LMK issues Area Forecast Discussion (AFD) at Jan 31, 3:09 PM EST447
FXUS63 KLMK 312009
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
309 PM EST Fri Jan 31 2025
.KEY MESSAGES...
* Isolated thunderstorms are possible across south-central Kentucky
late this afternoon into the early evening. Small hail and gusty
winds could be possible with strongest storms.
* Dry and unseasonably mild conditions for this weekend into early
next week. Next chance of rain Wednesday and Thursday.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 308 PM EST Fri Jan 31 2025
Synopsis...Positively-tilted shortwave trough will transition across
the region today while attendant occluded surface low moves through
the Upper Ohio Valley this afternoon and early evening. Although a
frontal boundary already crossed the region this morning, the large
cyclonic circulation will drag another cold front, currently stalled
over the Midwest, southward towards the Ohio Valley tonight. By
tomorrow, mid-level ridge building over the Central US along with
surface high pressure over the Upper Great Lakes will provide quiet
weather conditions.
Model Evaluation/Confidence...Convection-allowing models (CAMs)
haven continued to trend southward with the position of this
afternoon thunderstorms which upon quick inspection of the latest
satellite and radar imagery, those trends are verifying fairly well
as convection has initiated along the Western Kentucky/Tennessee
border. Therefore, forecast confidence remains relatively high this
afternoon regarding storms potential and location. For tonight,
confidence remains largely unchanged but the prospect of drizzle
chances for a few hours along the northern half of the CWA
introduces some uncertainty regarding depth of shallow moisture and
necessary low-level forcing.
This Afternoon...Convection initiation is currently underway
following a pre-existing moisture axis draped along Western Kentucky
and Tennessee. Unblocked radiation and boundary-layer moisture is
improving low-level lapse rates and increasing instability. SPC
Mesoanalysis indicates SB-CAPE around 100-250 J/kg, which is what
CAMs have reflected during the last couple of runs. ACARS soundings
at SDF and BNA indicate freezing levels around 2100 m; however,
presence of dry air could modify that height even lower due to wet-
bulb effect. Furthermore, initiating convection is moving into an
area where low-level (0-3 km) shear values oscillate between 30-40
knots. That being said, developing updrafts will have to overcome
mid-level dry air entrainment while fighting other cells for the
limited moisture and instability. All in all, there is a short-lived
conditional risk of graupel (small hail) and sub-severe wind gusts
with strongest cells that develop over south-central Kentucky. If
strongest low-topped updrafts manage to develop any mid-level
incipient rotation, then a very low and localized risk of severe
weather could yield larger hail and stronger wind gusts. This
afternoon shower/storm activity will be either dissipating or moving
out of the area around 23 or 0Z.
Tonight...Cold front will arrive with an influx of cooler air so
that lows will be 5 to approximately 10 degrees lower than the
previous night. At the same time, a surge of low-level moisture will
be moving ahead and along the frontal boundary (probably associated
with the comma head of the occluded surface low). GFS forecast
soundings show a sufficiently deep moist layer with enough forcing
to potentially boost drizzle chances between 3-9Z over the northern
half of the CWA.
Saturday...Mid-level subsidence, solar heating, and winds shifting
from the north to the south will start eroding the shallow moist
layer throughout the morning and afternoon. Latest HREF cloud cover
forecast and GFS forecast soundings indicate the possibility of
clearer conditions along and north of I-64 with more cloud cover
southward (closer to the position of the frontal boundary).
Temperatures will remain cooler than previous days with highs in the
mid 40s to low 50s.
&&
.LONG TERM /SATURDAY THROUGH FRIDAY/...
Issued at 308 PM EST Fri Jan 31 2025
Saturday Night through Tuesday Night...
Quasi-zonal pattern will keep us dry and unseasonably warm through
the first half of next week. Temp anomalies will approach 20
degrees with highs solidly in the 60s and lows in the 40s each
day. A weak mid-level wave Monday night will push a mainly dry
cold front into the Ohio Valley, with sensible wx impacts
limited to increased cloud cover and a wind shift as continued
ridging aloft keeps temps well above normal.
Wednesday through Friday...
Progressive upper trof will scoot eastward along the Canadian border
from near Glacier NP on Wednesday morning, reaching the Boundary
Waters Thursday morning and continuing into eastern Canada by Friday
morning. POPs ramp up Wednesday under warm advection and isentropic
lift, with some potential to get into the warm sector later in the
day. Another max in precip chances (and intensity) comes with the
trailing cold front on Thursday. Still plenty of uncertainty as
severe potential is dependent on forcing and instability happening
concurrently, and confidence in the timing is not sufficient yet.
CSU ML probabilities do show a 15% svr probability Wednesday across
portions of the Ohio Valley, so this pattern bears watching for now.
Temps will approach record highs on Wednesday depending on how
"clean" the warm sector is. Behind the front, we'll see a
significant cooldown on Friday compared to midweek temps, but
it will still be above normal for early February.
&&
.AVIATION /18Z TAFS THROUGH 00Z SUNDAY/...
Issued at 1234 PM EST Fri Jan 31 2025
Confidence/Impacts:
- High confidence in gusty winds decreasing this afternoon
- High confidence in MVFR/IFR ceilings tonight and tomorrow morning
- Low confidence in showers/storms at BWG late this afternoon
Discussion...Conditions will improve to VFR thresholds this afternoon
and early evening as departing low-level jet pushes rain out of the
forecast area. Incoming dry air will allow gradual clearing, as
already noticed in satellite imagery, so expect a few more hours of
wind gusts of 20-25 knots as daytime mixing increases. Winds will
let down, however, towards the early evening. An slight chance of
thunderstorms is possible late this afternoon across southern
Kentucky and although confidence in coverage is not high, decided to
include a PROB30 group at BWG to cover potential, short-lived
impacts. Finally, moisture accompanying the surface low will move
across the forecast area tonight supporting MVFR and eventually IFR
ceilings at all terminals. These low-level clouds will persist
through the morning hours with some models starting to lift
ceilings around 15Z or so.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
SHORT TERM...ALL
LONG TERM...13
AVIATION...ALL
Source:
LMK issues Area Forecast Discussion (AFD) at Jan 31, 3:09 PM EST---------------
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