FXUS63 KJKL 232011
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
411 PM EDT Wed May 23 2018
.SHORT TERM...(This evening through Thursday night)
Issued at 411 PM EDT WED MAY 23 2018
As of mid afternoon, an upper level ridge of high pressure
extended from the eastern Gulf of Mexico and Florida northwest
into the MS Valley. At the surface, an area of high pressure was
centered over the Great Lakes region. Meanwhile the boundary that
crossed the area last night continues to push farther southeast
and east of the area and extended from the mid Atlantic states
into the Appalachians and then west into the TN and MS Valley
regions. Cumulus has gradually been mixing out this afternoon as
drier air continues to advect into the region.
The axis of the upper level ridge is expected to approach the
area from the west through Thursday. Meanwhile surface high
pressure will remain in control tonight. With the high in place,
temperatures should reach the mid to upper 50s in the valleys or a
few degrees below current dewpoints. In addition, the ground is
rather moist from recent precipitation. With clearing skies and
light winds, the stage should be set for valley fog formation
tonight. In the deeper eastern valleys and river valleys, this
fog should become dense overnight. This fog should lift and
dissipate through 9 to 10 AM.
Meanwhile, the surface high is expected to move east and be
centered along the mid Atlantic to northeast US coast by the end
of the day. As this occurs, moisture is expected to return north
especially closer to the crest of the Appalachians as suggested by
guidance. Some cumulus development is expected in all areas, but
locations further north and west should generally be capped by the
drier airmass in place. Despite weak forcing, sufficient moisture
should return for mainly isolated showers and even a thunderstorm
to develop near the VA border generally after 1 PM. The GFS and
NAM both develop convection in the vicinity of Harlan county and
some recent convective allowing model runs also develop convection
in this area. Outflows from the convection could lead to activity
as much as a couple of tiers of counties north into the southeast
KY. Any showers and thunderstorms should wane on Thursday evening.
Some valley fog should again develop Thursday night, however,
dense fog is expected to have less of an areal extent.
.LONG TERM...(Friday through Wednesday)
Issued at 347 PM EDT WED MAY 23 2018
The upper level reveal the ridge will be in the process of
breaking down as a upper level wave develops across the Upper
Midwest. This will continue to weaken the ridging and bring more a
shortwave pattern into the region. Then we turn our attention to a
developing tropical system in the Gulf of Mexico. Surface wise we
will see a surface high that was across the Ohio Valley depart to
the east By Friday allowing more moisture to spill back into the
region. This added moisture and eventual interaction with
shortwave energy will keep the region under the potential for
mainly afternoon and evening showers and thunderstorms. The best
chances through the period will generally be closer to the higher
terrain. The aforementioned tropical system will play a role in
how much moisture we will receive and this will be dependent on
the track and overall evolution. That said, the GFS operational
solution is a outlier compared to the ECMWF, Canadian, and most of
the GEFS solutions, with its more eastern track. The better
overall plume of moisture seems to setup across the Carolinas.
Either way it does seem like a increase in moisture could at least
lead to isolated heavy rain issues given the potential for
afternoon convection each day.
.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED AT 215 PM EDT WED MAY 23 2018
Cumulus generally between 3 and 5kft were observed across the
region at issuance time, with VFR prevailing. Generally VFR
should prevail for much of the period with high pressure in place
across the region. The only caveat will be fog development
generally after 5Z. The fog should dissipate in all areas by 14Z.
However, this fog should become dense in the deeper valleys and
river valleys. For the TAF sites, some MVFR reductions are
anticipated between 8Z and 13Z at all sites other than SYM. Winds
should remain light and variable through the period.
FXUS63 KLMK 231845
Area Forecast Discussion
National Weather Service Louisville KY
245 PM EDT Wed May 23 2018
.Short Term...(This evening through Thursday)
Issued at 245 PM EDT Wed May 23 2018
In the near term, high pressure to the north will continue to build
into the region. We'll see an influx of slightly drier air with
dewpoints in the upper 50s to the lower 60s. Some high cloudiness
will continue to drift over southern KY this afternoon and evening.
Highs this afternoon will top out in the upper 70s to the lower 80s.
Temperatures this evening will fall back into the upper 70s before
bottoming out in the upper 50s to the lower 60s overnight. Could
see some patchy fog down in southern KY late tonight...mainly south
of the Cumberland Parkway.
Dry and tranquil conditions are expected for Thursday as high
pressure and mid-level ridging build across the region. Highs will
range from lower 80s in the Bluegrass region to the mid 80s
.Long Term...(Thursday night through Wednesday)
Issued at 245 PM EDT Wed May 23 2018
...Muggy and Unsettled Memorial Day Weekend On Tap...
High pressure is forecast to slide off to the east by late Thursday
and early Friday morning. Upper ridge will also shift eastward a
bit and we'll get back into a return flow regime by Friday. Deeper
moisture will start to pool into the region by Friday afternoon.
