Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 150501
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
101 AM EDT Mon Sep 15 2014

...Forecast Update...
Issued at 1255 AM EDT Mon Sep 15 2014

Will be watching fog potential closely overnight.  As of 1230am, no
fog was observed over central KY/southern IN but dewpt depressions
were closing quickly.  Fog was forming in eastern KY already.  0Z
NAM really hits fog hard over our area with the NARRE and simulated
WRF models also indicating fog potential.  Latest MOS guidance
dewpts were too low for current observations and thus overall MOS
guidance showed some fog but not widespread dense fog.  Will need to
keep an eye on conditions as we go through the night as the above
mentioned factors will likely lead to fog formation over our region
although the areal extent and density is in question.  Some factors
that may hinder fog development and density in our region include
incoming cirrus clouds(from the west) and slightly drier air sinking
south from central Indiana.  For the overnight forecast, will leave
the patchy fog mention as is for now but wanted to discuss pros/cons
for areal extent and density.

.SHORT TERM (Now through Monday Night)...
Issued at 320 PM EDT Sun Sep 14 2014

High pressure centered to our northeast will bring at least one more
dry day. A weakening frontal boundary, ahead of an upper level
impulse now along the Montana/Canada border, will move into the
region Monday night. This front will have little moisture to work
with, but cannot rule out some light rain showers. Will keep low-end
chances that night. Otherwise temperatures will stay below normal
through Monday. Monday night will be a little warmer ahead of the
front, closer to normal.

.LONG TERM (Tuesday through Sunday)...
Issued at 250 PM EDT Sun Sep 14 2014

The synoptic pattern at the start of the long term period will
feature a broad trough across the the eastern half of the CONUS.
This trough will remain in place for the majority of the long term
period, keeping rather tranquil conditions in place until possibly
next weekend.

The long term period will start out with a decaying front bisecting
the region from west to east.  Moisture with this front will be
limited (saturation only about 200mb deep), and ascent above it will
be weak given the upper-level forcing will pass well to the north
across IN/OH.  Debated adding in pops for Tuesday morning, but given
the above reasoning, will continue with a dry forecast.  We will
likely see some sprinkles across the region, but prospects for
measurable precip appear low Tuesday morning.

A sprawling ridge of high pressure will build into the Ohio Valley
for the remainder of the workweek, keeping conditions dry and
fall-like.  Temperatures through this period will be in the 70s,
with lows generally in the 50s.  The coolest night will likely be
Tuesday night into Wednesday morning, when lows may dip into the
upper 40s across some spots, especially northern KY and southern IN.

The next storm system will approach late in the upcoming weekend.
Out ahead of it, southerly flow will commence on Saturday, making
for a moderation in temperatures.  Highs Saturday will climb into
the low 80s.  Guidance differs quite a bit with the handling of the
next cold front that looks to push through the region.  Given the
disagreement, will limit slight chance pops to mainly southern IN on
Saturday night, with the bulk of the system and associated fropa
likely to affect the region after the long term period.

&&

.AVIATION (00Z TAF Update)...
Issued at 705 PM EDT Sun Sep 14 2014

Though high pressure will gradually lose its influence on us as a
very weak cold front approaches from the northwest, we`ll still have
a quiet TAF period thanks to a generally dry atmosphere. Hard to
tell if BWG will get any fog Monday morning or not, given the
aforementioned dry atmosphere plus it looks like a cirrus canopy
will stream in from the southwest right around the most
climatologically favored time for fog.  Can`t completely rule it
out, though, so will continue with the high-end MVFR BR that`s
already in there.

&&

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

$$

Update.........AMS
Short Term.....RJS
Long Term......KJD
Aviation.......13





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