Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 160713
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
313 AM EDT SUN JUN 16 2013
.SHORT TERM (Today through Monday Night)...
Issued at 300 AM EDT Sun Jun 16 2013
...A bit of a challenging forecast today with regard to where and if
any scattered thunderstorms may develop...
An east-west elongated closed low across the Canadian plains has
pushed the polar jet a bit south across our northern tier of states.
In fact, at 500mb, some westerly zonal flow will move as far south
as the Lower Ohio Valley.
This flow has also pushed ample Gulf moisture northeast across
southern Illinois and Indiana, although locations along and south of
the Ohio River currently still are pretty dry, with PWATs still less
than one inch. Several convective complexes have crossed the midwest
earlier this morning, aided by the development of a nocturnal jet.
Once MCS, in particular is currently (at 2AM EDT) decaying over
Moisture will increase today, especially along and north of the Ohio
River. Further complicating the matter, a weakening outflow boundary
will move southeast across southern Indiana during the pre-dawn
So...for this morning, expect occasionally cloudy skies across
southern Indiana with perhaps some isolated sprinkles or very light
showers left over from the decaying MCS. Think that locations along
and south of Interstate 64 will stay dry this morning. Expect
partial clearing north and partly cloudy skies south this afternoon
with an increasing likelihood of scattered thunderstorms developing
by mid afternoon along and north of Interstate 64, with just
isolated storms farther south, away from any richer moisture or
potential outflow boundary.
Any isolated storms will diminish this evening with only a slight
chance for some lingering showers through Monday morning.
Model guidance has been very consistent in forecasting a flat 500mb
wave moving across the Commonwealth late Monday. After a dry
morning, think that at some point late Monday, convection will
become likely, especially across central and southern Kentucky. Both
The NAM and GFS have convective feedback problems across the
Commonwealth late Monday. However, do agree that some locally heavy
rain may develop across central Kentucky late Monday evening through
Highs today and Monday will not stray too far from the mid 80s.
.LONG TERM (Monday Night through Saturday)...
Issued at 313 AM EDT Sun Jun 16 2013
Monday Night through Tuesday Night...
Fairly unsettled weather pattern looks likely at the beginning of
the forecast period. At the surface, a quasi-stationary front is
forecast to be lying across the Ohio Valley. Aloft, a mid-level
vorticity maximum is progged to slide eastward into the Ohio Valley
Monday night. This feature should bring a period of shower and
thunderstorms to the region. Highest PoP chances look to be Monday
night and during the day on Tuesday as the upper level system pushes
through. Some of the storms could be on the strong side. However,
severe weather threat looks less with each successive model run. In
general, the bulk shear forecasts are weaker and the amount of cloud
cover and precipitation will likely result in lesser amounts of
instability. Nonetheless, a juicy atmosphere will be in place and
torrential rainfall, gusty winds and plenty of lightning look to be
the main storm threats. The period of unsettled weather looks to
end Tuesday night as the mid-level wave pushes off to the east and
surface high pressure builds in from the west/northwest.
Lows Monday night will be quite mild with readings in the upper 60s
to around 70. Highs Tuesday will largely be influenced by cloud
cover and precipitation. Latest blend of guidance suggests highs in
the upper 70s to the lower 80s in the east with lower 80s in areas
west of I-65. Lows Tuesday night should cool back into the middle
Wednesday through Saturday...
Surface high looks to remain in control of our weather through the
first part of the extended forecast period. Baggy upper trough is
expected to persist across the eastern US, with the deeper moisture
being confined to the southeastern US and just south of KY/IN.
Overall forecaster confidence is average during this period and it
appears that Wednesday and Thursday will be mostly dry across the
region. Temperatures will moderate during the period with highs on
Wednesday topping out in the lower-middle 80s. Highs should warm
back into the mid-upper 80s by Thursday...while overnight lows
remain in the 60s.
By late week, the models are suggesting that the heat ridge will
build up once again across the Plains states while the Ohio Valley
remains on the eastern periphery of the ridge. A southerly flow
will likely result in more moisture being advected northward into
the region by Friday resulting in isolated-scattered convection
developing during the afternoon/eve. With the region being on the
periphery of the upper ridge, we will need to monitor disturbances
tracking around the ridge as one or more of these disturbances may
result in MCS activity affecting the area by Saturday. Tracking and
timing these features at this time range is quite poor...so plan on
sticking to climatological PoPs with this forecast. Highs Friday
and Saturday will be close to seasonal normals with highs in the
85-90 degree range and overnight lows in the mid-upper 60s.
.AVIATION (06Z TAF Update)...
Issued at 120 AM EDT Sun Jun 16 2013
Some mid and high level cloudiness associated with decaying
thunderstorms over Indiana will affect SDF and LEX through the
morning hours. These clouds will not affect general aviation and VFR
ceilings are expected through at least this afternoon. Nearly calm
winds will continue through dawn, with southwest winds around 5 to
10 mph developing by this afternoon and continuing through this
Humidities will increase later today, especially at SDF and LEX.
Isolated thunderstorms will become possible after 14z at SDF and LEX
while BWG will likely stay dry until mid afternoon. In any case
organized, widespread convection is not anticipated today, with the
majority of the day staying dry. Without a focusing boundary or
shortwave, think any convection will stay scattered at best,
concentrated around the mid afternoon or evening hours. Cannot
specifically attempt to time any potential storms.
For tonight through early Monday, isolated showers are likely at
best. Will keep any showers or thunder out of the TAFs through 12z