Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 202214
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
614 PM EDT Sun Apr 20 2014
...Updated Aviation Discussion...
.SHORT TERM (Now through Monday Night)...
Issued at 312 PM EDT Sun Apr 20 2014
An upper level ridge is in place across the region today with mostly
sunny skies and light and variable winds. Temperatures are currently
ranging in the low and mid 70s, on their way to the upper 70s to
around 80 for highs. Drier air is mixing down this afternoon, mostly
ranging from 36-41 at this hour. This process is occurring slower
than yesterday due to less mechanical mixing from lighter winds
today. RH values will hover in the 20-30% range for many hours this
afternoon, however winds are light enough that an elevated wildfire
threat is not a concern at this time.
The upper level ridge axis will begin to slide East overnight as a
shortwave approaches from the west. This will allow more mid and
upper level clouds to stream into the area, along with a slight
uptick in southerly winds. Previous forecast mentioned slightly
milder overnight lows for these reasons and will continue this
thought. Will call for lows mostly in the upper 40s and low 50s,
however dip bump a few of the cooler valleys down to the mid 40s
since we saw valleys in the upper 30s last night under similar
The majority of Monday will be dry, although will continue mention
of isolated to widely scattered showers and a t-storm along and west
of I-65 by mid to late afternoon. These chances will be due to an
isentropic ascent component combined with some weak instability, and
what appears to be an uncapped environment. Not too impressed if you
look at moisture profiles from a time height perspective as moisture
looks pretty limited. The main precipitation chances will come
overnight on Monday. Upper level clouds will limit heating just a
bit on Monday, although still expect solid upper 70s as we do pick
up a more steady SW wind and still see some peaks at the sun. If
there are any Fire Weather concerns tomorrow, it would be along the
Deeper moisture will arrive Monday night ahead of the upper level
trough axis and along the weak cold front trailing from a surface
low over the eastern Great Lakes. Mention of scattered to numerous
showers and scattered thunderstorms still seems reasonable. Areas
that do see rain should expect between a tenth and a quarter of an
inch, with up to an half an inch possible in the wettest spots.
Overnight lows will obviously be milder just ahead of the front,
ranging in the upper 50s to around 60.
.LONG TERM (Tuesday through Sunday)...
Issued at 310 PM EDT Sun Apr 20 2014
A cold front will be right over our forecast area at the start of
the period, with the chance for rain out ahead of it mainly in the
morning hours. The next chance for rain holds off until either late
Thursday afternoon or Thursday night, as another cold front
approaches the area. This front will be followed by another one
Friday night. The Thursday night system has the most moisture
available with it, and may set up with a line of storms developing
to our west and moving through the area as they weaken. The Friday
night front will not as much moisture to work with, so will keep
forecast dry for now.
By Sunday, the 00Z ECMWF allows the warm front behind these systems
to lift over us quicker than the new GFS, bringing rain chances back
to the region for Sunday. The GEFS lends credence to the pattern
over us, but the spread is high for the placement of a low pressure
center over the Central Plains, which if on the north end would give
us a better chance for the front to be farther north. Given the
differences here, will keep rain chances low for the end of this
Wednesday still looks to be the coolest day this period, with
temperatures in the morning in the low 40s and possibly some upper
30s in our cold spots. Winds still look to stay up Tuesday evening,
keeping us from the best chance for a quick cool down. Then on
Thursday and Friday temperatures bounce back above normal before
dipping back to normal for the weekend.
.AVIATION (00Z TAF Update)...
Issued at 614 PM EDT Sun Apr 20 2014
Tonight will be VFR with calm winds as a ridge of high pressure sits
just off to our east. Monday will remain quiet, though we`ll see an
increase in southwest breezes as we sit between the high to the east
and a cold front approaching from the west. Scattered showers may
begin to affect SDF Monday evening as the front gets closer.