Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 212314
Area Forecast Discussion
National Weather Service Louisville KY
714 PM EDT SAT MAY 21 2016
...Updated Aviation Discussion...
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 (00Z TAF Update)...
Issued at 713 PM EDT Sat May 21 2016
Weak surface trough will continue to drop southward overnight taking
the low cloudiness and light precipitation with it. VFR conditions
are already in progress at KSDF and KLEX. KBWG will see a few more
hours of MVFR conditions and then start to scour out by 22/01-02Z.
Winds will be light out of the northwest.
For the overnight period, mostly clear skies are expected. That,
along with light winds and moist ground raises the question of fog
potential. As previous forecast indicated, we do have some drier
air advecting in from the northwest which may help offset widespread
fog production and limit it mainly to the river valley locations.
For now, plan on just keeping a tempo group in at KBWG between 22/09-
13Z for some MVFR patchy fog.
Sunday will be a pleasant flying day as high pressure enters the
region from the northwest. Winds could get a little gusty at SDF in