FXUS63 KJKL 200025 AAA
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
825 PM EDT Sun Aug 19 2018
Issued at 745 PM EDT SUN AUG 19 2018
23z sfc analysis shows a washed out frontal boundary across the
area with little in the way of dry air brought into this part of
the state. A few pinprick showers remain along and south of this
front but the threat for thunder has ended. For this reason have
taken it out of the forecast for the rest of the evening as well
as lowering the PoPs. Currently temperatures are running in the
mid to upper 70s with dewpoints mainly in the low to mid 70s. The
small dewpoint depression has the potential to lead to more fog
later tonight as some radiational cooling takes place. However,
most of the near term models show only limited visibility
restrictions, likely the result of increasing mid and high clouds
inbound from the west. Accordingly, have limited the dense fog to
the usual river valleys and kept it off the ridges - unlike last
night when the stratus built down. Winds will be light and
variable through the night. Have also added in the latest T and Td
obs/trends to the grids. These updated grids have been sent to
the NDFD and web servers along with a freshened set of zones and
.SHORT TERM...(This evening through Monday night)
Issued at 422 PM EDT SUN AUG 19 2018
Looking at generally isolated convection across the area this
afternoon. Locations to the south and along the higher terrain
appear to be closer to widely scattered and may be scattered at
times through the late afternoon. Convection should die off
through the early evening with sunset and loss of daytime heating.
At present there is a boundary across the area but it is nearly
indistinguishable and has all but washed out.
Models are in good agreement and advertise the passage of a short
wave ridge aloft through the overnight period. But another low
pressure system and trough will encroach on the Ohio Valley
through the short term, making it as far as the western portions
of the Commonwealth by late Monday night or early Tuesday morning.
The corresponding surface low will move from eastern KS tonight
to Lake Michigan by Tuesday morning. This system will pull a
surface boundary eastward into the Ohio Valley by early Tuesday
morning, stretching roughly from Chicago to Indianapolis to
Nashville before turning back to the southwest.
Sensible weather portends the continuation of stormy weather that
we have become accustomed to over the past couple of weeks. At
present severe weather parameters appear to be lacking. There is
ample instability for thunderstorms but mid level lapse rates and
overall shear are not impressive. There is a window of impressive
PWATs (1.8 to 2.0 in) passing through the region leading into
Tuesday. But it is a short window and storm motions are relative
fast at 15-25 kts. Actually this system appear more progressive
and stronger than we have seen more recently. Consequently feel
overall threats will continue to be similar to the past week or
so. The potential for a few strong storms exists...it is summer,
and possibly even an isolated severe storm could not be ruled out
should a cell or two manage to over perform. Potential flooding
looks to be a greater possibility but even then would be limited
to training due to the higher storm motions and probably isolated
.LONG TERM...(Tuesday through Sunday)
Issued at 422 PM EDT SUN AUG 19 2018
A cold front, associated with a low pressure system moving into
Michigan, will progress through western Kentucky to start the long
term. This front will move quickly out of the Commonwealth later
Tuesday evening with the progression of the low pressure system from
the Great Lakes to the northeast. This will bring increased showers
and thunderstorms through Tuesday. The ECMWF shows a bit more QPF
during FROPA than the GFS. Adjusted PoPs slightly higher for this
based on the dynamic pattern and ample moisture.
Surface high pressure will then take hold for midweek until shifting
eastward by the weekend. Increased upper level forcing over the Ohio
Valley as well as warm, moist air from southerly flow will bring
showers back to the forecast this weekend for eastern Kentucky.
However, the models are not in good agreement with the strength of
this upper level forcing. The GFS shows a more amplified wave as
opposed to the ECMWF. Therefore, confidence is low and future model
runs will be needed to assess development of this system.
High temperatures will be around 80 degrees Tuesday afternoon, but
then cool down to be in the mid to upper 70s Wednesday due to FROPA.
Temperatures will gradually be on the rise through the week,
reaching the mid 80s again this weekend. Lows will follow a similar
pattern, starting out in the mid 60s Wednesday morning before
dropping into the mid 50s Thursday morning. Lows will return to
be in the mid 60s Saturday morning.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 825 PM EDT SUN AUG 19 2018
A boundary has stalled over the area, but only a few pinprick
showers are noted. Expect these to fad out shortly with a quiet
night on tap. The main concern through the night will be the
potential for river valley fog to affect the TAF sites.
