Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 240707
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
307 AM EDT Fri Oct 24 2014
.SHORT TERM (Now through Saturday)...
Issued at 301 AM EDT Fri Oct 24 2014
An upper level disturbance that slid southeastward from Illinois
into Indiana during the overnight hours will cross Kentucky this
morning and then move off to the southeast this afternoon. This
feature will be responsible for a fair amount of cloudiness this
morning, and maybe even a sprinkle or two especially in southern
Indiana. High pressure at the surface stretching from Texas to
Pennsylvania will keep winds light today. Temperatures this
afternoon will peak in the middle and upper 60s.
Tonight will be quiet with partly cloudy skies. We will get into
some weak return flow as the aforementioned surface high sags to the
southeast and a cool front approaches from the northwest. Also,
clouds will begin to increase towards Saturday morning, especially
in southern Indiana and northern Kentucky. We should end up with a
sizable temperature difference across the area for lows, with mid
40s to around 50 in the northwest (more clouds, closer to
approaching front) and around 40 in the southeastern valleys (fewer
clouds, closer to the surface high).
On Saturday the cool front will enter the region but will be
weakening as it does so, and will only have shallow low level
moisture associated with it. Clouds are expected, but not much in
the way of precipitation other than a sprinkle or two. Right now
will aim for high temperatures in the upper 60s in the Blue Grass
and low to mid 70s elsewhere, though clouds and fropa timing will
have an effect on where we end up.
.LONG TERM (Saturday Night through Thursday)...
Issued at 258 AM EDT Fri Oct 24 2014
The start of the long term period will feature northwest flow aloft
over the Ohio Valley as a ridge amplifies across the Central
Plains. This regime will turn to more southwesterly then more zonal
flow over the region through the period, making way for a
significant warmup followed by a return to cooler temperatures.
The long term period will start with a weak surface front pushing to
the east of the region Sunday morning. However, this front will not
get very far to the southeast as an area of low pressure develops
across the Central Plains. In response, this front will stall and
then begin to lift back to the north during the day on Sunday.
While the bulk of the warmer air will reside just to the west of the
region, the combination of the front sharpening and pushing north
coupled with expected sunshine, should yield temperatures in the
70s, perhaps upper 70s across southern KY.
Monday looks to be a very warm day, perhaps the last 80 degree day
of the year in some locations. The warm front will push well to the
north, leaving the Ohio Valley fully within the warm sector. This
seems to be a day where temperatures could overachieve as we will be
have a strong pressure gradient leading to good southwesterly
surface flow. Additionally, forecast soundings do not show much in
the way of low-level moisture, which should limit any cloud cover to
passing high/mid-level clouds. Therefore, have bumped temperatures
up a few degrees from the previous forecast, which puts readings in
the upper 70s to lower 80s.
The aforementioned surface low across the Central Plains will deepen
and push into southern Canada on Tuesday in response to an
approaching PV anomaly. The best synoptic scale ascent will trek
well north of the Ohio Valley with this system, leaving the region
with just the trailing part of the cold front. Given the amplified
upper-level regime, a deepening cyclone, and the fact that the Ohio
Valley will be on the trailing edge of the surface front, have
leaned on the slower end of guidance with the fropa. This puts the
best precipitation chances into the region Tuesday night. Given the
better dynamics passing to the north and still some questions
regarding timing, am a bit hesitant to raise pops too high at this
time range. Therefore, will limit them to around 60%.
Guidance had disagreed with the evolution of the front as it passed
through the region, but the 24/00Z cycle has come into better
agreement regarding the front stalling across southern KY. This
stalled front will keep precipitation chances across southern KY
Wednesday into Wednesday night. With the frontal passage,
temperatures on Wednesday into Thursday will fall back into the 60s.
.AVIATION (06Z TAF Update)...
Updated at 1238 AM EDT Fri Oct 24 2014
Surface ridging over Kentucky will keep SDF and LEX VFR with light
winds through the TAF period. Similar conditions will be found at
BWG, with the exception of the possibility of some MVFR BR early