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FXUS63 KLMK 211119
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
619 AM EST Wed Feb 21 2018

...Updated Aviation Discussion...

.Short Term...(Today through Thursday)
Issued at 256 AM EST Wed Feb 21 2018

At 07Z a sharp cold front stretched from Detroit to Paducah to east
of Dallas. This front will push through southern Indiana and central
Kentucky today, accompanied by showers and perhaps a rumble or two
of thunder, especially in the Lake Cumberland region this afternoon
and evening. Shower activity will decrease in intensity and coverage
today as the front slows, weakens, and pushes east into the
Appalachians. Rainfall amounts during the daylight hours should
range from around half an inch west of I-65 to around a quarter inch
in the I-75 corridor.

Winds have stayed up overnight and will still be capable of gusting
into the 30-35mph range this morning ahead of the front, primarily
during the pre-dawn hours.

Temperatures will fall behind the cold front into the 40s in
southern Indiana this morning and into the 40s and 50s in central
Kentucky this afternoon.

An upper wave over east Texas early this morning will head to the
northeast tonight as the surface trof sits just to our east and
south. As a result, another wave of rain will push through the
Tennessee and Ohio Valleys tonight, especially after midnight. The
most significant rains should fall along and just south of the Ohio
River where 1/2 to 3/4 of an inch is expected, with a few spots
possibly seeing more.

On Thursday showers with tonight's wave will gradually exit, with
another wave of showers possible in the afternoon in central and
southern Kentucky. High temperatures will generally be in the 50s
though there could be some 60s in the south as that surface trough
to our southeast potentially drifts back to the north a bit.

.Long Term...(Thursday night through Tuesday)
Issued at 308 AM EST Wed Feb 21 2018

...SIGNIFICANT LONG DURATION RAINFALL EVENT INTO THE WEEKEND...

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

The upper ridge east/trough west pattern will continue through the
first half of the weekend with a moisture feed persisting from the
western Gulf to the upper Ohio Valley. This corridor will sit under
the right entrance region of a 140kt upper jet over the Great Lakes
as occasional disturbances eject out of the mean trough over the
West.

Thursday night and Friday that moisture will continue to feed
northeast along a broad surface trough just to our south, resulting
in periods of showers and a few thunderstorms.

Energy diving into the base of the upper trough Friday night will
swing into the Plains on Saturday and begin to translate the trough
eastward. Lee cyclogenesis will take place at the surface south of
the Palmer Divide Friday night. The remnants of the stationary front
to our south will become a warm front and lift northward late Friday
night or Saturday, accompanied by showers and embedded thunderstorms.

Saturday night the Plains low will continue to deepen as it races
into the western Great Lakes and pulls its cold front through the
Ohio Valley. The front will have full access to the Gulf and will
give us one final shot of widespread showers and embedded thunder in
this wet pattern. It looks like the fropa will be a cool season weak
instability/strong shear set-up. Best chance for strong to severe
storms at this time appears to be from southern Kentucky into the
lower Mississippi Valley. Something to watch over the coming days.

Welcome high pressure will then move in to dry us out for the first
part of the new week. The high will be of Pacific origin, as opposed
to Canadian/Arctic, so mild temperatures will continue.

&&

.Aviation...(12Z TAF Issuance)
Issued at 616 AM EST Wed Feb 21 2018

A cold front moving through the region has brought rain and a quick
wind shift to SDF and HNB. This wind shift will occur in the next
couple of hours at BWG and LEX. Showers will continue behind the
front today. There may be a brief break in precipitation around mid
day, but another wave will bring an additional round of enhanced
precipitation tonight. The other concern will be ceilings. They are
expected to lower to IFR today and possibly even LIFR tonight. Winds
will shift from northwesterly right behind the front to
northeasterly by early Thursday morning.

&&

.Hydrology...
Issued at 401 AM EST Wed Feb 21 2018

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

Synoptic models continue to advertise 3 to 5 inches of rainfall over
the next four and a half days 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. 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 only 48 hours of future rainfall. Therefore, with the
additional rainfall coming later this week, these river forecasts
will likely trend upward over the next few days. Ensemble river
forecasts show that some of our points will rise into the moderate
flood range. It is important to note that there are some QPF
forecasts that could push some of our points into major flood
status. Again, these forecasts are *highly dependent* on where the
heavy rainfall actually develops.

Much of the following stage information comes from various ensemble
model packages, and is likely to change as new data are ingested by
those models. **Also remember that the rain that will 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 by ensemble
modeling to reach moderate flood levels. Current model forecasts
show that this could occur by Friday night at Tell City and over the
weekend at Cannelton and Louisville. At least minor flooding is
predicted at Clifty Creek, with moderate flooding possible.

...Green River and Rough River...

Minor to moderate flooding will be possible at Dundee by Friday
night.

At least minor flooding is expected at Woodbury Thursday night and
Rochester Friday night. Munfordville will approach flood stage.

...Rolling Fork River...

Boston may rise to moderate flood this weekend.

...Kentucky River...

Minor flooding is forecast by ensemble models to begin at Lockport
this weekend. Peaks Mill on Elkhorn Creek may reach moderate flood,
but this is a smaller, flashier stream and is more difficult to
predict very far in advance.

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.

&&

$$

Short Term...13
Long Term...13
Aviation...EER
Hydrology...13
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