Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 251720
Area Forecast Discussion
National Weather Service Louisville KY
120 PM EDT MON APR 25 2016
...Updated Aviation Discussion...
Issued at 1134 AM EDT Mon Apr 25 2016
No planned changes to the forecast at this hour. Temperatures are in
the 70s and on their way to forecast highs in the low 80s. A steady
SW wind is beginning to increase with a few gusts up in the 25 to 30
mph range this afternoon.
.SHORT TERM (Now through Tuesday)...
Issued at 320 AM EDT Mon Apr 25 2016
Other than a few high clouds, tranquil weather is expected across
the forecast area today. Early this morning, observations
revealed a wide range of temperatures. Some of the cooler valley
locations were in the upper 40s, while the ridgetops were in the low-
mid 50s. Out west of I-65, temperatures were in the mid-upper 50s
with some 60s out toward the Pennyrile region of W/C Kentucky. We`ll
see temperatures continue cool over the next few hours and then
rebound after sunrise.
For today, we`ll see an increasingly south-southwesterly flow across
the region as we will be between a high pressure system near the US
east coast and a developing low pressure system over the Midwest.
Winds will increase throughout the day under mostly sunny skies.
Winds will be in the 10-20 MPH range with some occasional gusts up
to 30 MPH at times. Afternoon highs should top out in the 80-85
As we head into tonight, clouds will be on the increase from the
west and moisture will start to pool into the region. Dewpoints
should continue to rise overnight which combined with the increasing
clouds, will keep overnight minimum temperatures up. Lows in the
upper 50s to the lower 60s are expected. A frontal boundary to the
north of the region will serve as a focus for thunderstorm
development. Some outflow from these storms may work southward into
the region toward Tuesday morning. At this time, the best chances
for any rainfall late tonight would be north of the Ohio River.
On Tuesday, latest model guidance still suggest surface frontal
boundary will be north of the region and our area will be
effectively in the warm sector. Dewpoints will continue to rise and
should be into the lower 60s by the afternoon. Some scattered
showers will be possible across the northern sections of the
forecast area Tuesday morning with diminishing convection moving
southward out of Indiana. During the day, a mid-level trough axis
is forecast to track eastward from the Midwest into the Mid-
Atlantic. A bit of brisk westerly flow in the mid-levels will
accompany this feature as it passes through the region. Model
proximity soundings suggest moderate mid-level lapse rates in place
during the afternoon hours, so convection should not have much
problem sustaining itself after initiation. Instability is a little
questionable at this time range as we will see more cloud cover
during the day. Though, with temps expected to warm into the upper
70s to lower 80s, that combined with dewpoints in the low-mid 60s
will result in decent CAPE values for strong convection to develop.
Overall, it appears that scattered convection will develop and move
eastward through the region during the afternoon hours. Main threat
here looks to be damaging winds and perhaps a few reports of large
hail with the strongest storms.
Showers and storms will continue into Tuesday night with gusty winds
being possible. However, the main threat by Tuesday evening and
into the overnight hours will be heavy rainfall. Torrential
rainfall and the training of storms may lead to several inches of
rainfall over a short period of time. Most problematic area looks
to be across southern Indiana and into the Bluegrass region of
central KY (along/north of I-64). Lows Tuesday night will be mild
with readings mainly in the lower 60s.
.LONG TERM (Tuesday Night through Sunday)...
Issued at 355 AM EDT Mon Apr 24 2016
...Very Unsettled Weather Pattern Expected This Week and into Next
Negatively tilted upper trough will slowly move from the Plains into
the Midwest on Wednesday. As this occurs, a stalled out frontal
boundary over the Ohio Valley will lift northward as a warm front
early Wednesday morning. As this warm front lifts northward, we
expect another round of widespread shower and thunderstorm activity
to move through the region. We may see a brief lull in the activity
during the afternoon hours on Wednesday. However, this will be short
lived as strong/deep synoptic scale forcing pushes in from the west.
Overall convective set up is rather messy and complicated at this
time frame. While dewpoints will be in the lower 60s and moderate
lapse rates and wind fields will be in place, overall instability is
still somewhat questionable. Nonetheless, the multi-model consensus
agrees that widespread shower and thunderstorm activity will move
through the region Wednesday night. Heavy rain threat will need to
be monitored here as the potential for training of storms will be
possible. Highs Wednesday should be a little cooler due to cloud
cover and precipitation, but readings will likely warm into the
upper 70s in the north with lower 80s in the south. Overnight lows
will be in the lower 60s.
For Thursday/Friday, the models remain generally consistent with
strong forcing moving through the region early in the period. As it
stands currently, much of the forcing looks to be off to our east by
Thursday morning. However, upper low and associated surface low
will remain to our NW and slowly move southeast during the day while
shearing out. Proximity soundings from the various models show
steep lapse rates due to cooling aloft, so a resurgence of
convection will be possible Thursday afternoon and evening. We`ll
be in between systems by Friday, so a drier day looks to be on tap
and should hold through Friday night. Highs Thursday will warm back
into the upper 70s to lower 80s, with slightly cooler readings in the
upper 70s for Friday. Overnight lows through the period will be in
the upper 50s.
Active weather pattern will continue as we head into next weekend as
another weather system will impact the Ohio Valley late Saturday and
into Sunday. Long range modeling has been showing a
strong/consistent signal here passing through the region in this
time frame. The evolution of the storm still is hard to pin down at
this point, but a potent upper trough should be migrating from the
Plains into the Midwest. This will likely result in another severe
weather outbreak in the Plains by late week and then heading
eastward toward our region. Multiple rounds of convection look
likely with strong to severe convection being possible. Given the
heavy rainfall expected earlier in the week...combined with more
rainfall during this time frame may start to result in some
hydrologic issues across the region.
.AVIATION (18Z TAF Update)...
Updated at 120 PM EDT Mon Apr 25 2016
Dry and VFR conditions are expected to persist through the afternoon
and night as high pressure holds over the region. Expect a few mid
level clouds with a steady SW wind between 10 and 15 mph. A few
gusts up around the 25 to 30 mph mark are possible this afternoon.
Winds will slacken this evening and back to a more SSW direction
around 10 mph with continue mid level clouds.
Low confidence forecast for Tuesday as a frontal boundary sinks
south toward the Ohio River. There is some question to whether
showers over IL/IN/OH will survive the overnight period and make it
into SDF/LEX around our after sunrise. Given our dry air in place
think most activity (shra/tsra) won`t get going until the afternoon
hours. So, will forecast low VFR ceilings with some showers in the
vicinity in the morning at SDF/LEX.