JKL issues Area Forecast Discussion (AFD) at Mar 26, 9:05 PM EDT
681
FXUS63 KJKL 270105
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
905 PM EDT Wed Mar 26 2025
.KEY MESSAGES...
- Patchy to widespread frost is anticipated tonight, most
extensive in sheltered valleys.
- Seasonal temperatures are expected through Thursday, followed by
a significant week-end warming trend.
- Multiple rounds of showers, and perhaps thunderstorms, are
possible this weekend within the warm sector of a strong storm
system moving towards the Greater Ohio River Valley.
&&
.UPDATE...
Issued at 901 PM EDT WED MAR 26 2025
Temperatures are falling through the 40s across most of eastern
Kentucky this evening and have even reached the upper 30s in some
of the coldest hollows. With dew points well below freezing and
mostly clear skies/light winds anticipated for most of the night,
anticipate frost formation in many locations by late tonight as
temperatures drop deep into the 30s for all, and into the mid to
upper 20s in many rural sheltered valley locales.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 522 PM EDT WED MAR 26 2025
The eastern CONUS upper trough of recent days will finally depart
to the east during the short term period, while surface high
pressure currently over the Ohio Valley also slips eastward off
the coast. Our flow near the surface will continue to generally
originate out of the high, tending to keep our air dry. However,
warm/moist advection overriding the surface air will lead to
moistening aloft, initially to our west and northwest, but getting
carried here by swift mid/upper level flow. At the least, this
should bring an increase in clouds on Thursday, with virga. A
question to be resolved is how much of this makes it to the ground
as rain by the end of the day. The NAM is more aggressive with
this than the GFS, and a model blend yields a slight chance to
chance POP for most of the forecast area. Moistening/warming
continues Thursday night, mainly in the 850-700mb layer. It's at
the point in the NAM that it generates weak elevated instability,
and a slight chance of thunder has been allowed to arrive from
the west along with a likely POP.
.LONG TERM...(Saturday through Thursday)
Issued at 900 PM EDT WED MAR 26 2025
When the long-term period opens Friday, 500 mb heights will be
rising over the Ohio Valley as ridging propagates eastward from the
Central/Northern Plains. Under the ridge, a southern stream trough
will be passing from the Southern Plains to Lower Mississippi
Valley. Further upstream, mean troughing (around a parent closed low
just off the Olympic Peninsula) spans the West Coast states.
Multiple shortwave troughs are rotating through the parent trough,
including one passing from the Central/Northern Rockies into the
Dakotas. Translating down to the surface, this disturbance supports
a sub-1000mb low over South Dakota. Modeled theta-e gradient
magnitude fields indicate a warm front extending southeast from the
slow across northeast Iowa, Central Illinois, and beyond into
northeastern Kentucky at daybreak.
The warm front will continue to lift northeast through the Upper
Ohio Valley and into the Northeast US/Great Lakes on Friday as the
associated surface low tracks toward the Great Lakes. Model
soundings show skinny but deep elevated instability with the warm
front, so a rumble or two of thunder cannot be ruled out (better
chances over the northeastern counties). Precipitation tapers
from southwest to northeast during the morning/midday as post-
frontal subsidence dries the column and mild southwesterly flow
warms 850mb temperatures to ~10-12C. This warming combined with
increasing sunshine and mixing should buoy our temperatures to
10-15+ degrees above normal. Also, BUFKIT shows relatively deep
mixing supportive of southwesterly wind gusts in the 20 to 25 kt
range during the late morning and afternoon hours. Late in the
afternoon, a subtle disturbance out ahead of the system over the
Lower Mississippi Valley will bring weak height falls. Limited
instability (up to ~500- 750 J/kg of MUCAPE as per the NAM12) will
be sufficient for convection but a few J/kg of MLCIN may keep a a
lid on convection. A slight chance of thunderstorms was retained
in the forecast for much of the afternoon, tapering off sharply
after 20z as instability wanes. Weak surface high pressure ridging
briefly noses northwest into the Central/Southern Appalachians
from its parent high over Bermuda on Friday night.
