Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 271922
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
322 PM EDT Wed Mar 27 2024

.KEY MESSAGES...

- Temperatures cool to within a few degrees of normal through
  Thursday, with the threat for sub-freezing temperatures
  returning for many western valley locations Thursday morning and
  most valley areas Friday morning.

- PoPs start to creep back in from the northwest this weekend,
  with temperatures returning to well above normal.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 322 PM EDT WED MAR 27 2024

Present surface analysis is a lot quieter compared to this time
yesterday. The cold front that was approaching the CWA has now moved
off to the east and mostly clear skies are in place as surface high
pressure builds eastward into the region. Lingering clouds are
continuing to hang around but are slowly starting to scatter out to
become mostly sunny. Southwesterly flow on the backside of the
exiting trough will allow for highs to climb into the low-50s to low
60s today.

Later this afternoon a closed circulation will pivot eastward and
bring a push of colder air into the region. Coupled with surface
high pressure and expected clear skies, overnight lows are forecast
to tumble into upper-20s in the valleys and lower-30s on the ridges.
Also, these colder temperatures will promote frost development in
the more sheltered valleys across the CWA. Thursday will feature the
area firmly under the dome of high pressure but aloft, northwesterly
flow will keep temperatures relatively cooler as highs in the upper-
50s to lower-60s are expected for Thursday afternoon. This
northwesterly flow will provide that extra push for continued cold
air Thursday night into Friday morning as overnight lows are
forecast to drop into the lower-30s for the valleys and mid-30s for
the ridges. Again, widespread frost will be possible for the more
sheltered valleys. Lastly, a weak, dry boundary will push through
the area early Friday morning but as moisture is limited, the area
will remain dry for the end of the period.

.LONG TERM...(Thursday night through Tuesday)
Issued at 501 AM EDT WED MAR 27 2024

Pattern aloft transitions from northwest flow to zonal for the
bulk of the extended, then to southwest flow by the end of the
forecast window. Pretty good agreement with main synoptic
features, but solutions do become muddled during the last 36 to 48
hours of the period. Main features of interest center on a subtle
short wave tracking through zonal flow over the weekend and then
additional impulses that originate out of deep western CONUS
trough and west coast...California Baja low that suddenly sweeps
eastward across the CONUS at the end of the period. At the
surface, pattern become conducive to a baroclinic, or frontal zone
of sorts that develops across the Midwest before dropping
southeast to the Ohio River Valley. Strengthening winds fields
eventually become parallel with this frontal zone over time.
Trends develop this baroclinic zone further north, closer to the
Ohio River and this feature has a more stationary flavor to it
than previous runs. In addition, the overall evolution of the
storm system has become more progressive.

Sensible weather features a dry start to the extended. Fire
weather interests will note that deep mixing takes place within
the boundary layer Friday afternoon, forcing surface dew points
into the mid 20s and minimum afternoon relative humidities between
20-30% for portions of the area. Strong mixing will also support
an increase in boundary layer wind gusts to near 20 mph Friday
afternoon. Temperatures moderate through the weekend, with highs
climbing into the lower to mid 70s for the weekend, and upper 70s
by Monday. Rain cooled conditions and cloud cover in combination
with lower heights aloft will drop afternoon temperatures back
down into the 60s for Tuesday. A cold front appears to pass
through eastern Kentucky at or just beyond the end of the forecast
window. Trends have also slowed the onset of rain across the
forecast area, with better PoPs holding off until Saturday night
and/or Sunday, and greatest PoPs until Monday night into Tuesday.

Main hazards for the extended begin with the potential of sub
freezing temperatures for many of our valley locations, but
especially eastern valleys Thursday night into Friday morning.
Time height analysis and sounding profiles show some moisture
(6-10 kft) across the area during this time frame, which if
substantial enough would tend to help keep overnight lows up
despite high pressure being a bit more centered over the region.
Moisture at the top of the boundary layer does not provide ideal
radiative cooling conditions. However, ensemble probabilistic data
shows only a 10-20% chance of cloud cover being GTE to 50%, and
only slightly higher probabilities for GTE 25%. This suggests that
while moisture may be present, it probably is not substantial
enough to equate to cloud cover. Thus feel fairly confident in at
least going with the COOP MOS values, or upper 20s for some of the
coldest spots. Otherwise, instability in combination with
effective shear will increase with time, to between 750 and 1000
J/kg MUCAPES and 35-45 kts effective shear from Sunday through
Tuesday. Thunderstorm potential appears to be a good bet for that
time frame. Finally, our forecast area is within a favorable area
of moisture transport and convergence along and south of the axis
of the frontal zone Monday night into Tuesday. But convective
steering winds back more from the southwest during that same time
frame (less parallel with the baroclinic zone). This combined with
a more progressive speed to the system as it pushes through the
region decreases the overall threat of hydro issues.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED AT 135 PM EDT WED MAR 27 2024

VFR conditions are prevailing across all TAF sites; however, a
stratus deck moving southeast into the area could cause KSYM, KSME
and KLOZ to drop into MVFR. Also, a few clouds are still keeping
KSJS around the VFR/MVFR threshold. The stratus deck is slowly
starting to dissipate and the clouds impacting KSJS are pulling
off to the east and this will continue to occur over the next few
hours. By 00Z/Thursday, CIGS will all be VFR and winds will have
diminished to light and variable.

&&

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

$$

SHORT TERM...VORST
LONG TERM...RAY
AVIATION...VORST


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