Indications are that there will be enough mid and high level
clouds around to keep the fog in check. SYM and SME will have the
best potential for seeing some MVFR fog for a time late tonight
but have left that out of the TAFs for now. On Monday, scattered
showers and storms will be possible by afternoon ahead of the next
system moving toward the region, though chances are too low to
include as prevailing in any TAF at this point so mention was
limited to VCTS. Winds will be generally light from the south on
Monday after being light and variable overnight.
FXUS63 KLMK 192337
Area Forecast Discussion
National Weather Service Louisville KY
737 PM EDT Sun Aug 19 2018
...Updated Aviation Discussion...
.Short Term...(This evening through Monday)
Issued at 313 PM EDT Sun Aug 19 2018
Temps have warmed well into the 80s this afternoon, with even some
upper 80s noted in spots. We've reached convective temps down across
southern and eastern KY where very isolated showers have popped.
Expect some brief heavy rainfall with any shower, and perhaps a
lightning strike, although have not observed any yet. Could also get
a brief wind gust with any shower as visible satellite imagery
appears to show cold outflow extending out from some showers.
Haven't seen any observed gusts yet, but with DCAPE values around
1000 J/Kg and the satellite evidence think we are seeing 30 mph
gusts with the stronger showers. It's also interesting to note that
visible satellite shows a more healthy cu field across the southern
and eastern CWA, and is coincident with the highest Td's and low
level moisture. Farther north, we've mixed out into the upper 60s
and think think this will limit fog potential in that area
overnight. However, do expect we could see some fog in the south and
east part of the CWA, before the warm front and thicker cloud cover
take hold later Monday morning. Also will have to keep an eye on
near surface winds across southern KY as they become a bit
stronger/mixier toward dawn and could mitigate fog formation just in
time. Overall, best fog chance in our eastern CWA and have included
mention there. Lows tonight should drop into the upper 60s to around
An unseasonably strong low pressure system will move from the lower
Missouri River Valley into the mid Mississippi River Valley on
Monday. As this occurs, the washed out frontal boundary that sank to
our south yesterday will reinvent itself as a warm front and lift
north through the day. Given increasing low level jetting and good
warm advection lift with the front, expect scattered to numerous
showers starting in the morning in our SW and moving NE through
early afternoon. The main concern with any of these showers/storms
will be heavy rain, especially over areas that saw a lot of rain
late last week. Suppose a stronger storm or two could occur with the
warm front activity, but not overly concerned at this point.
The warm sector gets firmly established over our area by late
afternoon into the early evening as the best forcing and the cold
front still lag back to the west. Think we'll see a relative lull
during this time, with a few breaks in the clouds and pockets of
heating/destabilization possibly occurring. Don't think it will be
enough to trigger much additional convection in the warm sector, but
will keep at least small pops in during this time as the upper
forcing will quickly be moving in around sunset or after. The long
term portion of this discussion discusses shower and storm potential
into Monday night with the cold front and better forcing. Highs
Monday should reach the low and mid 80s.
.Long Term...(Monday night through Sunday)
Issued at 221 PM EDT Sun Aug 19 2018
Thunderstorms from earlier in the day just to our west will push
through southern Indiana and central Kentucky Monday night. As they
move east and we get further into the evening, instability will
decrease and thunderstorms will become slightly elevated. With
unidirectional shear and a low level jet up around 35kt, could still
see some gusty winds make it to the surface with the stronger cores.
Speaking of which, precipitable water values will be around two
inches with a deep warm cloud depth and surface dew points in the
lower 70s, so locally torrential downpours will be possible.
Fortunately the storms will be moving along around 25-30mph so
hopefully they won't stay over one spot for too long. Also, the
storms will be moving ENE as part of a north-south band of
showers/storms so training may not be a significant threat.
Nevertheless, locations that have received heavy rain over the past
few days will want to keep an eye on this system.
