Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 221925
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
325 PM EDT Tue Apr 22 2014
.SHORT TERM (Now through Wednesday Night)...
Issued at 310 PM EDT Tue Apr 22 2014
A cold front has passed through the region today. Behind it, we can
expect gusty northerly winds (up to 25 mph) late this afternoon and
early evening with winds declining after sunset.
Skies should clear this evening as a drier, colder airmass works
into the region under sfc high pressure. A decent rad cooling night
looks to be in store although winds will stay slightly elevated
aloft with 3-8 mph northerly sfc winds which will limit the cooling
somewhat. Still overnight temps look to be quite chilly for this
time of year dipping into the upper 30s and lower 40s. Sheltered
locations and typical cool spots in the Bluegrass region may reach
the mid 30s with patchy frost formation possible. Thus, will
mention in an SPS the patchy frost potential.
Perhaps of greater concern will be an enhanced wildfire danger for
Wednesday afternoon. Dry air aloft looks to mix down to the sfc
resulting in relative humidity values dropping into the mid 20
percent range. Already dry ground fuels (5-8%) combined with low
humidity values will pose a risk for any fires to rapidly spread out
of control. NNE winds will remain fairly tame in the 5-10 mph.
Still, think that an SPS mention for enhanced wildfire danger is in
order for tomorrow afternoon/early evening.
Other than that, tomorrow looks to be mostly sunny with high
temperatures ranging throughout the 60s.
Wed night dry conditions will continue with upper level clouds
increasing. Low temperatures will rebound into the 40s as ridging
and warmer air arrives.
.LONG TERM (Thursday through Tuesday)...
Issued at 317 PM EDT Tue Apr 22 2014
This period begins dry as the aforementioned surface high moves off
toward the eastern seaboard and upper-level ridging across the south
moves along with it. By late Thursday night into early Friday, a
trough scooting across the Midwest and its associated surface
boundary quickly traverses through with models generally agreeing
that the precip will have exited by midday Friday. The ECMWF is the
outlier for PoPs Friday as it`s a bit slower clearing central
Kentucky and southern Indiana out. However the timing ends up
playing out, once the precip exits off to the east on Friday, expect
one more round of dry conditions through the middle of the
As mentioned in the previous forecast, Sunday onward looks
to be rather unsettled as an upper low spins across the center of
the country. At the surface, a stalled frontal boundary is depicted
on the 12z GFS and ECMWF to drape just north of the forecast area,
oriented east-west across the center of Indiana. Meanwhile, a
surface low associated with the upper low deepens and seemingly
wants to ride the track of where the boundary lays out late Monday
night through Tuesday. While the 12Z ECMWF has come into better
agreement with the 12Z GFS, there are still noticeable differences
temporally and spatially when considering how this system will
evolve. Therefore, have kept just chance PoPs from Sunday through
Tuesday until we get closer to that time frame and can grab a better
handle. It likely won`t rain during the entire time frame but since
we are approaching an unsettled weather pattern that won`t be
arriving until at least 5 days from today, the uncertainties force
PoP wording during the 12-hour time periods for early next week.
Given face value of the 12z model runs, late Monday through Tuesday
look to have the highest chances at this time. With respect to
thunder possibilities, model soundings point toward the same time
frame of late Monday through Tuesday and have indicated as such in
this forecast update.
Temperatures to start the long-term will be near to slightly above
normal with afternoon highs ranging from the mid to upper 70s on
Thursday through Saturday. The corresponding low temps will respond
similarly with mid to upper 50s Thursday night, lower 50s Friday
night, and then upper 40s across the north and lower 50s across the
south Saturday night. The temperature forecast then gets a bit more
tricky as cloud cover and precip could certainly play havoc until
the real airmass change comes through in the middle of next week.
Generally speaking though, cooler temps can be anticipated from
Sunday onward, especially as that upper low approaches the region.
.AVIATION (18Z TAF Update)...
Issued at 105 PM EDT Tue Apr 22 2014
The cold front was through BWG/SDF as of 1630Z and passing through
LEX. Expect winds to veer to the NW at LEX within the next hour.
Just behind this front, expect MVFR cigs to continue for a short
time before rising and scattering out. VFR conditions will then be
the rule for the rest of the TAF period as sfc high pressure settles
into the area for tonight and tomorrow. Expect clear skies
overnight with north winds under 7 kts. For tomorrow some upper
level clouds will begin to work into the region with winds shifting
to the NE and remaining under 7kts.