Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 182043
Area Forecast Discussion
National Weather Service Louisville KY
343 PM EST Wed Jan 18 2017
.Short Term...(This evening through Thursday Night)
Issued at 310 PM EST Wed Jan 18 2017
...Another Round of Moderate to Heavy Rainfall Expected...
Afternoon satellite imagery shows skies scouring quickly across
southern KY this afternoon. Skies were mainly sunny south of the BG
Parkway and some partial clearing continues to work westward and
northward with time. In the clearing temperatures have responded
with readings in the lower to middle 50s. Where clouds remain,
temperatures remain in the lower-mid 40s. For the remainder of the
afternoon hours, we should see some of that scouring to the south
lifting a bit more northward. Not sure if it will reach the I-64
corridor by this evening...but will continue to monitor.
For tonight, the clearing from this afternoon will be short-lived as
mid-high level cloudiness will roll into the region from the
southwest. These clouds will be in advance of the first in a series
of southern stream mid-level disturbances ejecting out ahead of a
closed low over the central Plains. Moisture will quickly stream
into the region late tonight and a few showers will be possible by
dawn Friday. Lows tonight will range from the upper 30s in southern
Indiana and the northern Bluegrass region with lower 40s across
central and southern Kentucky.
Main surge of moisture and lift will push into the region early
Thursday with widespread rain showers moving through the region. The
best chances look to be during the daytime hours across all of the
region with the action shifting to the east and northeast Thursday
night. Instability does not look all that impressive as mid-level
lapse rates remain nearly moist-adiabatic. Some ensemble model
soundings do reveal some elevated instability...so a rumble or two
of thunder cannot be ruled out...mainly south of the Ohio River.
Highs on Thursday will be mild with highs in the 50-55 degrees in
southern Indiana and the northern Kentucky. Highs in 55-60 degree
range are expected across southern Kentucky. Lows Thursday night
will cool into the upper 40s to the lower 50s.
Rainfall amounts from the deterministic models still show a bit of
spread. The 12km NAM remains most aggressive with 2-3 inches of rain
falling across the region. The GFS/Euro/SREF/GFS Ensembles and some
of the higher res deterministic models are a bit less suggesting
more of 0.75-1.5 inch amounts across KY with higher amounts to our
south and west. For this forecast and after collaborating with
surrounding offices, we went closer to the ensemble mean of 1.0-1.5
inches through late Thursday night. This rainfall falling on nearly
saturated ground may lead to some runoff and local hydrologic
issues. After extensive coordination with surrounding offices, will
highlight these threats in the Hazardous Weather Outlook. Should
future model runs suggest higher rainfall amounts, a Flood Watch may
be required in subsequent forecasts for a portion of south/central
Kentucky in later forecasts.
.Long Term...(Friday through Wednesday)
Issued at 342 PM EST Wed Jan 18 2017
...Above Normal Temperatures and More Rainfall Expected In the
An active weather pattern is expected across the Ohio Valley through
the extended forecast period. A very amplified upper level pattern
will exist during the period with several mid-level disturbances
moving through the region. The first of these will pass through the
region on Saturday with a more significant closed upper low that
will bowling-ball its way through the region on Sunday and into
early Monday. A brief period of ridging is expected by Tuesday
before another strong closed upper low make a run for the Ohio
Valley by mid-late next week with a colder airmass returning to the
Overall, the global guidance is in fairly good agreement with the
pattern over the US. There remains some timing differences with the
passage of the upper level disturbances as they roll through the
Ohio Valley. The Euro solutions are a little more progressive than
the GFS. An ensemble compromise in between the solutions is most
likely a better fit for the ongoing forecast at this point. As we
move into early next week, both models do show a break in the action
around Tuesday with the pattern ramping back up again by mid-late
week. The GFS is a bit more amplified in its upper levels than the
Euro. While the models both agree with a deepening trough out west
ejecting east, we`re likely seeing the usual bias of the Euro being
a bit too slow to that wave out. This results in some higher than
normal temporal spread by mid-late next week.
Model QPF`s are somewhat similar, the Euro has a higher axis of QPF
across the heart of Dixie with lighter amounts across the Ohio
Valley. The GFS has a bit more QPF spread out further north. In
general a total of 2-4 inches of rainfall will be possible across
our region by the end of the forecast period.
Overall preference in the forecast is for a blend of the Euro/GFS
solutions for the extended period. Forecast confidence on
temperatures being above normal through the period is above average,
with precipitation amounts/timing a little below average given the
increasing spread with time.
Sensible Weather Impacts
Generally cloudy conditions are expected on Saturday as a weaker mid-
level system moves through the region. Showers with an isolated
thunderstorm look possible across southern KY with a lesser chance
across southern Indiana and northern Kentucky. High temperatures
will be above normal with readings generally in the lower to middle
60s. Overnight lows should cool into the upper 40s to the lower
50s. Higher precipitation chances will arrive on Sunday as a large
upper level cut off low rolls across the northern Gulf coast states.
Deformation band on the north side of the cut off low will bring
widespread rainfall to the region Sunday through Sunday night.
Precipitation look to slide off to the east by Monday with a period
of drier weather coming into the region for Tuesday and into
Highs Sunday and Monday will be a bit cooler with readings on Sunday
in the upper 50s to the lower 60s with temperatures mainly in the
lower 50s on Monday. Overnight lows will cool into the 40s. Highs
Tuesday and Wednesday will remain above normal with lower to middle
A look ahead shows a return to more seasonal late January cold by
late in the week and into next weekend.
.Aviation...(18Z TAF Issuance)
Issued at 1220 PM EST Wed Jan 18 2017
MVFR stratus deck sticking around a few more hours, and are close
enough at LEX to IFR levels to have a threat there for at least
another hour. Still expect the stratus to erode as the layer of
clouds are fairly thin. By early evening, all sites should be VFR.
After a brief shot at fog at LEX toward daybreak Thursday, the next
issue will be a storm system bringing rain chances and lower cigs by
late morning at BWG and then afternoon at SDF.
Issued at 300 PM EST Wed Jan 18 2017
...7-Day Hydrologic Outlook...
Currently, most of our river basins are running above normal with
respect to water levels. Minor flooding has been observed the
Green River at Woodbury and Rochester. The latest deterministic and
ensemble forecasts suggests a couple of bouts of rainfall over the
next 7 to 10 days. Rainfall amounts of over the next 7 days is
expected to average around 1-2 inches across southern Indiana and
far northern Kentucky. Across central and southern Kentucky, 2 to
as much as 4 inches will be possible by the middle of next week.
Should these rainfall amounts materialize, river levels may exceed
action and/or minor flood stages in the Green River basin
(Rochester, Woodbury, Alvaton/Drakes Creek). Some rises will also
be possible down on the Salt River at Boston and at Elkhorn Creek at
Peaks Mill. Levels on the Ohio will remain elevated, but with the
heavier rains expected to fall on the southern fringes of the basin,
major rises are not anticipated. River levels up in southern
Indiana will also be running above their average winter pools. the
muscatatuck at Deputy looks to remain well below action stage
through the period.