Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 241654
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1254 PM EDT FRI MAY 24 2013
...Updated Aviation Discussion...
Issued at 640 AM EDT Fri May 24 2013
Current forecast continues to be on track. Drier air is starting to
win out as low-level cloud deck is start to erode nicely across
southern Indiana. Expect partly cloudy skies to give way sunny
skies as we head through the rest of the morning hours.
Temperatures should continue to fall over the next hour or so
bottoming out in the mid-upper 40s in the far north with upper 40s
to around 50 near the river...and in the lower 50s across southern
Kentucky. Afternoon high temperatures in the mid to upper 60s still
look on target.
.Short Term (Now - Saturday)...
Issued at 325 AM EDT Fri May 24 2013
Surface cold front continues to plow on off to the southeast this
morning. Rain showers have long ended across southern Indiana and
central Kentucky, but plenty of low clouds remain in place across
the region. Drier air is trying to work in from the west, but a
persistent north to northeasterly PBL flow is allowing the low
clouds to continue to flow southward this morning. In the near
term, expect mostly cloudy conditions to remain in place, though our
western sections will probably see a little more clearing due to the
closer proximity to the drier air in place to our west.
Temperatures will continue to fall with cold air advection
place...and we expect readings to fall into the mid-upper 40s by
For today, high pressure will slowly build in from the northwest.
Dry punch of air will continue to make headway into the Ohio Valley,
so we should see a rapid decrease in clouds during the morning hours
with mostly sunny skies expected today. Dewpoints will likely drop
into the 30s this afternoon and with a good amount of mixing and
cooler air aloft, we`re likely to see a bit of a temperature
gradient across the region. Afternoon highs will likely only top
out in the 61-66 degree range across the Bluegrass region of central
Kentucky with 65 to 70 degree readings in the I-65 corridor and
points west. Surface winds will be out of the N to NE and will
slacken later in the afternoon and into the evening hours.
For tonight, high pressure and light winds will be in place which
should set up a good radiational cooling period. The question
remains whether we`ll see the development of fog or a potential
frost. From a climatological perspective, the threat of frost is
fairly low here in KY/IN. For the most part, it looks like
temperatures will probably remain warm enough that we`ll see mostly
patchy fog develop. However, some of our eastern counties may get a
touch of frost...especially in our typical cold spots. For this
reason, we will issue a special weather statement this morning
highlighting the potential frost threat in the typical colder spots
in the eastern Bluegrass region. Lows tonight will likely be in the
upper 30s in the east with lower 40s in the central and western
Quiet and warmer conditions are expected for Saturday as high
pressure moves on off to the east. This should kick our surface
winds around to the south and eventually the southwest.
Temperatures should moderate a bit on Saturday with highs in the
65-70 degree range in the Bluegrass with 70 to 75 in the central and
western sections of the forecast area.
.Long Term (Saturday Night through Thursday)...
Issued at 310 AM EDT Fri May 24 2013
A amplified yet slowly progressive 500mb pattern will feature deep
troughs across New England and the Pacific Northwest late Saturday.
Eventually, ridging over the western plains will expand towards the
Lower Ohio Valley. This will enable temperatures to warm
substantially beginning Monday. High temperatures may actually
approach 90 towards the end of the next work week.
Canadian high pressure ridge axis will lie right over the Great
Lakes late Saturday, extending southward across the Commonwealth.
Cool weather with low dewpoints will continue through Sunday, along
with light winds. Despite the possibility of some increasing high
cloudiness associated with a warm front to our southwest, lows early
Sunday will fall well down into the lower to mid 50s.
Quite a bit of uncertainty and disagreement exists between some of
the long range guidance for the Sunday through Tuesday time frame.
Overall, warmer more moist air will attempt to move northeast into
the Lower Ohio Valley. However, a deep slow moving low over New
England and persistent northwest flow aloft over the Commonwealth
will retard the northeast progress of this boundary. It is likely
during the first couple of days of next week that several convective
clusters will develop across the midwest, aided by moisture
advection and the presence of a nocturnal low level jet. These
periodic thunderstorms may slide southeast, bringing at least a
chance of difficult-to-time thunderstorms beginning Sunday afternoon
and possibly continuing through Tuesday.
Both the ECMWF and the GFS forecast the surface boundary to stretch
early Sunday from northern Missouri southeast towards central
Tennessee. The consistent ECMWF has been slower in bringing this
boundary north across the Commonwealth than the GFS. However, by
Tuesday afternoon, both of these models have this boundary as far
north as southern Ohio. Will continue our forecast of at least a
chance of thunderstorms Sunday afternoon through Tuesday, with an
admittedly low confidence on attempting to time any areas of
convection moving southeastward along this boundary.
Highs on Sunday will likely remain in the 70s, warming to the lower
to mid 80s by Tuesday. For Wednesday and Thursday, mid-summer like
ridging will develop over the Tennessee Valley. Expect that these
two days will stay dry with quite warm temperatures in the mid to
.Aviation (18Z TAF Issuance)...
Issued at 1253 PM EDT Fri May 24 2013
High pressure is building into the region and will hold influence
through this forecast cycle. This will keep conditions dry and VFR.
Few - Sct cu should gradually mix out through the afternoon with a
steady NNW wind between 5 and 10 mph. Winds will go nearly calm to
calm tonight. Expect a light easterly wind on Saturday with Few to
Sct upper level clouds beginning to move overhead.