JKL issues Area Forecast Discussion (AFD) at Aug 22, 11:03 AM EDT198
FXUS63 KJKL 221503
AFDJKL
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1103 AM EDT Thu Aug 22 2024
.KEY MESSAGES...
- Below normal temperatures are expected today, with above normal
temperatures returning this weekend.
- Dry weather persists into early next week, before small rain
chances (20%) make a return towards the end of the period.
- Heat indices of 95 to 100 degrees return for some locations by
early next week.
&&
.UPDATE...
Issued at 1103 AM EDT THU AUG 22 2024
There are no changes to the forecast with the late morning update.
UPDATE Issued at 732 AM EDT THU AUG 22 2024
Hourly grids were updated based on recent observations and trends.
Temperatures have bottoming out in the mid 40s to mid 50s across
the region. The valley fog should gradually lift and dissipate
over the next couple of hours.
&&
.SHORT TERM...(Today through Friday)
Issued at 449 AM EDT THU AUG 22 2024
Early this morning, an upper level low was centered in the New
England vicinity with an associated trough axis south across the Mid
Atlantic states and into the Southeast. An upper level ridge was
centered over portions of the Southern Plains/western TX area. This
ridge extended northeast to the Upper MS Valley and western Great
Lakes. In between these two systems, northwest to northerly flow
aloft lingers. At the surface, a ridge of high pressure extended
from the Great Lakes across the Appalachians to the VA and Carolina
coasts. 850 mb temperatures are analyzed generally in the 10 to 12C
range at this point. Under the influence of the sfc high,
temperatures have cooled into the upper 40s to low 50s for most
locations with a few mid 50s on some coalfield ridges and in areas
of more open terrain. Valley fog was also present per satellite
imagery along area rivers as well as some of their larger tributary
creeks and adjacent lakes and was generally most prevalent south of
the Mountain Parkway.
Today and tonight, the upper level low initially over the New
England vicinity is expected to gradually track northeast toward the
Canadian Maritimes while a trough axis should extend south to near
Cape Cod and then east of the Mid Atlantic states to the eastern
Gulf of Mexico. At the same time, the upper ridge should become
centered a bit further northeast over the Southern Plains with the
axis of this ridge shifting into the Great Lakes. Locally, 500 mb
heights are progged to rise from around 583 dm at present to about
588 dm this evening and to near 590dm near sunrise on Friday. The
sfc high pressure ridge should shift east during this time and
become centered over the mid Atlantic states, though the sfc and
upper ridge will continue to remain dominant over the OH Valley and
Commonwealth. At the same time, 850 mb temperatures should rise to
about 13 to 15C by sunrise on Friday. Afternoon mixing should allow
dewpoints to again drop below NBM deterministic values with min
dewpoints in the mid to upper 40s in the north and east to the low
to mid 50s southwest. A general north to south gradient in high
temperatures should occur as well and the dry airmass should warm to
about 3 to 4 degrees warmer as compared to Wednesday. This would
again result in Max T below normal, but by only about 5 to 7
degrees. Min humidity should also have a gradient of lower values
north and east and somewhat higher values nearer to the TN border.
On Friday, further height rises at 500 mb are anticipated across
eastern KY as the upper level ridge builds from the Southern Plains
into the mid MS to OH and TN Valleys. The ridge of sfc high pressure
will remain across much of the eastern Conus during this time with
the center of the ridge moving to the eastern seaboard. 850 mb
temperatures are forecast to rise to about 16 to 17C. This should
result in highs about another 3 to 5 degrees warmer than today, with
highs nearing normals for this time of year. Rather deep mixing
should again result in afternoon min dewpoints below NBM
deterministic values of around 50 north if not a few upper 40s with
upper 50s to near 60 southwest.
As for sensible weather, the valley fog should lift and dissipate
within about 2 to 3 hours past sunrise or by the 9 to 10 AM EDT
timeframe. With the surface and upper level ridge in place, another
ridge valley temperatures split is favored tonight with upper 40s in
deeper sheltered valleys in the north and east to the 50s elsewhere.
Once again, valley fog is again expected to from along area rivers
as well as some of their larger tributary creeks and adjacent lakes
and should again be most prevalent south of the Mountain Parkway.
This fog will likely begin to form by around midnight or shortly
thereafter and lift and dissipate by the 9 to 10 AM EDT period on
Friday.
.LONG TERM...(Friday night through Wednesday)
Issued at 435 AM EDT THU AUG 22 2024
An amplified long wave pattern will control across the CONUS
through the period. The core of a southern Plains ridge will
expand northeastward into the middle Mississippi Valley through
the end of the week. In tandem, a deeper cut off low over the
Pacific Northwest will move east and dampen, while another cutoff
low drops southeast from Hudson Bay to Quebec. Early next week,
the timing and amplitude of short wave energy traversing the
north central CONUS become more questionable, as models disagree
on the outcome. In general, have sided more with the ECMWF camp,
which is slower compared to the GFS. Eventually, a diffuse surface
cold front will likely drop south across the Ohio Valley sometime
Tuesday into Wednesday, with enough heat and increasing humidity
in place to allow for a return of at least some slight chance
(20%) PoPs by the end of the period.
Temperatures will be on the rise through early next week, as the
center of the ridge curls in from the west, and high pressure
gradually dampens to our east. Highs will warm from the upper 80s
at the start of the weekend, to the lower 90s by next week. Lows
will moderate from the 50s to the 60s through the period. The
humidity will also be on the rise by next week, with heat indices
potentially peaking in the 95 to 100 degree range for some
locations by Tuesday. Dry weather generally holds through Tuesday,
before a small threat of afternoon convections returns for
Wednesday, with the approach of the weak cold front.
&&
.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
ISSUED AT 740 AM EDT THU AUG 22 2024
With high pressure dominating, VFR is expected to prevail through
the period, with one exception. Valley fog, with reductions to
MVFR and IFR, mainly along the largest creeks, rivers, and some
area lakes will lift and dissipate through around 13Z to 14Z with
improvements to VFR. Valley fog should again develop between
about 04Z and 07Z and reductions to MVFR or IFR should occur once
again late in the period. Winds will generally be light and
variable through the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...CMC
SHORT TERM...JP
LONG TERM...GEOGERIAN
AVIATION...JP
Source:
JKL issues Area Forecast Discussion (AFD) at Aug 22, 11:03 AM EDT---------------
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