Osborn, Kentucky Weather Forecast Discussion

587
FXUS63 KJKL 081731
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
131 PM EDT Mon Sep 8 2025
.KEY MESSAGES...
- Below normal temperatures and dry weather will persist through
  Tuesday.
- Temperatures will gradually warm to near normal by Thursday and
  continue into next week with no rainfall expected.
&&
.UPDATE...
Issued at 1146 AM EDT MON SEP 8 2025
Late morning obs are blended into the forecast without any
substantive changes.
UPDATE Issued at 805 AM EDT MON SEP 8 2025
Valley fog lingers across much of the region, but has begun to
lift. A few mid slope and ridgetop areas such as KBYL, KCPF, and
KPBZ are reporting dense fog. As we move through the next couple
of hours the fog should lift and dissipate with improving
visibilities in all areas by 9 AM to 10 AM EDT. Otherwise, under
high pressure, temperatures will moderate a couple of degrees
compared to Sunday, though still peak about 5 degrees below normal
highs for this date.
&&
.SHORT TERM...(Today through Tuesday)
Issued at 540 AM EDT MON SEP 8 2025
The period begins with an upper level low centered in the
southeast Hudson Bay/Northern Ontario areas and upper level
troughing south into the Great Lakes and eastern Conus. This
troughing was in between ridging in the western Atlantic and
another upper ridge extending from the Baja/portions of the
Pacific into the Four Corners and portions of the Rockies. West
of that, an upper level trough is nearing the Pacific coast. At
the surface, a ridge of high pressure extended from the Southern
Great Lakes to mid Atlantic sates and into the OH Valley region. A
few mid level clouds move across the region overnight, but skies
have generally been mostly clear. This has allowed for valley fog
to form and this has likely been dense in some locations per
region KY Mesonet cameras. Valley temperatures dropped into the
40s to near 50 with temperatures generally in the low 50s
elsewhere.
A general and gradual increase in 500 mb heights is progged across
the area today as the axis of upper level troughing works slowly
east and northeast of eastern KY. This trend of rising heights at
500 mb is expected to continue into tonight as well. This should
occur although a broad upper trough should persist from Canada
into the MS Valley and portions of the eastern Conus in between
upper level ridging in the Atlantic and upper level ridging from
northern Mexico north into parts of the Great Basin and Rockies
that builds into the parts of the Southern Plains to Central
Plains and High Plains. Sfc high pressure remains from the mid
Atlantic and Northeast into parts of the Appalachians during this
time despite inverted troughing extending into eastern KY that may
tend to drift westward. This inverted troughing could be a focus
for a bit more cloud cover at times. Otherwise, diurnally driven
cumulus should develop both today and on Tuesday after overnight
river valley fog lifts and dissipates. Temperatures will gradually
moderate today and into Tuesday, however they should remain below
normal.
.LONG TERM...(Tuesday night through Sunday)
Issued at 500 AM EDT MON SEP 8 2025
the period is expected to begin with an upper level ridge
extending from Mexico to portions of the Rockies and Plains with
another upper ridge in the western Atlantic centered northeast of
Bermuda. In between these two ridges, an upper level trough axis
is expected to extend south across the Great Lakes to the MS
Valley while an upper level low/trough will continue to work into
the western Conus. One shortwave working into or through the
eastern Canada to MS Valley trough should be nearing the Lower OH
Valley as the period begins with another upstream over the Upper
MS Valley western Great Lakes. At the surface, a ridge of high
pressure is expected to be anchored from New England to the
Southeastern Conus and also into the OH Valley.
From Tuesday night to Wednesday night, the initial shortwave
trough should merge with the one to the north that works into the
eastern Great lakes to OH valley with the axis of this trough
reaching from Quebec to the Lower OH valley to TN Valley by late
Wednesday night. Further east ridging remains in the Atlantic
while upper level ridging builds further into the Plains/Central
Conus including the Upper MS valley. Further west, the upper level
trough/low works slowly across the western Conus. Sfc high
pressure remains in place at the surface, with the passing
shortwave or shortwaves moisture starved and only leading to a few
clouds mainly on Wednesday afternoon and evening. The airmass
will continue to moderate and highs Wednesday should near normals.
Otherwise, sufficient breaks in the clouds at night should favor
small to moderate ridge/valley splits and valley fog in the
typically favored locations both Tuesday night and Wednesday
night.
Thursday night to Friday night, the axis of upper level troughing
will shift east and southeast of eastern KY through Friday morning
with upper level ridging centered over the Southern Plains and
extending across parts of the Central Conus building into the
Lower to Middle OH Valley as well as the TN Valley. Further west,
the upper low over the western Conus should meander into the
Great Basin vicinity. Meanwhile over central Canada an upper low
is progged to move from Hudson Bay to the James Bay area and
northern Ontario with an associated shortwave trialing into the
northern Great Lakes by late Friday night. A ridge of sfc high
pressure should remain in place across eastern KY during this time
as well. The airmass will warm a bit further with near normal
highs anticipated for Friday. Thursday night and Friday night
should feature more of the same as far as small to moderate
ridge/valley temperature splits and fog development in the favored
valley locations.
Saturday to Sunday, recent guidance generally has an upper level
trough axis nearing a Maritimes to St Lawrence Valley to Great
Lakes during this timeframe and upper level ridging remaining
from the Southern Plains in portions of the Central Conus and
another upper level trough nearing the west coast of the Conus. A
few shortwaves may move into parts of the OH Valley to end the
period. These systems and any associated cold fronts dropping
across the Great Lakes should be rather moisture starved while sfc
high pressure is progged to remain over the Southern Appalachians
to TN Valley regions. Guidance is largely rain free through the
end of the period, though some recent ECMWF runs have precipitation
reaching near the OH River or south near or after the end of the
period. 10 percent pops in the north is reasonable for now with
some uncertainty in the timing and evolution of the upper
trough/low. Temperatures should remain near normal for this time
of year next weekend.
&&
.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 131 PM EDT MON SEP 8 2025
Fog will again bring IFR or worse conditions to many of the
deeper valleys during the late night and early morning hours, but
it is not likely to affect TAF sites. Otherwise, VFR conditions
with winds less than 10 kts are forecast through the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...HAL/JP
SHORT TERM...JP
LONG TERM...JP
AVIATION...HAL

NWS JKL Office Area Forecast Discussion