JKL issues Area Forecast Discussion (AFD) at Dec 27, 6:00 AM EST
734
FXUS63 KJKL 271100
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
600 AM EST Fri Dec 27 2024
.KEY MESSAGES...
- Temperatures 10 to 20 degrees above normal are expected through
early next week.
- Widespread rainfall will affect eastern Kentucky at times from
today through Sunday. It will be locally heavy at times,
especially from Saturday night through Sunday morning.
&&
.SHORT TERM...(Today through Saturday)
Issued at 558 AM EST FRI DEC 27 2024
After a relatively quiet last couple of days, the forecast is
becoming more unsettled moving forward - starting today. An upper
level and surface low pressure system are currently located across
Arkansas as of 6Z this morning. They will continue to push north,
making it to western Kentucky by 12Z. WPC shows it as an occlusion
with the associated boundary traversing Kentucky during the day
Saturday. However, a swath of rain will reach eastern Kentucky well
before this front. This is likely due to an increased 850mb jet,
with strong SW flow pulling warm moisture in from the Gulf of
Mexico. This will also couple with cold air damming to our east,
ultimately resulting in overrunning precipitation throughout much of
the day today across the CWA. Rainfall looks to be moderate to heavy
at times, with totals generally ranging between a quarter and an
inch, with some locally higher amounts possible. By tonight, you see
the 850mb jet diminish slightly from west to east, and precip start
to fizzle out across much of eastern Kentucky accordingly.
During Saturday morning, despite the above-mentioned occlusion
passing through the state, all the CAMs show much of Kentucky,
especially eastern Kentucky, remaining fairly dry. The global models
have also trended drier, with a few keeping some isolated pops
across the area. However, the NBM was very gung-ho on scattered pops
across the region during this time. Collaborated with neighboring
offices, and nearly everyone agreed with the drier solution and
therefore reduced pops to only slight chances during this time
period.
Part of the reason for this drier trend is a new system taking shape
to our southwest, which is concentrating moisture along a developing
warm frontal boundary draped south of the state, and across the Deep
South. However, this drying will be short-lived, as throughout the
day Saturday this low pressure system will continue to push east-
northeast, reaching western Kentucky by 6Z Sunday. As this system
nears, the influx of warm air and moisture will quickly shift north
into the state and CWA, increasing pops once more starting Saturday
afternoon. Our location on the east side of this strengthening
system will result in strong S to SW flow at all levels of the
atmosphere (including a jet streak aloft), leading to deep moisture
advection and ultimately a completely saturated sounding column.
This will peak between 6 and 12Z Sunday, heading into the extended
period, when the low pressure system passes across western Kentucky
while strengthening from 1003 mb to 998 mb. WPC has been consistent
with much of the CWA being in a marginal risk of excessive rainfall
from Saturday through Sunday morning. Will continue to message the
likelihood of heavy rainfall with this event, which could lead to
isolated instances of flooding.
.LONG TERM...(Saturday night through Thursday)
Issued at 557 AM EST FRI DEC 27 2024
The 27/00z model suite analysis beginning Saturday evening shows
eastern Kentucky situated between a 500H ridge axis extending
from the Bahamas northward through New England and a trough axis
stretching southeastward from the an ~526 dam low over
Saskatchewan down through the Plains to along the western Gulf
Coast. Far to our west, a ridge extends from an ~589 dam closed
high (situated west of the Baja California) northward through the
West Coast states and on into British Columbia. Another trough is
passing through the North Pacific south of Alaska. At the surface,
a warm front over the Virginia Piedmont extends southwestward to
Georgia/Alabama where it wraps around the southern end of the
Appalachians and then westward to a developing low pressure over
the Lower Mississippi Valley.
As the 500H trough to our immediate west becomes more positively-
tilted Saturday night and Sunday, its surface low reflection will
strengthen and lift across the Lower Ohio River toward Lake Erie.
The southerly jet within the low's warm sector will push the warm
front northward Saturday night while also advecting a surge of
moisture northward across Kentucky (PWATs climb to around 1.25 inch
or in excess of the 90th percentile relative to climo). The system's
cold front then quickly wraps around the backside of the low and
crosses eastern Kentucky during the daylight hours on Sunday. Within
the warm sector late Saturday night and along/ahead of the cold
front, there does appear to be ample instability (MUCAPE up to ~500
J/kg) for thunder, especially closer to the Tennessee border.
Rainfall could be heavy at times, but the progressive nature of the
system should help limit the risk of hydro issues. Most locations
can expect 0.75 to 1.50 inches of rainfall, though localized swaths
approaching 2.00 inches are possible. Once the cold front moves
through on Sunday, light rain chances are likely to linger into
Sunday night as the low's parent trough moves over head.
Subsequently, surface and upper level ridging briefly returns
regionally during the day on Monday before the next Pacific 500H
trough approaches Monday night and Tuesday, causing another weaker
low pressure system to track along or just north of the Ohio River.
This system will bring the renewed threat for light precipitation
mainly during the day on Tuesday. Model agreement deteriorates
thereafter with respect to timing of when broad/deep troughing sets
up over the Central/Eastern CONUS for the latter portions of the
week. While the specifics are uncertain, a trend toward below normal
temperatures is likely along with opportunities for light
precipitation due to upslope flow and the possible passage of a
secondary cold front.
In sensible terms, look for showers and possible thunderstorms to
spread northward Saturday night. Locally heavy rainfall leading to
instances of high water cannot be ruled out. It will be very mild
with temperatures only dipping back in the 50s. Showers diminish
overall on Sunday but temperatures will still be very mild, ranging
mainly in the lower to middle 60s. Monday should be drier with at
least partial sun and highs in the mid to upper 50s. Rain shower
chances (70 to 90 PoP) return Monday night and Tuesday with the
passage of the second low pressure system. Behind that, colder air
gradually filters in on westerly to northwesterly winds, dropping
highs back into the 30s by Thursday. A few flurries or snow showers
are possible on Wednesday and Thursday but no accumulation is
expected outside of the highest peaks near the Virginia-Kentucky
border.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
ISSUED AT 1244 AM EST FRI DEC 27 2024
VFR conditions prevailed at the start of the period and continue
into Friday morning. Rain and MVFR conditions are forecast to
begin arriving in the JKL forecast area from the west between 15Z
and 18Z on Friday with further deterioration into the afternoon
as steadier rains push over the area. Look for light winds through
the night becoming southeast at 5 to 10 kts on Friday. There is a
potential for LLWS from the south just off the sfc at 45 kts
during the evening, and potentially continuing through the end of
the TAF period at 6Z.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...JMW
LONG TERM...GEERTSON
AVIATION...GREIF/JMW
Source: JKL issues Area Forecast Discussion (AFD) at Dec 27, 6:00 AM EST (https://mesonet.agron.iastate.edu/p.php?pid=202412271100-KJKL-FXUS63-AFDJKL)
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