Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 311555
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1155 AM EDT Sun Aug 31 2014
...Updated Aviation Discussion...
Issued at 1145 AM EDT Sun Aug 31 2014
Light to occasionally moderate rain will continue south of
Interstate 64 through early afternoon. The threat of thunderstorms
and associated heavy downpours has diminished greatly as dense cloud
cover and rain has precluded the development of any surface
instability. In general, most locations will stay under one half
inch of additional rainfall. Will almost certainly let the Flash
Flood Watch expire at 2 pm this afternoon.
In general, around 2 inches has fallen across our southern tier of
counties, including the Bowling Green area, with a few higher totals
where convection developed late yesterday.
Issued at 825 AM EDT Sun Aug 31 2014
Updated the forecast to remove a portion of the Flash Flood Watch
from the western and northern Bluegrass, while keeping it intact
across southern Kentucky and the southern Bluegrass. Not much rain
has fallen so far across the Bluegrass and northwest of the
Cumberland Parkway. Through 8 am, total rainfall amounts have ranged
from around 1 to locally over 2 inches across our southern counties,
with one spot in Simpson County receiving over 3 inches.
The bulk of any additional rain will fall across our southern
counties this morning through early afternoon, with an additional
inch or so expected. Showers will be much more sparse across
southern Indiana and southeast of the Ohio River, where, I think,
the bulk of today will be dry.
.SHORT TERM (Now through Monday)...
Issued at 315 AM EDT Sun Aug 31 2014
...Flash Flood Watch Remains in Effect for East-Central Kentucky...
Deep southwest flow will continue over the Ohio Valley today as we
remain positioned between troughing over the central CONUS and a
strong SE CONUS ridge. This flow will set the stage for another
impressive plume of moisture riding over the area, ahead of another
disturbance. The threat for heavy rain will continue along and east
of the I-65 corridor today, although all locations are likely to see
Current radar shows the CWA in a relative precipitation lull as the
evening`s initial surge of moisture moves off to the NE, and we
await another round set to arrive around dawn. There are scattered
to numerous light rain showers lingering across the area, especially
along and south of the Ohio River. Expect this to continue through
the pre-dawn hours.
Focus will then shift to the next plume of moisture (characterized
by PWATs in the 2"-2.2" range) ahead of a wave currently near
Memphis. A 30-40 knot low level jet will accompany this feature,
aiding moisture transport through midday east of I-65. Additionally,
have seen some baroclinic leafing on IR satellite over the Wabash
River Valley associated with the right entrance region of an upper
level jet. This will slide east through the morning, overlapping the
best low level moisture surge from the low level jet over the
current Flash Flood Watch area. The end result will be potential for
bands of heavier rainfall setting up along and east of a BWG to LEX
line, where an additional 1 to 2 inches of rain (locally higher)
are possible. Embedded thunderstorms are expected with this surge.
Therefore, will extend the Flash Flood Watch to 18z in coordination
with surrounding offices. One thing to note is that models have been
too far west with heaviest rainfall axis to this point. It is
possible that the heaviest axis will end up being further east by 50
to 100 miles if that bias continues. Areas outside of the watch can
expect another quarter to three quarters of an inch of rain through
Will also mention that a few storms could rotate with the LLJ surge
this morning. SPC highlighted where this LLJ core will track with a
2% tornado contour, however surface based instability should be hard
to come by so don`t expect any problems at this point. Just some
food for thought if we do start seeing a few storms rotate. Most
probable area for an issue would be toward the Lake Cumberland
Highs are not expected to budge a whole lot today as the mercury
struggles under heavy cloud cover and precipitation. Will call for
upper 70s NE to low 80s SW.
Precipitation will taper from west to east later this afternoon and
into the evening as the wave pushes east along with the deeper
moisture. Enough low level moisture will linger to leave mention of
an isolated shower through tonight, however most places are likely
to stay dry. Not too concerned about fog at this point since low
stratus seems to be the more likely player overnight. Look for lows
in the upper 60s to around 70.
Labor Day is expected to be a mostly dry day with fairly steady SW
winds in a tighter pressure gradient between a southern Plains low
and high pressure to our SE. Can`t rule out an isolated
thunderstorm, however the pattern seems benign of any real triggers
in the SW flow aloft. The combination of decent amounts of sun and
the warm advective component should bring temperatures back in the
.LONG TERM (Monday Night through Saturday)...
Issued at 300 AM EDT Sun Aug 31 2014
Models continue to show showers and storms north of our region at
the start of the period, near a front that will make slow progress
toward the region. It is looking more likely that at some point
Tuesday we`ll get another round of heavy rain, as precipitable
waters once again head up to around 2 inches. That rain will come
either as a low-level jet ramps up across southern IN early Tuesday
or with peak heating during the day Tuesday. Thus will ramp up pops
to the 50-70 percent range. Will continue to undercut guidance
temperatures based on this thinking, but readings still should be
Models had been portraying Wednesday as a transition day to hotter
and somewhat drier conditions for the rest of the period. However,
the latest GFS doesn`t have as strong of a ridge across our region,
in fact placing a weak upper low over the Wabash Thursday and mid
Ohio River Friday, then another disturbance enhancing rain chances
Saturday. The 12Z Euro hints at these features as well. NOGAPS
ensembles still show the ridge pattern in the mean fields, but the
spread fields are much more wavy, indicative more of these
disturbances being shows in the various ensemble members. Thus will
maintain chances for storms each day. Most likely the above normal
temperatures will continue through the end of this period.
.AVIATION (12Z TAF Update)...
Issued at 649 AM EDT Sun Aug 31 2014
A tricky forecast over the next 24 hours as a plume of Gulf moisture
streams through the Ohio Valley ahead of a disturbance embedded in
the deep southwest flow. Widespread rain is now impacting BWG, and
is set to reach LEX by late morning. Expect visibilities to drop
into the MVFR category with this batch of moisture. Ceilings outside
of the rain have been able to find their way into the IFR range at
times, however do expect improvement during the rain showers as low
levels get somewhat mixed by showers. Overall, expect BWG to see
improvement by 1 PM CDT, with widespread showers ending and ceilings
trying to find their way back into the VFR range. LEX should expect
improvement by 3 PM EDT, with only lingering showers and ceilings
hovering on the VFR/MVFR threshold.
SDF should stay more on the northern fringes of the precipitation
shield, with ceilings waffling in and out of IFR until numerous
showers arrive later this morning. Best timing looks to be between
10 AM and 1 PM EDT, before improvement takes over. Ceilings should
find their way back to the VFR range by mid to late afternoon.
Overall winds will generally be out of the south around 10 mph
through this forecast cycle.
Rain will be pretty well gone by tonight, however lingering low
level moisture will bring the threat of low stratus back into the
forecast. Expect at least MVFR ceilings through the overnight hours
as we head into Labor Day.
KY...FLASH FLOOD WATCH until 2 PM EDT /1 PM CDT/ this afternoon FOR