Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 212310
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
710 PM EDT Sun Sep 21 2014

...Updated Aviation Discussion...

.SHORT TERM (Now through Sunday)...
Issued at 300 PM EDT Sun Sep 21 2014

A cold front will move southeast of the Lake Cumberland Region by
late afternoon. A few showers and perhaps even a thunderstorm have
developed over the southern Bluegrass and Lake Cumberland Region
within a thin axis of instability right along this boundary. Any
storms will move southeast of our CWA by around 6 pm. In its wake,
significantly cooler air will arrive after midnight, as a sharp
500mb trough axis swings east of the Commonwealth by Monday
afternoon.

In the short term, skies will clear for a few hours across central
Kentucky by late afternoon. Despite brisk northwest winds this
afternoon, colder air will lag behind the actual front itself, so
early evening will stay relatively mild. Cloudiness will actually
increase by mid to late evening as steepening lapse rates may
promote some scattered to occasionally broken strato-cu diving south
from Indiana.

Robust surface high pressure will sag south and lie over Missouri
Monday morning. Skies will clear at least by dawn Monday and will
stay clear for the next several days. Lows by dawn will fall into
the lower 50s, and recover only to the mid 60s to around 70 Monday
afternoon.

With very light winds and ideal radiational cooling conditions,
temperatures early Tuesday will be the chilliest of this young fall
season. Lows early Tuesday may approach 40 across our nominally
cooler rural locations, while averaging in the upper 40s elsewhere.

.LONG TERM (Sunday night through Friday)...
Issued at 255 PM EDT Sun Sep 21 2014

Surface high will ridge into the Ohio Valley from the northeast for
much of the work week, maintaining dry weather and mild temps,
albeit with a gradual warming trend as the week progresses.

Coolest day will be Tuesday, with temps limited by a chilly start,
and shallow mixing in the NE flow. Might only mix to 900mb, which
would barely allow highs to crack 70. Have gone generally with lower
70s, in line with the NAM MOS guidance but undercutting GFS MOS by
several degrees.

Temperatures will begin a slow recovery on Tuesday night, as the
thermal trof will be solidly to our east. Latter part of the week
should see temps near climo as the building ridge evolves into a Rex
block with a closed upper high over the Great Lakes. The developing
upper low over the Deep South could start to turn the pattern more
unsettled next weekend. However, confidence remains limited this far
out, so will include no more than slight chance POPs for next
Sunday.

&&

.AVIATION (00Z TAF Update)...
Issued at 710 PM EDT Sun Sep 21 2014

A tight pressure gradient in the wake of the front that moved
through the area today continued to keep winds gusting to around
20kts or higher as of 2250Z. These should diminish shortly after the
TAF valid time as decoupling occurs as an inversion sets up at the
surface. However, current TAFS had these continuing through 02Z at
KLEX and KSDF, and instead of pulling them only to see them persist
beyond 00Z will leave them in for now.

Stratocumulus deck over Indiana and Illinois has decreased
considerably over the past few hours, with the leading edge along
the Ohio River now only showing up as FEW050 in SDF metar. Model
time cross sections continue to show a narrow layer of 80+ RH at or
below 850 Mb moving SE through the area overnight, but with
subsidence, this is not likely to result in anything more than
FEW-SCT overnight.

By sunrise Monday, clear skies and N-NE winds under 5 kts will close
out the valid period.

&&

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

$$

Short Term........JSD
Long Term.........RAS
Aviation..........JBS




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