Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 131046
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
646 AM EDT Sat Sep 13 2014
...Updated Aviation Discussion...
.SHORT TERM (Now through Sunday)...
Issued at 300 AM EDT Sat Sep 13 2014
Currently isld showers and patches of drizzle in low strato-cu
associated with a passing upper level trough were crossing the area
early this morning. We can expect these light, brief episodes of
precipitation to continue through mid morning before exiting the
Sfc high pressure will build in from the west this afternoon
bringing dry, cool air to the region. The temp forecast for this
afternoon will largely depend on clearing behind the trough. The
best timing for the majority of clearing to occur over southern IN
and central KY would be from late morning to mid afternoon which
would allow more solar heating than yesterday. Still overall the
airmass itself will be cooler than we`ve seen yet late this summer.
Thus, will continue high temps in the mid 60s to around 70.
For tonight and Sunday, dry conditions and mostly clear skies will
continue as sfc high pressure dominates the region. There is a
slight possibility for patchy fog to develop late tonight into
Sunday morning, but the drier airmass and elevated low level winds
on the south side of the sfc high pressure may prevent this. Thus,
will not include patchy fog for this forecast although it may be
considered in later issuances. The main forecast challenge for
tonight will be chilly temps. The cool airmass and good rad cooling
conditions should result in low temperatures in the 40s over most
locations except perhaps south central KY which may hold in the 50s.
Expect slightly warmer temperatures for Sunday as the airmass begins
to moderate. Afternoon highs should reach the low to mid 70s.
.LONG TERM (Sunday night through Friday)...
Issued at 300 AM EDT Sat Sep 13 2014
The longwave pattern forecast for early next week will feature
ridging long the Pacific Northwest coast and a broad trough centered
well north of the Great Lakes. Deep Gulf moisture will be confined
well to our south with surface ridging across New England, extending
southwest along the Ohio Valley. Temperatures will moderate a bit
Sunday night and Monday under mostly clear skies and light and
Average temperatures for early-mid September are generally around 80
for highs and 59 for lows. Early morning lows for Monday will range
from the lower to mid 50s. Nearly calm winds and clear skies may
even allow for some patchy fog early Monday. Monday highs, although
becoming warmer than Sunday`s, will still fall a couple of degrees
short of this mark.
A flat and progressive shortwave will move across the western Great
Lakes late Monday, with high pressure of Pacific origin building
across the upper midwest in its wake. A weakening front will move
south across the Commonwealth late Monday into early Tuesday. Any
forcing aloft will stay well to the north. Little moisture will be
available ahead of this boundary, and precipitation chances will be
quite minimal with this frontal passage. More likely, a few hours of
mid-level cloudiness will develop late Monday with just a few
sprinkles or a few hundredths of rainfall at best.
Tuesday through at least Friday will feature Ohio Valley fall
weather at its finest. Drier air arrives Tuesday as winds will
become light northerly as surface high pressure descends south
across Iowa. Both the ECMWF and the GFS advertise 500mb trough
amplification across the eastern Great Lakes and New England
Wednesday through early Friday. Colder air with this trough will
skirt the Great Lakes and invade New England, bypassing us to the
For us, this 500mb northwesterly flow pattern setting up will bring
an extended period of mostly clear days with generally light winds
beginning on Tuesday. Tuesday will cool a bit from Monday, with
highs only reaching the lower 70s. Expect slow moderation in
temperatures throughout the next work week with highs reaching the
upper 70s by Friday.
.AVIATION (12Z TAF Update)...
Issued at 645 AM EDT Sat Sep 13 2014
MVFR cigs will be common this morning across the region as an upper
level trough passes through. This trough may bring a period of low
end MVFR bordering IFR as well as a stray shower or some patchy
drizzle through mid morning. The trough will exit the region later
today with sfc high pressure and drier air working into the Ohio
Valley this afternoon. Thus, we`ll see improving conditions to
high end MVFR by mid to late morning and then VFR conditions are
expected by mid to late afternoon. Winds will remain northerly
through the TAF period becoming more NE by tomorrow evening. Wind
speeds will increase to 6-10 kts this afternoon. Some light br is
possible tomorrow morning.