LMK issues Area Forecast Discussion (AFD) at Nov 12, 6:52 PM EST ...Updated Aviation Discussion...558
FXUS63 KLMK 122352
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
652 PM EST Tue Nov 12 2024
...Updated Aviation Discussion...
.KEY MESSAGES...
* Rain Wednesday afternoon into Thursday with the majority coming
Wednesday night
* Temperatures remaining at or above normal through the next
Tuesday forecast
&&
.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 227 PM EST Tue Nov 12 2024
Pool of somewhat tropical air has been holding steady along the NE
Gulf of Mexico coast. Large upper trough across the Rockies now
will shift east tonight and tomorrow and really start pulling that
moisture northward. Already seeing some signs in the last hour or
two of that pulling, with the 1" threshold level now into east
central MS. By late afternoon Wednesday, expect a nice plume of
rains to be approaching from the west and southwest in response to
both the broad-scale lift as well as that moisture pool.
This forecast has fairly high confidence, with 80-100% rain chances
along and west of I-65 corridor by 7 PM Wednesday...the beginning of
the long-term period below. Precipitable waters likely will bump up
to around 1.5", which is above the 90th percentile for this time of
year. Can't rule out some isolated rumbles of thunder well south of
I-64 and along and west of I-65.
Outside of rain chances, look for temperatures to start inching a
little above normal tonight, as winds steadily switch from
northeasterly to easterly. During the day Wednesday, despite the
increasing cloud cover, more southeasterly winds will bring
temperatures above normal, with peak readings likely in the mid 60s.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Issued at 227 PM EST Tue Nov 12 2024
Synopsis...Medium-range period begins with shortwave trough moving
across the Mid Mississippi Valley and into the Ohio Valley while
becoming negatively tilted. At the surface, the forecast are will be
situated between a warm front crossing southern Indiana and a cold
front extending southward from a surface low over Iowa. Moderate to
heavy rainfall and isolated thunderstorms are expected through
daybreak Thursday as the shortwave trough and front system translate
to the east. For the weekend, strengthening mid-level ridge aided by
large blocking high over the Gulf of Mexico and regional surface
high pressure will keep the weather dry with slow temperature
recovery. Meanwhile, a series of Pacific shortwave troughs will
greatly amplify the pattern aloft across the West and potentially
Central CONUS, setting the stage for a complex forecast next week.
Model Evaluation/Confidence...Deterministic model agreement yields
relatively high forecast confidence through Sunday with increasing
uncertainty and, therefore, low confidence for next week given lack
of model skill in timing and intensity of shortwave troughs as well
as tropical interaction with a potential TC slowly tracking
northwestward across the Caribbean. Regarding rainfall accumulation
Wed night through Thursday morning, most of the guidance is showing
an areal average around 1.0" with UKMET, CMC, and GFS depicting a
maximum over south-central Kentucky around 2.0" (which agrees well
with latest HREF 24-hr LPMM). Another change noted is the slow
departure of a near-surface residual moisture layer that will most
likely foment partly to mostly cloudy skies Thursday and perhaps
Friday morning with ramification to the temperature forecast.
Finally, large forecast variability prevents from giving details for
next week as possibilities range from a rainy first half of the week
to mostly dry conditions.
Wed Night - Thursday...Isentropic lifting and PV advection ahead of
the shortwave trough will allow top-down saturation and force some
low-topped showers before the bulk of rainfall moves over during the
second half of the night. Developing 50-knot low-level jet will
foment anomalous PWAT values from tropical moisture lingering in the
Gulf of Mexico. Given recent rainfalls and mild temperatures, soil
moisture should have increased with respect to early November
values. As a result, incoming precipitation totals might cause minor
flooding issues in areas that previously received 2-3" of
precipitation. As mentioned above, the greatest storm totals this
time are shifted to the south where Flash Flood Guidance is
generally higher. As for river flooding, HEFS guidance is not
showing any significant probabilities of reaching minor flood stage
in any major basins. On the other hand, small creeks and low water
passages might quickly become overwhelmed during periods of heavy
rain. Based on the lack of instability, timing of the frontal
passage (instability minimum), and strong near-surface inversion,
chances of organized severe weather are negligible. Will mention
isolated lightning chances based on mid-level lapse rates in the
mixed-phase region shown in GFS soundings, especially around 14/06Z.
Although moderate to heavy rainfall will end by daybreak Thursday,
residual moist layer depicted in GFS and ECWMF soundings will allow
broken to overcast sky the rest of the day with winds turning to
the northwest towards the evening.
Friday - Sunday..Dry and mostly sunny weather will prevail next
weekend as mid-level ridging and surface high pressure bring dry
airmass and stable conditions to the area. Northerly winds will
advect a cooler temperatures to the region with near-normal
temperatures Friday into Saturday morning and trending above-normal
thereafter based on east winds on Saturday and southerly on Sunday.
Additionally, fog chances will be likely Saturday morning as high
pressure gets closer to the area, winds turn calm overnight, and
skies clear. Chances of fog Friday are lower taking into
consideration departing cloud cover and sufficiently high winds to
keep the boundary layer mixed.
&&
.AVIATION /00Z TAFS THROUGH 06Z FRIDAY/...
Issued at 651 PM EST Tue Nov 12 2024
VFR flight categories will remain through the overnight into the
early morning across all TAF sites. The changes come with a wind
shift towards day break with winds shifting from the east to more
southeast during the day tomorrow. Conditions start to change as an
approaching system draws in moisture from the Gulf and spreads it
northward into the Ohio Valley. Initially we will see high clouds
stream in with the moisture but CIG will start to drop and rain
showers are expected in the afternoon for HNB/BWG and SDF. Late
afternoon into evening we will see MVFR to even possible IFR
conditions by the end of the forecast period.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
SHORT TERM...RJS
LONG TERM...ALL
AVIATION...BTN
Source:
LMK issues Area Forecast Discussion (AFD) at Nov 12, 6:52 PM EST ...Updated Aviation Discussion...---------------
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