower levels, high pressure
gradually shifts off the East Coast as the aforementioned cold front
sinks southeast through portions of the Upper Midwest. The resulting
sfc pressure gradient will yield a steady, light south wind
overnight, which will keep temps well above normal for early
February. Mid 40s will be common early Monday, though the coolest
spots will likely dip into the lower 40s.
Tomorrow, the sfc cold front continues southeast through portions of
MO, IL, IN, and Lower MI as high pressure lingers over the western
Atlantic. Strengthening SW low-level winds and WAA will provide very
mild, breezy conditions. Expect the warmest day since mid/late
November, with afternoon highs in the mid 60s to lower 70s. The
warmest readings are anticipated across south-central KY and in
urban environments. Sfc winds will become increasingly gusty after
mid-morning, with widespread gusts of 25-30 mph in the afternoon.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Issued at 255 PM EST Sun Feb 2 2025
Synopsis...Large mid-level ridge, supported by subtropical high over
Cuba, will extend across nearly two-thirds of the CONUS at the
beginning of the forecast period while cut-off low rotates off the
NW Pacific Coast and the jet stream flows across the Northern Plains
and Great Lakes. Although positive upper height anomalies will
persist in the southern half of the CONUS during the medium range,
periodic shortwave energy emanating from the NW Pacific cut-off low
will flatten the northern section of the ridge, allowing a
baroclinic wave to set up across the Ohio Valley. Therefore, active
weather is expected again by the middle of this week and early next
weekend as the shortwave approach the region.
Model Evaluation/Confidence...As stated in previous forecast
discussions, there is substantial model spread starting on Wednesday
and continuing into next weekend. Factors such as intensity and
timing of the shortwave troughs as well as exact position of the
baroclinic wave and theta-e advection strength are still negatively
affecting forecast confidence. The latest run of the deterministic
ECMWF and CMC seem to favor the position of the stalling frontal
wave further north than the GFS and ICON. As a result, the former
solution would potentially favor warmer and moister conditions over
the Lower Ohio Valley with axis of QPF extending along the Ohio
River and southern Indiana. On the other hand, the second scenario
will support colder and less humid conditions with QPF axis closer
to the Tennessee border. Perhaps such spread is reflecting in the
ensemble river guidance as latest probabilities of reaching or
surpassing minor flood stage are not as high as one would have
thought. Independently of individual models, an areal and river
flooding threat will exist by midweek and especially next weekend
with the second wave. Also, CSU ML algorithm has maintained a low
chance of severe weather Wednesday and Thursday which is not out of
question considering mesoscale frontal convergence amid warm/moist
advection.
Mon Night - Tuesday...Anomalous mid-level ridge will be amplifying
across the Central US while, at the surface, high pressure quickly
transitions across the Great Lakes and cold front sweeps the Ohio
Valley. GFS forecast soundings show sufficiently deep low-level
moisture below weak frontal forcing Monday night to start
mentioning patchy light drizzle, mostly for the northern half of the
CWA. A few runs of the ECMWF p-type meteograms has shown very low
chances of rain, which given the mesoscale setup, is interpreted as
a confidence booster for light drizzle. Light northeast winds,
cooler airmass, and lingering clouds will account for lower highs
compared to Monday, but still above average for this time of the
year. Strong mid-level subsidence and dry air will maintain the
forecast area rain free.
Wednesday - Thursday...First shortwave trough of the medium range
period will eject out of the cut-off low and move towards the
Central Plains on Wednesday and over the Ohio Valley Wed Night into
Thursday morning. As mentioned above, forecast variability increases
during this timeframe with evidence in the intensity and track of
the attendant surface low. In this case, the ECMWF and CMC support
an slightly stronger surface low with a further northward track,
leaving south-central Kentucky under the developing warm sector on
Wednesday which increases the chances of surface-based convection
while surface inversion remains over northern Kentucky and southern
Indiana. On the other hand, the surface low on the GFS run is weaker
and tracks closer to the Ohio River, resulting in weaker theta-e
transport and restricted warm sector modification. The latter would
potentially favor elevated showers and convection as GFS forecast
soundings indicate strong surface inversion throughout the day. The
ECWMF EFI continues to depict an unusual CAPE and CAPE/SHEAR
environment for early February, increasing confidence in CSU's low
probabilities of severe weather. That being said, the CAPE 90th
percentile of the M-Climate distribution ranges around 10-200 J/kg
Wednesday/Thursday. Judging by the spatial distribution of the Joint
Probabilities of CAPE>500 J/kg and Bulk Shear>30 knots in the GEFS
and GEPS guidance for both Wednesday and Thursday, the highest
chances of surface-based severe weather are displayed across south
and central Kentucky with quick decrease to the north where still
elevated convection could produce some hail instances. As for
flooding concerns, based on recent rainfall and spread in the
highest QPF axis, there is medium confidence in flooding issues
arising by midweek, especially if training convection develops along
and north of the frontal line (ECWMF and CMC solutions).
Friday into Next Weekend...Mid-level ridge will build back north as
the first shortwave trough ejects to the Northeast US. Surface high
pressure will move across the Midwest while pushing the wavy
baroclinic zone south of the Ohio Valley. Much like Tuesday, Friday
will host cooler temperatures under northerly winds as well as
clearing skies as the rain follows the front to the south.
Nonetheless, another shortwave trough and attendant surface low
system will impact the region next weekend, renewing rain and
potentially storm chances. Although confidence in specifics is
rather low, it appears that another QPF axis could extend across the
area so that chances of areal and river flooding might go back up.
In this case, the best chance of impactful rainfall totals will
spread over the Green and Kentucky River Basins as this time the
front does not seem to make as far north. Finally, it is too early
to discern a signal (if any) of strong to severe storms.
&&
.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 645 PM EST Sun Feb 2 2025
Main impacts: LLWS, wind
Confidence: medium on LLWS, medium-high on gusty winds Monday
A low level jet riding up the length of the Ohio River will
introduce weak LLWS at HNB/BWG/SDF late tonight into early Monday
morning. As widespread nighttime cirrus thins out and pushes
northeast tomorrow, winds at the surface will increase and become
gusty to around 20-25kt from late morning through afternoon as a
cold front approaches form the northwest. As the front arrives at
the Ohio River Monday evening, moisture pooling ahead of the
boundary will manifest into a lower cloud deck. Might even see some
patchy drizzle, but it would be light and it's not until the last
few hours of the SDF TAF, so will keep the TAF dry for now.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
SHORT TERM...EBW
LONG TERM...ALL
AVIATION...13
Source:
LMK issues Area Forecast Discussion (AFD) at Feb 2, 6:45 PM EST ...Updated Aviation Discussion...---------------
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