Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 220542

Area Forecast Discussion
National Weather Service Louisville KY
142 AM EDT SUN MAY 22 2016

...Forecast Update...
Issued at 138 AM EDT Sun May 22 2016

Multiple observation sites showing 1/4 mile or less and dense fog is
showing up on area webcams. Therefore, a Dense Fog Advisory has been
issued. This may be expanded as needed through the night.

Issued at 1111 PM EDT Sat May 21 2016

There have been some reports of dense fog forming in some areas
tonight. It can also be seen in webcams, particularly in low lying
areas and river valleys. Went ahead and issued a Special Weather
Statement to cover this for now. However, will continue to monitor
the fog formation overnight as some of the high resolution guidance
is now suggesting it could become fairly widespread.

Issued at 923 PM EDT Sat May 21 2016

Made some quick edits to the grids to remove PoPs as precipitation
has exited the area.  Low clouds continue to clear on out of the
area.  However, have a pesky band of mid-level clouds pushing in
from central IL.  Current thinking is that these will continue to
move southeast and fade out overnight.  For now, have increased sky
cover slightly across the western half of the forecast area
overnight to reflect this.  As for the fog potential, latest
guidance and high res simulations are not suggesting any widespread
fog overnight.  Most likely due to the drier air working in from the
northwest and the increasing T/Td spreads.  Some high resolution
models suggest that the typical fog prone areas (low-lying and river
valley) could see some patchy fog.  Other weather elements look in
good shape at this time.  Overnight lows in the upper 40s to the
lower 50s still look good at this point.

Update issued at 707 PM EDT Sat May 21 2016

Did a quick update on sky cover and PoP grids to bring them in line
with current in-situ observations.  Clearing line working southward
across KY and we should see mostly clear skies in the 22/02-03Z time
frame.  This update simply removes the pre-first period wording in
the zone forecasts.  Will be re-evaluating the forecast in the next
few hours to assess sky cover and possible fog potential.

.SHORT TERM (Now through Monday Night)...
Issued at 236 PM EDT Sat May 21 2016

A weak surface trof pushing southward across Kentucky will switch
winds to the north and push clouds and showers out of the area this
evening. With clear skies, decreasing winds, and soaked ground, the
question of fog arises. At this time it looks like dry air advecting
in will help to keep widespread significant fog from developing, but
patchy fog in valleys and other particularly fog-prone spots is
still a possibility. It will be a good night for sleeping as
temperatures tumble to around 50.

High pressure moving from the upper Mississippi Valley to the
Appalachians will provide us with quiet, pleasant weather Sunday
through Monday night. A stray shower could pop up Sunday afternoon
east of Interstate 75, but otherwise we should stay dry. Highs
Sunday and Monday will be in the 70s, with an 80 or two possible
Monday. Lows will be in the lower and middle 50s.

.LONG TERM (Tuesday through Sunday)...
Issued at 315 PM EDT Sat May 21 2016

The long term period will start off dry and warm on Tuesday as we`ll
be under ridging aloft and will have a southerly flow at the
surface.  The ridging will likely hold throughout the day and then
start to break down Tuesday night.  A mid-level perturbation looks
to pass through the region late Tuesday night bringing a round of
nocturnal convection portions of the region.  At this time, it looks
like our northwestern/northern sections of the area stand the best
shot of picking up some precipitation with this system.  Highs
Tuesday look to warm into the lower 80s with overnight lows dropping
into the upper 50s to the lower 60s.

As we move from midweek towards the holiday weekend, an active upper
level pattern will take shape over North America.  This will likely
be a fairly decent episodic severe weather producer from the
southern Plains into the Midwest.  In this set up, a semi-persistent
long wave trough will set up across the western CONUS while a broad
area of surface high pressure will be in position across the
southeast.  This will allow the Gulf to be open for business
resulting in copious amounts of moisture to surge northward from the
Plains and into the western Ohio Valley.  While the bulk of the
severe convective weather will likely reside to our west, we will be
on the look out for perturbations heading eastward that pose a risk
of episodic convection in the Ohio Valley.  In general, several MCSs
may take aim at the region in the Wednesday night through Saturday
time frame.  At this temporal range, these are still difficult to
time.  Overall, this time frame will not be a total washout but
several bouts of showers and storms are likely.  Temperatures
through the period will be warm with highs in the upper 70s to the
lower 80s.  It will feel muggy as well as dewpoints will warm into
the mid-upper 60s during the period.  Overnight lows will remain
mild with low-mid 60s for lows.


.AVIATION (06Z TAF Update)...
Issued at 1245 AM EDT Sun May 22 2016

With indications of fog on area observations and webcams, issued an
update earlier for KBWG to have potential at least for IFR
conditions the rest of the night. They just dropped down to that
level in the last 20 minutes, and may still get down to LIFR/VLIFR
by daybreak. Will amend after watching trends. Latest GOES-R fog
probs indicates BWG is right on the edge of the worst area. SDF/LEX
later should be on the edge as well.  Went more optimistic, given
larger temp/dewpoint spreads, but will have to see how those trends
go as well. Once that fog burns off, we should be at VFR the rest of
the period, with winds gusting from the northwest during the late
morning and afternoon hours.


.LMK Watches/Warnings/Advisories...
KY...Dense Fog Advisory until 9 AM EDT /8 AM CDT/ this morning for



Short Term.....13
Long Term......MJ
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