JKL issues Area Forecast Discussion (AFD) at Jul 24, 11:29 AM EDT685
FXUS63 KJKL 241529 AAA
AFDJKL
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1129 AM EDT Wed Jul 24 2024
.KEY MESSAGES...
- Afternoon shower and storm chances continue into next week, but
the lowest chances are on Friday and Saturday.
- Through Thursday, any areas that receive successive rounds of
heavy rainfall could experience instances of localized flooding.
- Highs will be about 5 degrees below normal to near normal (mid
80s) through Friday, before trending above normal this weekend.
&&
.UPDATE...
Issued at 1129 AM EDT WED JUL 24 2024
A lingering diffuse surface boundary aligned from east to west
over northern Kentucky, along with faster 300 mb flow traversing
the Ohio Valley aloft, will allow for a renewed threat of
convection as we heat up. Southeastern Kentucky will likely
experience the higher PoPs, with scattered to numerous showers and
some thunderstorms developing this afternoon, closer to the
higher PWATs as well as more under the influence of the right
entrance region of the relatively higher upper level wind field.
Will have to keep an eye on any training convection, as southern
areas have seen larger footprints of locally heavy rainfall in
recent days. High temperatures look on track. Mainly freshened up
the hourly readings through this afternoon, accounting for the
slightly cooler start in places, where thicker low clouds have
been slower to erode.
UPDATE Issued at 804 AM EDT WED JUL 24 2024
Showers were most prevalent in the vicinity of the Mountain
Parkway corridor to Martin County at present as well as nearer to
the TN and VA border. Pops near the Mountain Parkway corridor to
Martin County area were increased over the next couple of hours
to better reflect this trend. Otherwise, grids were freshened up
based on recent observation trends.
&&
.SHORT TERM...(Today through Thursday)
Issued at 355 AM EDT WED JUL 24 2024
Early morning surface analysis has a wavering frontal boundary over
the CWA. This is continuing to keep PoP chances in place across the
area. Currently, showers are tracking northeast through the
southeastern portions of the area. Those showers will persist
through the morning with the potential for a few rumbles of
thunder as SBCAPE around 500 J/kg exists in this area.
While this boundary remains in place today and diurnal heating takes
place, showers and thunderstorms will increase in coverage this
afternoon. Those showers and storms will linger through the evening
before largely dissipating overnight Wednesday into Thursday. As the
large scale pattern hasn't changed, not expecting much in the way of
severe weather but can't rule a few SPS worthy storms this
afternoon. Also, PWs ranging from 1.50" to 1.90" are forecast this
afternoon and any efficient shower or storm could put down heavy
rain leading to localized hydro issues. Areas of valley fog will be
possible overnight Wednesday which will burn off early Thursday
morning.
A slight change in the pattern is expected for Thursday as a
positively tilted trough with a closed H5 circulation ejects
northeastward toward Ontario/Quebec. The vertically stacked
circulation will remain well north of the area but the surface low
will drag a cold front through the area Thursday into Friday.
Showers and thunderstorms are expected along and ahead of the front;
however, since FROPA is expected to be during the evening hours with
a lack of widespread forcing, severe weather will be largely
limited. Again, high PWs are in place, which if a shower or storm is
efficient enough, it could put down some heavy rainfall leading to
localize flooding. Showers and storms will linger through the end of
the forecast period.
Overall, the forecast period will be highlighted with periods of
showers and thunderstorms. Temperatures will be mostly seasonal with
temperatures in the mid to upper-80s and overnight lows in the upper-
60s to low-70s.
.LONG TERM...(Thursday night through Tuesday)
Issued at 458 AM EDT WED JUL 24 2024
At the start of the period, an upper level trough axis should
extend from eastern Canada to the St Lawrence Valley/eastern
Great Lakes and mid Atlantic states to the OH Valley region to
eastern TX vicinity. This trough axis will be between an upper
level ridge centered over the western Atlantic and extending into
the southeast Conus to eastern Gulf of Mexico and another upper
level ridge centered in the southwest Conus and extending
northeast to the Northern Plains and upper MS Valley regions.
North and northwest of the ridging an upper level low should
initially be centered in Alberta with an associated upper level
trough extending across the Northwest Conus. Meanwhile, as the
period begins, a sfc cold front is expected to extend from low
pressure in the vicinity of the Maritimes to the Northeast Conus
to mid Atlantic states to the OH Valley before turning northwest
and becoming stationary in the Plains.
