JKL issues Area Forecast Discussion (AFD) at Jan 28, 10:45 AM EST260
FXUS63 KJKL 281545
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1045 AM EST Tue Jan 28 2025
.KEY MESSAGES...
- Temperatures will gradually trend well above normal through the
end of the work week.
- A system will approach the area towards the end of the work
week, bringing a soaking rain.
&&
.UPDATE...
Issued at 1045 AM EST TUE JAN 28 2025
Brought the hourly temperature forecast in line with the
observations. Near-term forecast is otherwise on track.
UPDATE Issued at 700 AM EST TUE JAN 28 2025
Hourly grids were freshened up based on recent observations and
satellite trends. This led to some minor updates for the cloud
cover associated with the passing disturbance. Other changes were
adjustments to hourly temperatures where the mid and thicker high
clouds had arrived. Overall, the band of clouds should move east
and southeast with mostly sunny skies in all areas by mid morning
and continuing in the afternoon. Temperatures should average near
to slightly above normal for highs today.
&&
.SHORT TERM...(Today through Wednesday)
Issued at 510 AM EST TUE JAN 28 2025
Early this morning, an upper level low was centered over Quebec
with an associated trough, the axis of which extended south
across the eastern Great Lakes and mid Atlantic states and into
the Southeast. A shortwave trough extended from the eastern Great
Lakes to the mid and Lower OH valley with another shortwave
trough working southeast across Manitoba and Saskatchewan in
northwest flow between the troughing and upper level ridging
extending from the eastern Pacific into the Northeast Conus to
northern Rockies. A shortwave ridge axis extended north from
Mexico into the Southern Plains with a closed low in between
centered over the southwest Conus. At the surface, a cold front
extended from an area of low pressure in the Maritimes vicinity
and into the Northeast Conus to the eastern/southern Great Lakes
to a wave of low pressure over the Manitoba/Saskatchewan border
vicinity. Meanwhile, a ridge of sfc high pressure extended from
the Southern Plains into the Southeast with ridging extending
into the Commonwealth. Locally, more southern locations were
either clear or had just some high clouds while some mid and even
patchy low clouds associated with a passing shortwave extended
from WV into northeastern and northern Ky to IN. There were some
radar returns from this, but sfc dewpoint depressions are quite
large at present and this is probably largely virga with possibly
a few stray flurries reaching the surface. Temperatures ranged
from the upper teens to lower 20s in the more southern sheltered
valleys that were decoupled to the low to mid 30s on ridges and in
more open terrain areas and areas that are no longer decoupled.
Today and tonight, the shortwave trough will cross the region
through midday with a gradual increase in heights across the
Commonwealth as shortwave upper ridging builds east toward the MS
Valley. The axis of this shortwave ridge should reach the lower
to mid MS Valleys to end the period. At the same time, the axis of
the troughing from Canada into the eastern Conus will shift east,
but the region should remain in west to northwest flow aloft. In
fact the next shortwave working into the trough will reach Ontario
to the upper MS Valley later today and then rotate across the
Great Lakes to St Lawrence Valley and northeast from this evening
to early Wednesday evening. A sfc trough or weak cold front will
work toward the region as this system passes to the north with the
sfc trough/front crossing the area on Wednesday. This should keep
the 850 mb temperature trend from today to Wednesday similar if
not a degree or two colder. Thus, the continued warming trend will
be rather gradual across eastern KY.
Overall, the band of clouds with the passing shortwave to begin
the period should work southeast across the area through around
dawn and for a couple of hours after. Otherwise, mostly sunny to
sunny skies will prevail today with highs similar if not a degree
or two warmer than what was observed on Monday. Daytime mixing and
heating should also result in some late morning and after wind
gusts into the 15 to 20 mph range as well. The sfc high pressure
ridge should remained nosed into eastern KY tonight in advance the
approaching front/sfc trough. This scenario should result in
another ridge/valley temperature split and following anticipated
afternoon min dewpoints in the low to mid 20s today, sheltered
valley locations south of I 64 and east of I75 should reach the
mid 20s and perhaps the low 20s again in some cases. Meanwhile,
more open terrain locations and coalfield ridges should be
somewhat mixed ahead of the approaching front and not fall below
the low to mid 30s. With the passing front to be very moisture
starved with few if any clouds of note on Wednesday, temperatures
should moderate a bit more. More active weather should arrive as
we move into the long term period, though rather mild weather
should persist.
.LONG TERM...(After midnight Wednesday night through Monday)
Issued at 638 AM EST Tue Jan 28 2025
While the long term forecast period opens with relatively quiet
weather on Wednesday night and Thursday afternoon, our attention
quickly shifts towards a dynamic storm system approaching the area
on Thursday evening. The timely passage of a warm front overnight
into Friday morning will position Eastern Kentucky firmly in the
system's warm sector. As a result, widespread rain chances are in
the forecast through early Saturday morning. This rain may be heavy
at times, especially on Friday morning, but a few limiting factors
will reduce the concern for major hydrological impacts. In short,
expect January to end on a warm and wet note before drier weather
emerges for the first few days of February.
