Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 221152
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
652 AM EST Thu Feb 22 2018

.Forecast Update...
Issued at 651 AM EST Thu Feb 22 2018

Most of the heavy rain is now across the northern Bluegrass region
of KY and will continue to move out of the forecast area over the
next couple of hours. The lighter precipitation will hang on across
portions of east and south central KY through the morning hours. The
Kentucky mesonet shows a broad stripe of 1.5-2.5 inches of rain has
fallen across central KY since midnight. We have had some reports of
a few roads flooding across east central KY this morning. In
addition, the heavy rain has caused some of the smaller rivers to
rise to near flood stage. The forecast was updated based on the
latest radar data and was adjusted down a bit this afternoon as well.

&&

.Short Term...(Today through Friday)
Issued at 313 AM EST Thu Feb 22 2018

...SIGNIFICANT ROUNDS OF RAINFALL CONTINUING INTO THE WEEKEND...

...FLOOD WATCH FOR ALL OF SOUTHERN INDIANA AND MUCH OF CENTRAL
KENTUCKY THROUGH SATURDAY NIGHT...

The radar currently shows a widespread area of light to moderate
rainfall along and north of a line from Simpson county to Lincoln
county in KY and all across southern IN. This rainfall has been
heavy at times and multiple mesonet stations across central KY have
measured upwards of an inch of rain. The highest so far is in Hart
county where over two inches has fallen. This rain will lead to some
minor flooding on area roadways. The heaviest rain should lift off
to the northeast by around sunrise or shortly after with some
lingering showers across southeast central KY through the morning
hours. Widespread 1-2 inches of rain is expected across central KY
with this rain north of the line highlighted above. Southern IN will
see half an inch to 1 inch. Much of the region should dry out for at
least a portion of the afternoon into the early evening hours.

The front that moved through yesterday has stalled out across east
central KY. This front will move little through the day today.
However, it will begin to lift back to the north tonight as a warm
front. Another impulse riding along the edge of the upper level
ridge will bring another round of moderate to heavy rainfall late
Thursday night. This heaviest rainfall through the overnight hours
will be focused across southern IN. It will shift southward towards
the Ohio River through the morning on Friday and become weaker as it
heads eastward through the afternoon. Rainfall amounts through this
period will be heavies along and north of the Ohio River where 1-
1.5" of rain is possible.

There will be quite a gradient of temperatures across the region
each day depending on where the frontal boundaries set up and where
precipitation is heavies. The Lake Cumberland region will be the
warmest. In addition to the rain, it will be quite breezy across
east central KY on Friday with gusts in the 30-35 mph range.

.Long Term...(Friday night through Wednesday)
Issued at 334 AM EST Thu Feb 22 2018

For Friday night into Saturday, a low pressure system will deepen
across the Plains. A warm front associated with this system will
lift north across the region on Saturday. Rounds of showers are
expected as this boundary lifts to the north Friday night and
Saturday, though precipitation amounts should not be too high.
Saturday will be warm with highs in the mid 60s to lower 70s.

The low pressure system will quickly move through the upper Midwest
Saturday night into Sunday morning, swinging the cold front through
the lower Ohio Valley. Ahead of the front, we will become marginally
unstable and a low level jet will develop. Models show precipitable
water values rising to near 1.5 inches. A line of showers and storms
looks to develop and move through Saturday evening into the
overnight hours. These have the potential to become severe with
damaging winds likely the main threat. In addition, with the very
high precipitable water values, additional heavy rain of an inch or
more could cause some flash flooding in addition to the ongoing
river flooding.

Much of this activity should move out by around daybreak on Sunday
with high pressure building in behind the cold front. This high
pressure looks to actually give the region a few days of dry
weather, lasting through Tuesday. This will be needed as many rivers
will likely be in flood by this time frame. Another system will then
move in from the south on Wednesday.

&&

.Aviation...(12Z TAF Issuance)
Issued at 635 AM EST Thu Feb 22 2018

Light rains will continue near BWG/LEX through the morning hours.
IFR-MVFR conditions are likely through 12-15Z. By mid morning or
early afternoon, flight conditions should start to improve as the
shortwave exits the area and rains diminish some. By early to mid
afternoon, expect only VCSH and MVFR conditions. However, more rains
and deteriorating conditions are expected this evening as a frontal
boundary moves north through the region.


&&

.Hydrology...
Updated at 349 AM EST Thu Feb 22 2018

Minor flooding continues along the Ohio River at Tell City,
Cannelton, and Louisville.

Synoptic models continue to advertise an additional 2 to 4 inches of
rainfall through Saturday night across much of the region. This
range has been very consistent over the past few days. As with any
convective, long term event, some locally higher amounts will be
possible depending on where multiple axes of heavier precipitation
develop. The most likely geographical area to get the most rain will
be those locations west of I-65.

This rainfall combined with already saturated soils will lead to
excessive runoff through the period. This will result in flooding
issues in the typical low-land and flood prone areas and potentially
some flash flooding. In addition, ongoing river flooding will become
worse with time as the runoff makes its way into the rivers.

Current river forecasts that are out are based on forecasts that
contain 72 hours of future rainfall. Thus, the current forecasts
capture rainfall through Saturday morning. The forecasts that will
be issued later this morning will cover the majority of the rainfall
from this series of events - through Sunday morning.

Some of the following stage information comes from various ensemble
model packages, and is likely to change as new data are ingested by
those models. Other data is based on current official forecasts.
**Also remember that the rain that will be responsible for the rises
on the rivers hasn`t even fallen yet, so significant river stage
forecast changes should be expected over the coming days.**

...Ohio River...

The river from Louisville to Tell City is forecast to reach moderate
flood levels. This could occur by late Friday afternoon at Tell
City, Saturday morning at Cannelton, and early Sunday morning at
Louisville. At least minor flooding is predicted at Clifty Creek,
with moderate flooding possible.

...Green River and Rough River...

At Dundee, minor flooding is forecast by Friday.

At least minor flooding is expected at Woodbury today and Rochester
Friday night. Munfordville and Alvaton will approach flood stage,
but are not forecast to hit flood stage at this time.

...Rolling Fork River...

Boston is forecast to rise to flood stage this weekend and has a
chance to rise to moderate.

...Kentucky River...

Minor flooding may be possible at Lockport this weekend. Peaks Mill
on Elkhorn Creek is a smaller, flashier stream and is more difficult
to predict very far in advance but it may go into minor flood this
weekend as well.

Given the consistent and consecutive heavy rainfall forecasts from
the guidance, a Flood Watch is in effect for the northwestern 2/3rds
of KY and all of southern Indiana for the duration of the overall
event, through Saturday night.

Residents of southern Indiana and central Kentucky should remain
alert this week for flooding.  Stay tuned for the latest forecasts
and updates through the week.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...Flood Watch through Sunday morning for INZ076>079-083-084-
     089>092.

KY...Flood Watch through Sunday morning for KYZ023>043-045>049-
     053>055-061>065-070>074.

&&

$$

Update...EER
Short Term...EER
Long Term...EER
Aviation...AMS
Hydrology...EER


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