316
FXUS63 KJKL 070445 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1245 AM EDT Wed May 7 2025

.KEY MESSAGES...

- Valley fog is expected to affect portions of the area tonight
  into early on Wednesday, but should be less extensive and not as
  dense as it was on Tuesday morning.

- The periodic potential for showers and thunderstorms continues
  through the end of the week.

- Temperatures will average near normal into the upcoming
  weekend.

&&

.UPDATE...
Issued at 1135 PM EDT TUE MAY 6 2025

No significant changes were made to the forecast with mainly just
the inclusion of the latest obs and trends for the T/Td/Sky grids.
These minor adjustments have been sent to the NDFD and web
servers along with a freshening of the zones and SAFs.

UPDATE Issued at 740 PM EDT TUE MAY 6 2025

23Z sfc analysis shows high pressure finally in control of the
weather over eastern Kentucky. This is working to settle the winds
and clear the skies. Currently temperatures are running in the low
to mid 60s with some upper 50s noted in the sheltered valleys.
Meanwhile, amid light westerly winds, dewpoints are generally in
the mid 40s to lower 50s. Have updated the forecast mainly to add
in the latest obs and trends for the T/Td/Sky grids. These minor
adjustments have been sent to the NDFD and web servers.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 335 PM EDT TUE MAY 6 2025

As of mid afternoon, an upper level low was centered near the
PA/OH border with ridging over the western Atlantic to its east
with a narrow upper level ridge to its west extending from the
Gulf coast to the mid MS Valley region to the Dakotas. A general
area of troughing extended through much of the western Conus with
an upper level low centered in NM and another centered in NV.
Further north, a shortwave trough extended from Hudson Bay to near
the Ontario and Manitoba border with a wavy frontal zone
extending from Ontario to the upper MS Valley. Elsewhere at the
sfc, low pressure associated with the upper low to the northeast
of the region was tracking from the mid Atlantic states and into
the Northeast with the trailing frontal zone extending south near
the eastern seaboard into northern FL before extending across
portions of the northern Gulf to low pressure centered in TX.
Meanwhile, a ridge of sfc high pressure extended from portions of
the southeast to the Lower OH Valley and mid MS Valley. Fairly
extensive cumulus has developed across the region and remains in
place at this time.

Tonight and Wednesday, the upper level low to the northeast of
eastern KY will continue to gradually depart to the northeast,
moving across parts of the Northeast to St Lawrence Valley.
Meanwhile, mid level height rises are anticipated over eastern KY
tonight into early Wednesday as upper ridging shifts to the east.
At the same time, the ridge of surface high pressure will shift
east and northeast across the area and weaken. With the axis of
the upper level ridge shifting east, the upper level flow will
become become southwest to west as the upper level low currently
centered over moves into the Plains and should become centered
near the KS and OK border on Wednesday afternoon. Further north,
the upper level trough in Canada should progress to Quebec to the
Great Lakes by Wednesday evening and begin to interact with the
Central Conus upper low. Locally, one or more lead disturbances/
shortwaves should track into the OH and TN Valley regions on
Wednesday. The frontal zone to the south of eastern KY is expected
to remain in place and remain from TX east near or just north of
the Gulf coast. At the same time, the frontal zone to the north
should near the Northeast to eastern Great Lakes to mid MS Valley
by Wednesday evening. Moisture will increase across eastern KY
once surface high pressure departs with PW climbing to near 1 inch
along the TN border per the 12Z HREF mean by early to mid
afternoon and shift a bit further north through Wednesday evening.

Wednesday night, the central CONUS upper low should gradually
progress toward the mid MS Valley while the upper trough over
Canada should move into Quebec to the Southern Great Lakes by late
Wed night. The associated wavy frontal zone should move across
parts of the Northeast to mid Atlantic and sag toward the OH River
and into the mid MS Valley. Moisture will continue to increase
through Wednesday night per PW from the 12Z HREF mean with values
expected to reach 0.9 to 1 inch by the end of the period.

With high pressure in place, cumulus is expected to diminish
around or shortly after sunset, and light winds are expected.
This should set the stage for a minor to moderate ridge/valley
split in temperatures with a valley inversion developing with
patchy fog to areas of valley fog anticipated to develop near or
just after midnight and then dissipate within 2 to 3 hours after
sunrise. With the moisture gradient on return flow into the south,
a shower or perhaps thunderstorm is possible per some of the CAMS
and some of the other guidance. Slight chance to chance pops were
used for Wednesday afternoon and evening for this potential in
the southwest. With moisture continuing to increase and some weak
disturbances in southwest flow, additional showers or perhaps a
storm in the south are possible Wednesday night, when 12Z HREF
mean MUCAPE values increased to a few hundred J/kg.

Temperatures will moderate on Wednesday under return flow and
Wednesday night lows should also be milder than recent nights.

.LONG TERM...(Thursday through Tuesday)
Issued at 510 PM EDT TUE MAY 6 2025

There is relatively good agreement in guidance for the long term
period through Saturday, both model to model and run to run. The
period will start with an elongated, positively tilted upper
trough laid out from the southern plains through Quebec, and an
associated surface frontal boundary to our north from TX to New
England. A second frontal boundary will be laid out further south,
preventing the stymieing the northward flow of significant gulf
moisture.

The upper trough and surface front will progress southeastward,
with the cold front moving through KY on Thursday and Thursday
night. Despite surface dew points expected to make it only into
the 50s before cold fropa, the advancement of the upper trough
with its lowering geopotential heights and arrival of colder air
aloft should result in modest instability. This will likely result
in showers and possibly some thunderstorms. As the cold front
drops to our south, drier and cooler air will arrive over KY
Thursday night into Friday. As this happens, a couple of upper
lows will pinch off from the trough-- one of them over the
Arklatex region and the other in the vicinity of NY/PA on Friday
afternoon, with a col in between over our area. The northern one
will be close to the prevailing westerlies aloft and is expected
to get picked up and ushered out ahead of the next progressive
northern stream trough. The southern low essentially becomes cut
off and lingers over the lower Mississippi Valley. At this point
in the forecast, even though the most recent runs of the GFS and
ECMWF continue in relatively good agreement, run to run continuity
in the models over the last day or two fades. As is often the
case, there is trouble resolving the evolution of a cut off low
concerning how it weakens and moves. The most recent runs show a
northeastward drift, which brings precip into our area early next
week. With a lack of confidence in how things play out, the POP is
only in the slight chance to chance range (20-50%) for any given
forecast period early next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
ISSUED AT 1245 AM EDT WED MAY 7 2025

Under mostly clear skies, valley fog is likely to develop and
affect several non TAF locations from 06Z through around 13Z with
MVFR and IFR if not locally lower visibility. Some of this fog
could affect the TAF sites for a few hours between 08Z and 12Z,
with KLOZ, KSME, and KSJS more likely to be affected by some MVFR
reductions compared to KJKL and KSYM - per guidance. Once any fog
lifts and dissipates by 14Z, VFR again prevails through end the
period. Some cumulus may again form toward 18Z, but this should
largely stay in the VFR category. Winds will generally be light
and variable, under the influence of surface high pressure,
through the end of the period.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...GREIF
SHORT TERM...JP
LONG TERM...HAL
AVIATION...GREIF