Deeper moisture infiltrates eastern Kentucky again on
Saturday/Saturday night as the southern stream trough lifts
northeast with a secondary warm front. This will bring the renewed
threat of rain but instability appears meager to nil and any
rainfall amounts should be light. Later Saturday night and Sunday,
the aforementioned 500H trough, initially along the West Coast, will
eject off the Rockies and out onto the Plains. This system will
spawn multiple waves of low pressure near/over the Oklahoma
Panhandle Saturday night, one of which will likely consolidate,
deepen and track northeast toward the Southern Great Lakes during
the day on Sunday and on into the Eastern Great Lakes/Mid-
Atlantic on Sunday night. A majority of the model guidance shows
the system's trailing cold front dropping through eastern Kentucky
late Sunday night or early Monday morning, though a minority of
LREF members still feature a faster passage. There are multiple
issues that prevent the more favored slower frontal passage from
being a slam dunk severe event over eastern Kentucky. First, cloud
cover could remain rather extensive for much of the day on Sunday
behind the secondary warm front, thus limiting surface heating
and instability development. Second, the timing of the boundary is
less than ideal as most of the destabilization that manages to
occur on Sunday will have waned before the better forcing along
the front arrives. While a severe weather or low end flooding
threat cannot be ruled out at this point, the favored poor timing
of the boundary and likelihood of marginal pre-frontal instability
keeps forecaster concern lower at this point. With that being
said, this system is still several days out and it would be
prudent to keep an eye on this system in case a less likely but
more inclement setup becomes favored. Temperatures drop sharply
aloft on Monday behind the first cold front as troughing becomes
established over our region. An embedded shortwave trough and
secondary surface cold front drops through Monday night with the
possibility of additional light rain chances. If any precipitation
lingers early Tuesday, it should quickly diminish as high
pressure extends south from the Great Lakes and brings in a dry
and cool (850 mb temperatures near 0C) air mass. The fair weather
pattern will be short-lived as yet another trough and cold front
approach on Wednesday.
In sensible terms, showers and any thunderstorms early on Friday
depart to the northeast, leaving a mix of sun and clouds. A stray
shower or storm cannot be ruled out later in the day but most
locations should remain dry. It will be breezy and much warmer with
high temperatures forecast in the upper 70s to near 80. Variable
cloud cover is anticipated Friday night with lows in the 50s to
around 60. On Saturday, daily maximum temperatures may be a bit
cooler near/west of I-75 and near/north of I-64 where thicker cloud
cover arrives sooner. Look for thermometer readings only in the mid
70s there, but generally in the upper 70s to near 80 deeper into
southeastern Kentucky. Light shower chances rise from the west late
in the afternoon. The threat of light rain continues Saturday night
with perhaps a token rumble of thunder. It will be very mild with
low temperatures in the mid 50s to lower 60s. Sunday is forecast to
be the mildest day of the period with temperature readings topping
out in the mid 70s to lower 80s. Dew points rising to within a few
degrees of 60 near/west of the Escarpment could make it almost feel
a tad humid. Dew points should remain in the 50s further east. Cloud
cover extent and shower coverage are not as certain on Sunday, but
right now more cloudiness is favored with precipitation coverage
generally diminishing through midday/early afternoon. More
widespread shower and thunderstorm activity is expected to develop
late Sunday night into early Monday. Lower end shower chances
linger Monday and Monday night at many locations and by Tuesday
morning temperatures in the 30s to around 40 can be expected.
Tuesday's forecast is cool and trending drier with high
temperatures in the mid 50s, north, to mid 60s, south. Above
normal temperatures and rising rain chances are probable again by
Wednesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 740 PM EDT WED MAR 26 2025
VFR conditions and winds less than 10 kts are forecast through the
period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GEERTSON
SHORT TERM...HAL
LONG TERM...GEERTSON
AVIATION...GEERTSON/HAL
Source: JKL issues Area Forecast Discussion (AFD) at Mar 26, 9:05 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202503270105-KJKL-FXUS63-AFDJKL)
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