Differential heating will likely kick off some diurnal convection,
mainly across southern and southeastern KY Friday afternoon and will
likely linger into the evening hours. Highs on Friday will warm
into the mid to upper 80s with lows remaining in the middle 60s.
As we move into the weekend, eyes will be on the Gulf of Mexico as
the models have been advertising an area of low pressure moving
northward through the Gulf. Combination of the approaching tropical
system and ridge off the east coast edging to the east will funnel
deep moisture into the Ohio Valley Saturday through Monday.
Precipitable water values will increase to near two inches during
the period. That, along with increasing warm cloud depths will
likely lead to convection producing torrential rainfall, gusty
winds, and quite a bit of lightning. Localized heavy rainfall could
lead to some hydrologic issues from time to time over the weekend.
The unsettled weather pattern is likely to linger into early next
week as the models continue to differ on how the upper level pattern
will evolve and where the Gulf system will go after it reaches the
SE Coast. For now, the consensus blend keeps diurnally driven
convection going through the remainder of the period with the
highest chances in the afternoon/evening with lesser coverage
Temperatures through the period will top out each day in the mid-
upper 80s. However, with dewpoints in the mid-upper 60s, heat
indices over the holiday weekend will make it feel a bit warmer
than that. Overnight lows will mainly be in the upper 60s to near
.Aviation...(18Z TAF Issuance)
Issued at 108 PM EDT Wed May 23 2018
Low level fog and clouds are finally scouring out across southern KY
this afternoon. We should see continued improvement in conditions
at KBWG through the afternoon. Elsewhere, light northeasterly wind
flow is expected with speeds of less than 7 kts. For tonight, clear
skies and light northeast winds are expected. We may decouple
enough down at KBWG to see some light ground fog once again which
should mix out after sunrise. The outlook for Thursday is for VFR
conditions with a continued NE to ENE wind with speeds of less than
FXUS63 KPAH 232019
Area Forecast Discussion
National Weather Service Paducah KY
319 PM CDT Wed May 23 2018
.SHORT TERM...(Tonight through Friday night)
Issued at 319 PM CDT Wed May 23 2018
Dry surface high pressure has effectively scoured out the low-
level moisture and any chance of convection over most of the
region. There is some scattered convection just to the west and
southwest of Ripley and Carter counties, and satellite does not
show any enhanced cu development out there. Figure this area will
remain dry as well.
High pressure at the surface and aloft will keep the area dry
Thursday and Thursday night, before a weak mid/upper-level trough
moves into the region early Friday. The 12Z GFS is the most
aggressive in bringing convection back to far western portions of
southeast Missouri by daybreak Friday, while better resolved
guidance keeps the area dry. We will have very slight chance
PoPs to the west of Van Buren and Doniphan.
South winds will return Friday and that means mid and upper 60
dewpoints will advect across much of the region. This along with
the weak upper system in the vicinity should allow for some
isolated to scattered convection over southeast Missouri and
possibly portions of southern Illinois and west Kentucky on
Friday. Weak wind fields will prevent any storm organization, so
individual storms will be pulsy and relatively short-lived. Given
the presence of the upper system, this activity may not be purely
diurnal, so will spread some small PoPs across the entire area
High temperatures will remain well above normal through the
period. Lows tonight will mainly be in the lower 60s, and a few
local areas may drop into the upper 50s, which is close to normal.
Lows will trend warmer through Friday night when most areas only
drop into the upper 60s.
.LONG TERM...(Saturday through Wednesday)
Issued at 319 PM CDT Wed May 23 2018
There still remains quite a bit of uncertainty this holiday weekend
into next week as to the eventual track and effects of any tropical
system that manages to develop over the northern Gulf of Mexico this
weekend. Bottom line is that within our forecast period, the low
will likely stay well off to our south and southeast. A northern
stream mid level trof will also work its way into the MS Valley
region over the weekend and become nearly stable within a
mid level blocking pattern.
What this means essentially for us in the quad state region is an
extended warm, moist and somewhat unsettled weather regime right
through the weekend and through the rest of the long term period.
Thinking is that we will be looking at scattered, mainly diurnal,
thunderstorm chances each afternoon underneath the mid level
trough. Weak winds aloft should preclude much of an organized
threat, with the focus mainly on low level outflow boundary
interactions. Storms should tend to be rather short-lived as
updrafts are quickly cut off due to heavy precip loading. Still,
there will be a gusty wind, heavy downpour and deadly lightning
threat from time to time for those with outdoor plans throughout
the upcoming holiday weekend. Will definitely need to keep an eye
to the sky.
Issued at 1156 AM CDT Wed May 23 2018
The TAFs are VFR due to high pressure at the surface and aloft
through the period. A few SHRA/TSRA will be possible this
afternoon in the Van Buren and Doniphan areas of Missouri, but
this activity will be well west of KCGI. The lone threat to VFR at
the TAF sites will be fog potential, mainly at KCGI late tonight.
However, with strong mixing and dry advection today, confidence
in fog formation is too low to mention at this time.