The upper trough associated with this weather will pass overhead
Tuesday as the surface low crosses the Great Lakes and its trailing
cold front extends down to the Gulf Coast States. Lingering showers
and a few storms can be expected Tuesday as this system makes its
way through the region.
For the rest of the week high pressure will mosey from the Great
Plains...though the Ohio Valley Thursday...to the Northeast Friday
and then possibly build southwestward into the southeast United
States this weekend. As a result we should have mostly dry and
pleasant weather mid-late week. Some low chance PoPs will creep back
into the forecast this weekend as we get into some return flow.
.Aviation...(00Z TAF Issuance)
Issued at 735 PM EDT Sun Aug 19 2018
A surface warm front will lift northward toward the region tonight
ahead of a developing low pressure system over the eastern Plains.
Late tonight as the front approaches, we could see some lowering of
ceilings with scattered showers and storms developing north of the
warm front. This would be around sunrise at KBWG and in the mid-
late morning hours at KHNB/KSDF/KLEX. Winds will start off light
and variable and then become southeasterly overnight, shifting to
the south by Monday afternoon. Still think we could see a little bit
of fog at KBWG and KLEX prior to the front getting here. For now,
have still kept things at MVFR, but there is a possibility that we
could drop to IFR briefly if fog become more extensive than forecast.
FXUS63 KPAH 192255
Area Forecast Discussion
National Weather Service Paducah KY
555 PM CDT Sun Aug 19 2018
.SHORT TERM...(This afternoon through Tuesday night)
Issued at 1000 AM CDT Sun Aug 19 2018
Confidence is high in the short term with models in good agreement
for several days now.
Weak upper level ridging should keep us dry through the day.
Tonight however a closed upper level low will make its way into
the region as surface warm front lifts north through the region.
This will result in storms and showers across the region. There
will be a cold front in its wake but we will be in the warm sector
at least through Tuesday morning allowing for additional
convection. As the upper level closed low moves over us in appears
to open up which usually indicates it will speed up it eastward
progress. We will also be in a very soupy air mass with dew points
well into the 70s. SPC has already upgraded to a slight risk of
severe storms. The models are placing us in an area of CAPE's 1500
to 2k j/kg2 and LI's of negative 5. This could possibly elevate
us into a slight risk. In contrast...cloud cover and a worked over
atmosphere could inhibit this escalation. Winds have some
strength but they are unidirectional. The freezing level will
under 15k feet slightly so hail can not be ruled out but damaging
wind will likely be the main threat with any strong or severe
storms. Temperatures will fall well below normal after the cold
front passage starting Tuesday and last through the week.
.LONG TERM...(Wednesday through Saturday)
Issued at 1000 AM CDT Sun Aug 19 2018
Much improved confidence in the extended with models starting to
look much more in sync.
High pressure over the southwest will try to build into the region
in the extended. We will have surface high pressure in place over
the area. This should inhibit convection. However aloft the high
never really makes it into the area and places us in a northwest
flow aloft. Any perturbation that gets caught up in this flow
could result in at least slight chances of storms. Especially if
its combined with peak heating. On the good side severe weather is
not anticipated at this time. Most of the area should remain dry
through the week after Tuesday. There is a weak disturbance aloft
next weekend but the upper high over the southwest should make its
way east and be centered over the gulf states by then. This again
will inhibit convection. This weekend however temperatures will
increase to at least normal with both a surface high over the area
and an upper level high centered just south of the region. Until
then enjoy the below normal temperatures this week.
Issued at 555 PM CDT Sun Aug 19 2018
First couple arched band of clouds associated with closed low
over northeast KS/northwest MO (northwest of Kansas City at 23z)
moving through southeast Missouri, southern IL/west Kentucky
should remain VFR through the late evening hours. The more
significant line of convective activity should move into the KCGI
and KPAH TAF locations between 04z-08z Monday, working toward KEVV
and KOWB around 12z Monday. There may be a 1-2 hour delay
depending on any changes of the speed of the convective rain
bands. Kept ceilings in VFR category with a slight intrusion of
MVFR visibilities with thunderstorms.
Not enough confidence on timing and intensity of any renewed
convection Monday afternoon, so left out any significant mention
of ceilings below VFR and mention of thunderstorms over most TAF