LMK issues Area Forecast Discussion (AFD) at Dec 28, 9:17 PM EST321
FXUS63 KLMK 290217
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
917 PM EST Sat Dec 28 2024
.KEY MESSAGES...
* 1-1.50" of rain tonight into Sunday. Localized amounts of 2"
possible. Embedded thunder will be possible tonight but severe
storms are not expected.
* Sunday will be very breezy with high confidence in gusts of at
least 35-40 mph. Some data are suggesting the possibility of gusts
over 40 mph from southern Indiana to the Kentucky Blue Grass in
the afternoon.
* Another period of rain is forecast for Monday night into Tuesday.
By this time area rivers may be running high, though confidence is
low on whether or not there will be any flooding. Interests along
streams will want to monitor the waves of rain as they pass
through the district this weekend and early next week.
* A turn towards colder weather is outlooked for early and
especially mid-January.
&&
.UPDATE...
Issued at 917 PM EST Sat Dec 28 2024
Latest surface analysis places low pressure centered over north
central MS as the first wave of showers and thunderstorms has
entered into central KY. Current radar shows this activity slowly
waning in intensity as it pushes north into a more stable
environment.
The area will see a brief lull before the next round of moderate
rain, which is currently making its way through Nashville and likely
entering southern KY by 29/04Z. Still expecting to see 1.00 to 1.50
inches of rain as a stout 65kt LLJ rushes over the area by early
Sunday morning. Surface winds will also be picking up during this
time with gusts in the 25-30mph range.
No major changes needed to the going forecast, with only minor
adjustments made to the near term grids. No updated products
necessary at this time.
&&
.SHORT TERM /THROUGH SUNDAY/...
Issued at 319 PM EST Sat Dec 28 2024
Wet and breezy conditions are expected throughout this short
term period.
Tonight
Rain/flooding--
Confidence: High confidence in widespread light to moderate rains
with pockets of heavier rain, especially between midnight and dawn.
Medium confidence in minor local flooding, low confidence in
significant flash flooding.
Strengthening low pressure advancing from Arkansas to southern
Indiana tonight will have full access to the Gulf, and will pull
1.25" PWAT air well north into the Ohio Valley. A very strong low
level jet from Mississippi to Ohio ahead of a sharp 500mb trough
over the Mississippi Valley and beneath the right entrance region of
an upper jet streak over the Great Lakes will lead to widespread
rain. K Index in the 33-35C range and dew points in the 50s further
support the idea of moderate to locally heavy rains. Expected
amounts tonight into Sunday morning are around 1-1.50", with 1- and
6-hour QPF below FFG. Forward propagation of heavier cells within
the larger area of rain will be fairly rapid, on the order of 35 to
45 mph. Most area streams are well within their banks, with the
exception of the middle/lower Green, though that river is usually
slow to respond to heavy rains. So, at this time the bottom line
appears to be that the main flooding threat tonight will be minor
local flooding in typical areas that collect water easily.
Storms--
Although powerful storms will continue well to our south this
evening from Louisiana to Alabama, significant instability will
remain well to the south of Kentucky through the night. Local
sounding progs show a very small, thin positive area that may
support isolated rumbles of embedded thunder elevated above a
surface-based stable layer. Despite very strong deep layer shear,
the lack of instability and elevated nature of the convection
suggest the chance of severe weather is very low tonight. This has
been a consistent signal in the models and in SPC outlooks over the
past few days.
Wind--
Though the strongest winds are expected to remain aloft tonight,
gusty surface winds can still be expected after midnight in a tight
pressure gradient as the surface low passes by just to our
northwest. High confidence in wind gusts of 30-40 mph, especially
east of I-65.
Temperatures--
With the heavy overcast and surface winds becoming more southerly
with time as the low approaches, temperatures tonight will be nearly
steady in the 50s.
Sunday
The compact low over southern Indiana Sunday morning will continue
to deepen as it pushes off toward the Detroit area by evening.
