Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 211945
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
245 PM CDT Wed Jun 21 2017

.SHORT TERM...(Tonight through Friday night)
Issued at 245 PM CDT Wed Jun 21 2017

The primary concern is the upcoming heavy rainfall event
associated with Tropical Storm Cindy and its interaction with an
approaching frontal boundary. The models have accelerated the
timing of the system just a bit. A Flash Flood Watch was strongly
considered, but there is enough time for later shifts to evaluate
the placement of any future watch. Western Kentucky and extreme
se Missouri still appear in line for the heaviest totals.

As for tonight, a majority of models now bring qpf into southern
Kentucky before 12z. The pattern looks favorable for a PRE event
(Predecessor Rainfall Event) in that location, near the leading
edge of the tropical plume and just upstream of a shortwave ridge.
These well-documented events are usually poorly forecast by the
models or missed totally. Regardless of whether it meets PRE
criteria, rain will likely develop on Thursday morning across much
of the region.

During the afternoon, there will be some increase in instability.
Low-level shear will be decent as 900 mb winds average around 40
knots. A brief weak tornado or two cannot be ruled out, as
indicated by the SPC marginal risk area. However, the greatest
risk of tornadoes with landfalling tropical cyclones is usually on
the right side of the center`s track. This should be primarily
south of our region.

A plume of very rich, deep tropical moisture will become
established across our region Thursday night and Friday. Precip
water values will average around 2.25 inches, which is above the
99th percentile for this time of year. The copious amounts of
moisture, combined with the approaching frontal boundary, should
result in locally excessive rainfall. The ESF product will be
updated with somewhat stronger wording.

Rainfall will end or diminish late Friday and Friday evening with
the passage of the cold front. Total average amounts of 2 to 4
inches are forecast across west KY and adjacent counties of
neighboring states. There will likely be small swaths of higher
amounts due to embedded convection. The 12z nam and 12z gfs are on
the high end of guidance with 5 to 7 inches across parts of the
area. Again, later shifts can evaluate this potential and issue a
watch as necessary.

.LONG TERM...(Saturday through Wednesday)
Issued at 245 CDT Wed Jun 21 2017

We have low confidence in model timing precip chances after
Saturday. A broad long wave trof at the beginning of the period will
be across most of the CONUS with a ridge persistent over the SW U.S.
Some amplification will take place, with embedded s/wv energy moving
SE then E from the Upper Midwest, Great Lakes and Ohio Valley
regions on eastward. At the surface, some semblance of high pressure
is forecast for the duration.

We expect dry weather Saturday. From Saturday night through Monday
night, depending on which model you pick, there will be slight
chances of weak convection. The EC may be a bit overdone. But there
is not enough confidence to discount it at this point, especially
for the Saturday night, Sunday time frame.

Where confidence is higher, is with respect to temperatures. The
pattern favors cooler than normal temps and humidity levels, with
variable cloud cover expected.

&&

.AVIATION...
Issued at 1230 PM CDT Wed Jun 21 2017

Nothing more than a few cumulus clouds and high-level cirrus clouds
are expected through this evening. Moisture from the tropical
cyclone over the Gulf coast will arrive in full-force on Thursday.
Cigs will lower to mvfr around sunrise, along with some rain
showers. Details concerning the intensity of the rain and associated
vsbys will become more clear tonight. For the time being, will keep
conditions mvfr during the morning, though ifr is possible. Winds
will back from southwest to southeast over the next 24 hours. Speeds
will be mainly under 10 knots.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&

$$

SHORT TERM...MY
LONG TERM...CN
AVIATION...MY



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