Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 211734
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
134 PM EDT Sat Oct 21 2017

...Updated Aviation Discussion...

.Short Term...(Today through Sunday)
Issued at 225 AM EDT Sat Oct 21 2017

As of early morning, satellite imagery showed a steady plume of
cirrus from the Gulf Coast northward through the Tennessee and lower
Ohio Valleys. Winds were light and out of the southeast while
readings had dropped into the 50s. For the rest of this morning,
expect morning lows to range from the upper 40s to middle 50s,
warmest in the metro. Cirrus will continue to move over the region
through sunrise, which will also help limit fog potential for most
of the area. Some of the deepest valleys that decouple could see
some patchy fog around sunrise.

For today, plan on another dry and warm day with southerly breezes
picking up this afternoon. Expect highs to reach the 70s despite
cirrus overhead at times. Tonight will feature more dry conditions
but with better mixing in advance of the next weather system, lows
will be 3-5 degrees warmer /55 to 60/ across the region.

The advancing shortwave trough and cold front will very slowly
approach the area on Sunday though the bulk of the precipitation is
expected to remain west and south of the area through the daylight
hours. This will allow for warmer and breezier conditions to
develop. Forecast soundings show 20-25 mph gusts possible during the
afternoon as highs soar into the upper 70s. Some of the warmer spots
that see more sunshine could hit 80 degrees. Trended highs above the
model consensus with this setup, especially along/east of I-65.

.Long Term...(Sunday night through Friday)
Issued at 231 AM EDT Sat Oct 21 2017

The main weather highlights in the long term are the potential for a
soaking rainfall Monday and Monday night followed by seasonably cool
conditions mid to late week. Another weather system is possible next
weekend.

A sharp upper level trough will dive from the Plains through lower
MS River Valley Sunday and Sunday night. This will begin to pump
more Gulf moisture northward into the region. Widespread rainfall is
forecast to spread into central Kentucky Sunday night then across
the entire area Monday and Monday night. The air mass will be
characterized by unseasonably high PWATs /1.5 to 1.7 inches/ and
soundings show the entire column to be well saturated. So, periods
of heavy rainfall are possible through this period. Total rainfall
amounts are forecast in the 1 to 2 inch range with locally higher
amounts possible.

As the system lifts northeast into the OH Valley late Monday night
and Tuesday, it will begin to phase with an approaching shortwave
trough from the Upper Midwest. This will result in a deepening
trough across the entire region, bringing much cooler air into the
area. This deep upper trough will be over the area Tuesday through
Wednesday night. Plan on highs in the 50s both days, coolest on
Wednesday when lower 50s are expected. With colder air aloft, we`ll
probably see some continued lingering precipitation Tuesday and
diminishing on Wednesday. Lows Wednesday night will cool into the
mid-upper 30s. This could result in another frost threat, especially
if skies clear out a little faster than forecast.

For Thursday and Friday, the pattern will quickly relax and revert
back to a southwesterly flow over the eastern US.  This should
result in a drier and slightly milder pattern developing for
Thursday and Friday.  Highs both days will warm back into the upper
50s to the lower 60s with overnight lows mainly in the 40s.

As we move into the next weekend, another upper trough and front
could approach the area bringing a chance of showers and perhaps
some thunderstorms. In its wake, another surge of cool Canadian air
is suggested.

&&

.Aviation...(18Z TAF Issuance)
Issued at 130 PM EDT Sat Oct 21 2017

VFR conditions are expected throughout the TAF period.  However
winds will be on the increase tonight as strong southerly flow
develops ahead of an approaching upper trough and cold front.  A 35-
40 kt low-level jet is forecast to develop after 03z tonight at
around 1500 feet. So have included LLWS at HNB/SDF/BWG. LEX will
also see low-level winds increase to around 30-35 kts Sun morning as
well but feel this is just below LLWS criteria so did not include in
the TAF attm.  LLWS will diminish by 14-16Z as the inversion breaks
down and the atmosphere becomes mixy.  Southerly wind gusts of 18-
22 kts can be expected Sun afternoon.
.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&

$$

Short Term...ZT
Long Term...ZT
Aviation...AMS



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