From Thursday night to Friday night, the northern portion of the
upper level axis is expected to shift eastward to the Northeast
coast to Mid Atlantic coast. The consensus of guidance also has
is the upper level ridging remaining from portions of the western
Atlantic across parts of the Southeast Conus to the eastern Gulf
of Mexico while another upper level ridge builds into the Great
Lakes. As the upper level low in Canada works east to near the
Saskatchewan and Manitoba border region and a trailing shortwave
trough moves east near the US/Canadian border and upper troughing
moves into the western Conus, the weakening upper level ridge
should remain from portions of the Pacific into the Southwest
Conus. In general, weak troughing is progged to remain from the
Lower OH Valley region to the Southern Plains. At the same time,
the frontal zone should gradually sag south across portions of the
Commonwealth from Thursday night to Friday night, nearing the KY
and TN border vicinity as sfc high pressure builds from the Great
Lakes into the Northeast and mid Atlantic states. In this
scenario, isolated to perhaps scattered convection could linger
into late Thursday evening across much of the area. By Thursday
night and Friday, drier air would filter into northern sections of
eastern KY and result in a minimum in shower and storm chances
there. However, more substantial moisture should remain near and
to the south of the frontal zone, particularly for areas nearer to
the VA and TN border. Chances for convection will be higher in
those areas during this timeframe, with an afternoon to early
evening peak on Friday most probable.
Saturday to Sunday, the consensus of guidance is is that upper
level ridging should build from portions of the southeast to the
eastern Great Lakes and then to portions of the Northeast to Mid
Atlantic. Further west, an upper level low is expected to develop
in the OK/KS/MO/AR vicinity and then move into the mid MS Valley
and then toward the western Great Lakes to the east and southeast
of a more zonal pattern over the western Conus to Plains region.
Although the frontal zone will likely become more diffuse with
time during this timeframe, deeper moisture generally south of
eastern KY is expected to advect back into the region. 00Z LREF
PW means are initially forecast around 0.9 inches in northeastern
KY to 1.5 or 1.6 near the TN border on Saturday morning increase
to around 1.3 in northeast KY to about 1.75 near the TN border
Saturday evening. Then from Saturday night to Sunday, PW is
forecast to increase to the 1.6 to 1.9 inch range also per the 00Z
LREF mean. Chances for convection on Saturday will be greater in
the south and southeast generally during the afternoon to early
evening. However, the combination of increasing moisture, the
upper to the northwest and an associated shortwave trough nearing
the Lower OH valley as well as daytime should result in at least
scattered convection areawide on Sunday. If repeated rounds of
convection or training were to occur some concern could develop
for localized flooding as highlighted in WPC Day 5 marginal ERO
that extends into portions of eastern KY.
Sunday night to Tuesday, some amplification of the pattern is
anticipated in general. An upper level trough is expected to work
into the western Conus, with upper level ridging building over
portions of the Plains to Central Conus with an upper level
trough develop from the Hudson/James Bay vicinity to the Great
Lakes to portions of the eastern Conus. This scenario should
result in unsettled weather continuing. The shortwave trough
working across the OH Valley on Sunday should continue gradually
across the OH Valley Sunday night into Monday. Another shortwave
or two moving through the trough should cross the the area from
Monday night into Tuesday. Seasonably deep moisture should remain
over the area with the PW means per the 00Z LREF mean in about the
1.6 to 1.8 inch range to begin the week. Although a general
uptick in converge of convection is expected during the diurnal
cycle, with it probable for shortwaves to cross the area, chances
will linger at night as well.
Highs will be near normal, mid 80s on average to begin the period
on Friday, before trending a couple of degrees warmer to slightly
above normal over the weekend. Highs early next week are forecast
to return to right at normal with more cloud cover and convection
across the area. With some drier air expected to have moved into
the region, lows should begin the period a couple of degrees below
normal Thursday night and Friday night, before returning to near
normal to end the period.
&&
.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
ISSUED AT 706 AM EDT WED JUL 24 2024
Currently all TAF sites with the exception of KSYM are MVFR/IFR
and that will continue over the next couple of hours before fog
burns off later this morning. Showers moving across the area will
bring VSBY and CIGS down to MVFR/IFR through much of the TAF
period; however, there could be a few instances of VFR but largely
MVFR. Fog is forecast to burn off after 13Z but CIGS are expected
to remain largely MVFR through the remainder of the TAF period.
Aside from showers and storms bring gusty and erratic winds, light
and variable winds are forecast through the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GEOGERIAN
SHORT TERM...VORST
LONG TERM...JP
AVIATION...VORST
Source:
JKL issues Area Forecast Discussion (AFD) at Jul 24, 11:29 AM EDT---------------
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