JKL issues Area Forecast Discussion (AFD) at Apr 19, 1:34 AM EDT159
FXUS63 KJKL 190534
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
134 AM EDT Sat Apr 19 2025
.KEY MESSAGES...
- Above normal temperatures are expected for the next week.
- The next substantive chance at rain arrives Monday.
&&
.UPDATE...
Issued at 1107 PM EDT FRI APR 18 2025
Moderate pressure gradient over the forecast area is keeping all
but the most sheltered spots mixed late this evening. That
gradient may weaken slightly overnight and that introduces plenty
of uncertainty as to which additional valley locations might
eventually decouple and radiatively cool. Hourly forecast
temperatures were massaged in an attempt to capture the latest
observations and temperature trends. In general though, still
expect low temperatures to range from the mid 50s in the coldest
sheltered hollows up to the mid 60s over ridges and across open
terrain.
UPDATE Issued at 810 PM EDT FRI APR 18 2025
The Red Flag Warning was allowed to expire at 8 PM. Humidity
values, though still at critical levels at many locations, are
starting to rebound. The winds, on the other hand, have tempered
quickly to below critical levels as the the boundary layer begins
to decouple. No other substantive forecast changes were made.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 537 PM EDT FRI APR 18 2025
Ridging surface and aloft is over the far southeast CONUS late
today and will remain there during the short term period. An upper
level positively tilted longwave trough stretches from south
central Canada across the western CONUS, with an associated
frontal boundary over the Midwest. Upper level flow over the
Midwest and Ohio Vally is largely southwest to northeast.
A closed low will develop over the southwest CONUS in the tail end
of the trough, and creep eastward during the short term period,
starting to take on a negative tilt over the plains by dawn on
Sunday. Meanwhile, a significant but more open wave tracks
eastward across southeast Canada. This combination will buckle
the upper level flow over the eastern CONUS, with a flattening of
the upper level pattern to our north giving mores westerly flow.
This will allow the surface cold front to move southeast. Models
show it making into the JKL forecast area on Saturday night and
then slowing down or stalling.
Our very dry air will moisten some over the next 24 hours, but
truly good moisture for this time of year will still be lacking,
with the higher dew points remaining to our west and northwest.
Conditions should remain dry at least up until the front arrives,
and even then it does not look favorable for rain. Forecast
soundings look like it will be difficult to break through a cap,
especially with dry air aloft entraining into any convective
currents that might try to break through. The NAM shows
saturation occurring in the lower levels behind the cold front
Saturday night in our northern counties, but this is not as
pronounced or as deep in the GFS. Decided to hold off on the
mention of any light precip at this point.
.LONG TERM...(Sunday through Friday)
Issued at 425 PM EDT FRI APR 18 2025
The long-term period opens Sunday morning with an ~592 dam high
centered just off the Southeast US Coast and a negatively-tilting
500H trough extending from the Upper Missouri River Valley down
into the Southern Plains. At the surface, low pressure will be
organizing near/over Oklahoma, just to the east of the trough
axis. A cold front trails south from the low into the Rio Grande
Valley while another boundary stretches east and north of the low
through Mid-Mississippi/Lower Ohio Valleys and on across the
Central Appalachians (most likely just north of the JKL CWA).
The surface low will continue to organize and strengthen Sunday and
Sunday night as it lifts northeast toward Wisconsin. The boundary
initially lingering over the Ohio Valley and Central Appalachians
will lift back to the north as a seasonable surge of moisture
spreads across the Eastern Kentucky Coalfields on an intensifying
warm conveyor belt jet. Guidance does show sufficient instability
on Sunday afternoon for deep convection, but the potential for
capping keeps forecaster confidence low. Generally have included
at least a slight chance of a shower or thunderstorm on Sunday
afternoon/evening north of the KY-80/Hal Rogers Parkway corridor.
The best opportunity for some rainfall on Sunday, albeit still low
chance, is across the Bluegrass where weak pulses of energy will
be passing around the northwestern side of the 500H southeastern
high. It will be another warm day with thermometers climbing into
the upper 70s to near 80 over the Bluegrass and into the lower to
middle 80s elsewhere under partial sunshine. Expect the risk of
any shower or thunderstorm to diminish after sunset with the loss
of diurnally-induced instability. Most, if not all, of Sunday
night should be dry but mild with expected low temperatures in the
lower to middle 60s.
As the aforementioned surface low traverses the Great Lakes on
Monday, it will pull its trailing cold front into eastern
Kentucky. Instability does appear meager, likely due to increasing
cloud cover and the arrival of precipitation early in the day
before there is opportunity for strong heating. Expect high
temperatures in the 70s for many locations on Monday, though, if
sunshine persists long enough, some locations in far eastern
Kentucky could eclipse the 80 degree mark. By Monday night the
surface low and its parent trough will be lifting toward Quebec,
leaving the cold front with little forcing. As a result, expect
the cold front to stall south and east of Kentucky on Tuesday and
Wednesday. The deterministic 12z GFS more readily breaks down the
southeastern 500H ridge and pushes the front well beyond our
forecast area. The deterministic ECMWF/Canadian and a substantial
number of ensemble members are not so quick to push the front
through and in fact show at least some isolated to scattered light
precipitation lingering over southeastern Kentucky on both days,
especially during the afternoon and early evening, coincident
with peak diurnal heating. Tuesday should be seasonable with
afternoon maximum temperatures ranging in the 70s after morning
lows in the 50s. The coldest temperatures of the period are
forecast for Tuesday night when upper 40s to lower 50s could be
more common, especially in the more sheltered valleys. The air
mass modifies on Wednesday with more locations closing in or just
breaking past the 80F mark during the afternoon.
Better rain chances return for later in the week as the
baroclinic zone to our south drifts north and becomes a favored
corridor for a least a couple of waves of low pressure from
Thursday on into the last weekend of April. This will likely
translate into periods of unsettled weather at times with both
showers and thunderstorms possible, though the specifics remain
hazy this far out. Temperatures are expected to run well above
normal, with the mercury not far from 80F on both Thursday and
Friday afternoons.
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
ISSUED AT 134 AM EDT SAT APR 19 2025
Conditions will remain VFR through the TAF period, with
southwesterly winds through 00Z Sunday, after which light and
variable winds are expected. A low level jet will raise concerns
of wind shear through 12Z Saturday morning. 925-mb winds are
modeled around 40-45 kts. While most winds will taper off this
evening, some sites such as KSYM will continue to mix out through
the overnight hours with gusts of 20-25 kts. This is due to
conditions becoming more unstable through the night. Breezy
conditions will resume across all TAF sites tomorrow with daytime
heating.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GEERTSON
SHORT TERM...HAL
LONG TERM...GEERTSON
AVIATION...GINNICK
Source:
JKL issues Area Forecast Discussion (AFD) at Apr 19, 1:34 AM EDT---------------
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