Upper level ridging and southeastern surface high pressure will
foster clear conditions out ahead of Friday's event. On Wednesday
night, this will foster efficient diurnal cooling and ridge-valley
temperature splits. Overnight lows in the low 30s (ridgetops) and
mid 20s (valleys) will quickly recover into the 50s on Thursday as
surface flow shifts to the south and warm air advection kicks into
gear. As the day progresses, flow aloft will back towards the SW out
ahead of a closed upper level low ejecting from the Plains into the
Midwest. By Thursday evening, an intensifying low level jet will
push a warm front towards out area from the Tennessee Valley,
increasing isentropic lift and advecting increased amounts of
moisture/warm air into the column. Cloud cover and rain chances will
spread across the region overnight as this warm front moves NNE.
This will counteract the traditional overnight temperature drop, and
Thursday night's lows of 40-45 degrees will likely occur before
midnight. Surface winds will shift to a more SSW direction behind
this boundary on Friday morning, allowing the aforementioned
advective processes to continue. Friday's afternoon highs should
easily reach the upper 50s once again, but the bigger story here
will be the resultant potential for heavy rainfall.
As the advective ingredients maximize on Friday morning, there is a
signal for enhanced dynamic lift. Models resolve upper atmospheric
divergence and favorable cyclonic vorticity over the region during
this time frame, and the rainfall rates during the Friday morning
commute may be locally intense. The most recent run of the NBM
actually introduced slight thunder chances across southwestern
portions of the forecast area on Friday morning, but the best
instability looks displaced much further to the south. An isolated
rumble of thunder cannot be entirely ruled out, but thunderstorms
are not explicitly mentioned in this forecast package's grids.
Rather, a steady rain is forecast to persist through Friday
afternoon and then taper off on Saturday morning. Forecast rainfall
totals range from near one inch in our Southeastern counties to
about one and a half inches across the west. Probabilistic ensemble
guidance parallels the gradient in this quantitative forecast. Both
the NBM and the LREF resolve a 40-50 percent chance of greater than
one inch along the Virginia state line and a 65-75 percent chance
closer to I-75. The greatest amounts of rain are more likely to fall
further west in the commonwealth, and it is plausible that the
current quantitative precipitation forecast under-performs here in
Eastern Kentucky. In similar past events, stronger convection in the
Gulf states has reduced the efficacy of the moisture advection into
our forecast area and thus the rainfall rates. Likewise, the
southerly flow at the onset of the event may yield to orographic
drying on the northern slopes of the terrain in SE KY. If these
mesoscale features materialize, QPF may need to be reduced in future
forecast packages. In fact, this forecast package actually features
less storm total QPF than the previous ones. This is likely due to
the trend towards a more progressive parent system over the past few
model cycles.
The above limiting factors collectively reduce the likelihood of
significant hydrological impacts with this system. The temporal
buffer between the early-week warmth/snow melt and the heaviest
rainfall will reduce river responses, and recent river observations
reveal regular streamflows heading into the event. The NAEFS
probabilistic guidance for river rises remains more aggressive with
some of our westernmost river gauges during this event, so we will
continue to closely monitor mesoscale trends and the latest high-
resolution model data as the event approaches. Current thinking is
that these minor flood probabilities are an artifact of a few overly-
aggressive input models, and the hydrological impacts during this
event will likely be limited to more isolated instances of minor
areal/urban nuisance flooding. Even then, the recent reductions in
storm total QPF across the area resulted in the removal of WPC's
marginal Excessive Rainfall Outlook from our forecast area.
Regardless, readers are encouraged to find their raincoats and
umbrellas, as the last day of January looks to be a rather damp one.
In the wake of this system, cooler air briefly makes a return on
Saturday amidst NW flow. Expect an afternoon clearing trend, with
highs back in the 40s and then overnight lows in the 30s. This
cooler weather is only temporary though, as quasi-zonal flow returns
to the upper levels on Sunday. Surface flow shifts to the south once
again, allowing highs to warm back up into the upper 50s under
mostly/partly clear skies. The first 60 degree thermometer readings
of the year are possible on Sunday before a northern stream
disturbance approaches the area at the very end of the period.
Increasing uncertainty precludes the mention of specific details at
this time, but February 2025 should begin with a drying trend.
&&
.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
ISSUED AT 705 AM EST TUE JAN 28 2025
VFR conditions were reported at issuance time and VFR will
prevail through the period. A passing disturbance is bringing
some mid and even low clouds down into the 5 to 10kft agl range
generally east of I 75 and mostly south of I 64 with areas near
the VA and TN border currently mostly clear to clear. This band of
clouds should pass during the first 3 to 4 hours of the period. With
many locations becoming more mixy, the threat of LLWS early has
ended. Southwest to west winds generally between 5 and 10KT are
reported at issuance time and they should remain near or just
above these speeds through 23Z, with daytime mixing resulting in
some gusts into the 15 to 20KT range, especially between 15Z and
23Z. Winds will tend to slacken in speed to end the period, while
winds aloft should increase ahead of another approaching
disturbance and weak cold front. This will lead to a threat of
LLWS during the last 12 hours of the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GEERTSON
SHORT TERM...JP
LONG TERM...MARCUS
AVIATION...JP
Source:
JKL issues Area Forecast Discussion (AFD) at Jan 28, 10:45 AM EST---------------
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