JKL issues Area Forecast Discussion (AFD) at Nov 17, 9:46 AM EST644
FXUS63 KJKL 171446
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
946 AM EST Sun Nov 17 2024
.KEY MESSAGES...
- Temperatures rise to around 10 degrees above normal Sunday
through the first half of next week.
- Rain chances return late Monday night into Tuesday and continue
through the rest of the work week.
- A colder pattern by mid to late next week brings the potential
for gusty winds and wintry precipitation.
&&
.UPDATE...
Issued at 946 AM EST SUN NOV 17 2024
Fog is holding on in the deeper valleys of southeast KY, and have
extended it to later in the morning before it finally dissipates.
This is also holding temperatures back in those areas, and
adjustments have been made to slow the rise in this morning's
forecast.
UPDATE Issued at 646 AM EST SUN NOV 17 2024
No substantial changes were made to the forecast with this update.
Observations show widespread temperatures within a few degrees of
either side of freezing in most valley locales. Ridgetops are a
milder ranging from the upper 30s to lower 40s below 2,500 feet.
The strong subsidence inversion remains evident over the higher
mountains. Most notably, Big Black Mountain remains the warmest
location in eastern Kentucky, recently reporting air temperatures
in the upper 50s and dew points in the negative teens.
&&
.SHORT TERM...(Today through Monday)
Issued at 350 AM EST SUN NOV 17 2024
Calm winds, mostly clear skies, and very dry air just above a strong
low-level subsidence inversion have allowed for efficient
radiational cooling overnight. Lingering low-level moisture has been
sufficient for fog formation in the valleys of main stem rivers
and larger tributaries. The relatively shallow surface moist layer
is overtopped by a strong subsidence inversion around ~2,750 feet
and above. Below this inversion temperatures range in the lower
to middle 30s in most valley locations and closer to 40 on
ridgetops. A few of the more sheltered hollows have flirted with
29F, as per PWS stations in Laurel and Clay counties. Above the
subsidence inversion, the mesonet at 4,031 feet ASL atop Big Black
Mountain, reported temperatures peaking at 59F and a dew point of
-34F at 1:40 AM EST this morning, resulting in a minimum relative
humidity of 1.6%.
The latest surface analysis shows an elongated ~1020 high
extending from the Ottawa Valley southward to over the
Virginia/North Carolina Piedmont. The parent 500H ridge extends
from the Florida Panhandle northward across the Lower Ohio Valley
and into Lower Ontario. Upstream, 500H troughing extends from the
Western Canada down through the Lower Colorado River Valley. A
shortwave trough is ejecting out of the 500H trough and across
Southern Manitoba, supporting an ~994mb surface low. A cold front
extends southeastward from that low into Iowa and then southwest
to over the Texas/Oklahoma panhandles.
The aforementioned 500H shortwave trough will ride over the ridge
today and drop into Quebec/New England tonight/Monday. The
associated surface cold front will drift eastward and become
west-east oriented north of the Ohio River tonight and Monday,
leading to an increase in cloud cover over the Commonwealth but
little in the way of air mass change.
In sensible terms, look for sun filtered through high clouds today
after any river valley fog burns off. Temperatures will be warmer,
rising into the mid and upper 60s for most locations. Temperatures
drop off quickly this evening but then slow later in the night as
clouds increase. Look for lows ranging from the lower 40s in the
coolest valleys to lower 50s on ridges. Partly sunny skies are in
the forecast for Monday with high temperatures once again topping
out in the mid to upper 60s. A few readings in the lower 70s are
not outside of the realm of possibility, especially if cloud
extent is less than expected.
.LONG TERM...(Monday night through Saturday)
Issued at 411 AM EST SUN NOV 17 2024
The forecast period begins with the forecast area in the warm sector
ahead of an approaching shortwave and surface low. The forecast warm
front is expected to be draped over the Ohio Valley and lifting
north into the Great Lakes. The approaching cold front is expected
to be oriented north-south along the Mississippi River. Ahead of the
cold front, southwesterly flow will advect the warmest temperatures
of the period into the region but the cold front will quickly
approach the region and bring increased PoP chances through the
overnight into Tuesday morning. This evenings model suite has shown
a slight deviation in the pattern as this surface low is expected to
eject more northwesterly into southern Canada versus the previous
solution of the system ejecting into the Great Lakes. This new
solution will have FROPA occurring late Tuesday night with decreasing
shower chances for Wednesday. However,as the system tries to work
back to the southeast, increasing PoP is expected again to Thursday
through the end of the work week. As for the forecast grids, tried
to keep as much continuity as possible since this deviation could be
an outlier as its such a drastic change from the trends that have
been seen over the last couple of nights. As for the the
precipitation type expected Thursday through Friday, with the more
northwesterly push of the system, warmer air is forecast to work in
but as the system dives southeast, rain is forecast to mix with snow
and this solution is still found within the deterministic runs and
their associated ensembles. Therefore, kept the rain-snow potential
in the forecast through the end of the work week with mostly snow
occurring on the highest elevations of the southeastern mountains. To
the snow lovers, want to mention that the ground isn't frozen;
therefore, not looking at accumulations and confidence with this
event is rather low and the whole system is in flux. As the system
pulls off to the northeast Friday night into Saturday morning,
surface high pressure will build into the region but lingering
northwesterly flow could keep upslope snow showers over the
southeastern high terrain.
Overall the forecast period will be highlighted by multiple rounds
of showers on Tuesday into Wednesday and again Thursday through the
end of the work week. Rain is largely expected but snow is forecast
to mix into those rain showers Thursday into Friday. Temperatures
will start above average but behind these cold front, temperatures
will return to more seasonal ranges as highs in the 40s with lows in
the 20s build into the region.
&&
.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 637 AM EST SUN NOV 17 2024
VFR conditions were observed at the TAF terminals at forecast
issuance and are expected to persist through the period. The valley
fog that developed along the main stem rivers and larger
tributaries overnight should burn off by 15Z. High clouds will
move across the area today before lowering and thickening tonight.
Fog formation is anticipated in valleys again tonight but should
not impact the TAF sites. Winds will be variable to southwesterly
today at around 5kts or less.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...HAL/GEERTSON
SHORT TERM...GEERTSON
LONG TERM...VORST
AVIATION...GEERTSON
Source:
JKL issues Area Forecast Discussion (AFD) at Nov 17, 9:46 AM EST---------------
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