Widespread showers in the morning will become more scattered in the
afternoon. Strong gusty winds will continue, with high confidence in
gusts of 35-40 mph. It's possible we may end up needing a Wind
Advisory, primarily from southern Indiana to the Kentucky Blue
Grass. After coordinating with IND and ILN, will hold off on a
headline for now and let the mid shift take one more look at it.
Temperatures may lift a few degrees in the morning but then will
become steady or fall a bit in the afternoon as the low moves away
and our winds veer from south to west.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 319 PM EST Sat Dec 28 2024
Sunday night, the negatively tilted upper trough that is bringing
the system to the Lower Ohio Valley tonight will be centered over
the Ohio Valley. The eastern side of the trough will continue
pushing the surface low farther northeast, away from the CWA.
Pressure gradients begin to weaken, but west to southwest backing
winds around 10 mph could still gust to 25-30 mph. The best chance
for this will be across the northeastern side of the CWA, closer to
the surface low, but by Monday morning, gusts will be down to 10-15
mph across the northeastern parts of the CWA. The rest of the CWA
will be calm to around 5 mph, and just as the winds will taper off,
so will the precipitation. Areas of sprinkles and light rain will
continue working east-southeast across the CWA on the back side of
the low. Rain should come to an end on Monday morning. Most areas
will likely only receive another few hundreths of an inch to around
a tenth of an inch. Some isolated locations could see another
quarter of an inch.
Monday is expected to be dry as a small upper ridge moves overhead
ahead of the next system. Some sunshine could make it through the
remaining cloud cover. The best chance at sunny skies will be over
the southern and eastern parts of the CWA. Warm air advection will
push temperatures well above normal, in the mid 50s to low 60s.
Monday night, riding along in mostly zonal flow, the next low
pressure system will cross the Ozarks and arrive in southern Indiana
by Tuesday morning. There is strong model agreement with the
placement of the system as it works through the Lower Ohio Valley.
Rain is expected to arrive in our western counties Monday evening
and move east of the CWA by Tuesday evening. Current estimates have
the highest totals in southern Indiana, at about half of an inch.
Amounts are expected to taper over to the south, to around a quarter
of an inch in southern Kentucky. Warm air advection ahead of the
system's cold front will allow temperatures to reach into the low to
mid 50s.
Behind the cold front associated with this second system, cold air
advection will drop highs into the 30s and 40s from Wednesday
through at least Saturday, and surface high pressure should bring
sunnier skies for the end of the week. A possible shortwave could
move through the area Thursday night or Friday, but models currently
don't have a very good handle on this feature. It doesn't look like
it will be much of anything with enough moisture to wet some yards.
&&
.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 648 PM EST Sat Dec 28 2024
High confidence continues in deteriorating flying conditions as we
advance through this TAF period.
Latest surface analysis reveals low pressure near LA/MO/MS border
with a warm front lifting towards the TN/OH Valleys. Current radar
shows the first wave of moderate to heavy showers and thunderstorms
pushing across the TN/KY border while regional observations continue
to report MVFR CIGs across all TAF sites.
Expect CIGs to lower and VIS to reduce to MVFR conditions in
moderate rain showers, varying from light to heavy at times. Strong
winds with gusts in the 20-25kt range will steadily veer from SE to
S overnight as the warm front passes, and continuing to SW as the
cold front passes Sunday morning while gusts increase to 25-30kt.
Poor conditions will persist through much of Sunday with light rain
showers and possible drizzle at times, accompanied by strong WSW
winds with gusts over 30kt possible. Rain will taper off by late
afternoon and winds are expected to subside somewhat toward the end
of this TAF cycle.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
UPDATE...CG
SHORT TERM...13
LONG TERM...KDW
AVIATION...CG
Source:
LMK issues Area Forecast Discussion (AFD) at Dec 28, 9:17 PM EST---------------
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