387
FXUS63 KJKL 020335 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1135 PM EDT Wed May 1 2024

.KEY MESSAGES...

- Very warm with record or near-record highs on Thursday.

- Shower and thunderstorm chances return to the forecast Friday
  through Tuesday.

&&

.UPDATE...
Issued at 1135 PM EDT WED MAY 1 2024

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

UPDATE Issued at 845 PM EDT WED MAY 1 2024

00Z sfc analysis shows a relatively weak area of high pressure
sitting over eastern Kentucky. This has been able to keep the
skies mostly clear into the evening with fairly light and variable
winds. Currently, temperatures are running warm - in the low to
mid 70s most places - while dewpoints generally range from the
mid 50s to lower 60s along with some lower values on the ridges.
The current forecast is on track with an expected ridge to valley
temperature split developing - already some upper 60s are noted
in the deep eastern valleys - along with mainly river valleys fog
forming towards midnight. For the update, did add the latest obs
and trends into the T/Td/Sky grids. These minor adjustments have
been sent to the NDFD and web servers.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 450 PM EDT WED MAY 1 2024

Late this afternoon, a shortwave upper level ridge extended
across portions of the Southeastern Conus north into the Southern
Appalachians to portions of the OH Valley to the upper MS Valley.
Further west, an upper level low was centered near the MT and
Saskatchewan border with an associated trough south to the
southwestern Conus. Meanwhile an upper level low was passing
north of the Great Lakes across Ontario. Multiple shortwaves were
moving in the southwest flow from the Plains toward the MS Valley
region. At the sfc, a ridge of high pressure extended from the
eastern Gulf of Mexico across portions of the southeastern Conus
to the Southern and Central Appalachians. Further north an area of
low pressure was working across Ontario with a trialing frontal
zone to the mid MS Valley to the Central Plains to the western
Conus. Most of the cumulus that developed late in the morning to
early in the afternoon has mixed out with mainly some cirrus
passing by from time to time.

Tonight and Thursday, as the upper low initially north of the
Great Lakes moves toward the St Lawrence Valley, the upper level
ridge is expected to build across the Southeast to Great Lakes
regions with the axis of the ridge shifting east of eastern KY on
Thursday with the upper level flow becoming increasingly south to
southwest late in the day. Further west, the upper level low near
the US/Canadian border should meander and move little. Meanwhile,
multiple shortwaves are expected to move across the Plains and
from the Rockies into the Plains with the fit of these nearing the
Mid and Upper MS Valley on Thursday. Guidance brings a shortwave
trough east into the Great Lakes to Lower OH Valley region late in
the period as the axis of upper level ridging moves further east.
As shortwave trough moves across the Plains and toward the Great
Lakes tonight and Thursday sfc low pressure is expected to track
from the Central Plains to Upper MS Valley. This sfc low will
track to the vicinity of Lake Superior vicinity, the frontal zone
to its east will stall near the OH River before lifting north as
a warm front while the trailing cold front will move across the
Central Plains and reach near the western Great Lakes to mid MS
Valley to Southern Plains through Thursday night. Sfc high
pressure meanwhile that is initially across the southeast will
shift to the east and southeast Thursday and Thursday night. PW
initially in the 0.7 inch to 0.9 inch range tonight and Thursday
across eastern KY should climb late in the period into the 0.9 to
1.3 inch range by late Thursday night.

The ridging at the surface and aloft and a relatively dry airmass
in place should combine for a notable ridge/valley split tonight
with the airmass warming to or near record levels on Thursday.
Record highs are 87 from 2012 at JKL and 88 from 1959 at LOZ.
Valley fog will again be favored in this pattern along the larger
creeks and especially area rivers and lakes tonight. With the warm
temperatures in place, relatively humidity should fall to near 25
percent or below in many locations. Eastern valley locations
should likely decouple near sunset on Thursday night despite a
gradual increase in cloud cover including some mid clouds. These
eastern valley locations right along the deeper valleys could
again experience some fog on Thursday night as well.

.LONG TERM...(Friday through Wednesday)
Issued at 348 PM EDT WED MAY 1 2024

Core of westerlies remain to our north through the bulk of the
extended time frame, through the Upper Midwest and Great Lakes.
That leaves our area within weak flow aloft, with subtle
disturbances passing through the region at times during the
extended portion of the forecast. Low pressure drops out of the
northern Pacific and into the West Coast by this weekend. This
system then slides eastward over the Central Plains and eventually
noses its way into the Upper Midwest and Great Lakes regions by
the end of the forecast window. This will bring stronger winds
(core westerlies) across our region by the end of the period as a
broad trough is carved out over the lower forty-eight. In general
this will keep eastern Kentucky within the warm sector (south of
the polar jet) through the period. At the surface, and with little
or no support aloft, a cold frontal boundary appears to drop
southeast to the Ohio River by late Sunday, then stalls briefly
before retreating northward in quick fashion Monday. A cold
frontal system then approaches from the west by the end of the
extended. Several of the aforementioned disturbances will tend to
keep the threat of showers and thunderstorms in the forecast
during much of the extended, with a diurnal flavor to the
activity.

Sensible weather features seasonably warm temperatures running as
much as 5 to 10 degrees above normal. There will be at least a
chance of rain, or at least a climatological 30% or higher PoP
each day of the extended. A series of disturbances will pass
through the Ohio Valley during the period, the first roughly late
Friday into Saturday, with a second late Sunday into Monday and
then a third late Tuesday into Wednesday. The last disturbance at
the end of the period will be more closely associated with the
storm system approaching from the west. Other than thunderstorms,
not seeing much in the way of hazards through the period. QPF for
the extended does not exceed 1-1.5 inches in total, hardly enough
to be of concern at this time. We could experience some strong
thunderstorms, perhaps an increased potential for some severe
storms towards the end of the forecast window. Afternoon
instability increases each day, Monday through Wednesday, with
MLCAPES climbing from around 500 J/kg on Monday to close to 2000
J/kg by Wednesday. Only seeing marginal shear Monday at around 25
kts effective shear. That increases to around 30 kts by Tuesday
and then between 30 and 40 kts by Wednesday. Consequently,
thinking at this time is that a strong storm or two could not be
ruled out Tuesday, then some strong to a couple severe storm would
be possible by Wednesday with the approach of the storm system
from our west if current model solutions hold. Confidence is not
high due to the fact that this is still a week away. But NCAR
Ensemble C-Shield forecast would tend to support this line of
thinking.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 815 PM EDT WED MAY 1 2024

VFR will largely prevail through the period with sfc and upper
level ridging dominating. The exception will be fog potential
between about 05Z and 14Z again tonight, this should be more
confined to the river valleys and along some of the larger creeks
and lakes compared to last night. However, some limited MVFR fog
could still develop at a few of the TAF sites per LAMP guidance.
Any fog should lift and dissipate by 14Z, with VFR returning to
all areas at that time. Winds will remain light and variable
through the period.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GREIF
SHORT TERM...JP
LONG TERM...RAY
AVIATION...JP/GREIF