Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 221722
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
122 PM EDT Fri May 22 2015
...Updated Aviation Discussion...
.SHORT TERM (Now through Saturday)...
Issued at 304 AM EDT Fri May 22 2015
Patchy fog in central Kentucky early this morning will dissipate as
the sun comes up and temperatures start to rise.
A weak surface trof will slide southward today, reaching the Ohio
River by this evening and then washing out. The front will have
little effect on the weather though as we enjoy a day of mostly
sunny skies and west breezes. High temperatures should be in the
lower and middle 70s...just a few degrees below normal.
High pressure will build in tonight, especially over northern and
eastern sections of the forecast area. The mercury will drop well
into the 50s, with some 40s possible in the Blue Grass.
The high will move to the mid-Atlantic coast tomorrow. In the Ohio
Valley we will experience light return flow and increasing
thicknesses, leading to slightly warmer temperatures. Afternoon
highs should be near 80.
.LONG TERM (Saturday Night through Thursday)...
Issued at 255 AM EDT Fri May 22 2015
The synoptic pattern at the start of the long term period will
feature an amplifying ridge over the Ohio Valley in response to an
ejecting trough over the southern/central Plains. This ridge will
slowly meander to the east through the long term period, allowing
deep southwesterly flow to envelop the region. This regime will
bring an unsettled period of weather through much of next week.
While much of the long term looks active, the good news is that
Sunday is continuing to trend drier. The latest guidance suite
continues to suggest the ridge axis will remain over the Ohio Valley
through the afternoon hours, helping to keep the southwesterly flow
and associated impulses west of the region. Given this trend, have
continued to lower pops for Sunday afternoon, keeping only slight
chances in across the far western CWA. If the latest trends hold,
then we may be able to go completely dry for all areas on Sunday.
Certainly welcome news for those with outdoor plans this holiday
weekend! Given the building ridge aloft, 850 temps rising to around
15C, and less expected cloud cover, have bumped up temperatures for
Sunday which puts highs in the low to mid 80s.
The remainder of the long term forecast looks rather active as deep
southwesterly flow takes over in the wake of the departing ridge
axis. PWATS will climb to near 1.75 inches beginning Monday and
lasting through much of the upcoming week. Unfortunately, rounds of
showers and thunderstorms will be tied to very weak (some
convectively-induced) perturbations passing through the
mid/upper-level flow. Therefore, timing individual waves continues
to remain very difficult at this juncture. If we get a wave pushing
through overnight, then much of the following day could end up being
dry, and vice-versa. Therefore, will continue to hold pops in the
40-50% range through much of the extended forecast until the
mesoscale details can be ascertained. Widespread severe weather
continues to look unlikely. However, depending on timing, enough
instability in the afternoons may combine with just enough
mid/upper-level flow to produce some stronger storms capable of
With the uncertainty in convective timing comes uncertainty in
temperatures. Went with a guidance blend of low to mid 80s through
much of the week, but a day with more sun could push temps into the
mid/upper 80s whereas a cloudy day filled with convective debris may
keep temperatures in the upper 70s. Overnight lows will be rather
mild given the moist low-levels, with readings expected in the mid
and upper 60s each night.
.AVIATION (18Z TAF Update)...
Updated at 122 PM EDT Fri May 22 2015
A weak trough axis will approach the region this afternoon and
evening. This feature is expected to wash out as it pushes into the
region and is not expected to produce any sensible weather other
than some high cloudiness moving in from the west. High pressure
will build into the region tonight bringing VFR conditions.
Probability remains low for fog development due to the expected high